I would also just divide by four. A marking tool, like a pair of dividers are a great way of verifying the accuracy of measurements. Using an adjustable square works well to find the center on small pieces.
One would account for it as they saw. OP asked how to find the dots, not get perfectly matched dimensions after cutting. They're drilling holes for dowels.
Go 1/4 of the distance in from each short edge, mark half the distance top to bottom. The benefit to the method pictured is finding centers on pieces that aren't square, though step 3 requires a square to make the center line so it doesn't actually work for bisecting out-of-square pieces in two.
Ok so, I just looked this up. [heres the article](https://kmtools.com/blogs/news/how-to-find-center-of-a-board)
Method 5 is one of those tricks that’s so simple it feels like it can’t be true! Thanks for sharing this!
I have a doweling jig that uses the same method. You twist it against the edge of the board until the two pins engage the faces of the board, and the hole for the drill bit is exactly center. Seems to blatantly obvious in retrospect but when I first used it I was like “oh yeah… neat”
You can also use this method to divide a board into thirds, quarters, fifths, etc. Just use a ruler and tilt it until the desired units match up. Tilt the other direction (or slide it a bit) to mark a second set of points and you can connect them with lines, or just use a combination square to scribe through each mark.
For dowels you want to match the relative distance of the holes over multiple pieces of wood. You don’t want an exact devision on the cut plane every time. I would use this technique to mark a jig that I could fit over the end of those 2x4s. Then you get an easily repeatable and consistent drill pattern
i think it’s good to always strive for a high level of accuracy, but it is also good to understand and appreciate the tolerances required for whatever project you’re working on. becoming too focused on precision can and will get in the way of progressing as a carpenter and craftsman.
learning to recognize the bounds of what the project needs, and allowing for some flexibility within those bounds, was a threshold point where i recognized my skill had become more advanced and i was making better quality things.
Especially since 2x4s aren't spec'd to precise dimensions and are subject to expansion. Doing this with 2 combination squares based on only 2 sides will actually yield a more consistent hole spacing.
Thats absolutely true, drawing will definitely give you more consistently accurate points. But this is really not very much drawing so if you want to reduce it any more, measuring is probably your only option.
A lot of people here are missing your intent. Geometric calculation like this is just always going to be more dependable than mathematical.
This isn't much simpler, but you can draw a horizontal line on step 4, then you only need one diagonal apiece for each square on 5 and 6. Wherever that diagonal intersects the horizontal is center on a rectangle
It just looks like the middle of 2 squares. You divided the rectangle in half, and then found the midpoint of the 2 squares by making the X across the corners.
Width divided by 4, height divided by 2.
The X method is way too error prone in my experience (did alot of this for fret markers which is what this looks like to me)
I can't believe so many people think 3 and 4 are the same. Step 4 is clearly where you take a drink and rest up in prep for more drawing of lines. Rest is critical to success.
OP did say this was for dowel holes in a 2×4. A low-tech solution would be a card with holes punched in the right places. A slightly higher tech solution would be a thin sheet of plywood with two members at right angles all glued up such that the corner can slip on the end of the board. Measure once and cut as many times as you need
3 and 4 are the same
To do the same with less lines
Step 4: draw horizontal line in center
Step 5/6: only one diagonal line on each side is needed. Each will pass through horizontal on new step 4
If for some reason you want to get your compass involved:
https://preview.redd.it/wqjb403nq84d1.png?width=1280&format=png&auto=webp&s=13293ce919e7fac38da6a2e97b65056865f82b75
If you're certain the work piece is 2(x) by 4(x), then you can just draw a 45 degree angle off all the corners, the intersection will be the centers.
Otherwise, it's only 5 steps. And it's geometry, your plan will apply to any ratio of a work piece, every time. Math is awesome.
Step 7: arrange candles at the outside vertices and a pinch of salt in each triangle. Place a micrometer at the center, a compass to the left, and a calibrated measuring standard to the right. This will summon a machinist to help you.
Depending on the job, measuring is quite easy. Sometimes you can use one side as a reference, so you always measure from the same side if you're doing the same thing over and over.
There are three quick ways to do this.
1) Build a basic jig. If you are going to be making the same type of cut/drill repeatable, make a jig that allows you to recreate a setup on demand. You can buy things like [this bushing](https://www.leevalley.com/en-ca/shop/hardware/jig-and-fixture-parts/40089-drill-guide-bushings) for jig making. Do that setup once in a piece of plywood, install the bushings, attach that to some edge stops, and now you can just hold that jig against the end of a 2x4 and drill as many times as you need.
2) Use a pin locator. This is basically the same as the first option, but instead of using bushings, you drive some brads through the dots to create a jig you can just press into the end of a board to leave dimples. This approach works better if using brad point drill bits, which are easier to consistently locate.
3) Use a centring scriber. Get a self-centring scribe, which allows you to easily scratch a line through the middle of a piece. You can make them or buy them, but using them will get you a line in the perfect centre of a piece every time, which you can locate the two drill holes on. Then just use any spacer to set a fixed distance from the edge and drill.
Yes, but you lose some reliability and accuracy in the process.
You could measure and use math, but you actually end up multiplying each degree of error that way, instead of minimizing them.
You could also draw both the vertical and horizontal lines, and then only one each of the minor diagonals, to use one fewer lines. This removes a means of error checking, though, because the double minor diagonals mean that all points are referenced to the fixed corners directly. Also, if the piece is large, your square night but be long enough for the horizontal, and even if it is, the angle measurement increases its error with every unit further away from the reference surface.
Turn your rectangle into an ellipse and use the equation for the focal points of an ellipse.
F (+(h + a)e, k), and F'((h - a)e, k).
or just measure the height and divide by two and the width and divide by 4.
There is a difference between mathematical perfection and reality. In reality, use a tape measure and you’ll be done in 10% of the time and accurate enough for your needs.
Using math and technical drawing skills, you can find them with compass and rule, with like 3 steps, but since it is hard to use one near edges (it is hard to keep the dry leg fixed), totally not worth it.
Using a compass would make this a lot easier. The compass is set to the short distance, spin on axis of each corner, and then spin the compass from where the arcs meets the long on each side.
Edit:nevermind. This doesn't work at all.
~~That will only work with a 2:1 rectangle. Otherwise that finds the center of a square, that's the size of the short side. For a 2:1, that works correctly because the other sides of the square meet on the midline. If the rectangle was longer, there'd be a gap between the two square~~
I think they are suggesting that OP use the corners of the board as pivot point for a compass drawing a circle with the radius of the length of the short side. Where the two circles meet would be the center points OP is looking for. This would only work if the ratio L:W is 2:1.
Edit: It doesn't work at all.
https://preview.redd.it/b7vww6rh784d1.png?width=814&format=png&auto=webp&s=fc3516f385ceb015844118f3b4bb8b98175bbefc
Why do you need all these lines? Also this assumes your work piece is already totally square, which let's be honest, LOL.
Assuming the work piece is square, find the midpoint of a long side and draw a line from it to a corner. The midpoint of that is your dot. You can also do this quickly with a compass.
Maybe just hold a yardstick across, were starts at zero on the left, and ends on an even number on the yardstick at the edge of the board on the right (angle of yardstick doesn't matter, just tilt it until it hits an even number), then you can mark the two points by just dividing the yardstick by 4, then use a square to draw vertical lines at the two points. Do the similar technique for the other direction, lay yardstick across ( any angle as long as it lands on an even number at the edge of the board), divide by 2, mark point, use square to draw line across. boom, cross marks where the two points should be.
That's assuming the piece is square and straight.
If you have two combo squares that are big enough, this is a total no-brainer job. Measure the horizontal center line with a tape measure. Set your first square and draw the line. Then find more or less how far from the sides the blue dot has to be by dividing the length by 4. Set your other square accordingly, and draw the offset. Now do not re-adjust the squares until this part of the job is complete and keep transferring the measurements. It will not be dead on center but will be damn consistent.
Find the vertical midline, now you have two squares. Find the vertical midline of each square. Find the horizontal midline of the whole piece and you should be done. I’d do it this way because finding the midline is really easy to check and you don’t have to deal with diagonals and measuring from corners or dividing by 4 and having to use a ruler to mark each point.
How do you know the line in step 3 is parallel with the edges? You have to measure the long sides and find the middle right? So why even do step 2.
Just measure the middle of the long legs and then do step 5
2x4s don't really have good corners... so I wonder how accurate this really is? I'm assuming this is for alignment & not structural since butt joining two ends of a 2x4 isn't great.
The most sure way to make two dowel holes line up is use dowel center pin/punch (what are these called?) to transfer the a mark on piece B from the hole on piece A
A better/repeatable way is to
1. stick 2 pins in a piece of scrap
2. clamp it to any tool or anything you have with a fence
3. slide 2x4 along fence into pin
4. Repeat with following 2x4s.
(this give you one absolute reference point in case 2x4s aren't perfectly equal & lets you key them to control orientation if you so choose. If you have faith in your lumber you can use one pin & rotate 180 degrees for 2 marks from 2 reference points.
If you do this often make a jig. It could be a literal piece of paper.
Personally for a one off I'd use calipers. I've never used any of those new fangled digital calipers, but I wouldn't be surprised if you can buy one that will reduce a measurement by an arbitrary fraction. Otherwise one with decimal inches make division really simple.
One of those center finders that look like this |\_\_\_\_\_| with a hole in the center of the horizontal bar for a scribe/pencil are super handy & super cheap. You mark center of any stock that is smaller than the two posts. You can add holes for 1/4, 1/3 or an arbitrary fraction to suit your needs.
https://preview.redd.it/5xlbh38om74d1.jpeg?width=828&format=pjpg&auto=webp&s=40e6c57947ea8a533cc4f98ee32fa486c38ed27d
One red triangle one blue triangle.
Divide the width by 2 and the length by 4. Those 2 measurements are the 2 dots.
If you have a sashigane, or a tape measure with the shakume scale, then if you put the scale on the board at any angle with the beginning at one side of the board and an even number on the other side of the board. Divide the measurement by 2 and that number is the center.
Hod your tape on a diagonal. Find a round number like 4, 6, 10 etc..... and line it up on the edge. Cut that number in half that's canter. Divide the board side to side and top to bottom until you have your center.
Using a tape or ruler, place along the length. Keeping the left side stationary, pivot the ruler to the nearest whole number and mark the increments. (Example: If board is 11.75", rotate ruler until it meets 12", then mark 4", 8" 12"...)
Woodworking scribe: if it is truly twice as long as wide then setting the scribe to half the width will let you scribe these points with three lines. If some dimensions are a bit off you can scribe from both sides along the longer dinension and end up with sort of unfinished little squares or rectangles, the middle of which would correspond to those points.
But what is it you want? Do you want to find these mathematical points, or do you want pieces of wood to line up? Using the scribe set to the same value you can scribe both ends and make everything line up, regardless of whether or not it is exactly in the middle.
Set a [combination square](https://i.imgur.com/pGkYgsi.png) to 3/4" and use it to mark a center line on the end of the board the long way (horizontal in these pics), by holding a pencil against the end of the square and sliding it along the face of the board. Then use it make marks on this line 3/4" from each end.
Speed square. Put a hypotenuse corner at the board’s corner and trace up along the hypotenuse. Do the same from the other corner. The intersection of the lines is your point
I thought at first that you wanted to find the blue dots using a straight edge but without measuring. However, in step three you need to measure to get the vertical line. That being the case, you might as well skip all of the diagonals and just measure out 3 vertical lines and 1 horizontal.
You can get pretty close compass but that is fine for the end of a board but not a sheet of plywood for instance since who has a compass that large?
For small to medium an L square you can do similar (equidistant from both corners and edge length/2^1/2 , since 1 + 1 = 2)
At building scale you can use string, but most buildings have tolerances on the scale of a centimeter or two so the slop isn’t a big deal.
If you’re going to do this a bunch of times, just make a jig.
In step 4 you could mark a horizontal line through the middle. Which would mean you would only need one diagonal line in steps 5 and 6. Reducing the total number of lines required by one.
After step 3, draw a horizontal line. Then, draw a line from bottom left to center top, and from center top to bottom right. Saves a stroke.
In practice, it might be easier to make a template if you're gonna make a lot of them
The first reduces by one line without using a ruler
The second uses a measure ment only in the edges, which is less error prone and you do already anyway, right?
https://preview.redd.it/cx58rbfif84d1.jpeg?width=983&format=pjpg&auto=webp&s=3569728ca84f6389843a8624f7cd51b8ba09d2dc
Divide in half vertically and horizontally.
Draw a diagonal line between the the corner of the board and the center line on each side of the center line. Where the diagonal and horizontal intersect are those two spots. That accomplishes the task with 4 lines.
Drill holes in one side. Insert dowels. Color the end of the dowels with a marker. Push the two pieces against eachother. You now have black marks on the second 2x4 where you should drill. The holes will match up, so the actual location doesn't matter.
Or use a jig if you're doing it a bunch of times.
Skip step 4. If you're Sure the corners and edges are perfect then skip step 2. Do step 3 a few times and you're there. Divide in half both directions, then across the short way again on either side until it looks like this -|-|-|-
So if these blocks are actually twice as wide as they are thick, you could place two scrap sections over the drawing block and gently score the line between them. This would create the vertical line from steps 3/4.
Actual construction 2x4's aren't twice as wide as they are thick, though.
Not only is it easier to measure the board into fourths and in half the other direction, but also much more accurate than making a diagonal line off of the corners
On whatever rectangle you are working on, assuming it is actually a rectangle, measure a quarter of the long side and half of the short side, where those 2 intersect would be the blue points.
This is how I do fretboard makers (well except step 4) for the 12th and 24th frets... I mean it's a pain but you can't reuse numbers really cause the fret widths are all different, plus the kerfs...
Divide the width by 4 using math or this method: https://youtu.be/RpoBhYJ7l4I?si=FZqxgYRZxrDr0ZuA
You only have to mark at 1/4 and 3/4 of that length.
Divide the height by 2 by measuring 1 3/4" from either side and marking in between those two lines.
Your way finds centers in both directions without any measuring whatsoever. The only other way would be to measure halfway in one direction, and then half and then half again of each of those halves in the other direction.
Measuring is less lines being drawn and can also be done with small hash marks instead of full lines edge to edge but it has more math involved and can be harder to find half of smaller and smaller dimensions while still being accurate, for example if it were 18-5/8" the long way then half would be 9-3/16" then half of those halves would be 4-19/32". Those are sort of complicated fractions to come up with and most likely, whilst dividing, you will come up with even more complicated decimals which will then need to be converted into fractions.
Each way is just as good depending on what you're capable of and how you need the finish to look. If you don't want lines or scribe marks all over the piece then calculating is better but the first way by marking all the diagonals will be the quickest, most accurate way with no calculations although it technically is geometry and trigonometry at work lol.
This seems like a case where you might get a more efficient answer if you frame the question slightly differently.
Why do the dowels need to be exactly in those locations? In general I think it makes the most sense to treat dowels as "exactly a certain distance from the reference face, and exactly a set distance apart". That way, you're not going to have misplaced dowels if your stock isn't exactly the same or whatever.
My preferred way of dealing with dowels is a jig (high end options exist from the likes of dowelmax or jessem, cheaper or diy also can get the job done). With the jig I use, I'd set the fence to 3/4" depth, drop a locating pin into one side, then drill the holes. Easily repeatable on the other joined side as long as I make sure to use the same reference faces
As others have said. For me, center marker finds the middle horizontally. I then take a ruler across the long diagonal and adjust the angle so the distance between the outer measurements are a multiple of 4. But I think you’re overthinking. If you’re making a dowel joint it’s more important that the points are equal so the adjoining edges align. It’s not that important that the dowel position is accurately 1/4 the distance from the board edge
Unless you need to do this process tens or hundreds of times, there is no need to optimize an one off process. If you do need it many times, make a jig/template with two holes drilled at the desired positions on a piece of plywood.
That said, i will do it by just marking 3 lines: 3/4” from the bottom, and 7/8” from both sides, their interactions are your dowels.
you could use a compass i suppose, but honestly that process would probably end up looking just as or more complex lol. the easiest way is to measure it out. use precision tools like a dial caiper if you can.
With a centre zeroed ruler (a ruler that has zero in the centre and counts up in both directions) you can do this with 8 tick marks and 3 lines. This however—you can do with a sufficiently straight stick, no fancy tools required.
No need to reinvent the wheel on this one.
https://preview.redd.it/9v4ur4rzc94d1.png?width=496&format=png&auto=webp&s=a03ed26b75c31e48fdfc1d0883d28a1fabb4344f
Something like this might speed it up a bit: draw a + instead of an X, then two diagonal lines from the center of one edge to opposite corners
With steps 5 and 6, only do 1 of the lines. And instead draw a line through the middle horizontally. It uses the center to validate it's there (and it's allowed because it mirrors step 3). Cuts it down by 1 fewer line, but it's a long one.
I mean your "steps" are what? Some draw two lines, others draw one? Looks like we can assume you have a 90 degree tool?
Use a compass. Can do it in less lines.
If you draw the perimeter of the 2x4 onto a piece of paper, cut out thar shape,,and then fold the paper to find the two dots, you will not only be very precise, but you can also transfer the dots onto another 2x4 as well.
Folding paper has higher resolution than measuring devices and avoids the problem of the possible offset between your straight edge and marking device.
Its how I would do it, Though I'd only mark the top and bottom of the 1/2 way point of the length then use a long level or straightedge on the 45's to make my marks to drill on the dot.
Yes.
I'd draw it up in my cad software. Divide the rectangle into two equal squares. Then have the computer find the center point of each one. Then either have a laser burn a dot there or use a CNC machine to drill the hole for the dowel. Thats the easiest way I can think of for doing it. Would take 30 seconds.
How about if you don't have a CNC machine or laser engraver?
If I didn't have the cool tools in my cabinet shop I'd use one of those self centering tapes. Lufkin makes the ones I have. People can laugh at them all they want, they make jobs like that really easy. You divide it up into two squares again. Draw it on the wood. Then use the tape to find the center lines of each square. The tape is pretty good. It wouldn't be 100% accurate, but it would be 99.5%. I have the tapes to make it easier to draw center points on blanks for my CNCs. So its pretty fast.
This may be difficult to explain in words but I’m not sure what to google to help you visually. You take your ruler, and angle it between your two sides such that the reading on the ruler is a number divisible by the number of segments you require.
So in the case of your two “mid points” (they’re not midpoints in the overall shape, only in your divided shape), you’re really dividing the work piece into four segments. So you align the ruler to read a total width of some multiple of four. Then you just read off of the ruler at each increment. This solves your horizontal spacing. You can use the same technique to locate vertically, or use a square marking from each side, or use a centre finding tool, etc etc.
Try this:
Long ways = length = L
Short ways = width = W
Find nearest multiple of 4 > L = L_4
Find nearest multiple of 2 > W = W_2
Angle tape measurer across Length so that the two opposite edges of the board are at 0 and L_4 on the tape.
Make Mark at 1st and 3rd 1/4 of L_4 along tape.
Example: if L_4 = 16", then 1st 1/4 = 4" and 3rd 1/4 = 12"
Draw line parallel to Width at marks made for 1st and 3rd 4th. That's 2 lines drawn with very easy math.
Next, repeat across Width so that the two opposite edges of the board are at 0 and W_2 on the tape.
Make Mark at half W_2 along tape.
Example: if W_2 = 12”, then make Mark at 6".
Draw line parallel to Length at this third mark. That's one more like for a total of 3.
The vertices of the 3 lines are your 2 points of interest.
If you have a compass, you can draw circle arcs from all the corners starting from the opposite short side corner. Where the srcs meet on both sides are the blue dots.
E: I just realized that this requires knowing that the sides are 1:2 and corners are straight.
I have a neat one but Im not sure whether its easier!
from step 3, set a compass to the distance from the center point to the top edge, and while holding it there use the compass to draw 2 small arcs near where the blue dots will be, and then locate the blue dots with a square from the long edge, by finding where the square sits tangent to the arcs.
I recommend the Jessem dowel jig, its great. You can also use dowel centers which are very cheap! Ive dowelled lots of stuff and Ive never attempted to center a dowel like this because even if you cant afford a jig, you can use centers to mark the mating piece.
The best answer depends on WHY you want to simplify the process. For two dowel holes on a 2x4, one of the answers already posted is probably best. If you want to be able to do any number of holes/marks or get equal spacing relative to work pieces of any dimensions, there are a few different styles of equidistant divider tools.
Any of these could work, and there are likely more types not shown. Type A is primarily for sewing (marking button holes). B appears to be designed with woodworking in mind (B2 is a variation from Woodpecker, a bit like A but for woodworking). C is primarily for marking rivet holes. D for belt holes or hand-sewing holes.
https://preview.redd.it/u3gxz26c1b4d1.png?width=1200&format=png&auto=webp&s=364de96e4548bd13787ea89a7510bb477f1a44da
Yes. Skip step 4.
Lol, just realized I didn’t use that step in the picture.
Measure your board length and divide by 4.
I would also just divide by four. A marking tool, like a pair of dividers are a great way of verifying the accuracy of measurements. Using an adjustable square works well to find the center on small pieces.
The kerf tho
One would account for it as they saw. OP asked how to find the dots, not get perfectly matched dimensions after cutting. They're drilling holes for dowels.
Go 1/4 of the distance in from each short edge, mark half the distance top to bottom. The benefit to the method pictured is finding centers on pieces that aren't square, though step 3 requires a square to make the center line so it doesn't actually work for bisecting out-of-square pieces in two.
Just start on step 4. Draw one line dividing in half, and then X on each half.
This method is meant to find the spot without measuring. If we’re measuring we might as well divide by 4 long side and 2 short side.
Am I stupid or are 3 and 4 exactly the same?
I don't know, and yes.
...and I'm a locksmith.
Extremely niche and underrated comment
... And I'm a blacksmith.
You could skip step 3 instead. Good thinking.
[удалено]
You REALLY want to make sure you can see those lines, so you draw them twice
step one seems a bit unnecessary as well
Step 2 and 3 are also not necessary.
Thank YOU! I was like...what am I missing on step 4!? I know I'm getting older but...is this some magic eye stuff?
4 is a critical step. Step 3 is useless and can be skipped.
Draw a horizontal line in the middle and divide it by 4?
This is the easiest way but I think OP was looking for a way that doesn't involve measuring, just finding intersections.
Came here for this. Find center on each short edge. Connect and divide by 4.
Set your marking gauge to half the thickness of the 2x4 and quickly make 2 crosses on each side.
That's the most precise way I can think of. Depending on your error tolerance you could do the unthinkable and use a tape measure and division.
You will laugh, but I sometimes feel that measuring, dividing, then drawing the point sometimes is not as precise as I’d like it to be.
Why would I laugh? I'd only do that if it didn't really matter precisely where the hole was.
When machines look at "if else" like "maybe idk"
Check out Johnathan Katz Moses 5 methods to finding center. The fifth one is what I always use. It’s so so simple but hard for me to explain here.
Ok so, I just looked this up. [heres the article](https://kmtools.com/blogs/news/how-to-find-center-of-a-board) Method 5 is one of those tricks that’s so simple it feels like it can’t be true! Thanks for sharing this!
A point that eluded me for a bit is that the measurement has to be taken from the side of the tape measure touching the piece
I have a doweling jig that uses the same method. You twist it against the edge of the board until the two pins engage the faces of the board, and the hole for the drill bit is exactly center. Seems to blatantly obvious in retrospect but when I first used it I was like “oh yeah… neat”
You can also use this method to divide a board into thirds, quarters, fifths, etc. Just use a ruler and tilt it until the desired units match up. Tilt the other direction (or slide it a bit) to mark a second set of points and you can connect them with lines, or just use a combination square to scribe through each mark.
This is awesome and so simple
For dowels you want to match the relative distance of the holes over multiple pieces of wood. You don’t want an exact devision on the cut plane every time. I would use this technique to mark a jig that I could fit over the end of those 2x4s. Then you get an easily repeatable and consistent drill pattern
i think it’s good to always strive for a high level of accuracy, but it is also good to understand and appreciate the tolerances required for whatever project you’re working on. becoming too focused on precision can and will get in the way of progressing as a carpenter and craftsman. learning to recognize the bounds of what the project needs, and allowing for some flexibility within those bounds, was a threshold point where i recognized my skill had become more advanced and i was making better quality things.
Especially since 2x4s aren't spec'd to precise dimensions and are subject to expansion. Doing this with 2 combination squares based on only 2 sides will actually yield a more consistent hole spacing.
That’s why I measure the same distance from both sides and drill/cut between the marks.
Thats absolutely true, drawing will definitely give you more consistently accurate points. But this is really not very much drawing so if you want to reduce it any more, measuring is probably your only option.
A lot of people here are missing your intent. Geometric calculation like this is just always going to be more dependable than mathematical. This isn't much simpler, but you can draw a horizontal line on step 4, then you only need one diagonal apiece for each square on 5 and 6. Wherever that diagonal intersects the horizontal is center on a rectangle
It just looks like the middle of 2 squares. You divided the rectangle in half, and then found the midpoint of the 2 squares by making the X across the corners.
Check out the big brain on Brad!
It may not be two squares, they could be rectangle
If it’s 2x4 construction lumber, they’re almost certainly not squares
Width divided by 4, height divided by 2. The X method is way too error prone in my experience (did alot of this for fret markers which is what this looks like to me)
What are you like, running out of lead in your pencil?
If no measuring device is available then this this the most accurate way.
I can't believe so many people think 3 and 4 are the same. Step 4 is clearly where you take a drink and rest up in prep for more drawing of lines. Rest is critical to success.
Make a jig.
If they are all the same size, yeah, make a jig.
OP did say this was for dowel holes in a 2×4. A low-tech solution would be a card with holes punched in the right places. A slightly higher tech solution would be a thin sheet of plywood with two members at right angles all glued up such that the corner can slip on the end of the board. Measure once and cut as many times as you need
If they're not all the same sizes, the dowels are variably spaced. That's a worse problem than off-center dowels, most of the time.
And then dance a jig!
3 and 4 are the same To do the same with less lines Step 4: draw horizontal line in center Step 5/6: only one diagonal line on each side is needed. Each will pass through horizontal on new step 4
A tape and a combo square
bing bang boom, let’s move on
If for some reason you want to get your compass involved: https://preview.redd.it/wqjb403nq84d1.png?width=1280&format=png&auto=webp&s=13293ce919e7fac38da6a2e97b65056865f82b75
This is genuinely making me rethink my disregard for compasses in the past.
If you're certain the work piece is 2(x) by 4(x), then you can just draw a 45 degree angle off all the corners, the intersection will be the centers. Otherwise, it's only 5 steps. And it's geometry, your plan will apply to any ratio of a work piece, every time. Math is awesome.
Step 7: arrange candles at the outside vertices and a pinch of salt in each triangle. Place a micrometer at the center, a compass to the left, and a calibrated measuring standard to the right. This will summon a machinist to help you.
Just fold the wood in half, along that center vertical axis. Then go through the middle of both. So easy!
Depending on the job, measuring is quite easy. Sometimes you can use one side as a reference, so you always measure from the same side if you're doing the same thing over and over.
There are three quick ways to do this. 1) Build a basic jig. If you are going to be making the same type of cut/drill repeatable, make a jig that allows you to recreate a setup on demand. You can buy things like [this bushing](https://www.leevalley.com/en-ca/shop/hardware/jig-and-fixture-parts/40089-drill-guide-bushings) for jig making. Do that setup once in a piece of plywood, install the bushings, attach that to some edge stops, and now you can just hold that jig against the end of a 2x4 and drill as many times as you need. 2) Use a pin locator. This is basically the same as the first option, but instead of using bushings, you drive some brads through the dots to create a jig you can just press into the end of a board to leave dimples. This approach works better if using brad point drill bits, which are easier to consistently locate. 3) Use a centring scriber. Get a self-centring scribe, which allows you to easily scratch a line through the middle of a piece. You can make them or buy them, but using them will get you a line in the perfect centre of a piece every time, which you can locate the two drill holes on. Then just use any spacer to set a fixed distance from the edge and drill.
Set a combination square to about half way. Run a line from the top edge, bottom edge, and side.
Calipers are a wonderful tool.
Caliper, combination square, and precision square are used so much for me. Infrequently I'll measure to length.
Yes, but you lose some reliability and accuracy in the process. You could measure and use math, but you actually end up multiplying each degree of error that way, instead of minimizing them. You could also draw both the vertical and horizontal lines, and then only one each of the minor diagonals, to use one fewer lines. This removes a means of error checking, though, because the double minor diagonals mean that all points are referenced to the fixed corners directly. Also, if the piece is large, your square night but be long enough for the horizontal, and even if it is, the angle measurement increases its error with every unit further away from the reference surface.
Paging Euclid
Uhhhh…. Yeah? Measure width, mark the center. Measure length, divide by 4. Go 1/4 in on center line.
Measuring tape.
Entire length divided by 4
A ruler
Quarter it vertically. One horizontal line in the center.
Are we looking at the end of the 2x4?
Just do 1,3,5
Width divided by 2 and length divided by 4
Turn your rectangle into an ellipse and use the equation for the focal points of an ellipse. F (+(h + a)e, k), and F'((h - a)e, k). or just measure the height and divide by two and the width and divide by 4.
There is a difference between mathematical perfection and reality. In reality, use a tape measure and you’ll be done in 10% of the time and accurate enough for your needs.
Skip step 4
Use an measuring tape
Yea, learn to use a measuring device.
Using math and technical drawing skills, you can find them with compass and rule, with like 3 steps, but since it is hard to use one near edges (it is hard to keep the dry leg fixed), totally not worth it.
Using a compass would make this a lot easier. The compass is set to the short distance, spin on axis of each corner, and then spin the compass from where the arcs meets the long on each side.
Edit:nevermind. This doesn't work at all. ~~That will only work with a 2:1 rectangle. Otherwise that finds the center of a square, that's the size of the short side. For a 2:1, that works correctly because the other sides of the square meet on the midline. If the rectangle was longer, there'd be a gap between the two square~~
Yeah. Use a compass. Make it as wide as the board. Make arc. Do on all 4 corner. Where arcs meet is blue dot.
Either I am not understanding what you mean or you are wrong. Can you please draw your solution?
I think they are suggesting that OP use the corners of the board as pivot point for a compass drawing a circle with the radius of the length of the short side. Where the two circles meet would be the center points OP is looking for. This would only work if the ratio L:W is 2:1. Edit: It doesn't work at all. https://preview.redd.it/b7vww6rh784d1.png?width=814&format=png&auto=webp&s=fc3516f385ceb015844118f3b4bb8b98175bbefc
What they describe seems to find two points that mark the horizontal dividing line, but I'm fairly certain those are not the same two points OP wants
Why do you need all these lines? Also this assumes your work piece is already totally square, which let's be honest, LOL. Assuming the work piece is square, find the midpoint of a long side and draw a line from it to a corner. The midpoint of that is your dot. You can also do this quickly with a compass.
since 3 and 4 are exactly the same.....
Not quite, one says 3, one says 4.
Maybe just hold a yardstick across, were starts at zero on the left, and ends on an even number on the yardstick at the edge of the board on the right (angle of yardstick doesn't matter, just tilt it until it hits an even number), then you can mark the two points by just dividing the yardstick by 4, then use a square to draw vertical lines at the two points. Do the similar technique for the other direction, lay yardstick across ( any angle as long as it lands on an even number at the edge of the board), divide by 2, mark point, use square to draw line across. boom, cross marks where the two points should be. That's assuming the piece is square and straight.
Horizontal line. Circle in the middle. ??
Left to right in half, corner to corner
If you have two combo squares that are big enough, this is a total no-brainer job. Measure the horizontal center line with a tape measure. Set your first square and draw the line. Then find more or less how far from the sides the blue dot has to be by dividing the length by 4. Set your other square accordingly, and draw the offset. Now do not re-adjust the squares until this part of the job is complete and keep transferring the measurements. It will not be dead on center but will be damn consistent.
Find the vertical midline, now you have two squares. Find the vertical midline of each square. Find the horizontal midline of the whole piece and you should be done. I’d do it this way because finding the midline is really easy to check and you don’t have to deal with diagonals and measuring from corners or dividing by 4 and having to use a ruler to mark each point.
Divide by 4 on the length, come in from the ends. Divide by 2 on the height. Check by being 1/4 from the near side and 3/4 from the far side.
How do you know the line in step 3 is parallel with the edges? You have to measure the long sides and find the middle right? So why even do step 2. Just measure the middle of the long legs and then do step 5
2x4s don't really have good corners... so I wonder how accurate this really is? I'm assuming this is for alignment & not structural since butt joining two ends of a 2x4 isn't great. The most sure way to make two dowel holes line up is use dowel center pin/punch (what are these called?) to transfer the a mark on piece B from the hole on piece A A better/repeatable way is to 1. stick 2 pins in a piece of scrap 2. clamp it to any tool or anything you have with a fence 3. slide 2x4 along fence into pin 4. Repeat with following 2x4s. (this give you one absolute reference point in case 2x4s aren't perfectly equal & lets you key them to control orientation if you so choose. If you have faith in your lumber you can use one pin & rotate 180 degrees for 2 marks from 2 reference points. If you do this often make a jig. It could be a literal piece of paper. Personally for a one off I'd use calipers. I've never used any of those new fangled digital calipers, but I wouldn't be surprised if you can buy one that will reduce a measurement by an arbitrary fraction. Otherwise one with decimal inches make division really simple. One of those center finders that look like this |\_\_\_\_\_| with a hole in the center of the horizontal bar for a scribe/pencil are super handy & super cheap. You mark center of any stock that is smaller than the two posts. You can add holes for 1/4, 1/3 or an arbitrary fraction to suit your needs.
Well. If you insist on this way, you only need step 3 and 5, and 6. The long diagonals aren't used.
I am going to put forth the possibility that you could try to just do two triangles.
https://preview.redd.it/5xlbh38om74d1.jpeg?width=828&format=pjpg&auto=webp&s=40e6c57947ea8a533cc4f98ee32fa486c38ed27d One red triangle one blue triangle.
This is interesting. Is this assuming right triangles?
I don’t think it assumes anything. Except maybe finding a midpoint on the long edges.
step1 - put your 2x4's together and strike two marks across the gap by eyeball. step2 - use dowel jig.
A compass
Divide the width by 2 and the length by 4. Those 2 measurements are the 2 dots. If you have a sashigane, or a tape measure with the shakume scale, then if you put the scale on the board at any angle with the beginning at one side of the board and an even number on the other side of the board. Divide the measurement by 2 and that number is the center.
Hod your tape on a diagonal. Find a round number like 4, 6, 10 etc..... and line it up on the edge. Cut that number in half that's canter. Divide the board side to side and top to bottom until you have your center.
You could simplify with a compass.
Using a tape or ruler, place along the length. Keeping the left side stationary, pivot the ruler to the nearest whole number and mark the increments. (Example: If board is 11.75", rotate ruler until it meets 12", then mark 4", 8" 12"...)
Woodworking scribe: if it is truly twice as long as wide then setting the scribe to half the width will let you scribe these points with three lines. If some dimensions are a bit off you can scribe from both sides along the longer dinension and end up with sort of unfinished little squares or rectangles, the middle of which would correspond to those points. But what is it you want? Do you want to find these mathematical points, or do you want pieces of wood to line up? Using the scribe set to the same value you can scribe both ends and make everything line up, regardless of whether or not it is exactly in the middle.
Could always measure it out? Maybe im missing something.
Set a [combination square](https://i.imgur.com/pGkYgsi.png) to 3/4" and use it to mark a center line on the end of the board the long way (horizontal in these pics), by holding a pencil against the end of the square and sliding it along the face of the board. Then use it make marks on this line 3/4" from each end.
Speed square. Put a hypotenuse corner at the board’s corner and trace up along the hypotenuse. Do the same from the other corner. The intersection of the lines is your point
Find the center of two even squares.
the blue dots are center one way at 1/4 1/2 3/4 The other
Set tape measure to a number easily divisible by 4 for the vertical points, in half for the horizontal.adjust the marks to account for blade kerf
I thought at first that you wanted to find the blue dots using a straight edge but without measuring. However, in step three you need to measure to get the vertical line. That being the case, you might as well skip all of the diagonals and just measure out 3 vertical lines and 1 horizontal.
You can get pretty close compass but that is fine for the end of a board but not a sheet of plywood for instance since who has a compass that large? For small to medium an L square you can do similar (equidistant from both corners and edge length/2^1/2 , since 1 + 1 = 2) At building scale you can use string, but most buildings have tolerances on the scale of a centimeter or two so the slop isn’t a big deal. If you’re going to do this a bunch of times, just make a jig.
I’d use a marking gauge. Set the center lengthwise and mark it. Then set the next distance mark flip and mark again.
In step 4 you could mark a horizontal line through the middle. Which would mean you would only need one diagonal line in steps 5 and 6. Reducing the total number of lines required by one.
After step 3, draw a horizontal line. Then, draw a line from bottom left to center top, and from center top to bottom right. Saves a stroke. In practice, it might be easier to make a template if you're gonna make a lot of them
3 lines: 1 horizontal line, centered 2 vertical lines, respectively at 1/4 and 3/4 of the lenght
Draw a line down the middle and draw a cross in both halves.
The first reduces by one line without using a ruler The second uses a measure ment only in the edges, which is less error prone and you do already anyway, right? https://preview.redd.it/cx58rbfif84d1.jpeg?width=983&format=pjpg&auto=webp&s=3569728ca84f6389843a8624f7cd51b8ba09d2dc
Split it into quarters vertically, then half it horizontally. Your dots will be at 1/4 & 3/4 halfway between top and bottom.
Divide in half vertically and horizontally. Draw a diagonal line between the the corner of the board and the center line on each side of the center line. Where the diagonal and horizontal intersect are those two spots. That accomplishes the task with 4 lines.
Divide in 4ths vertically and half horizontally
Drill holes in one side. Insert dowels. Color the end of the dowels with a marker. Push the two pieces against eachother. You now have black marks on the second 2x4 where you should drill. The holes will match up, so the actual location doesn't matter. Or use a jig if you're doing it a bunch of times.
Center line… then divide into three by measure, or just choose 1 inch in from edge, about a third
Vertical line in the middle, then steps 5 & 6.
Just draw a 2x3 grid
Skip step 4. If you're Sure the corners and edges are perfect then skip step 2. Do step 3 a few times and you're there. Divide in half both directions, then across the short way again on either side until it looks like this -|-|-|-
IDK I feel so dumb when I see things like this where I would go, uh just measure total length then measure in from the end by 25% ?
So if these blocks are actually twice as wide as they are thick, you could place two scrap sections over the drawing block and gently score the line between them. This would create the vertical line from steps 3/4. Actual construction 2x4's aren't twice as wide as they are thick, though.
Not only is it easier to measure the board into fourths and in half the other direction, but also much more accurate than making a diagonal line off of the corners
What does a blue dot mean? I’m not a wood worker, but I admire all the great work I see here
1, 3, 5, 6
On whatever rectangle you are working on, assuming it is actually a rectangle, measure a quarter of the long side and half of the short side, where those 2 intersect would be the blue points.
Divide vertically and horizontally, then draw one diagonaal per side, and where they cross the halfway line is your dot.
This is how I do fretboard makers (well except step 4) for the 12th and 24th frets... I mean it's a pain but you can't reuse numbers really cause the fret widths are all different, plus the kerfs...
Divide the width by 4 using math or this method: https://youtu.be/RpoBhYJ7l4I?si=FZqxgYRZxrDr0ZuA You only have to mark at 1/4 and 3/4 of that length. Divide the height by 2 by measuring 1 3/4" from either side and marking in between those two lines.
Your way finds centers in both directions without any measuring whatsoever. The only other way would be to measure halfway in one direction, and then half and then half again of each of those halves in the other direction. Measuring is less lines being drawn and can also be done with small hash marks instead of full lines edge to edge but it has more math involved and can be harder to find half of smaller and smaller dimensions while still being accurate, for example if it were 18-5/8" the long way then half would be 9-3/16" then half of those halves would be 4-19/32". Those are sort of complicated fractions to come up with and most likely, whilst dividing, you will come up with even more complicated decimals which will then need to be converted into fractions. Each way is just as good depending on what you're capable of and how you need the finish to look. If you don't want lines or scribe marks all over the piece then calculating is better but the first way by marking all the diagonals will be the quickest, most accurate way with no calculations although it technically is geometry and trigonometry at work lol.
This seems like a case where you might get a more efficient answer if you frame the question slightly differently. Why do the dowels need to be exactly in those locations? In general I think it makes the most sense to treat dowels as "exactly a certain distance from the reference face, and exactly a set distance apart". That way, you're not going to have misplaced dowels if your stock isn't exactly the same or whatever. My preferred way of dealing with dowels is a jig (high end options exist from the likes of dowelmax or jessem, cheaper or diy also can get the job done). With the jig I use, I'd set the fence to 3/4" depth, drop a locating pin into one side, then drill the holes. Easily repeatable on the other joined side as long as I make sure to use the same reference faces
1, 2, and 4 aren't necessary at all
I mean it’s just a half of the thickness and a 1/4” of the width. Me dumb with math, but me finish carpenter for 12 years.
Draw this on a piece of plywood and then make a jig instead of measuring each time.
As others have said. For me, center marker finds the middle horizontally. I then take a ruler across the long diagonal and adjust the angle so the distance between the outer measurements are a multiple of 4. But I think you’re overthinking. If you’re making a dowel joint it’s more important that the points are equal so the adjoining edges align. It’s not that important that the dowel position is accurately 1/4 the distance from the board edge
Yeah fold the paper
Straight line down the middle then two x’s in the two boxes you created.
Definitely
Unless you need to do this process tens or hundreds of times, there is no need to optimize an one off process. If you do need it many times, make a jig/template with two holes drilled at the desired positions on a piece of plywood. That said, i will do it by just marking 3 lines: 3/4” from the bottom, and 7/8” from both sides, their interactions are your dowels.
you could use a compass i suppose, but honestly that process would probably end up looking just as or more complex lol. the easiest way is to measure it out. use precision tools like a dial caiper if you can.
With a centre zeroed ruler (a ruler that has zero in the centre and counts up in both directions) you can do this with 8 tick marks and 3 lines. This however—you can do with a sufficiently straight stick, no fancy tools required. No need to reinvent the wheel on this one.
Tape measure?
Woodworking?
Use trig. You know the length of the left side, which gives you the length of the diagonal you need. Then just mark half that length.
Wouldn't a drawing compass also work? You want the points to be half of the height from the edge? If the board is 2x4 it should work.
for an arbitrary rectangle? probably not. for a standard 2x4? you could make a jig.
https://preview.redd.it/9v4ur4rzc94d1.png?width=496&format=png&auto=webp&s=a03ed26b75c31e48fdfc1d0883d28a1fabb4344f Something like this might speed it up a bit: draw a + instead of an X, then two diagonal lines from the center of one edge to opposite corners
https://preview.redd.it/m90kxgy7e94d1.png?width=767&format=png&auto=webp&s=8ae509e1ea54e7ea033970587c2dee35fa6dd058 Saves a few lines...
You could do a horizontal center line and then draw a radius from corner to corner
Left to right, divide in half, then decide those halves in half. Then divide up and down once.
With steps 5 and 6, only do 1 of the lines. And instead draw a line through the middle horizontally. It uses the center to validate it's there (and it's allowed because it mirrors step 3). Cuts it down by 1 fewer line, but it's a long one.
I’m not a woodworker but I would make a jig if all the boards are the same
What is this for? And probably not because finding MP from corners is more efficient
I mean your "steps" are what? Some draw two lines, others draw one? Looks like we can assume you have a 90 degree tool? Use a compass. Can do it in less lines.
If you draw the perimeter of the 2x4 onto a piece of paper, cut out thar shape,,and then fold the paper to find the two dots, you will not only be very precise, but you can also transfer the dots onto another 2x4 as well. Folding paper has higher resolution than measuring devices and avoids the problem of the possible offset between your straight edge and marking device.
Its how I would do it, Though I'd only mark the top and bottom of the 1/2 way point of the length then use a long level or straightedge on the 45's to make my marks to drill on the dot.
I'd say make a center finding tool to get the vertical line through the center in one step. Thank do the little X thing to both sides.
Use a square, draw a center line horizontally across at 3/4”, step 2 measure 7/8 from each end draw line vertically, x marks the spat
Tape measure
Yes. I'd draw it up in my cad software. Divide the rectangle into two equal squares. Then have the computer find the center point of each one. Then either have a laser burn a dot there or use a CNC machine to drill the hole for the dowel. Thats the easiest way I can think of for doing it. Would take 30 seconds. How about if you don't have a CNC machine or laser engraver? If I didn't have the cool tools in my cabinet shop I'd use one of those self centering tapes. Lufkin makes the ones I have. People can laugh at them all they want, they make jobs like that really easy. You divide it up into two squares again. Draw it on the wood. Then use the tape to find the center lines of each square. The tape is pretty good. It wouldn't be 100% accurate, but it would be 99.5%. I have the tapes to make it easier to draw center points on blanks for my CNCs. So its pretty fast.
Divide the horizontal length by 1/3’s, and center vertically
This may be difficult to explain in words but I’m not sure what to google to help you visually. You take your ruler, and angle it between your two sides such that the reading on the ruler is a number divisible by the number of segments you require. So in the case of your two “mid points” (they’re not midpoints in the overall shape, only in your divided shape), you’re really dividing the work piece into four segments. So you align the ruler to read a total width of some multiple of four. Then you just read off of the ruler at each increment. This solves your horizontal spacing. You can use the same technique to locate vertically, or use a square marking from each side, or use a centre finding tool, etc etc.
Half way up and a quarter of the way from the edge. You only have to draw one line and measure.
Try this: Long ways = length = L Short ways = width = W Find nearest multiple of 4 > L = L_4 Find nearest multiple of 2 > W = W_2 Angle tape measurer across Length so that the two opposite edges of the board are at 0 and L_4 on the tape. Make Mark at 1st and 3rd 1/4 of L_4 along tape. Example: if L_4 = 16", then 1st 1/4 = 4" and 3rd 1/4 = 12" Draw line parallel to Width at marks made for 1st and 3rd 4th. That's 2 lines drawn with very easy math. Next, repeat across Width so that the two opposite edges of the board are at 0 and W_2 on the tape. Make Mark at half W_2 along tape. Example: if W_2 = 12”, then make Mark at 6". Draw line parallel to Length at this third mark. That's one more like for a total of 3. The vertices of the 3 lines are your 2 points of interest.
honestly, just need to measure the midway line and draw an x on each side.
Step one: Draw two equal x’s. Done
This is the most accurate way to find the blue dots.
If you have a compass, you can draw circle arcs from all the corners starting from the opposite short side corner. Where the srcs meet on both sides are the blue dots. E: I just realized that this requires knowing that the sides are 1:2 and corners are straight.
If you have a compass you can find these points easily if not having a lot of lines is your objective
I have a neat one but Im not sure whether its easier! from step 3, set a compass to the distance from the center point to the top edge, and while holding it there use the compass to draw 2 small arcs near where the blue dots will be, and then locate the blue dots with a square from the long edge, by finding where the square sits tangent to the arcs. I recommend the Jessem dowel jig, its great. You can also use dowel centers which are very cheap! Ive dowelled lots of stuff and Ive never attempted to center a dowel like this because even if you cant afford a jig, you can use centers to mark the mating piece.
Yes
Compass or nail+string as a compass could do the job quicker
Use a center gauge on all 4 corners: https://amzn.eu/d/6yWnDOX
I take your geometry, and raise you algebra. Other than division and measurements im pretty sure you are right on target
Most of the 2x4 I've seen have rounded edges. Are you able to find the corner precisely enough to make that geometry precise?
You can definitely skip step 1, 2, and 3 you Don’t need to draw 4 just mark the midpoint of the board on each side and continue to 5 and 6
Am I blind or is there no difference between steps 3 and 4
The best answer depends on WHY you want to simplify the process. For two dowel holes on a 2x4, one of the answers already posted is probably best. If you want to be able to do any number of holes/marks or get equal spacing relative to work pieces of any dimensions, there are a few different styles of equidistant divider tools. Any of these could work, and there are likely more types not shown. Type A is primarily for sewing (marking button holes). B appears to be designed with woodworking in mind (B2 is a variation from Woodpecker, a bit like A but for woodworking). C is primarily for marking rivet holes. D for belt holes or hand-sewing holes. https://preview.redd.it/u3gxz26c1b4d1.png?width=1200&format=png&auto=webp&s=364de96e4548bd13787ea89a7510bb477f1a44da
Is your original rectangle 2:1 ratio?
Cut out the rectangle. Fold in half vertically. Fold in half diagonally. Open fold and fold other diagonal in half. Presto.