In article L_JEb.89737$8y1.292664@attbi_s52,
Loren Coe wrote:

[ ... ]

If you have half-nuts (in the apron), you really need a
threading dial. And it is possible to *make* one for the lathe. One
quick-and-dirty way is by finding a gear with a tooth pitch which
matches the thread pitch of the leadscrew. You'll have to mount it on a

afaik, the screw is 8 tpi, most of these smaller imports seem to be.

shaft at a bit of an angle, to make up for the lead of the screw.
Better is to make one which is pseudo-hobbed by a tap which matches the
leadscrew, so you have a better match, and so the teeth are angled
properly to engage the threads on the leadscrew. The number of teeth
on the gear are critical -- and I would have to go to _Machinery's

this sounds like a decent project, i need to start doing some more
research. i never thought i would need much threading and that has
been true, but it still would be fun to accomplish.

Once you have the capability to do threading easily, you'll find
more and more uses for it. (One feature is getting the spindle speed
down slow enough so your reflexes are adequate without training. :-)

[ ... ]

You mean push it along -- no handwheel to move it?

yes, push it, but the handwheel is on the tail end of the screw.
you disengage the clutch, then turn the handwheel (half-nuts still
on). of course this means the handwheel also turns under power feed.
not really too neat.

Agreed. A CNC mill which I used for a while at work had
handwheels on the motor driven axes -- but the handwheels were cupped
discs, with a spring-loaded handle which was normally folded into the
disc. You had to pivot it out to use it manually. but it meant that
you would not get hit with the handle when it suddenly went from
creeping to a blur. :-)

[ ... ]

I understand. I started with a Unimat SL-1000 (the leadscrew
was the *only* way to move the carriage.) I then got an old
Atlas/Craftsman 6x18", which had the rack -- with the handwheel purely
manual -- and all power feed was via the leadscrew -- with a
basket-of-gears threading setup, and a chart on the inside of the gear
cover.

that is basically the 4015 lathe section, sans the rack gear. they
give you a 127/13x(?) duplex gear so you can cut metric threads, too.

O.K. The gears for the metric threading kit for the Clausing
are a 100 tooth and a 127 tooth (plus a few others to build up various
thread pitches).

[ ... ]

The ShopTask, however, has a dog clutch (which enages only at
one point in the rotation), to couple the spindle's rotation to the
leadscrew. (It also achieves reverse, by connecting to a
counter-rotating gear with a second dog clutch enaged by the same
lever.)

yes, that is what i _thought_ i had. this clutch is located in the base
of the pedestal and from the drawing, it looks like two "spiders" with
four legs. maybe that is a "dog clutch"? but just the one clutch.

Well ... the way I've been using the term (which may be
incorrect) is that a dog clutch goes from free rotation to locked with
no friction slip between the two. There are various ways to do this.
One involves two discs facing each other, with a set of pins in one, and
a matching set of holes in the other. One of the discs is able to move
towards and away from the other to allow them to couple or uncouple.

By contrast, the South Bend (and some other lathes) have a
multi-disc clutch to couple the feed to the cross-feed leadscrew, or to
the handwheel engaging the rack under the bed. Thus it can be started
smoothly at any speed, and set to slip when too much torque is being
required, making it fail softly. I would like to have that on the
Clausing, but what I have is gears which slide to engage the teeth on
other gears. (Mind you -- it is running slowly enough to not have a
jerk when it starts, anyway. :-)

Generally, dog clutches are designed so they will engage (or
disengage) under power. The releasing tap holders for threading in a
turret are designed so when the tap pulls the end of the tool out, the
dog clutch in it disengages, allowing the tap to spin freely with the
workpiece when it had gotten deep enough.

another poster suggested it s/b okay to use w/power on. will pull
that cover plate and then maybe give it a try. Thanks, --Loren

I suspect that you can. The Shoptask one seems to be so
designed, at least.

Good Luck,
DoN.

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