I was trying to put a M12 thread on a part and figured if I use a M12 bolt as a negative part or use the bolt to subtract (difference) it would do the trick. I printed the part and found the hole size was not true to size (smaller than it should be).
I did small test and printed 4 objects all on one plate: a M12x1.75 bolt, a M12 Nut and a cylinder with the Bolt as negative and a cylinder with the bolt subtracted from it.
The Nut and Bolt printed true to size and thread fine. The cylinders with the holes/threads are too small. The bolt will not thread in.
You can see in the image when it slices the objects the cylinder holes look smaller than hole in the nut.
I created ticket they just responded to try hole slice compensation. I will give that a try but this does not seem to be a plastic expanding issue that needs compensation but rather a calculation issue since the nut actually prints just fine.
I have adjusted thread clearance by scaling in x and y (not z so uncheck uniform scale). Often +.5% scale is enough for threads to work.
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In Studio Quality tab > “X-Y Hole compensation” is worth a shot, on most my Fusion standard threads I have to adjust in Studio by around 0.15mm for a nice fit. It can depend a lot on filament choice and needs to be adjusted to suit.
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I should work if you size the negative part bigger as Jon said. Most CAD software can only make metal threads which are never ideal for 3D printing, even if you make them a bit bigger. They will be better if you use a smaller layer height like 0.12 or less, because the female threads have a tendency to string across at bigger layer heights because of the steep overhang you’re printing. If you need it to interface with a metal bolt then you might look at getting a cheap set of taps to clean them up after printing. My advice is learn to model your own threads in CAD using 45 degree angles instead of 60 deg acme style.
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