Facing Mandrel - Ideas?

lesrhorer said:
One of the plates will have an arbor mounted in it consisting of a ball bearing and another mandrel mounted in the tail stock. The arbor will handle the (rather modest) horizontal loads and of course the face of the chuck will handle the axial loads. The lathe jaws handle the torque. Obviously, the cuts will need to be reasonably light.

I am hoping eventually to be making hundreds of these. It is a case for a battery bank.
Click to expand...
I think your idea will work fine. Go for it.
R
 
lesrhorer said:
That's a great idea! I didn't know they made them.
Click to expand...
If you're referring to the chuck, I'm not sure it's an over the counter item. You could make a backing plate that replaces the point in a live center to keep it simple though.

 
Firstram said:
If you're referring to the chuck, I'm not sure it's an over the counter item. You could make a backing plate that replaces the point in a live center to keep it simple though.

Click to expand...
Actually, it is. I looked it up. They have them on Amazon for as little as $75.
 
lesrhorer said:
You mean a plug to fit inside the pipe so the jaws can clamp on the outside without seriously deforming the pipe? That's a good idea. I was thinking of putting a 4" steel pipe clamp around the pipe and using the internal jaws on the 3-jaw chuck.

I don't think I can make one to fit, which is why I am thinking of using a mandrel. My lathe only has an 8" swing. The pipe OD is 4-1/2", leaving only 1-3/4" between the bottom of the pipe and my lathe bed. I don't think it's enough.
Click to expand...
1 and 3/4 is plenty.
you don't need to make a riser.
here's a pic I found online of a wood lathe steady, which would work.
you can do it simpler than this. this is built like a tank.

il_794xN.2130003058_f0p3.png
 
I'm not sure what can be made with PVC pipe that would have cause for .001 tolerance on the ends. Consider the anatomy of a tolerance value like that. The thickness, diameter, and concentricity specs of plastic sewer pipe is an order of magnitude more slack than that. The battery case assembly won't care if it's length tolerance is within the range of thermal expansion anyway, so why not make hundreds of these the easy way with a .010" or greater tolerance? Chuck it up externally in a 3-jaw, softly, forget about the plugs, and give the end the support it needs with a steady rest. Cut your faces, use a feed stop, and be done with it. It sounds like you're applying a scalpel to a sledgehammer's task. To me, that type of thinking is the difference between a $60k/year engineer and a $120k/year engineer.
 
pontiac428 said:
I'm not sure what can be made with PVC pipe that would have cause for .001 tolerance on the ends. Consider the anatomy of a tolerance value like that. The thickness, diameter, and concentricity specs of plastic sewer pipe is an order of magnitude more slack than that. The battery case assembly won't care if it's length tolerance is within the range of thermal expansion anyway, so why not make hundreds of these the easy way with a .010" or greater tolerance? Chuck it up externally in a 3-jaw, softly, forget about the plugs, and give the end the support it needs with a steady rest. Cut your faces, use a feed stop, and be done with it. It sounds like you're applying a scalpel to a sledgehammer's task. To me, that type of thinking is the difference between a $60k/year engineer and a $120k/year engineer.
Click to expand...
actually, with out the plugs, the pvc tends to fly out of the chuck. you can't put too much pressure on it, the chuck needs a rigid structure to grasp onto. so I'd go with a plug.. I've never really been successful w/out a plug... it's always a missle.
 
You're talking about single-pointing a piece of supported 3" PVC, right? Maybe I used my 6-jaw last time I did that, I'm not sure. If you want to add stacking tolerance error and fiddle with a plug, then by all means. But using a plug fixture piece means kissing that .001" magic number goodbye. When working with a carriage stop that doesn't move in addition to a plug that has many fit possibilities, the parts will come out varied compared to indexing the work from the face of the chuck. Just saying, before you pick a tolerance out of the sky you need to know why you're going to go to such an effort to attain it.
 
pontiac428 said:
You're talking about single-pointing a piece of supported 3" PVC, right? Maybe I used my 6-jaw last time I did that, I'm not sure. If you want to add stacking tolerance error and fiddle with a plug, then by all means. But using a plug fixture piece means kissing that .001" magic number goodbye. When working with a carriage stop that doesn't move in addition to a plug that has many fit possibilities, the parts will come out varied compared to indexing the work from the face of the chuck. Just saying, before you pick a tolerance out of the sky you need to know why you're going to go to such an effort to attain it.
Click to expand...
yea, I was never talking about 1 thou runnout, that's ridiculous, since pvc isn't exactly a precision extruded piece. Quite the opposite. Its round enough to get a seal with primer and enough glue (after twisting) but not 1 thou.. I was never in on that.
 
I think the OPs idea will work if he wants to go that route. If it were me, I would probably just rotate the piece against the disc sander to get the end squarish.
I had this same issue with 3" structural aluminum tubing. Problem is that it is not really round and the wall thickness varies. I used the disc sander to square it up.
Robert
 
You must log in or register to reply here.
Back
Top