# Help with End Mill for smooth HDPE bored



## DonKeli (Sep 18, 2010)

:help: I need help to bore or drill holes into 2 inch HDPE blocks. The drilled bores should be very smooth so i can insert shafts into it.

I have a Bosch Colt Router that I want to use for the drilling, can someone please suggest the right size and type of end mill or drill to use for this. 

Please I desperately need your help. Thanks :help:


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## Phil P (Jul 25, 2010)

Hi Kekeli

HDPE actually bores very easily with a drill press and engineers twist drills, just remember that this material has a tendency to self-feed. If you attempt to bore in one shot using a router bit it can clog and over heat very easily and even start to weld back in some cases. If you need a hole with an engineering quality surface I think you might be better off piloting slightly undersize with a twist drill then finishing with a solid carbide spiral bit in the router as this can be run at an appropriate speed. A two pass approach also counteracts the material's tendency to compress and spring back under cutting load (which leads to a washboard surface). In addition the best surface is normally obtained by _increasing_ the feed speed and _decreasing_ the rotational speed of the cutter the object being to produce a stream of curled chips as opposed to hot, sticky dust which indicates friction rub, short tool life and poor surface finish.


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