On 2009-02-11, Michael Koblic wrote:
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.
O.K. The "Quick change" here comes from the fact that you have
multiple blocks each with a specific tool mounted in it. The upright
screw near the gold colored post in the drawing at the top sets how high
the tip of the tool is from the surface of the compound. The
counterbore mounted screw at the lower right-hand corner clamps the
block at the split to grip the gold colored cylinder post. So -- you
can loosen the crew a quarter turn, lift the tool off the post, and put
another one on there which is already preset for its height and clamp
the screw in it.
What is missing here is provisions for making sure that each
tool holder slid onto the post is in the same position -- especially so
when you replace a tool holder which you removed earlier in the project
it will have its tip in the same position.
There seem to be provisions to prevent the post itself from
turning, but nothing to assure that the holders always go on in the same
position. So -- for my purposes, it is only part of a quick-change
toolpost.
It does avoid having to put a stack of shim stock under each
tool to raise it to the right height, so that is a major benefit from it
(also present in the Aloris style quick change toolposts which also
assure the position of the tool is always the same.)
Anyway -- if the tools can be used with very little extension,
as shown in the drawing you can get away with bits with smaller shanks,
other than the question of heat transfer which another mentioned.
Note that he frequently says "bold" when he means "bolt", but
that English is not his native language, so it takes a bit of knowledge
to interpret what he says in places.
It looks as though he has the information in several languages,
which makes it an even more impressive task.
[ ... ]
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 -- can she keep up that 120 RPM if you are taking a deep cut
at an 8" radius? :-)
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.
O.K.
Good Luck,
DoN.
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