I hope this is in the correct place. One tip I’m needing is what is the KERF of the laser beam? What it eh actual/practicable KERF of the laster cut.

I’m running int some difficulty by not adequately allowing for the KERF and glue-up allowance.


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Depends on the material. There are many threads here on how to test and measure it.

Edit… took me a second to find it - this is the one I find most useful.


It changes slightly for each material, and is based on the thickness of the material, and the speeds you are using to cut with.

I’ll generally start with an offset adjustment of 0.15 mm to 0.18 mm (which is half the kerf at the speeds I use), or 0.006 - 0.007 inches, run a small test cut or two, and then adjust from there.

You’ll want to run a few tests to determine the kerf adjustment that gives you a full fit, a snug fit, and a force fit for each material and thickness, then use those in your designing. Just keep in mind that they can still migrate a bit with different materials, and even different sheets of the same material.


@eflyguy and @Jules have given you a great place to start but the bad news is that kerf is as much art as science. After starting with a good guestement, it is best to try your settings on small test pieces until you have it the way you want it.

I always use joints that are like what the actual part will be as finger joints don’t kerf out exactly the same as tab and slot.


I’ll add - if it’s a critical project, it’s always a good idea to test with a piece of the material you’re using, and not rely on prior measurements.

Here’s one example of test pieces I made to work out the best glue-less press-fit I needed for a particular project.


This is great. I think you may have a great answer to what I’m struggling with. Would you be willing to share this file with me?

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There are two problems with this. First, and minor is that we don’t ask for files here (newbie mistake) second is that asking this question shows that you are not fully comprehending the use of sample joints. They have to be your own made for the material that you are using and then adjusted for a perfect fit to help.


Just a heads up my friend. I can’t read the picture to see what is printed on it. The only thing I’m looking for is enough clarity in the picture to see what the details were. I should have been clearer as to what I was trying to see. It would have been helpful since you can see I’m struggling with this (as I clearly stated) to have directed me to a resource in place of such a meaningless response.

Not all of us on here have reached an ivory tower status yet. Try being kind to those who are learning.


Thank you eflyguy for taking the time to teach. Responding in the way you did helped me have a better understanding.

I was afraid that that might be construed as unkind but it really was not meant to be.


Sorry for your frustration. Kerf can be a difficult concept to figure out. @markevans36301 is one of the stalwarts on the forum and he is pretty easy going. Just trying to cover @eflyguy I imagine since it is a forum guideline that we refrain from asking for files, in any situation.

Hard to figure out then what to do. I would say, “Any pointers in making files like this?” Is there a good source for them. The referenced topics have several, but @eflyguy’s is exactly what you were asking for.

There are lots of topics that post these types of files though. Hope you find one that you can use.

What material are you using? What is your design program? What kind of tabs and slots are you trying to make?


I would be happy to but I didn’t save it. I make them when needed.

It’s just a couple of rectangles with rectangles of the stated sizes added using union or subtracted using difference (Inkscape terms) - draw a larger box, draw the small ones in desired test sizes, use the align feature to get them on the edges, then the appropriate boolean command. Add text if you like.

The slots and holes piece was so I could check how wide (the smaller dimension) they needed to be to get a nice edge for corners, and a secure perpendicular joint for inner parts. As all my slots/holes were 5mm, the tabbed piece was so I could see the best length for 5mm long slot or hole (turns out to be 5.2, which means the kerf for this material is 0.1mm) and also the best depth/width for the tabs to give nice corners or a flush finish when inserted thru a slot.

I don’t use “box generators”, I prefer to test the material I’m using, then make my own slots/notches/tabs using the apps additive/subtractive technique.


I could have recreated it faster than it took me to type… so I did anyway, because I realized it would be handy to keep on hand as I recently started working with a couple of PG materials I haven’t used before.

I hope you understood how I made it and why I went with the sizes I did.

Here you go:

tab notch (7.3 KB)


It looks like you’ve already gotten some incredible guidance from the community. Thanks, everyone! Did their advice help you get the correct kerf for your projects?

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It’s been a little while since I’ve seen any replies on this thread so I’m going to close it. If you still need help with this please either start a new thread or email