Assignments for Level 3 and 4 of the (now defunct) Precision Machining programme at Sheridan College STC included a fairly large tap handle, a machinist's jack for supporting milling jobs, and a 5" sine bar.
The jack is far too large to use on the Taig mill, but it was still an interesting project involving tapers, knurling, threading and cross-drilling the cylindrical parts.
As the school did not have proper facilities available for hardening, I will (eventually) be milling off the top of the conical jack post and press fitting a ball-bearing into an axial hole therein.
In an attempt to keep the working surfaces of the sine bar from wear and, as the quality of the steel we used was fairly poor, I had the sine bar plasma (ion) nitrided by a friend. The ground surface finish became matte, but it has not corroded or otherwise degraded since being made several years ago.
I would like to upgrade the rollers on the sine bar, as mine were turned rather than ground (the shop's cylindrical grinder was out-of-order during the assignment), however I am in negotiations to obtain both a 3" and 5" bar soon. I can use the energy and time doing something else.
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