Yes, they seem flush.
Okay good - that means the problem is with the kerfâŚ
Hereâs a new version with the kerf upped to 0.01 inches from 0.006 inches. Letâs see if it tightens up.
Parametric Tab File 2 (0.01 inch kerf) .zip (32.7 KB)
i put this one in PDF format just so we could test that as well.
without cutting it, Iâm sure thatâs going to be too tightâŚif anything go inbetween with .008
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Okay, stand byâŚ
You Rock Laser Lady!!
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Didnt get a chance to run thisâŚtoo many other things begging for my attention todayâŚ
Will be in tomorrow for a bit and run it then.
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No rush! Really appreciate the use of your materials and machine!
(Got to feed the fella anyway - or he can get testy. Might shut me off.) 
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Once we get our GFs weâll just be able to send the print job right to the other persons unit⌠How cool is that? 
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Well not directlyâŚthey still have to accept it and run the printâŚ
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Yes, I know, but think of how easy it is to share ideas when you donât have to shlep files aroundâŚ
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Even better, once the forge is here⌠I can just cut the file! ROFL! 
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Just cut the new file with the .008 kerf adjustment, fits snug. I was thinkingâŚwhen I initially measured kerf, I had just painted the boardsâŚnow I measured and kerf is .008. Wonder if there was a bit of swelling from the paint involved initially. I usually work in acrylic so medium stays the same but I would think wood can swell and contract based on humidity or excess moisture, like from paintingâŚsomething to ponderâŚ
Or my caliper was off the first timeâŚlol
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Might have been the calipers - itâs just about impossible to measure that small accurately. (Iâm hoping the ones I just picked up out of the mailbox do a better job than the ones Iâve got now. - Okay, yeah, theyâre better.)
(Or could have been swelling in the wood too.)
So it fits perfectly with a 0.008 kerfâŚfantastic! 
Do you have any other material that you want to try, now that we have the kerf more or less figured out? If you have some smaller scraps of acrylic or something, but not enough to cut the whole box, we can test it by cutting just two adjoining pieces and see how they fit together.
Or if you have any chipboard or cardboard, we could test it on that as well. I would just need to know the actual thickness of the material, so i can run one last copy of the file.
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Youâve had kerf compensation figured out ever since before you made that tutorial. But if you change materials youâll have to make another adjustment to your drawing (unless, of course, the new material coincidentally yields a similar âenoughâ kerf).
If you know the kerf, and then compensate for it, the parts will come out the right size. Tests arenât really necessary once you know the cut parameters (speed, power, frequency, focal distance) and the kerf width for the material youâre cutting. The only caveats to this are the small radiuses in the corners and the taper of the edges.
A link to the tutorial that Jules wrote, in case anyone reading this thread hasnât seen it yetâŚ
OK, if you want to get technical... (click for disclaimer)
There are a couple more caveats, the material has to be consistent enough that the kerf stays the same size throughout the cut, the machineâs laser output and motion has to be consistent too. Parts that start on fire or melt as a result of being cut also wonât necessarily come out the right size. Thermal expansion may technically come into play if ambient temperature fluctuates. Acts of god, lost steps, inaccurate tuning, time/gravity disruptions, and/or black magic may negate this rule. âRightnessâ of resulting parts subject to stacking errors introduced by inaccuracies with the machine, the kerf measurement, the final part measurement, and rounding when converting units or interpolating tool paths.
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I was talking above about figuring out what the actual kerf value is for the machine that she is currently using to cut theseâŚwe inadvertently started out with an inaccurate measurement for the kerf. 
The good news is:
As far as kerf-adjustment goes, yes the tutorial does work once you get a good handle on what your beam width is.
The bad news is:
For a couple of the files that I have in mind to build - Iâm probably not going to be able to totally ignore the kerf. Thatâs a bit of a bummer, but I might just redesign the files to go with a mortise and tenon type join with glue, so that it doesnât matter if itâs a little loose fitting, since it wonât be seen.
(Iâll probably ultimately wind up doing something like that, because it would improve the overall appearance.)
The last phase of the testing (on a different material) has nothing to do with kerf - it has to do with checking to see whether I have programmed the parametrics for the tabs and slots correctly. (Those are a whole lot trickier to set up than kerf. ) 
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But once you have them setâŚ
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Yup! Big timesaver! 
(i should also mentionâŚthey are only tricky because I donât know what the heck Iâm doing yet. Chuckle!)
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Nobody did till the first time.
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Iâd suggest trusting the software as far as the material thickness variables are concerned. If 2mm material changes into 4mm material within Fusion 360 without breaking your model, youâre basically good to go. But I can understand why you might be trepidatious, especially if youâre used to art-centric design software like Illustrator instead of accuracy-centric design software like Fusion 360 or other CAD packages.
Iâm really confused here. The machine isnât the only variable in this equation. You didnât figure out the kerf value for the machine. Youâve only figured out the kerf value for that machine, using that material, using those cut parameters (speed and power, primarily). If you change anything you will likely have a different kerf value.
If you change the material: you can bet the kerf will effected.
If you change the speed: you can bet the kerf will be effected.
If you change the power: you can bet the kerf will be effected.
The laser isnât the same as a saw or router bit. For all intents and purposes, a typical âconsumerâ circular saw blade will leave a kerf of ~1/8", regardless of the material youâre cutting. Same for a router bit. If you use a 1/4" router bit to cut a channel into a piece of material, you can be pretty damn sure the kerf is going to be very close to 0.250" wide, whether that material was plywood, solid wood, plastic, foam, aluminum, pumpkin, whatever.
Lasers donât work the same way. Youâll have a kerf of 200 microns in one material and 80 in another, even though youâre using the same machine with the same laser tube and same optics.
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