Need help with threads

[Anonymous]

Bear with me here, until recently I was a Solidworks guy...

I have to draw in the physical threads on a part so that when I export out the toolmaker will have a 3d file that has the threads in the model, so I cannot use the thread command because it doesn't export the actual thread.

So the size of the thread is 1/2 inch by 20. I draw a half inch cylinder, extrude it one inch. I draw the detail to take away the excess material (basically a triangle). I use the coil command, and set the pitch size to 0.050 and run the coil command. Here is the problem, although the major and minor pitch are correct at the edge (in other words I have the thread pitch set correctly) the major thread does not look right and does not fit on a nut. I tried it and it won't work.

I downloaded a known good .iges file of a 1/2 by 20 bolt and a 1/2 by 20 nut and they do go together when I put them in an assembly.

I have drawn threads before in Inventor and I haven't run across this problem before. I either forgot something or never ran into this kind of thread before.

I am attaching the .sat file of the bolt, can anyone tell me how to get the thread detail from the .iges file to match model, or better yet, can someone draw a quick example and attach it to a reply? I am literally stumped...

[JDMather]

> better yet, can someone draw a quick example and attach it to a reply?

You didn't state what release of Inventor you are using.

Why did you attach an *.sat file - it is not a helical thread form. Attach what you have so far (the ipt file).

[JDMather]

> how to get the thread detail from the .iges file

What IGES file - I don't see it attached here?

[Anonymous]

Sorry, here is more of an explanation. The .iges file is a 1/2 - 20 thread. The .sat file is a 1/2 -20 bolt. The Inventor 2010 part called part7.ipt is my thread attempt. The issue is that although the thread looks spaced correctly, the thread does not follow the same outline as known good parts (the .iges and .sat parts were downloaded from a website where native inventor files were not available).

I need to make my threads match those threads on those .iges and .sat files. Is it some sort of weird 3D spline I have to draw? I am stumped.

Thanks for any input. I will upload the files one at a time.

[Anonymous]

Here is the bolt file.

[Anonymous]

Here is the Inventor 2010 thread I attempted to make.

[Anonymous]

Take another look at the .igs and .sat files and you will see that these are artistic representations of threaded features ... they were made using a single revolve around a non-collinear axis of the bolt and nut which was then arrayed at the appropriate thread pitch down part.

If you actually have parts made from these models, you will never be able to screw them together.

As for you .ipt file -- at least you have a true thread helix; however, I didn't perform a complete dimensions check.

HTH

[mcgyvr]

Get out your Machinery's Handbook, go to the page that shows proper dimensions for the screw thread you are using and model up the threads. A triangle is not the correct cross section for a unified screw thread. Make sure you allow allowances for plating too.

[Anonymous]

It does not matter that it is a triangle at this point, The thread pitch is correct but the thread profile doesn't match. I am at a loss to how to model it up correctly, I don't critiques of what the profile looks like. Thanks for being helpful...NOT!

[Anonymous]

Attitude is not conductive the getting help on this volunteer site. Check
out the coil command. You can use it to create threads.

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[mcgyvr]

The reason it doesn't work is the dimensions are incorrect. At first glance your minor dimension is too large. I stopped looking there. Get a Machinery Handbook and model the threads with the proper dimensions and you shouldn't have a problem. You have the technique correct.

[Anonymous]

Attached is a model of a nut with 1/2-20UNF thread (based on the Machinery's Handbook).

This does not match the .igs file -- see below for the reason.

Edit: Wasn't paying much attention to the rotation direction of the threads -- could be incorrect in the model for a standard hex nut but easy enough to change.

- - -

Note: Below this was posted by me before which you might have missed.

- - -

Take another look at the .igs and .sat files and you will see that these are artistic representations of threaded features ... they were made using a single revolve around a non-collinear axis of the bolt and nut which was then arrayed at the appropriate thread pitch down part.

If you actually have parts made from these models, you will never be able to screw them together.

As for you .ipt file -- at least you have a true thread helix; however, I didn't perform a complete dimensions check.

HTH Edited by: jconklin on Jul 15, 2009 3:14 PM