DIY Center Finder Tool





Introduction: DIY Center Finder Tool

About: Italian maker, law student, DIY enthusiast. I make lots of projects, I fix lot of stuff and I like to save and reuse materials taken from broken stuff.

Hi everyone!

In this quick ible I'm gonna show you how to make a useful Center Finder tool using just scrap materials that you can find easily in your home.

Thanks to this simple, yet accurate tool you will be able to quickly mark the center of your square or round workpiece, saving a lot of time.

Step 1: Materials & Tools


- 2x scrap pieces of wood

- 10cm x 10cm plexiglas
(the clear side of a CD cover would work as well)

- 3x long wood screws

- 2x flat-head screws


- drill

- wood glue

- clamps

- precision square

Step 2: Cut and Glue

First of all find or cut two small pieces of scrap wood (mine measure 8cm x 10cm).

Apply wood glue on the joint and clamp the pieces together being sure to let them dry in square (photo#1).

Step 3: Reinforce the Joint

After 15 minutes reinforce the "L piece" adding 3 long screws.

Be sure to pre-drill the holes in order to avoid cracks.

Step 4: Cut the Plexiglass

It's time to work on the plexiglass piece.

First of all cut a piece of the right measure (mine is 8cm x 10cm), and then make a 45° cut.

Plexiglass is an easy material to work with. You could cut it using a jigsaw or a metal saw but I found easier to cut it making a lot of scores with a knife, and finally I bent the piece with my hands breaking it along the line.

Step 5: Secure the Plexiglass to the "L Piece"

In order to secure the plexiglass to the wood I drilled two holes in both pieces, and then I secured it using two flat-head screws.

NOTE: don't tighten them too much or you will break the plexiglass.

Step 6: Use It and Find the Center of Everything!

And here it is! After just 20 minutes (I hate to wait for the glue to dry) we have a simple yet accurate tool that will save you lot of time when you need to mark the center of a workpiece.

It's specially useful for round pieces. Lay your workpiece in the corner against the plexiglass and the wood, mark a line along the 45° plexiglass edge, rotate the piece a little and mark another line. Congratulations! You found the center. (a 3rd line is needed just the first time to check that your DIY tool is accurate)

Thank you for reading my Instructable. ;)
Feel free to comment and ask if you need to know something!




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    Will this exact size jig, work with any size item needed to find center?

    4 replies

    No, it will only work with things that fit into the jig.

    However, there is no reason why you could not scale the whole thing up and use timber with a measurement of 500 x 500. This would allow you to find the centre of items up to a metre in diameter

    this will work on circles of any dimensions. you just need to mark a small line (even in the corners of the circle) and then extend the lines tool the end with a scale.

    Yes! You can scale it to any measurement that fits better your needs, or you could lay a ruler onto the 45° plexiglass edge in order to temporarily extend the capacity of this jig keeping it small enough to don't waste materials and space around your workshop.

    I'll upload this ible with a simple trick that can be followed to use it with circles or squares of ANY dimension. Stay tuned! ;)

    Hi Logwolf! The only limit of this jig is the 45° line.

    In my case (since I used just scrap materials and since I don't usually work with big workpieces) it measures about 8,5cm. This means that I'll be able to use the edge of the plexiglass to mark the center of a 12cm diameter circle or a 12cm square. (look the 1st attached photo)

    BUT since the 45° line passes through the center of any workpiece that is placed against the 90°angle (aka the wooden pieces faces), I could still use it to mark the center of a square bigger than 12cmx12cm, simply by placing it against the 90°angle, and laying a ruler onto the 45° plexiglass edge. (look the 2nd attached photo)

    You could use the same method to find the center of circles bigger than 12cm just if the height of the wooden pieces (from the origin of the 90°angle) is the same. In my case since I butt-jointed two pieces of the same measurements, I ended up with one side of 6cm, and the other of 8cm of height.

    Thanks to your comment I'll upload this ible with more infos about the limit of this jig, and with a simple trick that can be followed to modify this jig in order to use it with circles or squares of ANY dimension. Stay tuned! ;)


    I wish I had seen this years ago! Had wood and lexan laying around, had it all together in 20 minutes. Nice and simple!

    Pheww, now I can mark Centre lines without having to research mathematical techniques that I'd struggle to understand anyway! Thank you for the info

    1 reply

    no problem man! nice to know that I saved another life from math :P ahahahha

    great idea and real simple. My suggestion would be to use an old plastic mechanical drawing plastic triangle, or just buy a cheap new one. Sometimes getting plexiglas to score and break accurately is problamatic. The triangle is right on.

    11 replies

    If you score it 5/6 times along the line it becomes very easy to break along the line, but absolutely yes!! that is a quicker and easier way!

    Thanks for your suggestion! I'll add it in the ible!

    The biggest challenge will be drilling the plastic or plexiglas without it cracking.

    Drill Plexiglass with wider (flater) drill bit tip, aroung 120 degrees

    good idea since the bite will be less drastic and not as likely to produce as much stress.

    Perspex is a sod to work with and cracks just by looking at it - drilling is the worst. Drill slow and preferably in a drill press. Don't go for the finished hole size straight off, go up in drill sizes. Otherwise, use a reamer.

    The centre finder doesn't need clear plastic, so just use PVC sheet which is a doddle to work with.

    you are right but it's just "plastic"... let's not panic for breaking it ahaha

    make a small pilot hole, drill slow and the holes will be done!

    thanks for the comment anyway!

    I have worked with optical acrylics on military aircraft. They do make acrylic drill bits that have a longer. More pointed tip. But using a regular drill bit, drill at a fast speed but very low feed...almost spinning in heat up the plastic ahead of the drill bit tip. Also it is advised to drill a pilot hole then step drill with a unibit to the final size.

    right! a small pilot hole is a good suggestion

    I would suggest perhaps a small point soldering iron to melt through it. It should go through quite easily. I have put holes in plastic that way before. Works like a charm. No cracking.

    yes! and it reinforces the edges of the hole too. the only "problem" is to find a screwdriver of the right dimention

    you just need a drill bit of the right size and you have to drill the plastic at a very slow speed.

    another easy method is to heat a screwdriver with a lighter in order to melt the plastic creating the hole.