Carpenters Center Finder





Introduction: Carpenters Center Finder

About: iam mechanical engineering student hoping to have my own workshop soon

jig to find and mark center for Planck

Step 1: Principle

when a line is divided by three points the middle point will mark center at any angle to x axis

Step 2: Select Material

select a wood Planck(1" * 1/4 * 6 1/2")

mark middle line and mark three points ( two end points and mid points)

Step 3: Machining

drill three points for two pillars i used two nails and one small pencil as marker

Step 4: How to Use

use and mark as shown in pic



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This will always show true center, even if the workpiece is tapered, a favorite device of boatbuilders making wooden mast's and spars.

3 replies

Mmm... Not really. If the workpiece is tapered the pencil will be off center. If the taper is not very much then it won't be very much off center, but it won't be the true center. As the workpiece gets smaller the pencil gets farther off center. The more the taper is, the more off center the pencil.

I imaging this would work great for making masts and spars as the taper would be quite small and it would never get very thin.

spottd has the correct analysis of how it always works and why.

Sorry it took me so long to notice your reply.

As you can see in the drawing, the center point is not in the center of a tapered board. This is a very tapered board so the error is large. For a much less tapered board the error would be much less, quite possible within an acceptable margin of error, but it is not zero. It does not "always work" regardless of spottd's "analysis" of why.


If you have a drill press, there is an easier and more precise way to make one of these. 1) Drill a hole at half the length of a piece of wood or steel. I made my hole about the size of a finish nail. 2) Insert a finish nail in the hole and drive it a quarter inch or so into a board. 3) Clamp the board to the table of a drill press so the nail is an inch or an inch and a half from the tip of the bit. 4) Swing one end of the steel under the bit's point and drill a hole for one of the end posts. 5) Swing the other end of the steel under the point of the bit and drill a hole for the second end post. 6) Insert the end posts and fix them in place. (I drilled holes 1/4 inch in diameter and used steel rod for the end posts. I tack welded them on the top side to hold them in place. I also used a countersink on the center hole so it accepts a pencil lead or the point of a fine tip permanent marker more easily.)

I have not used this often, but I thank you for the idea.

3 replies

Thank you for your interest. I am away from home until early January. I will post pictures, maybe even an Instructable.

I used my son-in-law's shop to make a wooden version with no welding, and I wrote it up as an Instructable.

im a little confused as well how to use it exactly...

1 reply

nevermind! I figured it out as soon as I stopped looking at the picture and reading one of the comments. the nails go on each of the sides of the plank. if using to find the center of a tapered plank, you just keep some pressure on the nails to the side planks side. the pencil will naturally stay centered as you ride the jig up the plank.


Can anyone explain it? I'm not sure I understand it's use....

Is it to find the midle line of a board? or is for using in circles and finding the center?

Thank you!

Oooo, this is a good idea. Something I always have a little trouble, and this would make it much easier.

This is an excellent little tool. I need to make one. Thank you!