On 11/4/2020 5:41 AM, 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.



While I don't have direct experience I can refer you to YouTube where
there are a few bandsaw mill blade sharpening videos. A few show
commercial sharpening systems that I found to be very educational. Most
seem to us a diamond blade or wheel. The time per tooth for basic
carbon or even HSS teeth is very short.

I think a simple ratchet dog and a quick clamp would work for indexing.
Set the angles for your sharpener twice per simple blade. Once for left
set and once for right set. Due to varying blade lengths the tooth
count may not come out even so always remember to paint/mark your blade
so you don't start accidentally reverse sharpening teeth when you get to
the end.

For my upright and horizontal bandsaws I have pretty much decided that
sharpeni8ng is not worth my time when I can buy M42 blades made to
length. If I had a large gap (low pitch) bandsaw mill blade I might be
tempted to sharpen. I do have one carbide tooth blade that might
marginally be worth sharpening instead of replacing... and its dull.


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