How to flatten coarse stones?

[LuptonM]

I recently purchased one of these http://www.edenwebshops.co.uk/en/pt/-na ... rit-46.htm to grind my chisels and small plane blades, but I have been unable to flatten the stone using sandpaper and consequently I messed up a few blades that now need regrinding. It cuts reasonably fast (faster than the ax-minster wet grinder), but the fact its got a large hollow in it now makes it a bit useless.

I am thinking of using a brick or paving slab to flatten it but has anyone got any better suggestions?

 

[custard]

What grade sandpaper were you using and how were you using it (ie glued to a float glass plate or just wrapped around a cork block)?

 

[Harbo]

46 grit- that is very coarse what are you using it for ?

Rod

 

[Jacob]

You do it by carefully distributing the wear, as you grind. Use the whole surface.
If you are having to flatten it you are doing it wrong, as it was a new stone and presumably was flat to start with.
You can still work it flat (whilst grinding chisels/blades) if you try, without having to remove any stone beforehand. Then you aren't wasting energy (or stone, or buying more kit).
You might need to freshen the surface occasionally (not the same as flattening) for which I find a 3m diapad ideal.

 

[Chrispy]

try a piece of glass thicker the better with silver sand (the stuff they put in the joints of block paving) a splash of water and a bit of elbow grease will soon flatten it.

 

[LuptonM]

I am using the stone to grind old chisels back to a 25 degrees primary bevel, from whatever condition I bought them in. I am using the a honing guide to grind them square and at the appropriate angle- I know this doesn't help the hollowing of the stone but I want a nice clean square grind. Its not like an oil stone jacob, the grit is quite loosely bound

I've tried 120grit paper on float glass, but the coarse stone soon tears through the paper. I've tried the coarse 100 micron stuff from workshop heaven on mdf but it wears that out in about 30 seconds.

 

[mickthetree]

In all seriousness, bin it. (or send it to Jacob) ;-)

I bought a course waterstone from Axminster some time ago. It cut fast, but wore so rediculously fast and took over 15 minutes to get back to flat it wasn't worth the bother. Trying to make it wear evenly will not work with a honing guide.

Stick that 100 micron film to the MDF and use THAT to grind your bevel and flatten the backs of your blades. Takes seconds. and gives a good square grind.

I use the 100 Micron for inital grinding, course diamond stone for blade backs, then use 800 and 1200 and 6000 grit waterstones to hone.

I use the course diamond stone to keep the waterstones flat.

Thats what works for me anyway.

HTH

 

[Jacob]

....Its not like an oil stone jacob, the grit is quite loosely bound .......

I know it sounds too obvious but why not bin it and buy an oil stone? They last for ever. You have to freshen them up though, as I said above. Every now and then.

I still don't see why you won't keep it flat in the old fashioned way. Wosser problem? Seems a bit crazy to insist on wearing out a hollow and then having to waste time (and stone) flattening it. Or to buy a stone to flatten a stone! Creating work unnecessarily.

I do my grinding on a belt sander - recently upgraded to a Sorby Pro-edge, which is just that bit more convenient.

 

[jimi43]

What they said....it probably cost you more in paper than the £11 for the stone in the first place.

Jim

 

[Jacob]

.....
I've tried 120grit paper on float glass, but the coarse stone soon tears through the paper. I've tried the coarse 100 micron stuff from workshop heaven on mdf but it wears that out in about 30 seconds.

But it's a 46 grit stone isn't it? In which case you need 40 grit to flatten it.
When you get the paper instead of flattening the stone just grind the tools on the paper instead.
Save yourself a lot of pointless effin about.
Eventually aim at getting an oil-stone, say goodbye to crazy sharpening and join the real world!

 

[bugbear]

I recently purchased one of these http://www.edenwebshops.co.uk/en/pt/-na ... rit-46.htm to grind my chisels and small plane blades, but I have been unable to flatten the stone using sandpaper and consequently I messed up a few blades that now need regrinding. It cuts reasonably fast (faster than the ax-minster wet grinder), but the fact its got a large hollow in it now makes it a bit useless.

I am thinking of using a brick or paving slab to flatten it but has anyone got any better suggestions?

You're grinding - so use a grinder (hand or electric), with a decent wheel (not the burn-prone piece of junk they're normally delivered/found with).

Larry Williams (who grinds LOTS plane blades for a living) has some widely distributed tips on technique.

At the risk of partially agreeing with Jacob - what you're doing is not your best bet.

BugBear

 

[dunbarhamlin]

Online, Google is your friend.

When grinding with coarse waterstones, Steamrollers are your friends. Taking care to align the stone square to the axis of the roller, place it in the roller's path. Caution: exercise due care to avoid drubbing the corners or cracking the stone. Now step back. Wave cheerily to the driver. Catalogue those tasks which might now fit into a schedule cleared of futile flattening of friables. Smile.

As an aside, when using silver sand or coarse SiC grit on glass, I like to use a sacrificial thin pane on top of my flat surface. Cheaper and easier to replace than thick float glass.

 

[Harbo]

Acrylic works well with SiC


Rod

 

[custard]

Larry Williams (who grinds LOTS plane blades for a living) has some widely distributed tips on technique.

BugBear

I think it was Larry Williams who said words to the effect of, "don't be scared of grinding, even if you blue the edge you've not ruined the tool, all you've done is just take the hardness down to that of a good hand saw, and on the next grinding you'll remove even that".

I always thought that was good practical advice. Since then I've cheerfully blued everything in sight! :lol:

 

[urbanarcher]

I might get slated for saying this but I've been known to remove the hollow in old soft stone using concrete floors /blocks etc give it some water and rub like buggery then you'll need to check if its flat enough if so great if not then rub some more with pressure in the right place.

 

[Jacob]

I might get slated for saying this but I've been known to remove the hollow in old soft stone using concrete floors /blocks etc give it some water and rub like buggery then you'll need to check if its flat enough if so great if not then rub some more with pressure in the right place.

As I keep saying - it's a lot easier if you avoid getting your stones hollow in the first place.
I don't understand why nobody seems to favour this option. Can anyone explain this?
People really do seem to like the idea of sharpening being difficult!

 

[bugbear]

As I keep saying - it's a lot easier if you avoid getting your stones hollow in the first place.

Have you met the other Jacob, who says a hollow stone is not a problem, but is needed for putting camber on blades?

BugBear

 

[Jacob]

As I keep saying - it's a lot easier if you avoid getting your stones hollow in the first place.

Have you met the other Jacob, who says a hollow stone is not a problem, but is needed for putting camber on blades?

BugBear

If you want to keep a stone flat it is no problem.
If you want a hollow stone this can be useful for camber.
Either way you can choose and control the outcome without resorting to corrective measures involving paving slabs, plate glass, silver sand, granite, steam rollers, or any of the paraphernalia of crazy sharpening.

To hollow a stone to the extent of making it unusable, used to be highly deprecated. Quite rightly too - it is entirely unnecessary. Just say NO, and stop doing it!

 

[Jacob]

I keep editing the above (bin out all day, back now having a drink). So another post instead.
To say - I've been raising these points for some time but nobody yet has explained why it is necessary and unavoidable to hollow stones. Seems such a waste of time, effort and stone.

 

[Tom K]

Its like ***** Jacob it happens and then you deal with it #-o