Changes in kerf over time leading to loose fit?

I have a pattern and stock that I’ve been using for a while (3mm birch ply, simple finger joint box) and it always came out with a super tight friction fit. However, over the last week or so things don’t fit tightly and I’m seeing that I need to use glue to get the box together.

I’m not sure what is going on, to be honest. I may have juiced the power a bit (I’m using non-proof grade and had some stock with big glue filled voids). But it may also be a software update in terms of focus that changed the size of the kerf. Or perhaps the machine/laser is ageing and that accounts for it.

Has anyone else experienced inconsistencies like this over time?

do you measure your materials with calipers? even if it’s the same material, it’s not at all uncommon for one sheet to be a slightly different thickness than others. and that can affect the fit you get.

it could be worse, if it was slightly thicker, then you may have a fit that’s too tight.


I do measure the material with calipers and the older stock that had a tight fit (I have the leftovers) is about the same.

But I don’t think that thickness should come into play here. These are corner finger joints. If the thickness were off then the edges wouldn’t line up cleanly but the friction fit should still work.

You can make kerf adjustments to your file to enable a tighter fit. (If you increased the power, you are burning away more material giving you a bigger kerf, and yes, you will get a looser fit.)

Or you can use @dan’s ingenious solution here:

(I’ve just started using those and they are a whiz!)


I had already adjusted for the kerf and things had been working fine.

I think it was a difference in power. I played around some more today and now things are tighter. I was doing 130/FP and things were really loose. Taking it down to 160/FP made a huge difference in the kerf. More than I would have thought it would.

The serration trick looks really interesting. Not sure how it would work on corner finger joints though. Might be something to add to the OnShape extension I use to do the tabs.


They work fabulously on corner finger joints - you just need to add them to the tabs, not the receiving slots. (Built a large box with them that holds 10-12 lb rolls of wrap, no sweat.)

Thanks for reaching out.

Since this problem was seen on materials that were purchased from another company, we can’t offer support for prints that don’t come out as expected. That said, I’m glad you found a solution.

Should this happen with a print on Proofgrade materials, please open a new ticket in Problems and Support and we’ll help you right away!