DoN. Nichols wrote:
What *material* do you expect to cut?
Mild steel and brass.
A 3/16" tool would be
fine for aluminum or brass. A bit marginal with bronze, and quite
questionable for steel -- especially tough steel. (This is assuming
that you are talking about the shank of tools mounted in a
quick-change toolpost. In the old style lantern tool post and the
forged holders, 1/4 HSS bits would probably be within reason, as the
toolpost and holder offer more give than the tool itself does.
This has not been finalized by any means. This is the sort of concept I have
in mind:
http://www.majosoft.com/metalworking..._toolpost.html
Not quite sure where the "quick change" comes into it.
I have a boxful of 3/16 and 1/4" tools, toolholders with carbide
inserts, toolposts and something which I take to be a crosslide of
some sort into which all these things fit. They all look rather
puny. Would they do a job of truing up the edge of a 9"x 1/4" disk?
Would they face it? Or should I design around something more beefy?
If so, how much more beefy?
I would judge based on the standard tool holders for a
quick-change toolpost sized to fit the machine. A 9" lathe by South
Bend for example would use an AXA sized quick change toolpost, and the
standard holders for that accept up to 1/2" shanks. I'm using a 12"
swing Clausing, and I use the BXA toolpost which accepts 5/16" shanks
in the standard holders. Larger machines (say 15" swing) would use
CXA which will accept 3/4" shanks. These are pretty much scaled for
the load which the machine will put on them.
FWIW -- my 12" Clausing will go down to 35 RPM in back gear, and
to 210 RPM in direct drive. Most of the time, for what I do with
steel, when I'm in back gear I typically am at the middle speed --
100 RPM, though I am likely to go all the way down to 35 RPM when
knurling steel.
At this point my wife can crank the handle at 120 rpm but will slow down if
asked nicely.
But all of this assumes that the bed, the cross-slide, and the
compound are made proportional to the swing. Since you appear to be
considering making your own, you need to know how stiff these parts
are made first.
This is being currently determined by experiments. The small version - not
very. Produced an interesting pattern of chatter marks on the face. Perhaps
useful in future but not what I was looking for immediately.
--
Michael Koblic,
Campbell River, BC