India stone needs truing back to flat...

[dataphage]

My grandfather left me some of his tools in his will amongst which was a large brown India Oilstone (about 600 grit and cuts extremely quickly). There is one dawback, because of its age (pre war) this stone is no longer flat.

It is so hard that I haven't got a clue how to get it back to a useful shape - it laughed at wet & dry paper and coarse aluminium oxide paper. When I got it under a powered sander at home all it did was polish it. Does anyone have any experience or have any suggestions on how I can flatten it?

 

[Hoodoo]

Just sharpen your knives on each end and in about 10 years... :-D

I dunno. There are ceramic stones out there designed for flattening water stones. Maybe they would work on your india stone? Diamond bench stones are also used to flatten water stones and again, they might work on your stone. But is the price and the work worth the effort? Those dished stones aren't too bad for using on convex-ground knives. A 600 grit sounds pretty good for honing a convex edge.

 

[ESpy]

A handful of sand and a flat area of concrete. Round and round and round we go....

 

[C_Claycomb]

Peter, he wants to flatten the stone, not make a hole in the paving slab :-D When I did that with my water stone it made if flat, but took all the surface off the concrete and made it nice and smooth.

Anyone think that maybe a stone used for dressing bench grinders might work? It is too small to flatten it totally, but it might work the stone down a bit?

I know that you used to be able to get carborundum powder for lapping things flat. Not sure if it would work on a stone though.

Maybe Hoodoo is right. Those convex edges are the devil to get with a flat stone, maybe you have something going there :-D

 

[ESpy]

Peter, he wants to flatten the stone, not make a hole in the paving slab :-D When I did that with my water stone it made if flat, but took all the surface off the concrete and made it nice and smooth.

Oops, sorry - someone *else's* flat bit of concrete... :twisted:

Slabs work - they're a lot less friable than the older India stones. The newer ones are very hard and not terribly friable.

Anyone think that maybe a stone used for dressing bench grinders might work? It is too small to flatten it totally, but it might work the stone down a bit?

Dunno, I've only ever used diamond point & whatsity wheel dressers.

 

[woodsitter]

I have no idea.

Why the reply? Well, I live next to a diamond polishing factory (I live in the former Jewish quarter of Amsterdam) and about once a week they punt a crate on the side walk with their old grinders, waiting to be picked up by a van coming from Antwerp (the other diamond capital in Europe).

Now these grinders look a bit like spindle, a heavy steel axis thru a inch thick disk about 40 cm in diameter. They look like theirs just plain steel but I only see them when they are worn out, ready to be recycled. You can get a tour in the shop and watch them polishing the diamonds. They fix the diamond in some sort of handle and push it on the grinder, check it with a magnifiing glass and push it back on again, (and again and again).

Anyway, they carve, grind and polish diamonds with it. You can't get it any harder than that. I will not nick anything of my neighbours of course, but the thought occurred to me that it might be useful in sharpening knives hatchets of even flattening stones.

 

[MartiniDave]

Is it the kind of stone thats set in a wooden block? If so you may be able to carefully price the stone out and turn it over, revealing a new, flat surface. Of course, your grand father may have already done this.

I would be tempted to keep it for concave blades, and get a nice japanese waterstone from Axminster Powertools for your scandinavian blades.

Dave

 

[dataphage]

It is a free standing stone Dave and yes, both sides and both edges are bowed.

The stone has been used to sharpen woodworking chisels and so is sadly bowed along its length but accross its breadth as well, chisels being generally less wide than than the stone, making it fairly useless even for convex edges.

I think I may take your advice and buy (another :roll: ) waterstone and keep that one for chisels!

woodsitter - When I was at university we called it "creative acquisition" - though you may want to check with them before creatively acquiring a grinder - there is a minor industry in reclaiming diamonds from grinders & drills & they may being recycled

 

[C_Claycomb]

I have found that having a dead flat stone was far and away more important for sharpening chisels than it was for knives. Keeping the back of chisels flat is very important if you want them to perform at their best. I like to keep the main bevel dead flat too, no secondary bevel on the chisel.

Sorry that we haven't been able to help much. Oil stones do seem to be fairly difficult things to work with. Harder to keep flat and messier to keep lubricated.