SDS chisels - sharpening

[The Medway Handyman]

Couple of questions re SDS chisels.

They don't seem especially 'sharp' from new, but I guess this is not required for masonry. After a short time they become blunt objects & I sharpen them with an angle grinder.

Is there a specific degree of 'sharpness' required for masonry use?

Second question, I frequently come across tree roots that need cutting. How would I sharpen a wide SDS chisel to cut through?

I can grind the edge to a very sharp edge, but do I need to harden them in any way? Quenching & stuff?

[John Rumm]

Prefer a bench grinder myself, but I am sure the angle grinder does the job nicely... Try not to overheat the end (of you or the chisel! ;-))

I usually copy the original angle - about 45 degrees each side (i.e. the point being about 90 degrees).

Perhaps buying a SDS wood cutting chisel would be a better starting point - I would guess they will tend to have more temper than the normal masonry ones.

(a green wood blade in a reciprocating saw works a treat on roots)

Not my area of expertise...

[meow2222]

they're already hardened & tempered. Take care not to get it too hot when grinding and no need to do anything.

NT

[Bob Minchin]

Decent SDS chisels should be correctly hardened and tempered from new. Take care when sharpening not to get them too hot as this will draw the temper and soften them a bit. Don't sharpen them to too much of an acute angle. This will give a weak edge that will blunt quickly. You DO want an acute angle and a razor sharp edge for tree roots but this is not really the right tool for that job. If you must SDS a tree root then buy and adapt a chisel for that job alone.

hth

Bob

[newshound]

The screwfix SDS wood chisel goes through roots like a knive through butter, also for extracting old oak lintels. I had a chisel shank fail in fatigue during one particularly brutal job (but they are cheap considering the time they save).

[Andy Dingley]

They're not strictly chisels, as they don't form a cut chip. What they do instead is to concentrate the force into a small area so that the stone "crumbles" You need a narrow edge, you don't need anything remotely sharp. Unless they've started to turn back into a burr, you don't need to even try sharpening them.

Buy some SDS wood chisels (Bosch do a set) Different shape, different temper.