|old mart||20/10/2019 21:46:16|
|703 forum posts|
I happened to notice messages and when I looked at them, one was asking how I went about making a captive self extracting drawbar for a mill. Now I have read it, the message has disappeared and the name of the sender has vanished. So I thought I had better explain how I went about this modification.
Not all vertical mills will be suitable to fit a captive drawbar to. I was lucky because there was space inside the spindle to fit a nut close to the lower end of the drawbar and also not foul the tooling.Some measuring will be necessary before any work is carried out. I cut the thread on the 7/16" en19T drawbar blank on the lathe, and put about 2 1/2" on either end. I made the bronze nut (in black) long enough to Loctite securely with a flange thick enough to not be in any danger of breaking off. At the top end, I used two half nuts for locking and a piece of threaded hexagon bar large enough to ensure that the upper locknut didn't foul the ring spanner that tightened and released the tooling. I was lucky to find a stub ring spanner with a handle of just 6" long, which is plenty. Due to the design of the mill, I had to put spanner flats on the bottom of the spindle, as there was no lock,or any way to hold it. With a minimum endfloat on the drawbar, it breaks the taper in 1/4 turn.
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