In a recent post on another thread I mentioned an angle grinding jig I had built for my bench grinder, then realized I had never published a thread on that tool.
The jig consists of a sliding protractor plate that slides along a fence on the grinder. This picture shows the top of the plate. The arc of holes provides locations for the protractor arm every five degrees. The arm has a threaded, dog-pointed screw that locks into one of these holes and tightens down to hold the end of the arm down against the plate surface. The SHCS on which the arm pivots can also be tightened down to firmly lock the arm in place.
At the upper left and right of the plate you can see two brass nuts which lock two setscrews that project through the plate. These setscrews are used to tilt the plate up slightly when grinding relief on lathe tools.
Being aluminum, the plate and arm serve as a nice heat sink to wick heat away from tools being ground.
The bottom of the plate has a piece of angle screwed in place. This angle rides along the tool rest on the grinder to keep the table, and the tool being ground, a constant distance from the grinder wheel as the plate is pushed left and right.
And here's how it looks on the grinder. The small, crappy tool rests that came with the grinder were discarded and a long piece of aluminum sheet fitted across the front of the grinder. The plate rides back and forth on this extended tool rest; you can just make out the piece of angle on the underside against the front edge of the sheet.
I'm sure you clever folks can think of all sorts of attachments to ride along on the protractor plate. A dressing diamond with a micrometer feed mechanism is an obvious one.