On Wed, 4 Nov 2020 07:41:37 -0500, "Jim Wilkins"
wrote:

I'm trying to design a sharpening jig for my bandsaw mill blades that uses a
hand-held Dremel as a cam-guided router. I think I know how to make the
positioning fixture, and mill a cam to guide a bearing on the bit shank, but
I have no experience with milling moderately hard wood saw blade steel, or a
worn-out blade to practice on. Presumably the choices are ceramic or diamond
grinding bits or HSS or carbide milling cutters. The gullet curve has a
minimum radius of 3/32" which I'd like to preserve by using 1/8" or 3/16"
cutters so the blades can still be resharpened without difficulty on
commercial equipment.

The cam milling setup would be a pin the diameter of the cutter bit clamped
upright on the milling machine table, centered under an endmill the diameter
of the routing bit shank bearing OD, like 0.500. I have a short section of
new blade to clamp under the cam blank to trace the gullet shape against the
lower pin, and once the straight front and top rake sections have been
started they could be extended beyond the tooth tip by clamping the blank at
the 30 or 8 degree rake angle and moving the table. The limitation is that
there's no way to adjust for wear on the bit beyond moving it endwise in the
collet, thus an HSS or carbide cutter should be better than a stone IF they
hold up long enough.

The teeth have to be set sideways and perhaps reset to the opposite side so
they are are soft enough to file, which I just confirmed. My Scleroscope
doesn't measure the Rc hardness of objects less than ~1" thick reliably even
if they are solidly clamped in the milling vise. I checked it against
samples of known hardness while taking blacksmithing classes.
http://www.detroitflame.com/HardnessTester.htm

The shop that sharpens my blades told me they recently replaced some old
equipment, so maybe the problems I'm having will be gone when my resharpened
blades arrive next week.

A Dremel moto tool would be a poor choice for this aplication. I say
this because I just made up a half dozen blades for my 12" band saw
(wood) by silver soldering new and used 1/2" bade stock. I grabbed the
Dremel to clean up the joint after it cooled. On the second blade I
tried a mounted stone in my el-cheapo air powered die grinder and
finished off the five remaining blades in less time than it took for
the first blade. The Dremel just doesn't have the oomph that the die
grinder packs, plus the 1/8" spindled stone is about a quarter or less
the mass of the 1/4" mounted die grinder item.
How did I ever live in my shop before I got my old Gardner-Denver
compressor for $3 and spent ~$75 to get it up and running!