Threading HDPE results in material deformario

[AmericanMachinist]

I'm threading HDPE.. buttress threads. I had the material form rather than cut, so I turned down the scrap to about 3/4 and am doing some more experimentation.

The first pass (shown) was cutting half the length and then started to simply deform.

Then I had a couple passes successfully cut.

Then I had a pads deform the material rather than cut.

Is there a trick? I'm going to play with the rake and angles. I searched the web but didn't see a lot specific to HDPE.

Thanks.

 

[C-Bag]

Are you using carbide inserts?

 

[AmericanMachinist]

1/4" HSS ground to a 45* on one side of the tooth profile, 90* on the other side. The cutter is angled up as a function of the Armstrong tool holder and is on center.

 

[SLK001]

Are you using a center? Remember, your material is... plastic. It will need all the support it can get. Post pictures of your tool setup - you might be digging into the material.

Use a HSS bit ground for brass or aluminum. Use a VERY SHARP tool. Take LIGHT cuts. Use a center.

 

[C-Bag]

It can be very hard to tell how sharp your bit is by eye. Magnifying goggles help, even better yet is a stereo microscope. I picked one up local on CL and I learned a LOT about how I was grinding my bits. Solved so many problems.

 

[AmericanMachinist]

Not using a center. But the stick out is only about an inch on a 3/4" (actually metric) OD. But I can use a center on this part and will.

I'll set the setup back up and snap a few picks.

Thanks!

 

[Illinoyance]

It looks like you are trying to cut a buttress thread using plunge feed. From the 2nd picture it looks like your infeed may be double what is needed.
Try setting your compound so you can flank feed at 45*. You might also consider modifying the grind so you have positive rake to the cutting edge.