Shaft Collar Threads

rod_muirhead943

I am having a difficulty in creating the "V" cut threads for this 8-32 thread on the OD for the set screw.  How is this done.  The last thread that I finally got modeled on a round gear coupling was accomplished by making the thread surface flat and I don't want to have to keep making a flat for a thread on a round surface like a shaft collar.  Thanks

EvanReese

I'm not sure if this is much better, but here's one way. This could be improved, but it's a start. https://cad.onshape.com/documents/f2fc628186f196b5fd48c00e/w/7858c3138fc1dda12ac5c53c/e/0679b15218cf3a6e2da77c89

dirk_van_der_vaart

Think about how to produce the part, I think like this.
https://cad.onshape.com/documents/0cb2f0c3a0760634dacf9032/w/899a7f528138072f6d54c2e3/e/777be1488fb856aa6bac72e8

michael3424

I'm just a hobby machinist, but I usually mill a flat tangent to the OD, spot drill, tap drill and then tap the hole.  Is that the wrong way to do it?

dirk_van_der_vaart

Like this

michael3424

That looks like what I'd call a spot face.  I usually just traverse the end mill to make a flat like this:

mahir

Unless you're planning on 3D printing (not likely for 8-32 thd) or you're just creating the thread as an exercise, you don't really need to model the thread. Standard design practice is to create a tapped Hole feature that carries all the required thread information, but doesn't actually model the threads since that tends to be processor intensive during rebuild. To add the Hole feature just create a plane tangent to your cylinder OD, start a sketch on that plane, and place a point. That point can then be used to locate your Hole feature.

michael3424

@mahir - from past posts it seems that actually creating threads is important in some teaching disciplines and perhaps that's the reason for the OP's request.

mahir

michael3424 said:

@mahir - from past posts it seems that actually creating threads is important in some teaching disciplines and perhaps that's the reason for the OP's request.

Quite possible, but I didn't want to assume one way or another. That's why I mentioned 3D printing and/or modeling exercise as a possible rationale.

rod_muirhead943

Thank you all very much.  Great resolutions.  Inventor does not require a spot face to cut threads.  Got to break out of years of Autodesk Inventor!  Dirk, I'm a little embarrassed.  I know better since I supervised and managed the machine shop at the plant in private industry under the engineering dept. as a senior staff mechanical design engineer, machine equipment engineer, and tool and die design engineer.  Oops!.    

mahir

@rod_muirhead943 , Onshape doesn't need a spotface either. It needs some sort of planar feature to orient the hole, but this can be achieve via a tangent plane without cutting a spotface.

dirk_van_der_vaart

But in practice it's better to have a spotface, so why not design the part with that spotface.
How thing's are done in the real world, that's leading. Not what the software is capable of doing.