Compound table conversion of an old Deckel mill

[John11668]

When all the gear was in hand I went on to start fitting the leadscrews complete with bearings and ballnut mountings . These were to be simple billets of aluminium bored to take the cylindrical part of the nut then milled out to form a u shape allowing for relatively easy replacement if this became necessary. They were drilled and tapped for the ball nut fixings and drilled for fixings to the respective parts of the table . I had machine a seat on one face of the saddle, parallel to the dovetails to mount the X nut, and a pad underneath the saddle to fix the Y nut.
Both of these seemed to mount simply enough where the old feed nuts had been .





These performed fine initially, and I was able to machine a few components with simple G Code routines which I had written myself. I went on to fit the homing switches, rebuilt the control panel and went on to add a few enhancements including a new breakout board to give me spindle start/ stop and speed control, and had a satisfying hour or two of play as I watched a milling cutter routing a pocket , but during that work it became clear that my aluminium brackets were not really up to the task.




The X bracket seemed not too bad but there was significant backlash in the Y motion due to two factors. One being that the nut was not a great fit in its bore so was relying on its fixing flange alone. The second was that the “feet “of the U bracket which bolted onto the underside of the saddle were just too small for reasonable bearing of the bracket on its mating face, and would not really accommodate decent sized fixing bolts . It was also clear that Aluminium being soft and quite plastic was not really the best material for this job. So back to the drawing board !
Now as I have said before there were no calculations in this process. I went for the old principle of “give it plenty” and ordered a pair of cast iron blocks sawn from 70mm Meehanite bar. Then I set out to machine a new pair of ball nut housings which effectively would be as big as the table could accommodate .