Rookie mistake? - Chamfer prior to thread

[thoreaubakker]

Hi All.
I just started playing threads and 3D printing -- so cool!

I think I mad a mistake, but am looking for confirmation / insight.
I did a chamfer on a cylinder (screw) before applying the thread.

Printed out the male and female components, and there is no way they would thread.

Looking at my design in x-ray, I think it's the chamfer that's preventing the thread to enter. The angle looks wrong.

Can anyone confirm my mistake? 
Should I avoid a chamfer, or just make sure it's at the same angle as the thread? 

Thanks  🙂

[MRWakefield · Accepted solution]

What you need to do is add the chamfer after the thread feature. However, there's a little trick to getting it to work! When you first add your thread feature make sure it's just a cosmetic thread (make sure 'modeled' is unchecked). Then add the chamfer. Once you've done this go back and edit the thread feature and now check the 'modeled' checkbox. You should now have a modelled thread with a chamfer.

[thoreaubakker]

Hey that is a clever trick, thanks very much @MRWakefield 

[thoreaubakker]

ps since you know the tricks... 😉

When I cut off the chamfer of the 3D thread with a utility knife I could test the fit, and the thread was pretty tight. The printer I tested on at school is a pretty good one, but I can imagine my hobby printer at home will be even lower tolerance.

I read about a trick: click each face (top / bottom / edge) of thread and offset face something .2 or .02 mm (I forget which). Have you heard of that trick? Any alternate suggestions for adding some slop for 3D printed threads?

[MRWakefield]

Yes, you can offset one or both flanks to reduce the effective diameter (also known as pitch diameter) and also offset the OD and core diameters. There's usually more clearance between the OD and core dia's so you might get away without offsetting these, but while you're at it you might as well offset all of them. You might even want to offset the OD and core dia's a bit more as they won't affect the fit of the thread but will reduce the chance that they'll interfere with the mating part.

An alternative method to get 'custom' threads is to edit an existing XML thread file or create a new one. 3D printer. If you do a search you'll find discussions here on the forum regarding custom threads if you want to investigate this route.

[thoreaubakker]

 Hey those are some great tips!

Good to net some more detail on the OD / ID vs the flanks, and especially interesting is the custom thread from XML.

I was struggling to get a big enough thread, so that will come in handy.

Thanks for sharing the knowledge.

[MRWakefield]

No problem, glad to help. I did notice a small error in my last post where I hadn't finished editing so it didn't read too well (the mention of a 3D printer) so apologies if it confused anyone.

I did think of another way of creating custom threads and that's by using the Coil command. Again, search the forum and you should find a number of posts about this.

Happy printing!

[chrisplyler]

Did you MODEL the parts with recommended clearances for the fit you desire?

If so, I would worry first about the printer's calibration. I've never 3D printed anything, so I don't know much, but I understand that:

1. They need to be tested and calibrated.

2. The setup should have settings for something called flow multiplier, and filament diameter, and possibly other values that can effect the accuracy of printed results.

3. Some materials are apparently sensitive to temperature while they set, and may sag and bulge out a tiny bit as each layer is put down. This should be accounted for in the setup? Or perhaps your temperature environment doesn't line up with the recommendations for your printer and material?

4. Depending on the material used, running the threads in and out against each other a couple of times might loosen the fit up a bit.

[thoreaubakker]

Aha! Even more tips.
You're awesome thanks so much  🙂

[thoreaubakker]

Hey these are very good tips and I appreciate you pointing them out.

I often work with hobby printers (Creality / Prusa) and don't always have the time to do proper calibrations, so that's why I'm looking for a little slop.

I did manage to do exactly what you suggest in point 4, and the threads fit super snug / perfect after some hard turns back and forth for 10m.

I will still experiment with the earlier tips to get a forgiving fit, but your emphasis on printer calibration is a really good one I hadn't thought of. Appreciate it.

[chrisplyler]

If you're in a hurry, and just looking to correct for this particular print on this particular printer...couldn't you just grab all exterior faces of the threaded shank (except the tip flat) and Push/Pull them inwards two or three thousandths? Technically the thread form wouldn't be exactly proper anymore...but it would work and it would fit better.

[thoreaubakker]

yes exactly.. I think that's what we were discussing above.

[chris]

There is another way to add the chamfer to a threaded feature that might be a click or two less.   What I started doing is model the thread before I put on any chamfers.   So I model the thread then before doing any chamfers I right click on the thread feature in the timeline and suppress feature..  After suppressing this feature you can now add your chamfers.  Now un-suppress this feature and your threads will cut into the chamfer as it is supposed to.

[thoreaubakker]

Hey that's a good tip - thanks 🙂