Die Holder for long stock on the Mini Lathe

tkollen

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Dec 1, 2012
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When I decided to buy a milling attachment for my 7x16 Microlux Mini Lathe I came to realize how short the cross travel was and also how limited the use of a milling attachment would be. I decided to extend the cross travel with 1" before the centerline and 1" beyond the centerline, which meant that the cross feed screw had to be extended by 2". I decided to fabricate 2 extended cross feed screws, one by threading with a die and one by threading with the lathe. In the end I was going to choose the screw that fitted the nut the best.
Threading on the lathe was quite a challenge but also a great learning experience. Due to the length and the springiness of the 3/8" drill rod I was threading I had to use both tailstock and the follow rest in order to get a decent thread and consistent major diameter of the thread. At my first attempt without the follow rest the diameter in the middle of the screw turned out smaller due to the rod's springiness. In the end, and after several attempts, I ended up with a new cross feed screw that did fit the nut smoothly and with no noticeable backlash.

For my second attempt I did eventually find a 3/8" - 20 TPI LH Die overseas. I could of course not use my tailstock mounted die holder since it limited the thread length to a few inches only. Nor did I want to thread by hand for such a length using a die stock. Eventually I came up with the idea to make a sliding die holder that would guarantee that the die was perpendicular to the rod, both horizontally and vertically at all times. I used the steady rest, stripped from the finger assemblies and the bottom locking nut, into which I inserted a home made die holder that screws on to the steady rest. With a hand crank in the spindle I can now thread the rod and the freely sliding steady rest keeps the die absolutely perpendicular to the rod at all times.

I made the die holder out of 2 3/4" round aluminum that could fit 1 1/2", 1" and 13/16" dies. The holder was fitted to the steady rest from the back by 3 pcs M6 screws. The mounting surface on the steady rest was slightly grounded in order to make it absolutely perpendicular to the center line. Then 3 pcs M6 holes were drilled and tapped in the steady rest.

The threading operation with the die was a breeze compared to machine threading. I have yet to decide which screw came out with the best fit. My die is not adjustable so the only advantage with machine threading is that I can adjust fitness.

Tom


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