On 2009-02-10, Michael Koblic wrote:
I have sort of worked out the headstock which should spin things as low as
60 rpm.
I am kind of stuck with the tooling side: the carriage, crosslide etc.
One of the questions I am struggling with is the size of the tooling
appropriate for this job (turning disks up to 9" in diameter). Instinctively
I feel that a 3/16 tool is not going to cut it (sorry about the pun). But am
I right?
What *material* do you expect to cut? 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.
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.
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.
Enjoy,
DoN.
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