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.