According to Will :
"David Merrill" wrote in message
news:vc2Wi.179798$Fc.10546@attbi_s21...
The nomenclature is 'speed(s) and feed(s)'; here's one:
http://www.whitney-tool.com/html/cal...SpeedFeed.html
For cutting 1/4 inch stainless (let's say 300 series) which of the bit types
should we be preferring:
- high speed steel
Add "high cobalt steel"
- uncoated carbide
- coated carbide
The carbides have the disadvantage of being very brittle, and
can break if there is any side force while you're drilling.
High Cobalt Steel gives you a bit tougher steel than the
standard HSS, without being as brittle as the carbide bits.
If you are drilling a *lot* of holes, perhaps the coated version
of the cobalt steel would be better, and it might be worthwhile
consulting one if the major manufacturers to find out what works best
with the alloy you are drilling.
You also want coolant on the bit while you are drilling.
If it matters, then let's assume that the application is drilling 1/4 inch
diameter holes in the 300 series stainless plates that are about 1/4 inch
thick.
Which 300 series steel? 304 is a lot nastier to work with than
303.
All of the figures are in _Machinery's Handbook_, among other
references. (And there are even nomogram slide rules for selecting the
proper (maximum) drill speed. As has already been mentioned, too fast
will burn up the bits rapidly, too slow only costs you time. If you are
not drilling a lot of holes all of the time, it won't hurt to run too
slow, and you'll gain a bit of bit life. Those maximum speeds are based
on a tradeoff of cost of machinist's time vs cost of replacement drill
bits.
And having the bits sharpened as "split point" will let you keep
drilling with somewhat less force than a standard chisel-point drill bit
will require -- which helps a cheaper machine do the job.
Proably for 1/4" holes, even one of the cheaper bench-top drill
presses will do -- if the motor can handle it. (Often the import drill
presses have shall we say "optimistically marked" horsepower ratings, and
often burn out quickly with serious use -- after which you replace it
with a *good* motor. :-)
Good Luck,
DoN.
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