Flattening sh***pening stones

[Cheshirechappie]

One 'old' way of flattening oilstones was to use a handful of sharp sand (it must be the sharp stuff - crushed rock, effectively - rather than the rounded-off beach sand or soft builder's sand) with a splash of water on a flat surface of some sort. I'm not sure this would an answer to the OP's problem, since it would, I imagine, take a fair bit of work. However, once flat, most oilstones wear only slowly, so it wouldn't need to be done very often.

Sharp sand can be bought in small bags in garden centres quite cheaply. Probably easier to get hold of than graded silicon carbide powder, and certainly a lot less expensive. One bag would last several lifetimes if only used for stone flattening.

The quick answer would be a large grinding machine equipped with a diamond wheel and flood coolant. They're not ten-a-penny, though. I quite like the idea of a belt sander to take the bulk off, but I think to finish to the degree of flatness most people would regard as acceptable in a bench stone would need a final hand-lapping session with abrasive grit of some sort on a flat surface.

 

[Carl P]

I've flattened slate & washita stones with 100 wet n dry on glass with water, it seemed reasonably quick to get the worst out.

Cheerio,

Carl

 

[Fat ferret]

I have two oilstones the same. Every once in a while I slaver them in WD40 which lifts the rubbish off and rub them together which makes them orange again. They cut better after.

This way they don't get badly out of true.

 

[Billy Flitch]

I`ve seen people use the method that Fat ferret describes and Ive used it my self and it does seem to refresh the cutting edge of the stone.But I don't think I would try and flatten them like that just to laborious for me.
I can remember a while ago being at a craft fair and a Lady was polishing stones on a machine about 12" square that had a little table on the top of it, the table vibrated and had some form of abrasive on top of it and water it really did polish the stones up so you could see the pattens in the stones. How long this took I have no Idea I didn't hang around.
I can remember thinking that it would be ideal for flattening a oil stone but I`ve never seen one since, but to be honest I haven't been looking for one.

I thought I would tell you this little story that happened to me when I was a young apprentice. I was working on the bench with a old hand, the first shock for me was he was using a butt chisel I`d never seen one before and I just thought " god he`s wore that chisel away there".Any way he wasn't happy with the edge on it so he put his oil stone on the bench and took the lid of it What I saw shocked the life out of me I`d never seen any thing like before or since. Talk about dished this stone was like a ski jump you didn't need a straight edge he was at one end of the bench and I was at the other and I think I would have seen it if I was at the end of the shop. He just spat on the stone and gave it a few rubs felt it with his thumb and lapped it on his hand in front of him.

I was in a total state of shock talk about gob smacked, I don't think any one else in the world could have used that stone and got a edge on a tool. About the only thing I learn t from that was given enough time I think you can get use to just about any thing and his sharp edge tools where sharp, strange old world.

 

[D_W]

I thought I would tell you this little story that happened to me when I was a young apprentice. I was working on the bench with a old hand, the first shock for me was he was using a butt chisel I`d never seen one before and I just thought " god he`s wore that chisel away there".Any way he wasn't happy with the edge on it so he put his oil stone on the bench and took the lid of it What I saw shocked the life out of me I`d never seen any thing like before or since. Talk about dished this stone was like a ski jump you didn't need a straight edge he was at one end of the bench and I was at the other and I think I would have seen it if I was at the end of the shop. He just spat on the stone and gave it a few rubs felt it with his thumb and lapped it on his hand in front of him.

I was in a total state of shock talk about gob smacked, I don't think any one else in the world could have used that stone and got a edge on a tool. About the only thing I learn t from that was given enough time I think you can get use to just about any thing and his sharp edge tools where sharp, strange old world.

The stone in the picture above would be easily usable as is, but there's been a fair amount of inaccurate information presented by folks telling beginners that they must flatten and have perfectly flat stones all the time. The old stones like the one above are hollow along their length, but not across their width, and they are 2" wide instead of 3 to promote that. A stone that's hollow across its width is difficult to use well, but one like the picture above hollow along the length is not, especially if it's the last stone used - some part of it needs to be able to touch the wire edge on the flat side of the iron, but that's about it.

I have bought a lot of stones, maybe more than 100, including barber stones that would never have been used by an amateur and quite a lot of even the most delicate things (Straight razors) were sharpened on stones like the one above. That community also provides the advice that people need to "power up" on a large progression of stones and flatten them religiously. The old hand you're talking about probably would've thought we were wasting our time flattening stones, and he's probably right.

 

[heimlaga]

I use a piece of 40 grit belt sander band flat on a piece of mild steel plate. I dip the stone in water every now and then as i work.

Works pretty good for my fairly soft Västilä stones....... but I think that for hard Arkansas stones you would probably need a better way.

 

[deema]

All my stones are of the 3" wide variety, the problem I have is that they wear to be out of flat across their width. To correct this I have to flatten the whole stone again.

I hand sharpen so a dished length ways stone is not a big issue, however dishing across the width is as I want to contro, the camber on the blade myself. I can see thanks to the advise and links provided that a DMT 10" x 3" stone can be obtained for about £70. Two questions

1. What grit is best? Course, XCourse of something else?
2. I know diamonds are one of the hardest substances in existence, but, will using them in stones cause a problem. I bought once upon a time some small diamond stones from Axi and wore them out in a week. That was about 7 years ago!

Thanks

 

[D_W]

I don't favor any diamond hones for significant amounts of oilstone work, especially DMT. They become worn fairly quickly.

That said, I have a 220 bench stone that I use after following up with coarse work on any oilstones that I find. I also have one of the 325/600 combination DMTs that I would not want to use for any kind of flattening work, it became very tired very quickly and is very slow now.

220 would be my answer. Hard stones that are not fine are always hard on diamond hones.

 

[yetloh]

These makeshift solutions such as concrete slabs don't appeal to me because I can't see much point in flattening a stone with something that is not truly flat itself - it is ofcourse true that flatness only matters across the width of the stone - but most people will hollow a stone in both length and width. I use a 120 grit DMT diamond plate (much cheaper from Dictum or Dieter Schmidt) and it is fast and effective. On water stones at last, they last a very long time and in my view, are well worth the money. Lifespan may of course be different with natural stones.

Jim

 

[Jacob]

You don't need to flatten oil stones ever, if you just stick to normal freehand sharpening. You spread the work about to keep them reasonably flat. They often end up dished from one end to the other but this doesn't matter much.
If you've got a diamond stone I'd use it for sharpening and not waste it pointlessly flattening oil or water stones. It's a waste of diamond stone, a waste of time and a waste of oil stone; they last for life normally but won't if you keep flattening them every time they are less then flat.

However it's good to freshen up an oil stone every now and then and I use a 3m diapad. They seem to last forever and are bendy so they follow the dips and hollows. A flat rigid diamond stone is useless in this respect.

 

[D_W]

These makeshift solutions such as concrete slabs don't appeal to me because I can't see much point in flattening a stone with something that is not truly flat itself - it is ofcourse true that flatness only matters across the width of the stone - but most people will hollow a stone in both length and width. I use a 120 grit DMT diamond plate (much cheaper from Dictum or Dieter Schmidt) and it is fast and effective. On water stones at last, they last a very long time and in my view, are well worth the money. Lifespan may of course be different with natural stones.

Jim

I think stones can fit in two categories - 2" stones which were very deliberately that width because they were used by freehand sharpeners.

And now 3" stones that are sold so that an individual who doesn't understand much can run an entire jointer blade back and forth on them and not have to think about too much.

The trouble is the 3" stones get hollow across their width unless a freehand sharpener plays attention to the wear pattern on the stone. With an oilstone, this is a nuisance.

I don't have any significant amount of hollowness across width on my oilstones, and I presume not much along their length though I haven't measured, and the oilstone I've used the most has only gone a little more than a year without flattening.

As far as concrete blocks go, some of them are probably flatter than the low cost diamond hones. At least in the states they are. The forms are very flat. I wouldn't use them for anything other than a soft stone, and only in a pinch (it would seem to me that they could just waste stone off).

Japanese natural stones of any value have always been 3" wide, I'm not sure what the virtue is there. Their market has almost no regard for a 2" wide stone (it literally costs 1/4th or less the amount of an identical weight stone 3" wide, and it doesn't seem at all unreasonable for me to sharpen japanese planes on such a thing).

 

[Beau]

You don't need to flatten oil stones ever, if you just stick to normal freehand sharpening. You spread the work about to keep them reasonably flat. They often end up dished from one end to the other but this doesn't matter much.
If you've got a diamond stone I'd use it for sharpening and not waste it pointlessly flattening oil or water stones. It's a waste of diamond stone, a waste of time and a waste of oil stone; they last for life normally but won't if you keep flattening them every time they are less then flat.

However it's good to freshen up an oil stone every now and then and I use a 3m diapad. They seem to last forever and are bendy so they follow the dips and hollows. A flat rigid diamond stone is useless in this respect.

If you let your stone get dished how do you polish off the burr from sharpening?

 

[Jacob]

You don't need to flatten oil stones ever, if you just stick to normal freehand sharpening. You spread the work about to keep them reasonably flat. They often end up dished from one end to the other but this doesn't matter much.
If you've got a diamond stone I'd use it for sharpening and not waste it pointlessly flattening oil or water stones. It's a waste of diamond stone, a waste of time and a waste of oil stone; they last for life normally but won't if you keep flattening them every time they are less then flat.

However it's good to freshen up an oil stone every now and then and I use a 3m diapad. They seem to last forever and are bendy so they follow the dips and hollows. A flat rigid diamond stone is useless in this respect.

If you let your stone get dished how do you polish off the burr from sharpening?

On a flat enough part of the stone.
It would be perfectly possible to remove the burr even on a spherical stone, if you had to. Not that I recommend it particularly! Though come to think I sharpen a scythe with a tapered rod shaped stone. If that's all you had you'd find a way with plane blades and chisels too.

Modern sharpeners are beset with strange rituals, imaginary problems, fears and anxiety. It makes it easy to sell them stuff.

 

[Beau]

Modern sharpeners are beset with strange rituals, imaginary problems, fears and anxiety. It makes it easy to sell them stuff.

Agreed but IMO keeping the backs of chisels and plane irons flat is very important and trying to do this on a dished stone is nigh on impossible. For instance trying to do paring cuts with a chisel with a convex back is a complete pain in the rear end.

 

[MIGNAL]

Just go across the stone. Think about it. Even if you had just one point of contact on the stone (highly unlikely) you would be able to remove a wire edge.

 

[Beau]

Just go across the stone. Think about it. Even if you had just one point of contact on the stone (highly unlikely) you would be able to remove a wire edge.

Completely disagree. Sorry

You need a flat and I mean flat stone to remove a wire edge consistently. You might get away with it to start with but the back of the blade will soon become uneven so removing the wire edge will be very hit and miss. Been there and done it but now very careful about dressing the stone. You can minimise this by doing the back on the ends of the stone that don't get much use when sharpening the bevel.

 

[Jacob]

Modern sharpeners are beset with strange rituals, imaginary problems, fears and anxiety. It makes it easy to sell them stuff.

Agreed but IMO keeping the backs of chisels and plane irons flat is very important

Exaggerated. It's part of the new sharpening belief system.

......For instance trying to do paring cuts with a chisel with a convex back is a complete pain in the rear end.

Have you tried this? Most old chisels have very slightly convex faces - presumably no problem to the original user but does seem to bother the new sharpeners. This perfectly flat and polished face idea is just a new fad.

 

[Beau]

Modern sharpeners are beset with strange rituals, imaginary problems, fears and anxiety. It makes it easy to sell them stuff.

Agreed but IMO keeping the backs of chisels and plane irons flat is very important

Exaggerated. It's part of the new sharpening belief system.

......For instance trying to do paring cuts with a chisel with a convex back is a complete pain in the rear end.[/quote]Have you tried this? Most old chisels have very slightly convex faces - presumably no problem to the original user but does seem to bother the new sharpeners. This perfectly flat and polished face idea is just a new fad.[/quote]


Yes of course I have tried it. Been a professional make for 25 years so tried most things. I am a fussy git and if I did joinery could probably wing it with a squiffy chisel but I am cabinet maker where precision matters.

 

[MIGNAL]

Just go across the stone. Think about it. Even if you had just one point of contact on the stone (highly unlikely) you would be able to remove a wire edge.

Completely disagree. Sorry

You need a flat and I mean flat stone to remove a wire edge consistently. You might get away with it to start with but the back of the blade will soon become uneven so removing the wire edge will be very hit and miss. Been there and done it but now very careful about dressing the stone. You can minimise this by doing the back on the ends of the stone that don't get much use when sharpening the bevel.

No you don't need a flat stone. Let's approach it another way. Lets say we have a wire edge on a 2" wide plane blade. Let's lay the blade on the bench, wire edge facing up.
Now let's take a very narrow diamond needle file and run it across the entire width of the blade.
The diamond needle file is far too narrow to be termed 'flat' in our sense, yet it will remove the wire edge and it won't cause a hollow. Don't forget that when you are using a sharpening stone there is a degree of 'averaging' that goes on. Unless you are very careless the hollowness across the width of a stone is never going to be problematic, even then I doubt that it will be problematic anyway.

 

[Beau]

Just go across the stone. Think about it. Even if you had just one point of contact on the stone (highly unlikely) you would be able to remove a wire edge.

Completely disagree. Sorry

You need a flat and I mean flat stone to remove a wire edge consistently. You might get away with it to start with but the back of the blade will soon become uneven so removing the wire edge will be very hit and miss. Been there and done it but now very careful about dressing the stone. You can minimise this by doing the back on the ends of the stone that don't get much use when sharpening the bevel.

No you don't need a flat stone. Let's approach it another way. Lets say we have a wire edge on a 2" wide plane blade. Let's lay the blade on the bench, wire edge facing up.
Now let's take a very narrow diamond needle file and run it across the entire width of the blade.
The diamond needle file is far too narrow to be termed 'flat' in our sense, yet it will remove the wire edge and it won't cause a hollow. Don't forget that when you are using a sharpening stone there is a degree of 'averaging' that goes on. Unless you are very careless the hollowness across the width of a stone is never going to be problematic, even then I doubt that it will be problematic anyway.

How did I get sucked into a sharpening thread :roll:

Yes you could remove the edge but you would also be messing up the back of the blade. After a while your cap iron won't seat well on the back of your blade and then all hell breaks loose.

Sorry OP for this derail