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Re: Scott gap or small drill walking



In a message dated 4/15/00 11:09:57 AM Central Daylight Time, 
tesla-at-pupman-dot-com writes:

<< The only potential problem with drilling is the possibility of the
 drill 'walking' while the hole is being drilled. This can happen even if
 you use a drill press and rigidly position the workpiece if the diameter
 of the drill is too small relative to the depth of the hole being >>

Au contraire,

Always use a centerpunch. The drill won't walk.  A slanted or angled hole can 
be a problem especially with "jobber's grade" wire drills. The best solution 
is to use a hardened drill. A trick is to expose no more than 1/2- inch of 
the drill for the first bite and then gradually increase the exposed length 
of drill.  In plastics and laminates like G10 always
start with a small drill to establish the center. Drill all the way thru so 
as you work up to the final hole size the cutting dust will fall thru the 
hole. In metals and materials like G10 the material has a strong tendency to 
grab or ride up the drill. Very tuff on the fingers. :-((
Also, blasting thru with a large drill produces a ruff hole. In G10, blasting 
thru with a single 
large drill will produce chipping on the backside. The largest holes for 
Scot's gap are the 1/4-inch holes for the brass support rods. Even the 
1/4-inch holes should be drilled in
at least 3 steps. Withdraw the drill several times to allow it to cool. This 
tends to keep the drill hard and will help eliminate slanted holes. I used 
zirconium drills.

When laying out the measurements for Scot's gap. Wrap the two slabs in duct 
tape, carefully layout the holes and drill right thru the duct tape.

Happy Day,
Ralph Zekelman