Perry;

with a couple decades of experience in using one of the 12 inch disc sanders, I offer you this information.

Not all the 12 inch disc sanders are created equal --specifically in the amount of runout of the disc and vibration of the combination disc and motor. When you receive the sander check the runout of the disc and if it is not within a very few thousands of an inch carry it back return it and get another (check it out as well). Same with vibration--return it if vibration is too much. My 12 inch disc is made of cast iron and I think the new one are made of aluminum. Excessive runout of the disc will not allow you to grind the pad a few thousands of an inch at a time which you need. Of course if you have a metal lathe with more than 12 inch swing you can true the runout of the disc, which is what I did on mine to get the runout to Zero and I also drilled balance holes in the back of the disc to get the vibration to near Zero. The balance was accomplished by taping weights(brass flats) to outside of disc and turning it (disc and motor) by hand for balance and then drilling shallow holes with a flat tip milling cutter behind the taped weight area to take away metal equal to the weight of the taped on weights.

I use my 12 inch disc for making leather covered recoil pads and when I need to final finish the pad taking only 2-3 thousands of an inch at a time, I switch the motor off and as the disc is coasting down at about half speed or less I then begin to grind the 2-3 thousands of inch away from the pad--I usually have to use the switch off method several times to super finish the sides and top of the pad. Of course the 12 aluminum disc will not have the long lasting coast down speed that a cast iron disc will have. Here is where a AC or DC variable speed motor would be ideal.

Rig you shop vacuum cleaner pipe to the opening in the base of the 12 inch disc sander.

Set the table angle to the face of the disc at less than 90 degrees (experiment) in order to have the angle of the sides and top of the pad after grinding will have a graceful angle that duplicates the same gentle and graceful angle of the buttstock---this is a very important technique in order for the pad to look perfect when fitted to the buttstock.

Use fine grit sanding discs not coarse ones---you will need to decide by experiment what grit works for you best.

Finally, I will say that with the advancement in belt sander design in the last 10 years I believe a belt sanders now are the likely better to use for general recoil pad work (non leather covered). Knife makers have created a whole new world of belt sander designs.

The best recoil pad craftsman I ever saw was back in the 1960's, who used a 6 inch rubber sanding disc and taped the buttstock with cellophane tape and ground the pad on the buttstock setting all the angle by his eye and experience and when he was finished the buttstock had no marks at all on it. He would have done recoil pad jobs on hundreds of Browning A-5's back then, maybe even a thousand. He cut all the angles on the buttstock to get the LOP, pitch and so forth correct with a home made wooden miter box that he called his "money box".