I just used my Delta mortising chisel kit for the first time on my drill press. After just 8 mortises in maple (3/3 inch sieze), I find the bit actually deformed. Just getting it to cut involved a lot of fiddling with the drill bit height setting relative to the mortising chisel. There was a lot of heat build up and it seemed to take a lot of force to make a hole. Any suggestions on this?
Try polishing the outsides of the chisel until they are mirror bright. I do this on a flat plate with fine sandpaper (400 then 600). You can take off any inside burr by holding the sandpaper around a small dowel. Keep the sharpening flat to avoid roll-over of the cutting edge. This will help in the cutting process. Also the bits usually need to be sharpened and honed before they are used. You just need to fiddle with the height adjustment to get it right. Good Luck
The cutting edge of the bit must not be in contact with the chisel. This will cause inefficient cutting and heat buildup, causing the bit to overheat and deform. The clearance distance varies slightly from wood to wood. Try starting with the cuting edge of the bit approximately 1/8 inch below the chisel. Adjust from there for optimum results.