Love alliteration. Turned a tube held on the inside by the chuck jaws. If the workpiece is small enough, heat from the boring operation will expand the tube enough that the jaws will let go. Clamping from outside collapsed the hollow part of the now very thin walled tube (bored 1.03" OD tube to .965" ID). Tomorrow, bore the .965" hole in one end, lock it the same way but keep it wet to cool, and turn the other end to .850" as several operations with significant cooling time between.
On the Sherline lathe, if chatter seems out of control, check the gib adjustment that holds the carriage to the bed and lead screw. The gib is locked into its position by an 8-32x3/16" setscrew. Enough use and the steel setscrew chews away the threads in the aluminum of the carriage. My solution was tap 10-32 threads and get a 10-32x3/16" setscrew at Home Depot. At some point, I will have to repeat, perhaps one size up. Beyond that, replace the carriage. Or look for an aluminum 10-32x3/16" setscrew to save the threads.
Holding thin wall tube in a chuck is nearly impossible. I found a suggestion of using SuperGlue to hold a spacer inside so clamping is more secure, then dissolving with acetone afterwards. Fortunately I can remove a .965" eyepiece barrel from an eyepiece that is exactly the right diameter, because that is what will go inside that end of the tube.
Absolutely Adore Alliteration.
ReplyDeleteYou could also use a helicoil. http://www.helicoil.in/helicoil.htm
ReplyDeletePete: I need threads one end of the adapter and none on the other end of the tube.
ReplyDeleteRegarding that gibb screw: can you add one or more? Having multiple points of locating can make a big difference, especially if it is a tubular or rotating interface. The problem with those is that unless it is a press fit, you end up with a point (setscrew) and a line contact (3D circle in circle, line across the short surface). That is not a very stable contact situation, it will always be "working" under load.
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