Advice on threaded parts

[thegammaray]

I'm printing threaded parts - both male and female - but I'd rather not reinvent the wheel. The diameters are large: a minimum of 25mm, up to about 100mm. To achieve the threads in my CAD software (Cubify Invent), I'm just sticking a triangle point into the surface and doing a helix revolve. Since these parts only need to attach to each other (i.e. not to third-party hardware), pitch and other parameters are variable. I plan to move the layer changes to the outside of the prints in the future since the tiny blobs cause slight binding.

Any suggestions? I'm new to modeling, printing, and building things in general, so don't assume anything is too basic. Are there best practices? What angles/pitches/depths should I be using? I'm printing 0.2mm layers right now; should I lower the layer height to 0.1mm? What kind of overlap is optimal between the inside and outside pieces?

Thanks!

[PcS]

Or go to mcmaster carr and download cad files of the actual bolt and use those.

[jsc]

I threaded a part recently: viewtopic.php?f=6&t=3369

If you're using "real threads", according to metric or SAE standards, you should look those up. Your CAD program might have an option for those. You CAN print working real threads (I've done M5 thread successfully), but they won't be very strong and you have to be ginger with them. In those cases, I suggest using real screws and gluing in nuts or sinking in heat set inserts.

If you're just making it up, here are some suggestions:

Try to have the thread be at least four to five layers tall to give it some hope of lasting. So, at least .8mm tall.
Have the helix revolve extend past the end of the mating part, so that when you subtract it to form the female thread, it cuts all the way through so you can actually start the thread.
Similarly, you may wish to extend the helix past the end of the male part, then split it with the end face and remove the extra bit, so that it ends up flush.
Offset the female thread surfaces a small amount. I've found 0.2mm works well.
Make sure you leave a gap between male OD and female ID. Again, a 0.2mm seems sufficient.

I'm sure there are best practices for thread angle, etc., but for my purposes I just eyeballed it.

[Slipshine]

when your doing threads for printing run the pitch diam .01 inch big on the id and .01 small on the od.

also rather than having your triangle at 60 deg. make it 66 deg . When printed the should take a standard fastener.
I have had success with this between 10 and 28 tpi.

[willnewton]

Also, there is this nut/bolt customizer on T-verse.

http://www.thingiverse.com/thing:193647