On 2008-03-10, Joseph Gwinn wrote:
In article ,
"DoN. Nichols" wrote:
On 2008-03-09, Joseph Gwinn wrote:
In article ,
"DoN. Nichols" wrote:
On 2008-03-08, Joseph Gwinn wrote:
[ ... ]
But the carbide tool has more uses.
Not if if is ground to cut Acme thread profiles at the 10 TPI
size. There is not much else that it can do.
Right.
And solid carbide tools are *expensive*. I've got a 1/2" solid
carbide boring bar with a silver-soldered end which forms the pocket for
an insert (with flats on top and bottom to assure the proper rotational
angle and keep it from squitting out from under the clamp screws), and it
was something like $135.00 on an eBay auction -- and in catalogs it is
well over $200.00, so I figure that I got a deal at that price. And at
least that has replaceable inserts, so I can use it for boring for quite
a while. It is amazing how little chatter you see with as much as 6"
extension of that 1/2" diameter rod. So -- if you could find an Acme
insert, this would be the tool of choice for making internal threads,
except that it is too large to produce a 1/2" Acme -- and based on other
information later on, I think that the leadscrew in question is smaller
than 1/2". Hmm ... let me go down and check on that before it gets too
late.
Solid Criterion or Criterion-like bars turn up used around here for a
few dollars, but usually need some cleanup with a grinder.
O.K. I wish that *I* could come up with such steals.
And the Chinese are learning how to make these as well.
But -- are they learning to make them *well*?
O.K. The spare compound has a 3/8-10 Acme leadscrew. Now how
much can you do with that and a between centers bar? A 1/8" tool bit
would not have *any* meat around it after leaving clearance for the
threads. Let's see -- total height of thread is 0.060" for 10 TPI,
times 2 = 0.120" subtracted from major diameter of 0.375 gives us
0.255". For a rod to fit into that, with a transverse square broached
1/8" hole leaves us 0.065" total wall thickness -- not much for a
setscrew to hold the bit -- and that leaves no clearance for the chips or
for withdrawing from the thread between passes.
There are smaller bits than 0.125", which is far larger than needed to
cut a 10 tpi acme thread. In round numbers, if the pitch is 0.100",
then the tool width is something like 0.060", which can be made from a
piece of 0.1" drill rod, leaving ample space for a small setscrew.
With round, you have the problem of rotational positioning which is
locked in nicely with square tool bit. Of course, you could grind a
flat on top prior to grinding the Acme profile on the end.
[ ... ]
No -- I think that I would turn the needed thread in drill rod,
cut flutes, harden and draw it, and grind the flutes to sharpen it.
This is indeed the traditional approach.
For good reason with smaller internal threads.
[ ... ]
so -- with a 3/8" rod, and max diameter you would have 0.0025"
clearance
for the chips -- and all other options are less. Anything smaller than
3/8" diameter would be even worse in terms of rigidity (and even windup
of the rod). I don't think that I would want to single-point that
thread.
The center of the rod could be turned down for chip clearance without
badly reducing the stiffness.
As long as you have the diameter small enough to fit into the
pre-threading bore. And since it turns out that the thread is a 3/8",
the bore is noticeably smaller.
Hmm ... since it is also a right-hand thread -- can I find a
3/8-10 standard thread to use as a roughing tap? Hmm ... looks as
though that is a special, too. I guess that we make both the roughing
and finishing tap.
[ ... ]
I visualize it as having a small bit held in a cross hole, held by a
perpendicular setscrew. One may need to use a 1/8" bit, such as used
for jewelry lathes.
Covered above -- now that we are down to a 3/8" thread, there is
not even enough meat for this -- complete with about 1/16th inch of
sidewall for the threads for the setscrew. And the setscrew could not
be allowed to stick up above the bar, either.
Also covered above. Jewelers and clockmakers do this kind of stuff all
the time - same idea, but in miniature.
I could picture them doing it for small boring, but not for
internal threading, since jeweler's lathes typically don't have power
feed, let alone threading feeds.
[ ... ]
By loosening the setscrew and moving the bit, using a depth mike to set
the protrusion as one creeps up on the correct cut depth.
A tricky bit of work -- especially with such a tiny setscrew. I
would rather try making a tap to serve the function.
Not that tricky. But I'm coming around to the make-a-tap school as
well. One can also order taps made. I don't recall the price, but it
wasn't astronomical. This was discussed on RCM a while ago.
Yes -- it all depends on how many of the threads you need to
cut.
[ ... ]
I missed that you said "Compound Slide" at first -- which
changes everything. The "Tee" shaped nut is for the main cross-slide,
not the compound. (Just to be sure -- which *is* it which is so loose?
My backlash was in the cross-slide -- the one which always moves at
right angles to the lathe bed, instead of the one which can be set to
different angles depending on need.
The looser axis is the one closest to the T-Slot, and which can be set
at various angles to the lathe bed ways.
O.K.
The axis perpendicular to the bed ways is also loose, but far less so.
While my compound leadscrew was quite tight (and still is),
while the cross-slide was the one with 0.075" backlash (3/4 of a turn of
the crank).
[ ... ]
Oh -- you are talking about the nut for the *compound*, not the
cross-slide. That looks even smaller in the drawings -- perhaps 3/8"
instead of 1/2". I thought that we were talking about the cross-slide
on the carriage, not the compound top slide.
How did we get that far apart?
I've been trying to follow the nomenclature in the Clausing manual, for
better or for worse, even when it seems counter-intuitive. But I
suspect that nomenclature isn't uniform between manufacturers, which is
why I started to give the actual part number as well.
O.K. Let me define *my* terms so we can be talking about the
same thing:
[ ... ]
It's a logical system for sure. But honored in the breech, as discussed
below. This is why I try to say how far from the T-slot or bed way an
item is.
O.K. Most of the "breech" which I have experienced was in UK
references to lathes -- which would also call a 12" lathe (like my 5418
or your 5914) a 6" lathe -- rating it by the radius from the center of
the spindle to the lathe bed.
They would also be likely to call a "compound" a "top-slide" --
in part because some common lathes had the compound only as an optional
fitting, not as a standard part of the lathe.
On the 5914, the slide is flat-topped, not humped.
You mean the compound, not the cross-slide? I wonder why?
In the 5914 manual (page 30), that T-slotted part is flat-topped and is
called the "Tool Post Slide" (704-033), and is dovetailed to the
"Compound Slide" (704-034), which in turn rotates upon the "Cross Slide"
(704-032).
In the 5418 manual (page 19), that same part is humpbacked and is called
simply the "Slide" (C-330), and is dovetailed to the "Lower Compound"
(DL-460), which rotates upon the "Cross Slide" (DL-458).
So, even within Clausing, the nomenclature varies. Thus the confusion.
O.K. if you are in doubt as to the correct term -- *ask* so we
can know that there is a possibility of difference.
Thus my listing of my own usage of the terms above -- so we can
talk about the same thing.
And the taper attachment only works with the cross-slide
leadscrew, not the compound leadscrew.
Yes. Makes sense, and the drawings support this. Any you have one and
can look at it.
That does help -- but it would have been nice to have the manual
pages too as I was trying to make sense of what was missing.
[ ... ]
Yep. And now to find one.
It took me two or three years, of following eBay auctions to
find one which I *thought* would work -- and then some time to figure
out how it was supposed to work (and what parts I needed to make to
complete it) once I got it. Later, I got a manual for both it and the
telescoping one and discovered that I was right -- and only slightly off
in one thing -- a washer under the clamp for the "traveling nut" which I
made on the surface grinder to be the right thickness should really have
been bent from the proper sheet steel to this shape (be sure to view
with a fixed pitch font like Courier to avoid distortion of the image):
/|_______/|
// O //
|/ |/
+--------+
Note that the hole designated by the 'O' should be centered in the
bottom plate -- but I would have to make the ASCII drawing much larger
to allow that -- and I still could not keep the scale right, so I'll
leave it as it is.
I assume that anti-rotation is the intent, and that one could make this
washer with a vertical mill as well.
The primary function is spacing the traveling nut down from the
bottom of the cross slide -- especially when the clamp is tightened, so
you don't have the leadscrew bent up at the tail and getting tighter the
closer to the nut the handwheel gets.
Remember that the traveling nut is shaped like a narrow but tall
quonset hut, and has a square bar bent into a very long and narrow 'U'
brazed to the bottom. The bar is inset into the base of the hut to
define the width like this (view with Courier again):
/// ///
____/// ///
/ /\/ /// -- part of long 'U' shape. U-turn is at the
/ / \ /// upper right and cut off in the drawing
/__ / \//
/ \ /|
/ () \ // -- this is the nut, and the top is not a meeting
/__ __\// of planes as shown, but rather a smooth curve
|__|__|__|/ which I can't draw with ASCII. Also the hole
shows as way too small.
Anyway -- the nut is shown upside down (for ease of drawing) and
the washer from above (also shown upside down) reaches down beside the
'U' while the thickness of the washer holds the centerline of the nut's
thread at the right distance below the cross-slide itself. (And the
normal tail cover of the cross-slide is replaced by a very long one with
a slot in it which extends over the follower on the taper bar.
Below the washer and the 'U' bar is a nut which is round, with a
pair of steps milled to either side of the threaded hole. This extends
down between the arms of the 'U' and prevents the nut from turning. A
square-headed screw (made to match the wrench which comes with the lathe
and the various other square-headed screws as part of the taper
attachment) pulls it up tight against the 'U' and the bent winged washer
when you wish to lock the nut to the cross slide for normal turning
using the leadscrew. When turning tapers, this is loosened, and another
square-headed screw is tightened down to lock the follower which
straddles the taper bar to the extension of the tail of the cross-slide,
and this pushes the tool back and forth instead of the leadscrew. The
taper bar pivots on a block which slides in dovetails on an extension
bolted to the back of the lathe carriage, and which normally travels
with the carriage -- until you clamp an extension towards the tailstock
to grip the back way of the bed so it stays stationary and the taper bar
(if not set parallel to the ways) will move the block and the
cross-slide back and forth as the carriage moves along the bed.
[ ... ]
I don't find anything useful with a Google search using the
words Diamond and toolpost. Actually, I find mostly woodworking tools
in the first hits. :-)
That was my experience too. But I've seen that trademark before on
tools.
O.K. My original thought when "diamond" was mentioned was about
the non-slip texturing of the surface on which the tool holder rests.
It has those to, but this is clearly a trademark symbol, not a
functional feature.
Understood.
I'm going to Aloris as well.
The better way for almost everything. Unless you get to one of
those really expensive toolposts which let the tool holders lock at 15
degree intervals. :-)
[ ... 6x18" Atlas/Craftsman lathe ... ]
I think I would have made the replacement out of good quality cast iron,
not steel, so if something is to break in the future, it will be the
T-slot, not the saddle or whatever. Think of the T-Slot as a mechanical
fuse.
At the time -- cast iron was not available to me. I was working
with scrap available at the local shop at work (along with the tools to
shape it) and had no idea where to order such things.
Now -- it looks so much nicer than the original (thanks to the
surface grinder final finish) that I am reluctant to change it -- and I
don't use that lathe any more, anyway. (There are enough other problems
so it is not worth the effort, and it is in the cellar, not the garage
which became the shop. For things that small, I have the 5" CNC lathe
by Emco-Maier which is a much better machine than the old
Atlas/Craftsman with the bronze spindle bearings and the worn
flat top ways.
OK. That makes sense.
I suppose I will outgrow the Clausing someday, but it won't be that soon.
I don't think that I will -- unless someone gives me a Monarch
10EE or a Hardinge toolroom lathe -- and even so, I would probably keep
this for the turret and just keep the turret set up full time, instead
of the tailstock being set up most of the time.
Enjoy,
DoN.
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