Wes fired this volley in
:


What would you consider slow? I was doing about 900 rpm, feed tended
to be agressive in order to get chips that would break off when I
retracted.

I run about 700rpm doing holes that large, and feed as fast as the bit
will go through the work without hogging. With standard rake angles
you're going to get on non-custom bits, you really need to clamp the work
down well, and use positive feed, or 1) the work will climb the bit, or
2) the bit will self-feed at way to high a rate to break off the chips.

Most of my HDPE holing is in the range of 10mm to 22mm, so I run more
like 1000rpm on those, but the other rules still apply.

I also check my bits for running true before using them. The odd bit
(even the good brands, and ALL of the Chinese junk) will be slightly
larger at one gullet, or have a slightly deeper cutting blade on one side
than on the other. The tend to score the wall of the hole. With a
really good bit, I can get a hole in HDPE that almost looks polished.

LLoyd