Back plate for 4 inch rotary table

[moditwell]

I build a backplate for this 4 slot 4 inch rotary table because one was available for sale. First make a MT2 brass arbor that will center the whole process of marking the holes for all the bolts. 8mm thick aluminium plate was used and the pictures speak for themselves. Special T slot M4 nuts were also made with close fitting tolerance to just slide into the rotary table slots. To make this project a success, attention must be given to the close fitting of the brass arbor to the backplate's center hole. The final runout was 0.05mm. All bolt holes were counterbore and the counterbore tool was also modified so that the pilot guide was 5.96mm as 6.2mm was just too big and the bolt were have a sloppy fit. The M4 bolt heads were also reduced slightly to have a better runout to just fit the counterbore hole. What I like about this project is that it makes you think how to mark and make accurate holes. There is only one position for all the 8 bolt holes. One mistake and you start all over again.