In article ,
xray wrote:
On Mon, 18 Jul 2005 18:58:30 -0700, Grant Erwin
wrote:
What kind of lathe? What kind of spindle nose?
Well, mine has a 2 1/4 x 8 TPI threaded spindle with an internal
(appears to be) MT 5 taper.
A faceplate held in the lathe chuck would be marginally useful IMO.
Why? It would not have occurred to me, but after seeing it in the video,
it seems like a reasonable idea with some real advantages (and maybe a
few disadvantages.)
Its advantage is that you can move a project between the lathe,
milling machine, and drill press. But, you can do the same with an
adaptor machined to duplicate the lathe spindle nose on a rotary table
on the milling machine or clamped to the drill press.
And -- if you can't easily find a faceplate for your lathe's
spindle, you could use it there -- with the disadvantage that the
faceplate may be more off center (in a 3-jaw chuck), or may require
tweaking (in a 4-jaw chuck), -- *plus* -- that moving the faceplate a
greater distance from the spindle nose increases the likelihood of
chatter.
[ ... ]
Lathe dogs are excellent to buy imported. They are low precision items.
You didn't answer my question about how many are needed to cover a range
of diamerters. Maybe it's a stupid question, but I don't know the
answer.
Neither did I. I didn't because different sets of lathe dogs
need different numbers to cover a given range. So -- start out with
*whose* lathe dog sets -- and the answer will be in front of you in
their catalog.
If you buy them used from eBay auctions, you will likely get
them one or two at a time. Beware that the tails of some may be too
thick to fit the slot of the dog driving plate for your lathe, so you
may have to grind down the thickness of the tail, or widen the slot.
Fork-tail dogs or straight-tail dogs are used with plain
faceplates, where a screw is fed through one of the slots in the
faceplate, and secured to the tail of the dog (if a straight tail dog),
or passed between the tails (with a fork-tail dog).
There are all kinds of designs. Straight-tail, bent-tail,
forked-tail. The older ones have a longer square-headed screw, which
has been superseeded by shorter slotted headless screws, because the
square heads are more likely to catch in a sleeve, and pull you into the
running machine. The slotted headless screws are shorter, so they cover
a smaller range, needing more to cover the whole of your range.
There are also bar-type dogs, which consist of two parallel
bars, joined by two square-headed screws, and a bent tail from one of
the two bars. One of the two bars will have a 'v' at the center, and
this will cover a much larger range (given long enough screws. But it
is normally used on a dividing head for turning a mandrel for something
like slotting the teeth in a gear.
To go with that, I've seen centers which had a T-bar at the
pointed end, with slots in the ends to steady the tail of such a dog as
in the paragraph above. The slots each had a screw to clamp the tail
into a fixed position. (Sometimes, lathe dogs were tied in place with
wet rawhide, which would then shrink as it dried, holding the workpiece
firmly against chatter.)
I've seen ones which were obviously made for a single diameter
workpiece, with two U-shaped slots on the ends for screws to attach it
to the faceplate. Those have a very short setscrew.
So -- I hope that you at least now understand why you aren't
getting a fixed number for the size range which you specified.
Good Luck,
DoN.
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