[kNucklBustr]

Besides Onsrud 1 flute bit, what is a second alternative end mill to use cutting UHMW ?

Using 1/16 - 5/16" dia end mill. (Onsrud 5/16 is $60, not going there)

Ive tried a HSS 3/8 2F CC end mill at F8, spindle at 1750 w/ decent results.
However, the walls of a 1/2" deep slot have these tiny vertical uniform lines.

Used UHMW on a lathe and know how this stuff can get real smooth.

Pic of mill cut

[A1CNC]

What is your max spindle speed? I machine literally tons on UHMW. @1750 rpm you are only at ~170 fpm, You want ~500 sfpm and ~ .002"/tooth for a finish pass. What I see in your picture is not uncommon if your going too slow either spindle speed or feed. You can always run a finish pass too to clean it up.

I use accupro, Onsrud carbide ALOT. I run a 1/2" 2 flute 6krpm, .5" doc. 95- 100 "/min.

Hss cutters are frequently sharper edged than carbide and sharp is your friend with UHMW but.. when planning a surface a small radius on the corner of the cutter is a big help.

Roughing feeds of .006 - .01"/ tooth is not uncommon.

[kNucklBustr]

What is your max spindle speed? I machine literally tons on UHMW. @1750 rpm you are only at ~170 fpm, You want ~500 sfpm and ~ .002"/tooth for a finish pass. What I see in your picture is not uncommon if your going too slow either spindle speed or feed. You can always run a finish pass too to clean it up.

I use accupro, Onsrud carbide ALOT. I run a 1/2" 2 flute 6krpm, .5" doc. 95- 100 "/min.

Hss cutters are frequently sharper edged than carbide and sharp is your friend with UHMW but.. when planning a surface a small radius on the corner of the cutter is a big help.

Roughing feeds of .006 - .01"/ tooth is not uncommon.

Thanks for the info. 6000rpm is quite diff than my 1750.
Not a router. 2200 is top rpm for this older mill, but I keep it at 1750, not sure the spindle bearings cond.
Ill try diff feeds. Purchased a mess of new helix 30deg cutters 2F, 1F for plastic see how that improves.

I was using .002-.003"/tooth. Ran this at 12ips, .160" DOC/pass. No finish pass.

[Fastest1]

A full depth finish pass with a small engagement would clean that up. Same thing in metals.

[rowbare]

Also make sure that the end mill you use for the UHMW has never been used to cut metal. The same holds true for any plastic. Start with new endmills and use those for plastics only.

bob