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Reclaiming hook angle on bandmill blades.

Started by Delawhere Jack, March 08, 2017, 06:26:46 PM

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Delawhere Jack

This might be useful to some of you guys who sharpen their own bands. If you get lazy about keeping the grinding wheel profiled, and the corner nearest the tooth gets rounded, you can end up with this.


 

The interface at the root of the tooth and the gullet gets rounded. The tooth also has 0 degrees hook angle. Having the band clamp set too loose can also contribute to this, as the band will slid forward as the rock makes contact.

Color me guilty....  ::) Anyway, this not only makes the bands less efficient, it can result in them breaking in use.

So I've been putting these bands aside in the junk pile corner of the basement. Now I've figured out how to restore them. I replace the grind rock on the sharpener with a Lenox 4" diamond wheel cutter.


 

The arbor hole is 5/8" on this wheel, and my arbor on the sharpener is 1/2". The little piece of wire under my thumb is a piece of bailing wire, which conveniently happens to be exactly 1/16" thick, used as a spacer.

I put the mis-sharpened bands on the sharpener and adjust the feed paw so that the diamond wheel drops down right along the point of the tooth, and adjust the drop of the wheel so it will just cut to the root of the tooth. The little hand wheel that tensions the band clamp has to be locked down tight for each tooth. Otherwise the band will shift under the diamond wheel, same as it does under a grind rock.


 

It's a bit tedious -- advance band, lock clamp, drop wheel, raise wheel and lower it again, release clamp, advance band, repeat. It takes about 3x's as long as a regular sharpening, but I'm saving a band that still has a lot of life in it. Here is a band after reclaiming the proper tooth angle, followed by a regular grinding. Looks almost like new


 

bandmiller2

Jack, what do you use for a grinder home made or store bought. I think maybe you grinding wheels are a little soft and wear too quickly. You are right though as the side of the wheel towards the tooth wears you will loose hook. I check mine often with a protractor head and can adjust my cats claw to compensate. I use the Cooks blue ceramic wheels and they seem to last forever I can sharpen at least 50 bands before replacement. Frank C.
A man armed with common sense is packing a big piece

Delawhere Jack

Frank, I use a home built sharpener with Cooks blue wheels. Guess I've been a bit lazy about dressing the wheel. I might try one of their harder grinding wheels, but I just bought three of the blue ones a few months ago.

A reminder for those just starting to sharpen their own bands. As I mentioned on the FF a couple years ago, the arm carrying the grinder should be set with 1 1/2 - 2 degrees more angle than the tooth you're grinding. That way you can set the stone to just barely kiss the face of the tooth just as it it is lowered to the root of the tooth. This helps minimize rounding over the corner of the stone.

bandmiller2

Jack those Cooks blue ceramic are about as hard and durable as your going to find. I do little dressing, but use a diamond grit dresser that shapes the wheel quickly Frank C.
A man armed with common sense is packing a big piece

jaygtree

i thought i was wrong once but i wasn't.   atv, log arch, chainsaw and ez boardwalk jr.

Delawhere Jack

Used 4 of these bands yesterday on some wide oak and poplar. They cut like new.

Should also mention, bands need to be thoroughly clean before sharpening. Any sap on the band will cause them to drag while passing through the band clamp resulting in poor profiling. I've started filling my utility sink about 1/3 full and mixing in 1lb of lye. Soak three bands at a time for 20-30 minutes, then rinse and go over them with a scrub brush in the other half of the sink. Excellent results.

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