How do I cut the sharp knife edge off of a thread start

[Spurs]

I am using Solidworks 2007.

I would like to remove the knife edge at the thread start.

So far I created a plane perpendicular to the end of a 2nd helix that I drew into the model to locate where I would like the cut to begin. In the JPG attached, I would like the thinner knife edge thread up and to the left of the plane removed right down to the root diameter of the thread.

How would I best do this?

 

[MadMango]

Think about how the part would physically been machined. I would use a cut-revolve of some shape to remove the sharp edge (similar to turning a physical part).

"Art without engineering is dreaming; Engineering without art is calculating."

Have you read faq731-376 to make the be

 

[Spurs]

MadMango

To do a cut revolve, you need to have a plane that is perpendicular to the axis of the part. This is not perpendicular to the helix.

If you use the plane that I created in the picture, then it is not aligned to the root diameter.

Hence my dilemma.

 

[rollupswx]

>To do a cut revolve, you need to have a plane that is perpendicular to the axis of the part.

Two of your base planes should be going through the axis of the part (just like the real world on the lathe).
Create a sketch on one of those two planes and Revolve-Cut (just like the real world on the lathe). (turn on temporary axis)

Depending on your design intent you might also do a bit of "milling".

You might start out your helix with a bit of taper for lead-in from the root diameter to the crest diameter. I can't think of the modeling process being much different than the manufacturing process.

If you have trouble figuring it out supply the *.sldprt
Roll up the feature tree before zipping to make the file size as small as possible.

 

[zakk]

What you are trying to do is known as a "Higbee Cut" or "Blunt Start" of a thread. I've done it on Solid Edge, but I haven't sat down and figured it out on SW, but I'm expecting the process to be similar.

In Solid Edge, there's a command called Helical Cutout. You create a plane at the point where the thread exits the part (the very last scratch). Make the plane perpendicular to the helix. Draw the profile for the cut (usually an oversized rectangle) so the bottom of the profile is even with the minor diameter of the thread and the top extends above the major diameter. In the Solid Edge Helix Cutout command, you can specify the Start Radius, End Radius and Angle (distance around) for the cutout. In SW, the process is about the same, except you play with the Variable Pitch command and it should get you to the same place.

I attached a pdf for a Solid Edge part to show the results. The sharp point at the beginning of the thread is gone and I can vary the length of the cutout as much as I want. I agree with MadMango, imagine how you would machine it and it helps. Our CNC's perform this in a similar fashion.