FWW article - always hollow grind chisel / plane blades?

[Will Blick]

This months FWW magazine had an article for sharpening.... the author had an interesting take on the subject. His position was, always hollow grind chisel and plane blades. His reasoning is, with a hollow grind (on a grinding wheel), you should have a nice recess between two exposed surface areas, one at the edge, and the other where the iron meets the start of the angle for the edge. Then, you can sharpen free-hand on water stones, as you always have two reference points, which keeps the blade from rocking.....which is what often happens if you only use a micro bevel, which a honing jig does nicely. But the authors point was, with a hollow grind, no reason to waste time jigging up the blades in a honing jig, as its just as fast and accurate to free hand.... makes perfect sense to me... I thought this was a brilliant contribution, which I have never seen before..... at least the "reason" for the hollow grind. Anyone agree? Anyone do this now?

[Mike Henderson]

The woodworking school I attend teaches the same thing. The problem is getting the hollow grind. If you use a medium or high speed grinder (1725/3450 RPM) grinder, you risk overheating the tool, making the edge soft. The other alternative is to purchase one of the slow speed water cooled grinders but they're expensive. The other problem is space. If you don't have room to leave it set up all the time, it's a real pain to get everything out and do the sharpening. The school has a "sharpening room" where everything stays setup - and they have a bunch of the low speed water cooled grinders.

I use a hand jig (the LV MKII) and put a 25* bevel on my chisels, then free hand hone to a higher angle as needed in use. For me, with limited space and money, that's a better solution.

But the hollow grind idea is not new - it's been around for a long time. In fact, I was surprised that they were publishing it because I thought it was very well known among woodworkers.

Mike

[Also, I don't know if he says this, but you should not hollow grind Japanese chisels.]

[Will Blick]

Hi Mike, I too use the LV MKII for plane blades and chisels, a very well made jig.

I realize the hollow grind concept has been around forever, but the part I never heard before was.... produce the hollow grind to free yourself of using the honing jig every time you need a tune up on the edge....

He did mention in the article about the risk of over heating..... I never found the jig that time consuming where I thought it was an issue....but, free hand with equal results would be nice....and encourage me to tune-up more often...

I wonder if a round metal file would be a safer way to gain a hollow grind. Interesting how there is always a con for every pro...

[Mike Henderson]

Will - I think you can ignore the jig for honing once you have established the original bevel. The reason I start with a 25* bevel is that I can then add a secondary bevel of greater than 25* just by free hand honing.

So after I do my original sharpening (at 25*), I start using the chisels. On hard use, the 25* edge dulls quickly. I take the chisel and hone it on a fine waterstone, drawing it backwards freehand, until the edge is smooth and sharp. Then I go back to work with a bevel that's greater than 25* - I don't know what it is and don't care. When that edge dulls, I go back to the fine stone and do the same freehand honing. When the microbevel gets too long, or the secondary bevel too steep, it's time to go back to the jig and re-establish the original 25* bevel.

Anyway, that's the way I work and it works out well for me.

Mike

[Will Blick]

Mike, I follow you..... but the argument in this article, which I seems very sensible... is.... with only a micro bevel, free-handing becomes hit or miss....why? Because it may seem like you are holding that micro bevel flat to the stone when free-handing, but in reality, it doesn't have enough surface area to provide sufficient feel to keep it flat... hence the authors recommendation of the hollow grind, which gives you, in essence, two micro bevels, (one on each side of the hollow grind) so you have a long platform of surface area that hits the stone, making free-handing easier and supposedly a more accurate micro bevel.

I am not suggesting your method is not sufficient for your work, I was just exploring this article.... before doing something dumb :-)

[Mike Henderson]

Originally Posted by Will Blick

Mike, I follow you..... but the argument in this article, which I seems very sensible... is.... with only a micro bevel, free-handing becomes hit or miss....why? Because it may seem like you are holding that micro bevel flat to the stone when free-handing, but in reality, it doesn't have enough surface area to provide sufficient feel to keep it flat... hence the authors recommendation of the hollow grind, which gives you, in essence, two micro bevels, (one on each side of the hollow grind) so you have a long platform of surface area that hits the stone, making free-handing easier and supposedly a more accurate micro bevel.

I am not suggesting your method is not sufficient for your work, I was just exploring this article.... before doing something dumb :-)

Yep, I understand. That's what the school teaches, also. My problem is getting the hollow ground (because of the issues discussed earlier).

I don't in any way disagree with you. I was just offering an alternative.

Mike

[Robert Rozaieski]

I hollow grind and hone freehand. Works great even for thin Stanley plane blades. I use a regular old high speed ginder with no problem. Just dip the tool in water every couple passes over the wheel. If it starts to feel warm, dip it. Once I started using this method, I sold off my honing guide as I quickly was able to learn to go without it. I hone much more often now as well and tend to work with sharper tools as I don't put off touching up a slightly dull edge since it now takes mere seconds to do. No more time wasted setting up the training wheels. I highly suggest you try it.

[Will Blick]

Ahhhh, a supporter of this system, thanks Rob. I think we would all hone more often if we could avoid the jig....

Question: what is the "ideal" diameter grinding wheel to create an optimum hollow grind on chisels and plane blades?

[Robert Rozaieski]

"Ideal" is a personal preference. I use a stanard 6" high speed grinder. A cheap one at that. No fancy do-dads and a shop made tool rest. Other people like 8" but they are a lot more expensive so 6" works just fine for me. I use oil stones as well but with this method of honing, stone type doesn't matter because you aren't taking off a lot of metal with your stones. All types of honing methods work; oil stones, water stones, sandpaper. Like Nike says, just do it! You'll like it .

[Michael Faurot]

Originally Posted by Mike Henderson

The other alternative is to purchase one of the slow speed water cooled grinders but they're expensive.

I think that would depend on what you consider expensive. If we're talking Tormek--I'd agree those devices and most of the clones seem expensive to me also.

Grizzy has two slow speed wet grinders that don't seem all that expensive to me. The G1036, which looks to be a clone of the Delta 23-700 (which also isn't all that expensive) and the T10010 which looks to be a Tormek clone. Harbor Freight also has a Tormek clone.

One potential issue with any of these wet grinders is they all have 10" wheels, except the Harbor Freight model which has an 8" wheel. With the larger wheel the hollow grind will be less.

I have the Delta 23-700 myself and like it for putting a fresh grind on things and then finishing things up with water stones.

[Jim Becker]

I just read that article today and frankly, it makes a lot of sense to me. I do sharpen free-hand and it's pretty clear that the hollow grind reduces the work a bit, etc. Do note the comments around working the back of the blade...stopping before lifting clearly can be pretty important to avoid an unwanted back bevel.

[Raney Nelson]

I am a very strong proponent of this system. I'm one of those guys who bought and tried every jig and device you can find. I've used a Jet SS grinder, a LV MKII flat disc grinder, three or four different jigs, sandpaper and glass, and on and on. Once I started turning, and got somewhat comfortable with my grinder (a Woodcraft 8" 1725 RPM) I tried the hollow grind and freehand - which is a very common technique. Honing the blade is incredibly fast, and touching up is as well. I would say it takes me 2 minutes to refresh a grind and hone the blade. Touch-ups take under a minute. Literally. I would say I re-hone five to ten times before re-grinding, and then only because the bevels are beginning to get larger and honing takes longer. I usually go from the grinder to 10 strokes or so on 4000 waterstone, then 10 strokes on 8000, a few back and forth strokes to remove the wire edge and voila!

The one thing that I think is a possible barrier for this, as Mike rightly pointed out, is that you really need to be able to leave your grinder set up. I bit the bullet and devoted a small utility table in my shop to sharpening - I keep my grinder, space for stones, and an inset tupperware tub of water. This makes it seriously easy and quick to touch up an edge, which I find is really necessary for me - otherwise I tend to 'push' longer between honing than I really should.

I cannot recommend hollow grinding and freehand honing stronly enough. WIthin a month of beginning to experiment with it, I sold my Jet wet grinder, all but one of my honing jigs (I kept an eclipse-type for the occasional use - I still use it for some of the narrower plow plane blades, and for a couple of my paring chisels.).

[Peter Quadarella]

You guys have faster mail than me . The technique is tempting, but I'm not sure I'm willing to dedicate space to a grinder yet. It may come to that though.

[Don C Peterson]

I'm a fairly recent convert to hollow grinding. I just picked up a couple of old hand powered grinders on ebay and was pleasantly surprised at how easy it is to hollow grind (once I made a decent tool rest) and then how much easier it was to get a razor edge on all my tools.

[Greg Campbell]

The school I'm attending teaches hollow grinding for both plane blades and chisels. Plane blades are honed using the hollow grind to register as described above, but we were told to hone chisels with a secondary bevel. This way the grinder can be set up for 25 degrees (for both chisels and plane blades), then the secondary bevel raises the chisels grind to 30 to 35 degrees to make the edge more durable.

I have japanese chisels and have hollow ground without chipout problems as longe as I keep the secondary bevel at 30 degrees or above. I ground them around 25 degrees once and they cut great for 2-3 hammer blows, then chipped out badly.

At school, each bench has a sharpening station and we are taught to hone freehand. Takes a while to learn, but makes resharpening really easy and quick. They also use hand crank grinders with 6" white/pink grinding wheels. Hand grinding also takes a while to get used to, but you get good results pretty quickly and overheating is much less of an issue since the grinder speed is low. This is the setup shown in the Krenov books.