How do you know the appropriate size hole to model for a heat set insert (3D printing)?

[ejowalter]

I am designing a part for the first time that includes a heat-set insert. I have the correct insert in the model but I not sure how to size the hole so that the part has the right amount of plastic to melt into.

Any suggestions on where I could find out what size to model the hole for this type of part?

[helibum · Accepted solution]

What thread size? I typically use 5mm for M3 heat inserts. You can get a pretty good idea by measuring the overall diameter with a caliper and then reduce that by 0.5mm or so.

[ejowalter]

M4 which at it's widest is 6mm.

So I assume you'd just model it 5.5mm dia?

When you do a hole that isn't completely through the depth of the part, do you allow any particular clearance at the bottom of the hole?

[helibum]

I usually try to leave a 1mm gap at the bottom of the hole, so if your M4 insert is 5mm long for example, I'd make the hole 6mm.

[mandicreally · Accepted solution]

I measure the narrowest diameter of the Heat Insert (usually the very base of it) then model the bore to be that diameter.  As it melts in it will form as needed.  I also add a slight chamfer to the opening of the hole to help guide the insert in to start. Never had an issue with doing it that way.  Prints usually slightly shrink so you normally have to oversize a hole for whatever purposes you have, but in for this the melting just does the job and provides a secure hold in my experience.