I would set it up in a mill and cut the hole with a solid carbide center cutting end mill. If you want to drill it, I would start small and step up in size, using cobalt steel bits with  TiN or TiALN coating.  I would not try to hand drill - either a very sturdy stable drill press or a vertical mill.

Joe

---- Original message ----
>Date: Sun, 29 Jun 2008 22:05:41 -0400
>From: Ernest Christley <echristley@nc.rr.com>  
>Subject: [FlyRotary] PSRU oil drain  
>To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
>
>I've got to put an oil drain in my PSRU.   I can put a 1/8" hole in, and
>have it route around the ring gear; but I don't think 1/8" is large
>enough.  I started trying to put a 1/4" hole through the ring gear, but
>it seems to be harder than the bits I have.
>
>How does one put a hole in the hardened steel, or is 1/8" large enough.
>
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