Excellon and TrueDrill both used air powered drill in their NC equipment.
They had radial air bearings but I'm not sure if the thrust bearings were
air or mechanical. When I left the industry they were running 120K rpm and
would drill through a 4 up stack of .064" FR4 plus entry and backup sheets
in about 1/4 second. With time for travel they managed 100 to 120 hits pre
minute.
Air powered drills can be the ultimate, but you need good bearings. If the
bearings aren't up to the task, you'll find out fairly quickly. Many
handpieces have fairly good radial bearings to handle side loads (dental
handpieces for example), but they have relatively poor bearings to handle
the axial loads from drilling. You probably won't know until you give them
a try.
----- Original Message -----
From: "Bill Maxwell" <wrmaxwell@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Thursday, July 14, 2005 7:53 PM
Subject: Re: [Homebrew_PCBs] PCB drill recommendations
>>
>> What i really wanted to say, has anyone tried the air powered drills?
>> They are fairly high speed (op to 60k RPM).
>>