I have a Delta 14-070 drill press and a Delta 17-905 mortising attachment. I am having lots of different problems in my first real attempt at using the mortising attachment. At the moment I am using a 3/8" chisel. It is as sharp as I can make it.
1. I find it very difficult to clamp the collar of the chisel holder around the split ring bushings in such a way as to keep it the split in the bushings aligned with the split in the collar and to keep both halves of the bushing aligned horizontally.
I have replaced the 5/16-18 nut and bolt supplied with a piece of threaded rod and two pairs of jam nuts and it is better now, but still slips from time to time.
2. I am running the drill press at its slowest speed (250 rpm) instead of the recommended 650-2000 rpm because of the awful screeching noises I get at the higher speed and the amount of heat generated at the chisel tip. I actually have not tried any speed above 650 because my ears could not stand it.
3. The interior of the chisel gets packed with the shavings from the drill bit and not only don't the shavings fall out of the open side of the chisel by themselves, they have to be pried out with an awl which means that each 3/4" deep mortise takes 5 or 6 sequences of drill-stop drill press-clear shavings-start drill press-drill. Really boring (pun intended) and inconvenient.
I have waxed the inside of the chisel, basically by mortising a block of wax. This helps, but not too much.
I have tried using this mortising attachment in pine, maple and matai. All with approximately the same results. Are there tricks I should know? I have RTFM-ed several times. Is this a bad mortising attachment? Should I buy another model? Or should I go back to doing my mortises by hand or router? (My current project involves several linear feet of mortise, 1/4" from the edge of the workpieces. This seems an ideal application for a hollow chisel mortiser.)
Any advice appreciated.