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General sharpening direction help

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choochoo_baloo12/09/2021 11:38:57
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270 forum posts
57 photos

I’ve been reading up and watching videos and sharpening various workshop tools Working through my various scissors using the DMT mini hones. However there is an inconsistency (which is never good in this hobby of ours!)

DMT say scissors/knives should be stroked back from the edge/edge first.

Whereas a lot of woodworkers sometimes sharpen plane blade & chisels edge first on first grind (eg a Tormek water cooled wheel), but then final grind is back to edge/edge last on a waterstones.

My thinking is that sharpen any blade shouldn’t matter on the tool; it seems natural to do edge first strokes throughout, so that burrs are pushed away from the edge. Is this correct?

Any comments gratefully received.

Dave S12/09/2021 11:46:30
266 forum posts
56 photos

Depends if you want the burr or not. I was taught to do chisels so the burr was there, it giving a razor edge.

Similarly cabinet scrapers actually use the burr as the edge (although generally deliberately hooked over)

The burr edge is of course not very strong, so I guess less frequent sharpening with the compromise of slightly less sharp is a way to think of it.

Scissors of course cut by shearing, so require a fairly blunt angled edge, but with a good corner - a burr on that would not work.

Dave

Martin Kyte12/09/2021 12:25:20
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2609 forum posts
45 photos

You don't want a burr on chisels or scissors. My chisels are finished on a leather impregnated with honing compound. A few strokes side to side with back of the cisel removes the burr. Scisspors are a different animal. I tend to sharpen scissors diagonally along the edge. They are always a little 'gritty' for the first cut but any raggged edge is removed very quickly. They always cut fine. Don't however grind the face of the scissors. They should be hollow ground and should meet from back to tip progressively. When closed there should be a curved gap between the blades except at the extreme tip. Knives are a little different. My Kitchen knives always have a slight ragged edge from the steel sharpener. This tears the skin of things like tomatoes and they slice far more easily.

regards Martin

Howard Lewis12/09/2021 13:31:23
5562 forum posts
13 photos

Scissors, and garden shears, by their very name, are different from chisels, plane irons and drills, end mills or slotting drills.

These latter are ground with two reliefs. (In this context drills are meant be four facet ground )

The usual advice is to grind the larger secondary clearance first, followed by the smaller primary clearance. In this way a four facet ground drill shows a chisel point.

Scissors cut by shearing the material, so have only one clearance angle. If grinding / honing produces a slight burr (A "Wire Edge" ) the usual advice is to wipe the edge across a piece of wood to remove the burr without affecting the actual cutting edge. The same technique would be applied to a plane iron or wood chisel.

This should produce a set of shears which will cut paper, if not human hair!

Rotating cutters tend to be ground either along the edge or away from it so that no burr is produced.

Howard

Zan12/09/2021 13:52:52
293 forum posts
19 photos

Double angles on chisels etc are there to make the final honing on oilstones easier and quicker so there is less chance of rounding the edge with less material removed to get them sharp. Chisels a have burr and is removed by a quick running on the edge of the wooden housing for the stone along ithe edge length. The old workers with leathery hands would then use their hands as a strop as indicated above. When sharpening a classroom set of chisels one becomes very quick at the sharpening process and the pre grinding becomes more important .

sharpening invariably caused burr due to the tool being moved in both directions on the stone. While your at it, a figure of 8 pattern will preserve the stone, and cause crossed micro scratches meaning less stropping is needed

bernard towers12/09/2021 14:39:34
343 forum posts
89 photos

Just to be awkward Howard I sharpen my drills the opposite way round, front face first then clearance face as I find that as you are grinding a larger area of material you have a bit more control. More than one way of skinning a cat eh!

Robert Butler13/09/2021 23:19:22
303 forum posts
6 photos

Rather a general question which appears to relate to hand tools. The correct answer will depend on the edge you are trying to create or restore. Tormek have a good reputation and have a vast array of jigs (at suitable prices!) and their instructions are concise.

Sharpening tooling for Lathes and Milling Machines is another matter

Robert Butler

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