Getting Nerdy: My Adventures in Kerfs, Parameters and Test Fit Octogons

I’d be interested in seeing what you guys come up with too. The first one that I fully parameterized and kerf adjusted had 289 interdependent formulas in it.

Took a while. :smile:
(But it did work perfectly. After about three weeks of fiddling.)

(Oh, and then I scrapped the design.) :smile:


I’ve really found that trying to kerf adjust in the sketch makes for too many complications. I use the CAM module to make it significantly easier. I’ll add that to the video I’m working on.

Now that I’ve packed up my GF to ship back, I’ll have to keep myself occupied until my replacement arrives. :cry:


Fusion 360 is a great way to do it. (I actually did that one while learning to use the software, long before i got the PRU.)

Gives you something to do while you wait. :slightly_smiling_face:

I like that it is in the “Julie’s First Project” folder. Very ambitious. (a battery holder is near the top of my to do list)

Tough to keep the batteries from getting stuck going down, which was why I parameterized it to build for the different sized batteries.

I did eventually design one, slightly simpler, and it’s somewhere in the Made on a Glowforge category. :smile:


Oh you guys… getting me all curious 'bout stuff.

Here’s a link, easier for me to show, than tell. :slight_smile:

One hiccup though. Because I am using Mirror command to generate the tabs on opposing sides, there’s a limitation. I created this with the number of tabs set at 20. If you set that to a higher number, the added tabs will not mirror because obviously those bodies did not exist in the timeline before the Mirror command. If it’s set to a number less than 20, you just get the yellow warnings because those bodies referenced within the Mirror command no longer exist. This doesnt break the model though.

IF I was using Pro/E or Geometric Design I would just be able to Mirror the Pattern command and everything would show up OK. I tried that in Fusion and it doesnt seem to be available.

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I think my technique solves all of these problems. I need to re-record the audio when I have quiet in the house.

Just updated the file. I put the patterns into Components and now they mirror.

The Test Fit Octagon™ is golden. Never thought to do several trials on one piece. I’d do one, then adjust on a piece with just one slot Duh. Great share.


Oh hey, happy birthday @jbpa!

Getting confused on these tags.
Is that Birthday or Founders Day?

Birthday. I’m getting old.

Slice of cake is Anniversary of when you joined the forum. (We call it Cakeday.)

Full Cake is Birthday. :slightly_smiling_face:

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Yay! I remade the bottom of the box that can control the quantity of tabs. I asked Lars Christensen about it. He has an AMAZING YouTube channel with tons of Fusion 360 tutorials and has multiple live streamed training sessions each week. He pointed me to using parameters in the Rectangular Pattern.

It worked! This is the same exact box with different parameters.



I know there are a lot of other parametric boxes on the forum but I just wanted to see if I could squeeze it out of my own brain. Plus I wanted a shout out to Lars who is killing it!

Now on to the sides with kerf compensation.


I love Lars, and I need to find this video and try out this technique. I’ve been using the secondary sketch method but I’m always up for a better way.

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He pointed me to two videos to help with parameters.

One problem I hope he can help with and (I asked about) is this. I set my sketch to have 4 tabs and extruded it. But when I modified the sketch to have more tabs they weren’t extruded. So I have one more little bit I am missing. STAY TUNED!


OK here is where I got. In the parametric box bottom above, I designed it with 4 tabs by putting little rectangles on the outside of a larger inner rectangle and extruding that. But that put a line between the main rectangle and all of the tabs

That means that to make the extruded body you selected the inner rectangle and all the tabs. The problem arose if your changed the number of tabs in the parameters beyond the amount of tabs you extruded originally, those additional tabs did not extrude. (as you can see above)

So I redid the parametric box bottom so that I defined the spaces between the tabs and had them positioned inside the main rectangle. What that leaves you with is an unobstructed extrudable space.

But I found that if I changed the tab quantity beyond the original extruded amount it still omitted the remaining tabs. So I rolled back in the timeline and changed the sketch to have 100 tabs per side that were then extruded.

Now I can change the number of parametric tabs in the box bottom (up to 100) and the sketch stays in tact.


@Jules You use, or have used, AI, Inkscape, Fusion 360 etc. After using them, which software is your go to for doing inlay with kerf adjustment? I’m trying to figure out if it’s worth spending the time to learn Inkscape or just upgrade my AI CS3 to Adobe Cloud.

For kerf adjustment I prefer Illustrator. (Easy enough to just offset the path by half a kerf-width, then either combine the two shapes or delete one of the lines.)

You don’t need to update the CS3 though - you can do everything you need to do in that version very easily. :slightly_smiling_face: