Thread: Waterstone difficulties again.....

With plane blades and normal chisels you only need as little as 1mm to be flat behind the edge (just as long as two polished tips come together), but practically speaking you probably will do up 20mm to ensure registration of the back on your medium of choice whilst executing the flattening.

These paring chisels are a different kettle of fish though - the backs have to be as flat as a plane sole does, and for the same reason - registration on the surface to be cut. They don't have to be polished all the way along - the usual amount for any blade edge is fine for that - but they do have to be flat.

O'course, as luck would have it, my low spots at at the bloody bevel edge aren't they? Again, it doesn't matter too much if you have a low spot in the body of the blade, as long as the edges around it are all flat with the main part (like the hollow ground backs of Japanese chisels that hiroller is referring to). All the remaining low spots from the 2 or 3 chisels that I tried on the waterstones (for flattening) are at the bevel edge, and so can't be ignored.

That may give a clue to my slurry theory. If that part of the back (i.e. near the bevel edge) was already one of the low spots when I went to flattening on the waterstones, then as the blade is pushed forward then slurry will be let in underneath the low spot (which is not touching the waterstone as such). So, as the whole back of the chisel now has abrasive matter in contact with it, the whole back will be abraded according to its original shape, more or less, and therefore never become properly flat.

I just put the feeler gauge on a couple of the troublesome ones, and a 1 thou gauge won't go under the low spot, so for practical purposes in woodworking tolerances that is fine. What is not fine is that because it's at the bevel edge it has to be as flat and polished as the whole rest of the edge otherwise that part of the edge will be virtually serrated.

Originally Posted by Simplicity

Was expecting to see a little bit more blood and gore in this discussion guys

Not an unreasonable expectation.

Exactly what's a bored middle age something something to expect lol

Originally Posted by FenceFurniture

Funny you should mention that Gavin. I was looking at a pic of one the other day, and it seems to me that either one of two things can happen there. Either you throw the chisel away when you've sharpened past the flat part, or you re-flatten it and have a much thinner chisel blade (not desirable of course). Am I missing something? I understand that it will a while to go past the flat part, but some of them don't seem to have much.

most westerners would just take a bit off the back to reestablish the flat behind teh cutting edge,
experienced Japanese craftsmen would tap out a bit of the hollow. of course tapping out is much easier to do with a plane blade than a chisel

Originally Posted by ian

most westerners would just take a bit off the back to reestablish the flat behind teh cutting edge,
experienced Japanese craftsmen would tap out a bit of the hollow. of course tapping out is much easier to do with a plane blade than a chisel

Tapping out on a Japanese plane blade is an imperative...and fun! But, I did read that one never taps out a chisel. The few I've owned have lasted ages. Sharpened maybe really carefully once a week and then just 8000 for a stroke or two before use for the day (unless I really work it hard that day, that's different)

The planes are sharpened every single day. They don't treat you nicely if you don't love them.

FF, I only use Japanese water stones, I sold that damn water grinder. It was terrible. Though I do have a grinder with 80 and 180 CBN wheels exclusively for the lathe tools.

The planes and chisels are all exclusively on the water stones. Even my non-Japanese chisels and planes (bahco, marples, Stanley and a few generic) are sharpened on them.

FF, I have 2 natural stones and they are simply AWESOME, but I did sell my kidney for them. The others are king and shapton artificials. I flatten the backs quite faithfully to a very bright reflection and right up to the tang to start, then process front. I don't do any of that micro bevel crap.... It's all just two flat intersecting faces.

The jap chisels sharpen really well. The big iron back and small section of Hard steel means you are not removing a massive slab of very hard metal to repair a knick...like the very hard European ones I have.

I freely admit I'm a total Japanese convert. I even have a Veritas, which from an engineering perspective is really impressive, but the Japanese stuff really does just work for me. I can't quantify it, but they are just "better" in my hands....which is weird as I'm very tall and my hands are big too, but the balance is nice, the handles wonderfully proportioned and the angles work.

I can try to be objective and replicate FF's concerns. I have 27 new Japanese chisels to prepare over the next week or two. Some are very old, most are brand new and they range from 3mm to monstrous 48mm ones. I'll carefully watch what happens while I go through the process.

One thing that has me thinking though, is these stones have been used for hundreds of years and the edges of Japanese tools are legendary: http://youtu.be/kFLt0duNrgc and http://youtu.be/JrmCyADNhe0

FF, where did you source your cast iron plates?

A forum member made them for me. He has more material, and we have discussed getting some more made (for other people), but right now I think he is moving house so no more progress.

Brett

Now I know what you have been up to and why so quiet (for you .)

A couple of comments (my dictionary says that is four or more):

I never use water stones for flattening the back of chisels and plane blades. In the past I have glued numerous grades of Wet and Dry paper to glass for this purpose. I gradually go through the range from 240grit to 2000grit.

That was my cheap skate method and it worked very well. I used the paper dry and would constantly clean the paper with a brush. I did invest in some 3M Microfinishing film to do the same process and have never got around to using it. It is still sitting in the envelope it came in .

In practice I find that that I work on about 50mm on the back of a chisel or plane blade. This is to achieve the truly flat land immediately behind the cutting edge and as you have pointed out it need only be a single millimetre.

However to flatten the full length and breadth of a chisel would be a hard ask and in your long parers; Maybe it is impossible by hand.

Just returning to my method of flattening with W & D, I do use it dry so the vacuum effect once water is introduced is not present.When I made a set of chisels (6mm to 70mm) from recycled truck springs I used this method and there is a lot of flattening involved with a leaf spring that has spent 30 years under a truck.

When you look at bench grinders you may find that you don't need anything too special. I know all the theories about slow speed machines and water bath styles and I have to say I have been tempted.

However I have seen and read that some of the experts just use a standard grinder (with an appropriate choice of wheel) and go a bit slower with the human side of the grinding. Don't be tempted to press too hard or keep the tool on the wheel for too long. Keep water handy and use it; Often! At least one major tool maker, of whom you are a fan, recommends this technique.

I think choice of wheel type is more important, but I am not best qualified to offer advice in this regard.

I hope all this helps or does it put you back to square one ?

Regards
Paul

Cheers Paul. Indeed I went back to a sheet of 120 Colour Coded Grit last night and it was significantly quicker. I sprayed the back with PSA glue, and when it is full of swarf I vac it off.

Beware of the glue on the 3M Microfinishing abrasive. I have two grades and whilst one of them pulled off the granite reasonably easily (when I wanted it to come off, that is) but the other one stuck like the proverbial. It was tremendously difficult to get off and when it did it brought chips of granite with it - thus pitting the granite sheet. Not such a big deal with my kitchen grade granite, but with your big reference jobbie it could be catastrophic.

The discussion brings to mind 2 medieval swordsmen, a Spaniard and an English Knight. The Spaniard through up his silk 'kerchief and cut it in two with his fine bladed sword. The Knight withdrew his broad sword from his belt and with 2 hands around the handle cut a steel chain in two (just another piece of information that resides within my nut)

Sheet abrasive stuck to a flat surface* has its own limitations - typically the cutting edge corners get more exposure to fresh abrasive and wear away more quickly. I got resigned to this and made lapping the first step in rehabbing old clunkers, then doing the bevels making sure to bench-grind away the drop-off.

In my experience lapping backs on ceramic whetstones when carefully flattened to begin with I saw variations in flatness from stone to stone but going up through the grits they got cancelled out.

* eg. a sheet stuck to glass with the tool moved across it. Powered abrasives - disc or belt - are much less prone to drop-off but a dedicated user can still make it happen.

Originally Posted by rsser

Sheet abrasive stuck to a flat surface* has its own limitations - typically the cutting edge corners get more exposure to fresh abrasive and wear away more quickly. I got resigned to this and made lapping the first step in rehabbing old clunkers, then doing the bevels making sure to bench-grind away the drop-off.

In my experience lapping backs on ceramic whetstones when carefully flattened to begin with I saw variations in flatness from stone to stone but going up through the grits they got cancelled out.

* eg. a sheet stuck to glass with the tool moved across it. Powered abrasives - disc or belt - are much less prone to drop-off but a dedicated user can still make it happen.

Ern

Your post reminded me of something that becomes painfully obvious as you go through the process of flattening using any paper or film stuck to flat surfaces:

It is that we go to extraordinary lengths to find a truly flat surface, be it Brett's granite off- cuts, surface plates (I think there are three grades available there for a start) or plate glass, and then horror of horrors, we spray glue on the surface which immediately produces an uneven surface.

This is perhaps not so noticeable in the coarser grades, but in my case at 800grit and above I could see the pimply bits where the spray glue was not uniform. Having said that, I used it for the leaf spring chisels to great effect and subsequently have used for every other chisel and plane blade I have ever flattened.

In fact some times, if not much work is required, I don't even glue the paper down and hold it flat with the fingers of one hand while the other hand tries it's best to cut them off ! I don't recommend others follow this practice.

I also concede there is a big difference in flattening high carbon steel leaf spring and modern m2, A2 etc., but I have flattened those too by this method.

Regards
Paul

Yes.
A spray of water can also be tried to hold a sheet down - let stiction work for you for a change.

Originally Posted by Bushmiller

.... we spray glue on the surface which immediately produces an uneven surface.

Yes, the same thing has crossed my mind on many occasions, so I try to spray it as evenly as I can, starting and ending each stroke of the spray can outside the sheet. Then of course there's the never ending battle of keeping dust etc off the granite sheet before the sticky abrasive is applied.

Mind you, in some sheds that last part is less of a problem.