|Roger Hulett||27/10/2016 16:30:16|
|131 forum posts|
How do you reduce the o/d on a steel tube 70mm o/d. 100mm long. I can hold one end in the chuck, but how do I support the other end. because it is so short I cannot get a steady in,and the i/d 60mm is too large for the tailstock.
|Roger Provins 2||27/10/2016 16:36:58|
|342 forum posts|
Turn a shouldered plug to fit in the tailstock end.
|Neil Wyatt||27/10/2016 18:18:48|
16585 forum posts
Buy a copy of the world's greatest workshop magazine and it will tell you how!
|Martin W||27/10/2016 18:35:15|
|792 forum posts|
As they say 'A picture is worth a thousand words' and there's enough in Neil's post to cover a lot of awkward challenges.
16288 forum posts
The only thing to remember with the large centres as shown on the mag cover is that they really need a true end to the tube to seat correctly. If you have a sawn end that may be a bit off then if you make your plug with a long reduced dia section to fit well inside the tube you can still hold the work true even if not all the shoulder is making contact with the end of the tube.
On large dia work like your 70mm tube a bit of MDF will do to make the plug rather than waste metal.
|Jeff Dayman||27/10/2016 19:44:38|
|1622 forum posts|
The plug idea will work but another approach is a cathead. This consists of an axle held in the drill chuck in the tailstock, and a hub free to rotate with a close fit to the axle. In the hub drill and tap 3 or 4 holes for hex head screws to fit. The screw heads are turned to a dome shape to support the tube at 3 or 4 points and allow rotation for adjustment. In use the cathead is offered into the tube end while tube is in chuck. True the tube by adjusting screws inside the tube until it runs true. Careful not to adjust the screws too hard and pull the tube out of round. Catheads should be used at slow speed only.
If you only need to square the end of a tube, not machine the OD, you can wrap it with a piece of heavy paper, aligning the edges and taping the overlap, wrapping it tight to the tube along the length of the paper. If wrapped tight and over a good length, the edge will be very square to the tube. Mark a line, then belt sand or grind to the line carefully. Check with a square afterward, you will be surprised how accurate it is. JD
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