Print Tolerances for Prototyping.

[bonifacio]

When prototyping fitting parts, what tolerances do you use?
I've been just guessing to offset the expansion and imperfections.

For example, let's say threaded parts. Do you shrink the male part or enlarge the female part?
I'm always resizing and reprinting. Just estimating. Sometimes I'm on, sometime's too tight.

Most of the time I'll just go .2mm smaller, do you take it down further?

[Infraviolet]

I usually find, 0.2mm change to a RADIUS (so 0.4mm to a diameter) to be confident of a snug fit of a printed pin in to a printed hole, 0.3mm for a looser fit which might be expected to move, 0.15mm for snug tolerances between a printed part and an accurately sized purchased part (metal rods or similar).

On a pair of parts you could pick to enlarge or shrink one part or the other, or to offset both by half the tolerance you're leaving.

[bonifacio]

I usually find, 0.2mm change to a RADIUS (so 0.4mm to a diameter) to be confident of a snug fit of a printed pin in to a printed hole, 0.3mm for a looser fit which might be expected to move, 0.15mm for snug tolerances between a printed part and an accurately sized purchased part (metal rods or similar).

On a pair of parts you could pick to enlarge or shrink one part or the other, or to offset both by half the tolerance you're leaving.

So if it was threading and the space was 15mm diameter, you would take the object to 14.6mm? Just verifying. I'd would go to 14.8mm. I guess that's why it's always too tight.

[Infraviolet]

Yes, 14.6 diam for going in to 15mm, if it is too loose you could always redesign for 14.7 or 14.8. With threading make sure the threads are pretty big so the print has enough resolution for them to be worthwhile, and as threads will mate together you might even still get a fairly tight fit for having a <14.6mm diam. There might well be, specifically for threaded parts, some sort of "thread calibration" models on the likes of hingiverse or printables, which you can use to get a feel for how different thread sizes and tolerances would come out from your printer.

[bonifacio]

Thanks for the revelation. Never really thought about it until now. Normally going .25mm total. When it really should have been .25mm each side. I really should just get a tap and die set. Lol.

Thanks.