Multiple Start thread

Anonymous · ‎05-11-2016

I just started in Fusion 360 and love what I've seen so far, especially since they have a set of "standard" threads.

However, I was wondering if there is a feature or procedure for modeling a thread with multiple leads or starts; I didn't see an option for lead starts in the "create: thread" menu. Ideas or suggestions? Or a possible future feature?

jeff_strater · ‎05-12-2016

Thanks for the suggestion, @Anonymous. I learned something today, as I did not know about multiple lead threads. Very interesting.

Unfortunately, Fusion today does not support this, as near as I can tell. I will investigate this and first, make sure that my statement is correct, and second investigate what kinds of standard multiple lead threads exist.

If I am correct, and Fusion does not support this in the Thread command, you could maybe model these yourself using the Coil command, although that would be cumbersome to do. Some clever person could easily write a script to do this, I'll bet.

If nothing else, this is a good Fusion Idea Station request.

Jeff

Jeff Strater
Engineering Director

I_Forge_KC · ‎05-12-2016

As Jeff said, this isn't an option now (that I am aware of)

You could model this though...

1. Create a spiral around the circular geometry you wish to thread (using the triangle internal option) using the pitch you desire. Create this spiral as a new body.

2. Create a new sketch on the triangular face of the spiral that matches the thread profile you want to model. Keep in mind that the internal point of that triangle will be a sweep path - so offset accordingly.

3. Finish the sketch and sweep the sketch profile along that inner point. Use the cut option to remove the material.

4. Use the pattern command to get your number of paths.

There is a great deal of detail work required to pull this off... but if you need to do it for machining, this is how I would do it. In this screencast, I just did this super fast with no regards for dimensions or actual usable geometry... just to show the process.

K. Cornett
Generative Design Consultant / Trainer

jeff_strater · ‎05-12-2016

I did check, and verify that Fusion does not support this today. You can try to emulate it using the Coil command, but the options that are available there are not ideal. I made this using this method:

I can show you how I did this, but there are definite limitations to this method.

Jeff

Jeff Strater
Engineering Director

Anonymous · ‎05-12-2016

I'm glad I was able to introduce this topic; multi-lead screws are awesome; it's a fantastic way to move something REALLY fast. A lot of ships and subs use them in their doors, so you can close them real fast in a hurry with a lot of force.

I like all these suggestions; I'll have to try them later when I've got my Machinery's Handbook back in my possession.

I also saw this, er, thread. (sorry, puns).

http://forums.autodesk.com/t5/ideastation-request-a-feature-or/non-standard-threads/idi-p/5717744

Really all a multi start thread is a "normal" thread broken up. Ususally though, it's reserved for larger diameters. (an SAE example would be 1-4 w/ 4 leads; it would result in the same pitch, but with what appears to be 16 threads per inch). The only issue would be the model geometry could overlap if someone isn't careful.

VoidstarSolutions · ‎07-02-2016

Hey all, I just came across the need for a 4 lead metric lead screw and was able to get exactly what I needed by duplicating the original threaded object, rotating, and combining at the end. looks beautiful.

scirpion.te · ‎10-28-2017

I am trying to do the same to create an internal TR8*8 thread.

Could you help me with duplicating the thread and rotating it?

greatguitartist · ‎02-26-2020

I_FORGE_KC's method, while effective, doesn't keep the thread form perpendicular to the cylinder body. I have listed below, a video and steps for accurate multi-start thread form generation. The video shows the process of creating a 400mm Tr8x8(p2) threaded rod, but the principle is the same for any thread form. The thread form sketch dimensions were obtained by Googling "Trapezoidal Thread Form"

1. Create an 8 mmx410 mm coil using the "Height and Pitch" coil type. Set the coil section to "Triangular - Internal" and the section position to "Outside". The section size was set to 1 mm, but you can leave it at default size as well.

2. Create an 8 mm dia. x 410 mm tall cylinder inside the coil (sharing the same center point as the coil)

3. Create a sketch of the thread form on the triangular face of the coil. Project the coil path onto the sketch to be used for the sweep function and then hide the coil body. Also, make sure the thread form's sketch extends past the cylinder wall.

4. Use the "Sweep" function with the type set to "Path + Guide Surface" and sweep the sketch along the projected coil path with the face of the cylinder as the guide surface. Use the option to cut the sweep along the cylinder body

5. Use a circular pattern to replicate the sweep cut 3 more times.

6. Sketch an 8 mm dia. circle on one end of the threaded rod and extrude -5 mm to cut. Repeat step on the other end of the threaded rod. This will clean up the ends of the sweep cut.

7. OPTIONAL - Add a 0.5 mm chamfer to the 4 edges on each end of the threaded rod

This will ensure the thread form remains perpendicular to the cylinder walls.

greatguitartist · ‎02-26-2020

I have listed below, a video and steps for accurate multi-start thread form generation. The video shows the process of creating a 400mm Tr8x8(p2) threaded rod, but the principle is the same for any thread form. The thread form sketch dimensions were obtained by Googling "Trapezoidal Thread Form"