[TheForge] cutting off copper ferrules?

[xlch58 at swbell.net]

Bruce Freeman wrote:
> Lots of good ideas.  Thanks.
>
> I'd heard copper worked differently on the lathe than other metals,
> but I didn't know what to do about it.
>
> I tried a sharp parting tool and had trouble.  Strange that a slightly
> dulled one should work.  I guess it's a question of grabbing the
> copper.  I also tried a hacksaw while the tube was spinning in the
> lathe, and did not have good results.  I probably should get an
> assortment of good hacksaw blades, but this approach wasn't promising.
>
> I think I'll try them in this order:
>
> 1) Tubing cutter with a 1/2" rod inside the copper tube.  The burrs on
> the end are the killer.  I could tolerate it on one end, but not on
> the other where it has to slip on.  Clearance is too tight.  If the
> burr were tiny enough I'd just clean it up with the file, but I was
> getting substantial constriction of the tubing.   I have a drift for
> swelling the end of soft copper pipe to obviate using a union, but I
> doubt it has a purely 1/2" diameter section.  I'll check.  If I don't
> have 1/2" rod or dowel, I can easily get one.  I like the idea of
> doing this on the lathe.  I could probably use the roller assembly
> from a tubing cutter as a lathe tool...
>
>   
If you don't want to try a negative rake, then I would suggest the 
following:

1. mount a 3/4 inch diameter 3 inch long W1 carbon steel rod in the 
lathe.  2. turn a one inch length of it down to a half inch, or the 
maximum that your tailstock chuck can take.
3. Reverse it in the lathe, mounting and centering the half inch 
diameter spigot in the jaws
4. Set your compound rest to a very shallow angle of of 3-5 degrees and 
start cutting the bar down so that the section next to the chuck is a 
tad over the inside diameter that you want. Use a high speed, very fine 
feed and light cuts to get a good finish.
5. Assuming that you have a clean finish polish it using strips of one 
inch wide abrasive paper. 6. If you have a knurling tool, knurl the very 
tip for an half inch or so.
7.  Harden the tool using standard blacksmithing procedure.  Leave the 
shaft end that will go in the chuck as soft as possible.

Now,
1. Mount your new tool in the tailstock chuck.
2. Mount the tubing in the lathe as you have been
3. Put the lathe in the lowest gear ( for your atlas this would be the 
chance to use the backgear)
4. Put a normal plumbers tubing cutter on it. Or you can use a cuttoff 
tool with a negative rake.
5. Turn the lathe on low.
6. After the tubing section comes off, then advance the tailstock tool 
into the pipe to ream and swage the end
7. Repeat.

This will result in an assembley line procedure for making tube sections 
with two very clean ends, and one end with the diameter properly 
sized.   There is a science to cutting steel by the way.  What many 
people don't realize is the cutting surfaces of the cutting tool do NOT 
actually cut the metal, the material pushed ahead of it does.   Steel 
behaves different from non ferrous metals.  Positive rake for steel,  
negative rake for brass, aluminium etc.

Charles