We’ve been grinding a lot of recoil pads with the B&R recoil pad grinding fixture at the shop lately. Our current mounting fixture leaves a lot to be desired.
If you look in the bottom right corner of the image above, you’ll notice the block of aluminum clamped to the table. Years ago, when I got the 2×48 Baldor belt sander shown above, I needed a way to mount my B&R fixture (available from Brownells) to it. I was lucky enough to find that oddly shaped piece of aluminum in the scrap bin, so I drilled a 5/16″ hole in it, mounted the fixture, clamped it to the table and never looked back.
While the current set up works, it is mostly in the way when I’m not grinding recoil pads. This isn’t good if you are working on a few different jobs, and beyond looking a little “field expedient”, it was hard to adjust during set up. I decided there had to be a better way, so I decided to make an aluminum tooling plate.
A tooling or fixture plate, is typically a plate of steel or aluminum used in machining to set up different operations. Typically it has a series of holes that are threaded and/or accept pins. This allows the machinist to locate work. For this sander, I don’t have the need to locate pins, however, I do have the need to secure the B&R fixture, which has a 5/16-18 thread. So I decided to make a tooling plate, out of aluminum, with a series of 5/16-18 holes in it for my sander.
I began with a piece of 6061 aluminum (normally machinists will make fixture plates from a type of cast aluminum known as MIC-6) that was 4″ wide, 8.25″ long and .75″ thick. I selected this size because I had a piece on hand. I secured it in the mill on a set of MITEE-BITE vise jaws and faced the surface.
Next, I contoured the outside dimensions of the plate. I settled on a finished width of 3.9″ and length of 8″. This allowed me to cut all the edge from my piece of rough stock.
On this plate I decided to place my holes on a 1″ grid. I spotted each location with a spotting drill, and followed up with the drill bit (letter “F”).
Holes drilled, I was ready to tap. This is a 4-flute hand tap and is a poor choice for aluminum and machine use. However, this is the only 5/16-18 tap I had in the shop, so I used it.
To finish the top side of my plate, I chamfered all the holes and the outside edge with a .040″ width chamfer.
To machine the bottom I held the plate on a set of parallels in the jaws. I faced the plate, then machined a shallow pocket in the bottom of the plate to receive the sander table.
To mount the tooling plate to the sander table, I decided to use the threaded holes in the fixture plate. To locate the holes, I used a transfer punch. The transfer punch fits inside the threaded hole; when inserted, you tap it with a hammer and it marks the location of the holes.
Holes in place…
And now I can use a couple of socket head cap screws to bolt the plate to the table.
Now this looks way better, and best of all, I have enough table left to grind parts while the support arms of the fixture are still in place!
Works like a champ!