Sine Plate Fabrication
My initial test setup was for an 85 degree angle (referenced from the mill table). I have the Sine plate configured for using a 6" reference hypotenuse. It was made so that 3", 6" and 9" references are also available. According to the calculations, I needed a 5.977" Sine reference. The bottom of the plate uses a half-round located exactly on top of the 6" reference location. This half-round is 0.5" radius. I therefore needed a 5.977" - 0.5" = 5.477" Sine reference (actual). I also setup my angle gauge to 5 degrees to see how well it matched up to the face of the rotary table when it was configured.
From what I can see, the angle of the faceplate and the angle gauge are close enough for my needs. The edge of the plates (10" x 10" x 0.5") have been drilled and tapped ľ-20 at 1" intervals starting from the center of the hinge pin (3/8" steel rod fitted into a hinge made from Ĺ" OD 3/8" ID steel tubing). The turn-buckles are used to pull the half-round down on top of my adjustable (poor manís gauge blocks). I used a couple of thread couplers held together with a Ĺ-13 allen setscrew and a couple of bolts screwed into the ends. I set my caliper to the desired length and unscrewed the bolts until they adjusted to the correct length. (Itís not perfect, but so what, Iím not either). Actually, someday Iíll buy some real gauge blocks.
The turn-buckles (with about 1-1/4" travel) are rated at 190 lbs of force, so they should be adequate for the purpose (time will tell). The idea of using the tapped holes on the plate edges, was that there should always be a pair of holes available, regardless of the angle. The turn-buckle ends have a ľ" long copper sleeve insert inside to hold the ľ" washers apart. This allows the ends to turn and not be bound-up by the bolts through them.
The three countersunk allen bolts that run along the axis of the mill table, are threaded into a steel guide bar that will just barely fit into the slot of the tee-nut track on the mill table. There are 2 additional holes available (using the same center hole) should the Sine plate need to be rotated cross-wise of the table.
The other 4 recessed bolts are threaded into tee-nuts to hold the plate down onto the table. The top plate has been drilled Ĺ-13 in four places to allow for either the rotary table or my small Kurt vice to be mounted. Either one can be mounted in two orthogonal directions. The hinge can be seen at the junction of the two plates, and is made up of 5 segments separated by copper washers. They were placed into a milled out shelf ľ" deep by Ĺ" wide across the end of each plate. This gave a precise measurement reference as to exactly where the center of the hinge pin would be located relative to top of the bottom plate and the bottom of the top plate. The hinge segments were welded to the ends of the plates in an alternating sequence.
The plates were all surface planed to setup flats relative to the mill table top. (note: I will never make anything that needs machining out of hot rolled plate again. During the surface milling, there were yellow and orange sparks flying off the tool that completely ate up a new set of $$ carbide inserts. The tool is 5" diameter and holds 10 inserts. Whatever was trapped in the surface is extremely hard. Once it is broken through, there is not a problem. Only at the surface)
The reason for building the Sine plate was to allow me to use a slitting saw to rough-out some gear teeth on the edge of a trunion (used to tilt the top of a table saw for wood). A replacement for the original is no longer available. It was made from potmetal with lots of cracks and a missing tooth or two. The gear teeth have a 5 degree slope from the plane of the teeth and the Sine plate allows me to set them horizontal.
Layout of the parts can been seen in the following drawings.
Acknowledgements: I would like to thank Jack R. Slack for getting me started on this project by sharing pictures of his Sine plate. Pictures ARE worth a 1000 words.