Well I borrowed a mortising machine from a guy I work with. Its the
older model delta and this guy and the guy he got it from said it works
great. Additionaly there was an article in last months FWW about
mortiser setup. With all this I did a modest initial tune up on the
mortiser to make a couple of test cuts since I have not used one
I guess the part I was most surprised about and was wondering if it was
normal was that the sides of the mortises seem to have scalloped edges.
As if the edges of the auger bit are wondering a few thousands outside
the edges of the chisel. Albiet, the scallops are very small but I was
expecting the walls of the mortise to be very smooth. Can anyone shed
some light on this. Is this normal? Is it the bit or is there a lot
of runout on the bit. Also I set the bit and chisel clearance as per
the FWW article and the bit seems to get very hot. Enough to make
white oak smoke. Is this right?
Without seeing the scallops I would offer two guesses: 1.) Your chisel is
not quite aligned with the fence and your stock. This will cause an
enlongated "Z" pattern down the sides of the slot. 2.) Your hold-down
hardware is not quite doing the job (loose, mis-aligned, etc.) My first bet
would be on 1).
Also I set the bit and chisel clearance as per
Some smoke with hardwood is not terribly unusual. Your bit might be getting
a little dull, but once you get shavings inside of the chisel heat builds.
Hardwood cuts a little slower causing the problem to worsen. Make sure your
chisel is installed to allow the shavings to escape to the side or out the
front. If they build up against the fence and hold-down (rear exhaust) it
will worsen the problem.
Thanks guys. I will make sure everything is square and sharp. These
were just preliminary practice cuts so I'm sure I can tune it up a bit
better. Also in the FWW article were tips on sharpening the chisel and
bits so I will do that as well.
One more thing. How much deeper should the depth of the mortice be
than the tenon or what part of the bit do you use to gauge the depth of
the cut because I did notice that the auger obviously goes a tad deeper
than the chisel but it isn't really a flat bottom.
Go at least a hair more. Radial or tangential shrinkage is much higher
than longitudinally, and you don't want the joint to pop. This is
becomes more of a concern the deeper the motise, eg. timberframing.
Well these mortises are going into quadraliner posts I've constructed.
The post walls are 3/4" plus a 3/4" backer I put on the inside face to
recieve the tenon. What about making it a thru tenon except that the
end of the tenon is on the inside of the post? Any drawbacks? I
suppose that was about as clear as mud.
Welcome to the wonderful world of shitty hollow-mortising chisels. You
join a long line of forum posters. (No butting.)
The problem I had with mine was corrected by shrinking the diameter of
the cutting portion of the bit itself.
Notice when you rotate the bit within the chisel that the outermost
part of the cutting portion of the bit protrudes beyond the sides of
the chisel. Bad.
In order to correct mine, and three of the four provided with the
machine were defective, I chucked the bit into a hand drill, set it to
_reverse_, and with INCREDIBLY light pressure held it sideways against
some taped-down emory paper. Note the above capitalization...if you
put much pressure on that bit, and by 'much' I mean essentially any,
you will snap it in half like a twig, only the twig is sharp and
rotating at 2500 rpm. Also bad. They're just not meant to take much
lateral loading at all.
I used a very low speed (not 2500 rpm), very aggressive paper, wore
every piece of safety equipment I could find, including
industrial-grade high-impact safety goggles, and I think I may even
have been in a different room.
A safer solution would be to either have a sharpening service correct
it for you, or to file it by hand.
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