What's wrong with this idea?[sharpening]

Folks,
Don't think I've heard of anyone doing this, so I'm guessing there's a reason!
I'm thinking of picking up a combo sander (likely 6x48 belt + 9" disk); how would the disk work as a way to establish a primary bevel on either chisels or plane irons?
I know rpm is going to be a factor -- I've looked at several combo units; the rpm of the disk has either been 1720 or 3450; I would think with care, I could avoid too much heat, especially with a 1720 rpm unit.
So, what else am I missing? Any thoughts, horror stories, or words of encouragement?
Regards,
JT
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IIRC a pretty common prractice. The closer to the center of the disk, the less heat from cutting speed.
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Only reason I can think of is metal residue getting onto wood. I've used my sander for metal with good results. I have a belt sander also and it sharpens the lawnmower blade a couple of times a year.
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On Wed, 20 Oct 2004 19:28:27 +0000, John Thomas wrote:

Sharpening books mention belt sanders. If you have the combo, why would you want to use the disk? Lacking a belt sander, I use a sanding disk in my clamped electric drill to shape carving blades. It's ugly, but it does work. I wouldn't touch a plane iron to the contraption, though.
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You have heard of "Scary Sharp" ??? Well, with your method, it's "Really scary to Sharpen" but I must admit that my hoe(ho) and my axe(ax) get a little of the old 6x48 from time to time.
Just be careful... You don't want to be flinging(throw) any sharp tools at yourself during the operation.
Of course you will be wearing safety glasses during this.
John Thomas wrote:

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But of course! I'm married to Mrs Safety. And that's a good thing.
Seriously, I've gotten some good input so far, thanks everyone!; Regards, JT
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On Wed, 20 Oct 2004 19:28:27 +0000 (UTC), John Thomas

just fine.
be extra careful about heating the steel.

keep a water can at hand and cool it before it gets hot.

the cost of the disks? this could end up being a pretty expensive way to grind blades.

there will be some technique issues that are pretty much specific to this setup. go slow at first.

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One caution: Don't be stupid as I was and leave a dust collection bag on the sander. My belt sander bag now has several patches. Sparks and sawdust don't mix.
Don
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I use my 6x48 belt sander exclusively for primary bevel on plane blades. Built a jig that mounts on the sander to hold the blade at a 30 degree angle to the platen.
scott
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John Thomas wrote:

I've been doing this for a long time. A belt sander is a fast way to really screw up an edge, so that's why I use a suitable angle guide.
I have a 4"x36" combo with 6" discs. I drilled/tapped holes onto the side of the platten for mounting an auxiliary table. I mount a plane blade or chisel in a Lee Valley angle jig flummy, then I put the initial bevel on it on a 100 grit belt. I find I rarely have heat problems, and can just about leave the blade in contact with the belt continuously. On smaller edges that heat up faster, a rocking sand-rest-sand-rest motion is sustainable pretty much forever without overheating. I don't think I've burnt an edge yet.
The auxiliary table isn't exactly in the same plane as the belt, and the thickness of the belt, and the little hump where the seam is all conspire to produce an angle that's a little off compared to the target. However, it does the muscle work, and I can run through the rest of the grits (from 100 again up through 2,000) pretty quickly to put on a perfect mirror edge that can cut the hair off a gnat's ass. The beauty of my system is that the tool stays in the same angle guide throughout both phases of the operation. It does introduce small errors, as I've said, but I feel like these are easier to cope with than having two completely different angle setups, and trying to keep both of them in sync.
I've been sharpening things this way for a pretty good while now, and it works fine for me. With the sander you're talking about, it might work even better. Larger belt, more surface area to dissipate heat. I would guess. Motor speed and roller size could both add up to your sander tearing up ground a lost faster than mine. YMMV. Caveat emptor. Batteries not included. Not all parts included with all sets. Color and finish may vary from those depicted here. Some assembly required. DANGER: SHARP EDGES. The lacquer finish is not covered under warranty.
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On Wed, 20 Oct 2004 19:28:27 +0000 (UTC), John Thomas

Badly. The variation in surface speed is too great across the width of the disk, relative to the width of a plane iron.
The belt will work though. . Try the knifemaking group, rec.knives. Most professional knifemakers are working with a slack-belt linisher.
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on that small of a disc for sure. plus the abrasive will wear pretty fast too.
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If you use the unit for woodworking also, just be careful that sparks from grinding metal don't ignite any sawdust. Otherwise, just use the smae precautions against overheating the steel that you would use with a regular grinder.
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Larry Wasserman Baltimore, Maryland
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