Add hollow grind to blades using a "regular" 6" grinder?

[Doug Hobkirk]

Already covered somewhere? Please point me...
I am trying to figure out if this is a worthwhile experiment. This is my feasibility study!

You guys are so passionate about sharpening! Please forgive my including an electric tool in my query. Or move my thread if it breaks the rules.

Why do I want a hollow grind? It seems to me I would need to sharpen less steel on each blade (just the two edges on either side of the hollow). Is this correct? Does this apply to plane irons as well as chisels?

I have a Ryobi 6" grinder with a white stone wheel that disintegrates quickly. It seems to do an excellent job grinding. I don't remember the details but I suspect some of you know what I am talking about. The other wheel is one of the wheels that came on the grinder - gray, coarse. (I also have an 8" antique grinder but that's dying - although I might be able to revive it.)

Is a 6" wheel about the right size to put a hollow grind on a blade? An 8" wheel just seems like the diameter would be too large, but that's just a gut feel. I don't know. That's why I am asking.

I can't afford a pro setup. But I certainly am impressed by the Tormeks. I note the T3 has an 8" wheel turning at 90RPM (!!!) plus it runs in a water bath. That really is pretty impressive. And I am sure the jigs that hold the blades are well designed.

If the 6" diameter is good, I figure I could:

figure out the angle the blade needs to make contact with the grinding wheel
make a sled that would allow me to clamp a blade and slide it right to left


Is the soft stone I described likely to work? Or would another type of stone be preferable?

Thanks, thanks, thanks...

[David Weaver]

https://www.youtube.com/watch?v=3Hm4HiN2Lww

Any stone is fine, decent grinding allows you to use anything - even a dirty old washita stone that's barely cutting.

I like a "regular" 6" grinder better than anything else, and I've owned nearly everything except one of the flat rotary sharpeners. I *had* a tormek for a while but liked it so little and liked the idea of finding a buyer and shipping it halfway across the country that I put it in a box and sent it to George to free up bench space.

A good coarse wheel on a 6" grinder and you can refresh your hollow without getting the blade too hot to place it in your palm and hold it there.

Avoid the small wet sharpeners, I had the sheppach version (8"), and the sheppach is maybe slightly easier to use than the tormek because the wheel doesn't glaze as fast. I gave that one to a buddy when I bought the tormek.

And I have the viel belt grinder (the red one LV sells) and the kalamazoo version of the same size (like the kalamazoo better, but it's not suited for grinding right out of the box because the rest is a little cheapy stamped steel rest and won't go less steep than about 45 degrees. Fixing it would be as simple as drilling a hole in the stamped frame where the platen is on the grinder and relocating it. The kalamazoo has a much better motor than you'll ever find to put on the viel (tons more power) and the belt speed is a lot more suitable for grinding and keeping heat down.

Anyway, the high speed bench grinder is far and away my favorite maintainer. I like even the $40 ryobi that I had with a two piece rest better than any of the other power grinding tools I've used.

Chris G. got a decent chinese made variable speed 6" grinder. I replaced my ryobi with a baldor, but there is no practical gain over what Chris got, I bought it on principle and they have since become more expensive, to the point that I think they don't make money sense vs. a chinese grinder.

[Mark Kornell]

I've got both a 6" and an 8" grinder. Paid $30 for the 6" and $15 for the 8", both new. And made myself an adjustable grinding rest with a sled, basically a wooden knock-off of the Lee Valley rest. Both grinders work just fine for hollows. More important to performance was balancing the wheel and truing it.

I've put away the 6", and now rely solely on the 8" for a reason that has nothing to do with how it grinds. The 8" has an integral gooseneck light, the 6" doesn't - the light makes it easier to see how I'm doing.

[Matthew N. Masail]

I use a regular 6" Ryobi grinder with a 46grit white AO wheel, and a veritas tool rest.


the stock gray wheel are just fine, you just have to be a little more carful about heat and it takes longer.


The veritas tool rest is great enough that I went through the trouble getting it here, but a wooden one can be made to do well too. if you do make a wooden one, I recommend doing in this style: a friend of mine made it, it's simple and as solid as you'd want. my first wooden version had too much flex.
287934

[Jessica Pierce-LaRose]

If the 6" diameter is good, I figure I could:

figure out the angle the blade needs to make contact with the grinding wheel
make a sled that would allow me to clamp a blade and slide it right to left



The sled thing seems like more work than it's worth in my experience; about the only time I've used any sort of guide when grinding is working something like a drawknife, where I'm not holding the blade flat on the rest. (the guide in this case is just a pin for the back of the blade to rest against) With something like a chisel or plane blade, where the blade lays flat on the tool rest, doing it by eye seems quicker and less finicky and seems to get me just as good results, if I need a little more accuracy, I can carefully grind the edge blunt and square to a line scribed on the back of the iron, and then grind until that flat disappears. If you've already got an iron ground how you want it, it's just a matter of watching and grinding evenly. Sometimes I hook a finger around the back of the blade to act as an impromptu guide. I use the Veritas tool rest, the lines scribed on the base do help to visually make sure you're grinding perpendicular. I have the tool guide that works with that grinding rest, and have really only bothered with it when I was grinding a chisel with an oddly shaped back, which made holding the tool flat to rest awkward.

[Andrew Fleck]

I also have both a 6" and 8" grinder. I use the 6" with a Norton 3x 46 grit and never have any issues grinding hollows. As a matter of fact I just leave the rest set at 30° which is the angle I grind at most often. I leave the 8" with factory coarse wheel on one side and a wire wheel on the other side. I use the 8" for blunting edges and just general grinder work. It leaves the 6" always ready for a hollow grind. I also don't bother with any kind of sled or holder. It just take a little bit of practice to get good at hollow grinding. I have a couple Lakeside irons that I learned on rather than grind more than necessary on my decent irons.