3D printing and threads (like for a bolt :).

[IPT]

So i noticed in Fusion 360 there is an option to model threads in a hole. Apparently you can choose the thread size and pitch. I am totally new to 3D printing (haven't even built my printer yet!) but wondered if a printer is able to "print" this well, or if it is better off just putting an appropriately sized hole and using a traditional Die and Tap to thread it?

[Ditchrat]

Originally Posted by IPT

So i noticed in Fusion 360 there is an option to model threads in a hole. Apparently you can choose the thread size and pitch. I am totally new to 3D printing (haven't even built my printer yet!) but wondered if a printer is able to "print" this well, or if it is better off just putting an appropriately sized hole and using a traditional Die and Tap to thread it?

No you can not tap the hole, because it isn't a solid object, and there just isn't enough meat.


However the threaded option in fusion works just fine. I literally just threaded 3mm x 12mm long threads into ABS and was able to torque them down as hard as in aluminum or nylon.


I have also done it in PLA which is softer but you can achieve a snug fit for most items.

[IPT]

Originally Posted by Ditchrat

No you can not tap the hole, because it isn't a solid object, and there just isn't enough meat.


However the threaded option in fusion works just fine.

Thanks, good to know.

I am a novice machinist but I do have a question then. I'll go the Fusion route, however, when taping a hole (this is the procedure where you screw something in a blank hole to create threads to receive a bolt or screw, yes?)
don't you use a certain size drill bit before hand to create the hole that needs to be threaded? If I just designed a hole the same diameter wouldn't that give me essentially the same starting point? A moot point if I can just save the step and build the threads in, but just trying to clarify my knowledge base.

[Almighty Malach]

Originally Posted by IPT

Thanks, good to know.

I am a novice machinist but I do have a question then. I'll go the Fusion route, however, when taping a hole (this is the procedure where you screw something in a blank hole to create threads to receive a bolt or screw, yes?)
don't you use a certain size drill bit before hand to create the hole that needs to be threaded? If I just designed a hole the same diameter wouldn't that give me essentially the same starting point? A moot point if I can just save the step and build the threads in, but just trying to clarify my knowledge base.

Yes. I deal with SLS printed parts a lot and its easiest to draw your hole to the correct tap diameter, then ream it to size and tap the first few threads. Let the bolt form the remaining threads to keep as much material in the threads as possible. Otherwise they'll strip out much sooner.

[Gramps]

I have a case for sd cards that has a screw on lid, it was all 3D printed using PLA. I didn't design the case I got it off Thingverse.com

[Voodoobrew]

I just tell fusion 360 to make a 2.5mm hole, no threads. Then I drill that out with I don't know what size standard bit (7/64 or 1/. Its plastic, so the M3 screw will just thread itself into the material. I print with petg, which is less brittle then pla, so pla you could tap it. The tap seems to gum up more then the drill for me.

My guess is the threads made in fusion 360 don't print anything near accurate, just the hole size is close to correct so things work out. After you turn your solid file into an stl you lose the accuracy in the threads, you lose more accuracy in the threads when the slicer slices it up (this all depends on what size bolt your using too, I am basing this off of the M3 screws we use for RC cars) .

When you put a 2.5mm hole in fusion 360, the hole gets printed with sidewalls so there is "meat" there to tap it.

The 2.5 mm hole is to small for an m3 to just screw in, for some reason I haven't tried printing a 2.8mm hole but that should be about right.

[edit] I agree with Almighty Malach...

[Edit 2] Using the threaded option might work great for printing like Ditchrat says, but it requires more cpu processing. My concern and why I haven't done it this way was because if my printer is out of calibration and prints the hole too big, the screw just strips. I prefer to start with a small hole and make it the right size after printing. Try it both ways. I am going to make a test file after seeing this article myself to try out Ditchrats idea and different sized smooth holes to see what works best (no I wont share my findings, cause every printer prints differently and ymmv).

[IPT]

Thanks VooDoo - yeah, all good insight. For this particular project I actually have a larger diameter nylon screw going into a flat plate to push against a wall behind it an anchor the plate stationary. I'll just have to do some experiments and see what works best. Once I get the printer built I have tools to do it either way so time will tell what prevails for this particular job.

[Heckler]

I thread my printed parts all the time in all plastics, PLA, ABS, Nylon, PETG, etc. I model the holes in Fusion 360 in the diameter common for the thread I need, for instance M3 x 0.5 screw I would make the hole 2.5mm, after printing I will chase the hole with a 2.5mm drill in case the hole is undersized (typical) and then tap with a FORMING tap, like this: Thread Forming Tap

These do nut cut the threads they form them, using the screw itself does work also but I find I get a bit better fit using the forming tap, I also put a drop of vegetable oil on the tap and it makes clean threads that almost look like they were machined..

One key to the success of this is to make sure you have your slicer settings set with enough shells (outlines) to support the depth of the threads and then some, for a typical M3 threaded hole I will use a minimum of 3 shells, more if there is sufficient room to do so depending on the load on the screw/hole itself.