Tailstock Cam Lock |
|
OK,
here we are with another project. This one waited on a 4 jaw chuck for the
lathe and the mill. I combined two slightly different approaches, and if you
see yours here, then I’ll apologize in advance for the liberties I’ve taken
with it. I do want to say that so far, on the basis of about 15 minutes
worth of use, that the cam lock modification is a bit more complicated than
I thought. Adjustment is a bit fierce, and the lathe bed is not even under
the ways. This makes a difference.
|
|
I don’t regard this project as
finished, because I still want to change how I did the handle. There’s a bit
too much stress on it, and I’ll get in to that later. However, so far it
does work, it just doesn’t work quite as well as I wanted. Details on the
construction follow: |
|
I bored a 3/4 inch bolt through
with a 1/2 inch diameter hole. 15/32 would have been a bit better, it would
have allowed me to turn down the camshaft. One problem is that the bolt did
not fit flush to the tailstock, I hadn’t milled enough off. The second
picture shows that fixed. |
|
The same bolt, what was
happening was that the bolt was still slanted a bit, caused by the small
amount of a shelf to the left in the top picture. I cleaned that up, and the
bolt fits better. The only nuts I could find were very thick, so I decided
to use the head of the bolt, which was easier to turn down. It’s about 1/4
inch thick at this point. |
|
I did the aluminum adaptor, and
had great fun machining it and getting the angle just right. The angle will
force the bolt to tilt if it isn’t correct. It’s supposed to be 14 degrees.
However my good angle vise hasn’t arrived yet. The nut brings the control
arm nice and far away from the tailstock. |
|
One view of the camshaft. It’s a
bit over engineered. There’s a flat milled for the setscrew of the handle,
and that really does need to be about 90 degrees away from the minimum
diameter of the cam. The cam slopes out to the original 1/2 inch rod. That
slope keeps the cam aligned.
|
|
On the back of the cam, away
from the minimum diameter, there’s a small flat. This is intended to lock
the cam in place. It would work better if the cam follower didn’t have a
round hole. However, it does work a bit. I could have probably left it off. |
|
The handle cap before tapping
for the handle. I don’t like this design, much after the fact, because it
doesn’t handle stress well. The angle vise is set to the exact angle of the
slope. You can use a 1/2 inch mill end as a flat, and look for an even gap.
That gets it close enough to drill well. |
|
I replaced the original clamp.
It’s a piece of 1/4 inch steel that has been rounded at the front ends. The
carriage bolt head has been turned down to allow maximum clearance from bolt
to the lathe bed. The nut holds the thing in place. The hole in the clamp is
actually square, and was milled out, then filed a little to take care of the
taper in the bolt head. Next to it is the cam follower. |
|
The cam follower is a piece of
aluminum, 1/2 inch hole inside, 3/8 by 16 thread into it for the clamp.
There’s a small spring and washer that I installed to keep the clamp down
when installing it. That would be a good mod for the lathe, anyway. There’s
a small nylon washer used between the bolt head and the follower, which
keeps the follower in place. |
|
This is how the whole clamp
assembly fits. The spring helps keep everything aligned, and the carriage
bolt square hole helps the alignment, too. This is somewhat of a picky
adjustment when it’s gotten right. |
|
This is the cam and follower
assembly. There is a 1/2 inch collar on the end of the cam that locks it in
place. The lowest position of the follower almost sits on the tailstock, the
highest part comes close to the top. The nylon washer is used to space the
cam follower away from the bolt head. I want another nylon washer between
the collar and follower. |
|
Here’s the problem with the
handle, it’s just too weak. The handle shifts as the tailstock is locked, so
the handle points in all sorts of different directions. I think I’ll make a
different handle adaptor and a much more sturdy, but shorter, handle.
There’s a lot of force on the cam as it locks into place. The handle (1/4
inch steel) is soft enough to want to bend easily. I’m going to 3/8 inch. |
|
While you can’t quite see it
here, the handle is bent. Next set of pictures will show the fixed handle.
So far, though, not so bad.
|
|
OK, I have the new handle made.
This one was easy, take a 3/8 inch bolt, cut off the head, turn down and
smooth the end, and trim the threaded end so it fits. I like this handle
much more. It doesn’t bend, and doesn’t get in the way.
|
|
Note that I have put some nylon
washers between the cam follower and the shaft collar.
|
This
was a learning experience. One is that an off center cam turned on the lathe
puts a lot of stress on the lathe itself, due to the intermittent contact.
Take very light cuts! A second is that the HF lathe bits, 1/4 inch
carbide, are made of very soft steel, and will bend easily. They will go
back again when whacked with a hammer. Not Impressed.
Another is that there’s a lot of force used to get that cam to lock, and
I didn’t want it to come loose when I was using it.
|
Another
lesson was that the cam follower did not work as smoothly as I had wished.
For it to lock, the top surface needs to be flat, and so does the top of the
cam. The hole in the follower should probably be D shaped, if I decided to
do that.
I’m going to think about it, I might mill the hole out a bit, but not
very much. I’ve almost run out of adjustment room on the follower, and to
get it to work would mean cutting down the lock bolt and perhaps milling the
bottom of the follower a bit.
I’d like to hear from people who have a lathe that already has the cam
lock tailstock, perhaps someone could give me an idea of how well it works
and what the relative pressure needed happens to be.
I’ll keep working on it a bit more, and certainly put in a better handle.
As you saw, I changed the handle, while keeping much the same piece of
aluminum. I like this design a lot more, it seems to be much more sturdy.
The handle is designed to move 180 degrees with the unlocked position away
from the head, and the locked position towards the head. I’ll plug the old
hole in the handle with something, perhaps just a piece of aluminum driven
in and turned to match.
UPDATE: This design depends on the underneath of the bed ways being
more or less consistent through the length of the lathe bed.
Otherwise, the camlock structure will not work as well.
|