sharpening stones

[wallace]

During my workshop cleanup I found a few stones all in their own wooden boxes. What is the best way to clean then and flatten them. Can they be boiled.

 

[Lurker]

During my workshop cleanup I found a few stones all in their own wooden boxes. What is the best way to clean then and flatten them. Can they be boiled.

Paraffin and a scrubbing brush works.
If you can find a concrete paving slab that’s nice and flat. I found a scrubbing motion in all directions worked well. Don’t get too hung up about flatness.

 

[Mike Jordan]

I think flattening is best done with yellow building sand and water on piece of thick glass. It takes time to do but is important. You can sharpen plane irons on a worn stone but chisels must have a flat back face.

 

[Argus]

I may be wrong..... and I hope that I don't start a 'Sharpening debate',....but old (from pre-honing-jig-days) oil stones were frequently worn hollow across through decades of use, not necessarily wear.

Sharpening by hand on one of these stones usually results in a slightly concave bevel on your chisel or plane as a result .

Unless a user is wedded to using honing jigs and the wear is excessive, is an old 'hollow' stone unusable?

 

[AndyT]

The answer, I think, depends on the stones.

They could be man-made or natural, coarse or fine, hard or soft.

If there is a glazed layer of old steel dust and dried oil, it can be cleaned off by brushing, or with solvent, or detergent, just like you would get old dried oil and rust off old machinery or tools. I'd advise the obvious, of starting gently before getting more drastic. Heat might speed things up but in a man-made stone I don't think it would help the background matrix that binds the abrasive particles together.

For flattening, if you have decided it's necessary for the way you want to use the stones, the best modern options are coarse hard abrasive cloth/paper, or a coarse diamond stone, now widely available for very little money.

 

[Mike Jordan]

This is a Norton Abrasives “India medium” oilstone which was 25mm thick, it’s had 53 years of wear and flattening.

 

[Trevanion]

WD40 and a good scrub will clean off the surface layer of gunk off most stones, man-made stones like India stones can be a bit more involved as they're more porous than natural stones and if they haven't been looked after (typically from using too heavy of an oil or contaminated oil, I.E. used engine oil) they can be quite gummed up and prone to not cutting very well.

Flattening a stone is a contentious topic, but I personally prefer my stones flat and I've done it using a cheap Faithfull diamond plate, a bit laborious but you'll get there in the end.

 

[Cabinetman]

I flattened mine on a bit of sandstone with grinding paste on it, didn’t take long at all really. But when I had finished I wondered why I had bothered as I realised I’m not one for using the whole length of the stone anyway, and as long as I’ve got a small area that’s flat to do the back on, the shape of the stone doesn’t seem to bother me.

 

[Woodbloke]

Flattening a stone is a contentious topic, but I personally prefer my stones flat and I've done it using a cheap Faithfull diamond plate, a bit laborious but you'll get there in the end.

I'd agree; I've just bought some Shapton Pro ceramic stones together with a coarse Atoma diamond plate and it's dead easy do do a couple of swipes with the diamond plate each time they're used. I've no experience of trying to sharpen on a very old, dished India stone as using a stone that's always 'flat' makes the whole process, IMO, so much easier. Hoarses for dooberies as ever with this sort of topic :eusa-whistle: - Rob

 

[wallace]

Many thanks for all the advice. I recently got one of those diamond dressers used for surface grinders to true the wheels on my holroyd grinder. I just thought I could always put it in the recessor and flatten the stones.