10-09-2013, 07:08 PM
Finally finished this project. After trying it in aluminum I continued on steel. After centering a piece of 1/2" drill rod in the 4 jaw I slide the 1/2" diameter ER32collet onto it. Taking John, Doubleboost's, advice I centered a dial indicator right at the Lathe's center line. Then started running the dial indicator on the compound back and forth until it the dial never moved.
After that I used a short boring bar to taper the inside bore. Once the opening was about 30mm I used a permanent marker on the 1/2" collet, stuck a piece of 1/2" drill rod in it and twisted in the bore. It showed a nice overall light scratch pattern on the collet.
Then I turned down the outside to 40mm for the closing nut. Turning the outside Metric thread was an interesting exercise.
It does take some extra care and thought since you can't dis-engage the threading half nut until the full thread was cut.
Anyway, it's done and works great.
Run out is less than .0005" (I think I currently don't have a DTI I trust). Here's a short video of it running with a dial indicator.
http://www.youtube.com/watch?v=SP2gxIxLmDI
After that I used a short boring bar to taper the inside bore. Once the opening was about 30mm I used a permanent marker on the 1/2" collet, stuck a piece of 1/2" drill rod in it and twisted in the bore. It showed a nice overall light scratch pattern on the collet.
Then I turned down the outside to 40mm for the closing nut. Turning the outside Metric thread was an interesting exercise.
It does take some extra care and thought since you can't dis-engage the threading half nut until the full thread was cut.
Anyway, it's done and works great.
Run out is less than .0005" (I think I currently don't have a DTI I trust). Here's a short video of it running with a dial indicator.
http://www.youtube.com/watch?v=SP2gxIxLmDI
If it's crazy but it works, it's not crazy.