Yesterday one of the Carborundum stones I ordered arrived in the mail. A 7" x 2" combination stone, I think it's from the 60s.
The coarse side was slightly dished, but not too badly, so I tested it as is with an O1 plane iron I made last weekend. Weaver heat treated it in his shop, so tonight it was fresh from the oven.
This will be its first sharpen, so it doesn't have an edge yet, there's less than 1/32" of metal to remove at the bevel.
15 minutes later I got a burr. The stone's dishing is not worst than before.
A few passes on the fine side and an edge was formed.
Not the first time I grind a bevel using a SiC oilstone, crystolons from Norton, and it's not an arduous or long process. This Carborundum stone didn't disappoint. It was a similar experience as with the crystolons. I'll keep using it.
Is that the same as Crystolon? I was scratching my head on the difference then I noticed that your stone was not a Norton. I'm guessing Crystolon is Norton's trade name for carborundum.
How do you have such a clean stone after removing all that metal?
I like that iron. My LN smoother is such a nice tool except for the A2 iron. Such a disappointment.
Yes, Carborundum from Niagara Falls, NY. They invented this type of stone. I got it after a comment by Jack Dover. I had used only Norton stones up to this point. The stone in the picture was wiped after I ground the iron, I used plenty of oil and tried to distributed the wear around the whole face of the stone.
I have used Carborundum stones for over 60 years. The first one I used was from around 1950 and came in a yellow box. In 1978 I used a Norton Crystolon that belonged to someone else. It seemed to me that it had a harder binder than the Carborundum and glazed more easily, so I bought two more Carborundum stones which came in red boxes. They were more like the Norton than the old Carborundum. I think I am on my fourth stone.
The Norton company bought out Carborundum some years ago and I think there is no more Carborundum brand sharpening stone.
I use an 800 water stone for plane irons and most chisels, and Carborundum for things that would dish the water stone: turning gouges, firmer gouges, narrow chisels and the like.
I have gotten paranoid about putting the face of an iron against anything that might be a little dished, but I have a feeling it’s due to a misunderstanding or wrong technique on my part. Grinding and honing a bevel doesn’t give me trouble but on the flat side I end up taking forever to get a polish to the edge. Frustration with this, especially when I know I just did it earlier, leads me to half measures with my sharpening.
I know I’m not the first, or there wouldn’t be a market for diamond plates and surface ground laps, so my question is, is there a technique for the flat side of the iron that obviates the dependence on perfect flatness?
That's exactly my stone. Mine was a bit dished too, I think this is due to a manufacturing process. Wasn't too bad and it didn't dish afterwards, or maybe I finally learned to use the lightest pressure that gets job done. Or maybe these stones aren't as consistent and there's a chance to get either a softer or a harder wearing stone.
I overhang the iron off the stone and use the high areas of the dished stone (crystolon) to grind the face when restoring and old iron. On an already prepared iron I do the same, but on the washita or finer stone and not too aggressively. I also use diamond stones.
The iron above was a little bellied, i prepared it using sandpaper glued to a slab of granite, then diamond stone. That got it ready, but I haven't finished honing it yet.
I do the same, but don’t get results that seem practical. Some say it’s a piece of cake, others have tons of gadgets and ruler tricks etc. I think it’s odd that I haven’t seen any mention of flattening in books before the 20th century (the probably exist but I haven’t seen) and all the old irons I’ve gotten are super rough on the flat side.
The Norton company bought out Carborundum some years ago and I think there is no more Carborundum brand sharpening stone.
"Carborundum" is just a name for the SiC, 'cos originally it was believed to be a compound of carbon and alumina (carbon + corundum = carborundum). Afaik Niagara Abrasives is still an independent company, but it doesn't matter really, I just found their stones to cut well and very affordably priced, like, a half of a Norton stone and very, very similar characteristics. SiC stones are probably the most popular on this planed, but many of them either have a binder that's too hard or too soft. A good stone is hard enough to prevent instant dishing, but also just enough soft to release crystals and expose a fresh layer.
Curious about red Norton Crystolons. Their new stones come in a yellow box with a tiger, single grit stones are in a blue box. I had a stone in a chevron box, but it was rather a carrot color. Is it an older stone? Those has a big red label over some patterned box, never had a chance to use one. Not that I need yet another stone, it's just once you stat playing with them it's really hard to stop.
It really depends on how flat you want them. If we're talking about toolroom grade B flatness abrasives alone wouldn't do it, for example.
But you probably mean something called "dubbing" - it's when areas closer to edges are sunken, really aggravating when it's right next to an edge. This happens not only because of a dished stone, but also because of free abrasives, a fairly well known issue in lapping. This is why lapping on a sandpaper glued to a hard substrate produces a flatter surface. If we're talking about restoring chisels and irons I don't see why would anyone use anything else besides 80 grit sandpaper, it works so fast and so great that everything else really pales.
Also, I don't think you want to touch a back with anything except your finest stone once it's lapped. Usually when a tool is restored, it's flattened and then polished, and if you're using sandpaper for this, I don't think there's an oil stone that has comparable grit. My finishing stone is very, very fine, it gives a true mirror polish somewhere around 2.5-3k patriotic grits. It's also glass hard and flat. But if my highest grit would be soft Arkansas or a fine India - that would be the only stone I'd use and only a few swipes per sharpening. I would also re-flatten and re-polish occasionally.
You could do it on stones though. Diamonds will work, just slow. Properly flattened oil stones and water stones will work too, just switch direction often: 10 swipes along the length, 10 swipes across the length, a few swipes to flatten a stone every 5 mins or so. But it kills the point I think, since we don't really want to flatten a back once a lifetime and never do it again, we just don't want to spend too much time doing it. After re-discovering various sheet abrasives I relaxed a lot about flatness: worst case scenario is extra 10-20 mins during the next mass resharpening, not a big deal at all.
Flattening on PSA paper is what has worked for me, as well. What I have been frustrated by has been in normal resharpening, there seems to be wear on the edge on the flat face opposite the bevel, is it your approach to grind the bevel back past that worn area and not work the flat face with anything coarser than a polishing stone?
Couple things about working the back to remove the lower wear bevel:
1. Relying on finish stone to get the wear bevel off the back won’t get it, unless using Charlesworth’s ruler trick or equal blade lifting.
2. For back, suggest 2000-3000g or so, including washita or Japanese natural stones. Key is to bias pressure toward the edge, without actually lifting the blade.
3. (option, caution) Adapt Weaver’s buffing technique: don’t round the back—that is catastrophic and hard to repair—but a barely tangent buff on soft medium will get the last hidden wear off the blade back. But careful.
Thanks Wiley. I had gotten the impression that wear bevels have been a topic of some debate in the past.
What I’ve been doing is what you suggest, I’m just taking so long to get a polish (with bias directly downward on the bevel itself) that I feel like something must be off.
In my work people bring me their broken toys and they always have an idea what is needed, usually they have already tried to fix it, and from experience I can usually tell at a glance where the problem is. If I were relying on their explanation, I would be in the weeds because they only know what they know. With this flattening issue, I’m in that same position of having answers to all my questions but pretty sure there’s a question I’ve missed that is dogging my efforts.
What I truly wish is that there was someone who could look at what I’m doing and say, oh don’t do that thing with your left ankle, or whatever it is.
I got the impression you’re in california, do you know of such a place?
EDIT: What I’m fighting is getting a back all polished out and then having to do it again upon resharpening. It’s not that I can’t get a polish but that I have to restore it so often and at the cost of so much time.
First a disclaimer...I am the person least qualified to answer whatever question you have, which I think I must not understand.
That said....I ground, then polished the back of my edged tools in the beginning. Depending on when it was done I would have used abrasive sheets on glass, or diamond plates.
Subsequently for the last up to a decade or more I have not screwed with the backs. There was no need to. I hollow grind the bevel, refine on a fine diamond plate, finish with 1 micron loose diamond on cast iron, rub the first inch of the back a bit on the 1 micron plate and done.
It works for whatever I need to do with a chisel or plane. I don't see a reason to ever go back to messing with the back once it is flat and polished. Or I don't understand your question, which is probably likely.
Flattening on PSA paper is what has worked for me, as well. What I have been frustrated by has been in normal resharpening, there seems to be wear on the edge on the flat face opposite the bevel, is it your approach to grind the bevel back past that worn area and not work the flat face with anything coarser than a polishing stone?
That has been my suspicion. It seems that the initial small burr that presents itself is not consuming the wear on the back of the bevel. It would then follow that either coarser abrasive at resharpening is called for or a ruler trick used a couple of times with finer touchup abrasives with a periodic refresh to ensure the wear bevel is removed.
Despite taking more care to avoid dubbing of the backs I notice that burrs persist after stoning the backs of plane irons and that there is a tiny line of reflection between the burr and the flat polished flat.
I believe that is the same thing that Mike is describing.
The burr starts forming slightly before the wear on the back has been taken care of. If the wear is significant, it could be quite a bit before you are done.
The amount of burr that is necessary for sharpening is dependent on how dull the edge is. If the edge is not bad, very little burr is formed before you have sharpened enough. If the amount of wear is great, you have to sharpen well beyond the point where a burr can be detected. This kind of thing takes experience to learn.
I think you are not grinding the bevel sufficiently. In my case I sharpen when driven to by the blade not picking up a shaving. At this level of wear it would take forever to grind away the wear on a stone if there was no hollow grind to lessen metal removal. It was sharpen more often or hollow grind with a grinder. You may be facing the same choice.
Warren makes a huge point here. To keep the edge maintainable, sharpen early. Once it’s rounded-dull, you’re looking at a lot of grinding to get past the wear on the back. If the plane is no longer pulling itself into the work, it’s time.
Relying on finish stone to get the wear bevel off the back won’t get it, unless using Charlesworth’s ruler trick or equal blade lifting.
Well, what can I say? Don't wear it that much, and grind the bevel such that a burr "eats" the back's wear. I can tell whether a bevel is ground enough by how many strokes did it take to chase a burr off on a finishing stone. Usually it jumps off after 5-10 strokes, if it takes longer I might step one grit back and re-grind\re-hone.
My finishing stone (that unidentified pink brick) is quite fast while being very fine, it blackens honing oil readily and removes quite a bit of metal, so I think the back wear is addressed. Or at least I can't detect a difference between a freshly lapped sharp chisel and what was just resharpened.
Also I don't think that the ruler trick was intended for chisels. At least I have never seen or heard from Mr. Charlesworth. What I think is going to happen is what happens when a chisel was accidentally lifted. A minute back bevel will form and, since it's not touched by abrasive, a chisel needs to be lifted up again, and again, until this bevel becomes so pronounced that either we have to flatten it again or it becomes a carving tool. It's similar to old chisels that have a very pronounced curve on the back right at the cutting edge. They're almost impossible to sharpen without getting rid of it, so I'm definitely not doing it deliberately.
We’re not far apart, if at all. I should have qualified my statement to apply to sharpenings between hollow grindings.
As you point out, if one sharpens frequently enough that the tool is never really dull, or if one substantially grinds away the wear bevel on every sharpening, then a finish stone will do fine for the back.
I generally grind to a burr every half-dozen sharpenings, and it is these in-between sharpenings I had in mind, where IMO something more than, say, a 10K-13K stone is needed. I mentioned 2K-3K or similar in natural stones, and would add Bill Tindall’s 1-micron diamond on cast iron, as 1u diamond is quite aggressive and punches above its mesh rating. I find a DMT 8000g fixed diamond plate also works well for frequent resharpening.
