Project advise needed

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mickri

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I need to turn down an aluminum tube, 1.375 OD by 1.125 ID, to 34mm OD to fit inside a rigid boom vang for my sailboat, I would like to do this between centers but don't have a live center for the tailstock or a dead center for the headstock big enough for the tube ID. I could 1) make adapters that would fit on the live and dead centers that I have, 2) buy a live center for the tailstock end and use a 4 jaw to hold the headstock end or make an adapter like in option one for the headstock, or 3) 4 jaw on the headstock with a steady rest for the tailstock. Turn the tube down to 34 mm except where the steady rest is and then move the steady rest to turn down that portion of the tube. The tube is 16" long. I only need just over 14" for the part that I am making. It would be a tight fit to have the steady all the way to the end and turn between the 4 jaw and the steady. Might not be enough room.

Suggestions please.
 
Personally I would chuck up a piece of stock in your 4 jaw and turn it small enough for a press fit in the tube. Then make a centering point using a center drill. Part it off and press it into the tube. This end can be on the tailstock so almost any size live or dead center can be used.

For the headstock end I would chuck up another piece of stock and turn a section to a 60* point. Leave it in the chuck to act as a center. Place a lathe dog over the tube and use one of the chuck jaws to power it.
 
I have done option 1, I made a couple of flanged bushings to tight fit into the ends of the tube, one with a "center" hole for the tailstock end and one with a shank for the chuck end, then super glued them in. After turning, I removed the ends with heat. The tubes I was working with were already faced off square, I suppose you could take care of that with the steady-rest if necessary.
 
I should also mention that the 34 mm is not a precision fit. It is rather sloppy.
 
Like Eddy said . Make 2 tube plugs with centers in them . Think barrel plugs . I used to pack thin wall stuff with wet sand when cylindrical grinding or even rough turning on the large lathes to add stability to the tubing .
 
I am only taking off .036 to go from 1.375 to 34 mm. Two passes at .009 DOC will get me there. So I am not worried about tweaking the tube. Just looking for the different ways to do this.

I will have to look to see if I have anything on hand to make the plugs that have been suggested.
 
This might be a good time to buy a live center kit that includes a bull nose center.
 
I have looked at bull nose live centers. They range in price from under $20 to well over $100. I did not find any bull nose dead centers to fit in the headstock. Would have to make one. Not a difficult project. Might be fun to cut a mt3 taper on one end and a 60* taper on the other end. I wonder how big I should make the 60* end to be useful for other currently unknow future projects. Due to cold, rainy weather I have not been in my garage for the last several days to look at what I have in raw materials. Too cold. Don't think that it is a good idea to wear gloves when I am fiddling with my machines.

Regarding tapers I have always wondered why dead and live centers have a 60* taper. Is there some reason that 60* was chosen over say 45* or some other random taper? Or was it just by chance machinists started using 60* and it became a standard?

I do have a huge live center bull nose that came with my lathe. It has a rather large unknown taper that doesn't fit in the tailstock or the headstock. Have no idea what the original owner of my lathe used it for.

IMG_20230322_084342.jpg
 
Why not chuck one end and support the other on a bull nose center? Turn as much as you can and flip the part, then turn the rest.
If you want a bull nose center in the headstock, just chuck up a short piece of bar and turn a center on it.
Some bull nose and pipe centers have a much steeper taper than 60*.
 
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