I just started using my delta hollow chisel mortiser yesterday. The clearance between the bit and chisel was set to 5/64. (Manual recommends 1/16 to 3/16.) Worked fine for a while. (White oak cutting perpendicular to growth rings) Then started to clog with small chips and dust and bake them into charcoal (White oak cutting PARALLEL to growth rings). I tried lubricating the auger and setting the gap slightly wider and slightly narrower. More charcoal.
Do I need a different clearance or feed rate? Any ideas?
Replies
My suggestion would be to take many small bites with the HCM. Take a shallow "bite" and then pull or retract the chisel and auger fully out of the wood. Then take a deeper plunge and so on. I've noticed that wood chips like to hang up between the auger and chisel. This causes friction and heat to build up. Extracting them both out of the stock and not taking an agressive plunge allows the auger to cear the chips through the slots in the square chisel.
I have a chisel honing set but have not used it yet. I haven't really used my HCM either, all that much. I've also heard that you're supposed to deburr the inside of the chisel with sandpaper wrapped around a dowel. This allows more clearance between auger and bit.
Thanks, taking 'smaller bites' made a big difference. I also opened the clearance to 1/8 inch, the middle of the recommended range, ant that seemed to help, too.
Hello. I don't know if this helps but 2 things that I do on mine to help with the ejection are; as the previous post states, take short plunges and retract the bit as opposed to 1 continuous plunge. The other thing is I always face the slot in the chisel towards the already cut mortise. This gives the chips somewhere to go, obviously not on the first plunge but any sucessive ones. Lastly I also scribe a line that is the center of my mortise, I leave a large gap between the chisel and bit and this scribed line helps to keep the bit from walking away from its center.
Good advise. That really allowed the chips to clear better. I also stuck the end of a small shop vac hose over the end of the hold-down fork and it helped clear the discharge. Thanks for the response.
Glad that helped, Santa Fe.
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