On 2008-02-25, Joseph Gwinn wrote:
In article ,
"DoN. Nichols" wrote:
On 2008-02-24, Joseph Gwinn wrote:
In article ,
"DoN. Nichols" wrote:
On 2008-02-23, Joseph Gwinn wrote:
[ ... ]
[ ... ]
Another factor for thread cutting inserts is that there is not a
single anvil -- there is a range of them, each tilting the insert to one
side or the other by a specific angle to match the thread pitch angle
for the given diameter.
Clearly intended for large production of a specific thread, not a series
of one-off jobs.
Actually -- for large production, you buy a full profile insert.
(Of course the Acme inserts are exactly that. :-) But for most
general-purpose threading, you buy inserts which are sharp V and don't
cut the thread crest, so one insert is usable for many pitches. The
angled anvils allow the insert to be ground with just enough clearance
for the task, without having to remove so much material that you weaken
the insert tip. This allows the same insert to be used for both
left-hand and right-hand threads, as well as being used for coarse
pitches on small diameters (steep angle) or fine pitches on large
diameters (very close to vertical angle).
As a hobbist, the only time I would buy a full-form thread
insert would be when I needed to do a production run for something where
the thread must have the rounded bottom to minimize stress risers. And
most of those I would cut with the Geometric die head anyway -- if it
did not need to be so long a threaded section that it would hit the center pivot rod for
the turret.
That's also the size of the slot in the lantern toolpost that comes with
the Clausing 5900 series lathes. I got the toolpost, but missing the
crescent-shaped rocker.
O.K. I wouldn't know, because mine came without a toolpost at
all. (And, I didn't miss it. :-) I had an old turret toolpost which I
could use while waiting for the Phase-II clone of the the Aloris BXA to
arrive, but I was very glad to retire it as soon as possible.
My theory is that it is useful for use with big knurlers and the like,
which come up used for small dollars, and they don't fit Aloris B-series
toolholders.
Even on the Clausing, I would use scissors style knurlers --
less wear on the cross-feed leadscrew if nothing else. I normally use
the BXA size knurling tool with two arms on a common vertical dovetail
and a left-and-right handed leadscrew to move the arms together and
apart in a balanced manner, so one height setting will work for all
sizes of knurls.
Of course, on the turret, I would use the T-style knurlers,
which also have two knurls pressing form opposite sides of the
workpiece.
[ ... ]
Hmm ... sounds like you need to combine a radius turning tool
with a small toolpost grinder. Start with a collet-held fixture which
has a slot for the rocker-to-be, add setscrews tapped in from the side
to grip the blank rocker, then turn the end of the fixture to a sphere
of the proper radius. If necessary, stop with the radius just a little
long, remove the rocker-to-be, harden it and draw appropriately, then
put it back and use the toolpost grinder mod to the radius turning
fixture to take it to final dimensions. (I would suggest you rig some
kind of holder for a small air-driven die grinder, and mount it to serve
as the die grinder.)
I've been thinking about this a bit. I think the easiest way is to hold
a piece of octagonal 5/8 thick plate in the 3-jaw chuck by means of a
large bored hole in the center, or bolt the octagonal 5/8 plate to the
dog driver plate, and machine the outer edge of the 5/8 plate to fit,
using a sphere-turning tool of some kind. When done, cut crescents from
the edge of the plate, and mill the sawn surface flat in the vertical
mill. Harden to taste. Given that one plate will yield multiple
rockers, hardening is probably not required.
Hmm ... that sounds interesting. But do you mean that you will
cut them as a partial torus around the hold-down bolt? I'm afraid that
won't produce the compound curve you need. Instead, turn a ball on the
end of a section of rod of perhaps 1-1/2" diameter or so (double the
measured radius of the ring), and then cut radial sections out of that.
On the horizontal mill, I would use a slitting saw and an index head
with a 3-jaw chuck to cut those. You could even set up two slitting
saws on an arbor with a spacer defining the width of the sector. I
might consider leaving the boring of the center hole until after the
sphere is turned and the slots cut.
Hmm ... is a Woodruff key made large enough? :-)
Also -- there is another trick for putting a spherical surface
on the end of a rod. Mount a boring head in the mill with the cutter
facing inwards instead of outwards. Then set up an index head at
something like a 45 degree angle, put the end under the center of the
boring head and start cranking the index head as you slowly bring down
the spindle with the boring head. Stop as the boring head is cutting a
circle around the center of the intended sphere. You can adjust the
size of the neck left by tuning the angle. I've seen this done to make
the ball-handle on a rifle bolt.
Enjoy,
DoN.
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