[Hyperryd]

Hey there I’m a newbie to the CNC world. I am going to be cutting out 3/4” HDPE parts. What would you recommend for the best 1/4” endmill. What feed rate and spindle speed should I start at with said end mill. Any help would be appreciated.

[Jim Dawson]

My prefered end mill for HDPE is an Onsrud O flute. I normally cut at 13,000 RPM, 40 IPM, 3/8 DOC using a 1/4 inch bit.

O Flutes For Mechanical Plastics | Documents

[Hyperryd]

Up or down cut?


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[Hyperryd]

Or straight cut?


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[Jim Dawson]

I use an upcut. A straight flute doesn't shear the way a spiral flute does, you need the shearing action for a decent cut and proper chip formation. An alternative bit is the 2 flute, solid carbide router bits from Home Depot (Diablo) or Lowes (Bosch), both work well, and are available on a Sunday afternoon

[Hyperryd]

So the onsrud 63 series. What is different from 63-724,725,726...?

[Jim Dawson]

So the onsrud 63 series. What is different from 63-724,725,726...?

The length of cut.

Series 63-700 | 1/4" Solid Carbide One Flute Upcut O Flute for Hard Plastics (Item 63-724) | Item Detail | LMT Onsrud

[Hyperryd]

Forget it I found the chart. So 63-725 should work for a 3/4” depth. Right?

[Hyperryd]

Thank you for your help Jim. How about cutting 1/4” aluminum? What do you use for that?

[Jim Dawson]

Forget it I found the chart. So 63-725 should work for a 3/4” depth. Right?

Maybe, I normally go with the next longer size to help with chip removal. In this case it looks like the next size is 1 1/4 cut length. Having said that, I have successfully used a 1 1/4 cut length to cut 1 1/4 thick HDPE, using 0.050 DOC on the final pass.

[Hyperryd]

I got a little trigger happy and ordered 2 of the 725s. I’ll give them a try and if I need to, I’ll get the 726. 1 1/4” seemed like a big jump.


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