Basic hollow-grinding technique

[Schuyler]

Gene,

Yes indeedy, I haven't done it, but I know a well-known folder maker who heat treats his profiled blades first, then hollow grinds them with a water cooled set-up. Prevents losing the temper from overheating.

As Kung Fu once said, "there are many paths grasshopper"

Keep us posted on your progress.

[Don Cowles]

Gene, that works very well on stone wheels that are pedal-powered, or which otherwise turn at very slow speeds. Most bench grinders, however, run at 3600 RPM, and at that speed, the water would be thrown off (and into your face) in a continuous roostertail.

Many of the 3600 RPM grinders come equipped with a small quench tray attached to the base. If you keep that (or any other container) filled with water, you can dunk the workpiece every few seconds. That's a pretty good workaround.

[Gene]

He what??

Man, I'm dumber than I thought - I assumed you HAD to do the grinding BEFORE heat and cold treating! In fact I thought you had to do EVERYTHING other than the final polishing prior to heat and cold treatment.

But I guess I'd better not run down THAT rabbit trail here on this thread, or I may get shot down by one of the thread cops.

Thanks, though - I'm definitely gonna try the water cooling system when my 8" JET arrives.

You CAN buy water cooled bench grinders, I'm sure you know, but the largest one I found - turning at normal grinder speeds - was a 6" grinder. Of course there are a lot of water and oil cooled bench grinders with big 10 and 12" wheels, turning only 70 rpm, for knife SHARPENING, but that would patently not work for hollow grinding.

Thank you!

Gene

[ron p. nott]

i have made alot of knives since 1992 and only about half of them came out good and that has been in the last 3 yrs . one of my biggest problems is grinding double edges like dagger blades . my knives are usually 3.5 inches closed. and the other style of blade is person double grind ..any suggestions thanks ron p. nott

[Gene]

Hi Ron -

If you don't already know it, I'm the newest and dumbest kid on the hollow-grinding block, but I did see a terrific-looking "Double Hollowgrinder" rig for sale in the latest Blade (page 85). And I called the guy, Bill McCann, "The Iceman", and it sounded like the real berries. But the price was WAY out of MY ball park. Perhaps not yours.

It's just two counter-rotating grinding wheels, like bench grinders, and they whack off the steel on both sides of your blade simultaneously, as you feed your blade down between the two wheels, sharp edge down.

I would recommend you call him, in Alabama, at 205-744-0383.

Best wishes!

Gene

[Bob Warner]

Gene,

I have seen this before. Jim Pugh (one of the founding members of the Knifemakers Guild) has water pray onto his belts, right above where he grinds. Keeps things cooler but he still has to hit the water bucket to cool things off. I thought about it but don't know how much benefit there is to it. The grind and dsip method works well enough for me.

[Gene]

Ah, gee, no, I'm sorry Coles to be compelled to contradict you, but you are mistaken.

At least several water cooled bench grinders are readily available on the net today, and at least two of our erstwhile knifemakers here have in the past or currently do water cool their grinders - with none of your "rooster tails" or other imagined hazards.

For openers, there's a jim-dandy water-cooled bench grinder for sale at http://www.uselectricaltool.com/model10wg.html, and your "rooster tail" problem is eliminated by hoods, catchment systems, etc. No problems.

Plus there's also a much less expensive water-cooled regular bench grinder, on the net, turning some 3000 rpm or so, which I considered purchasing. The only reason I did not was because it only carried 6" wheels, and I have to have 8" for this particular blade.

But it simply has a little water cup over each wheel, with a brass petcock with which the operator controls the volume of water dripping on the wheel. And it did have hoods over each wheel, but nothing at all out of the ordinary. Plus it has a pan under each wheel which catches the water.

But it is an odd-looking grinder, with a pivoting bench on each wheel.

So water-cooled bench grinders are alive and well today. Voila!

Cheers anyway!

Gene

[C L Wilkins]

Gene,
When you do your grind with the stones (or grinding wheels), let us know how it turns out. I wish you the best.

Craig

[Gene]

Thank you very much, C. L - and yes I shall indeed. I owe all you guys for your great help.

Yesterday I hollow ground the swedge on the obverse, on this big Persian fighter, and it just went in zip, zip, zip - no problems. I've read that most folks don't sharpen the swedge, but - just to make them look a little more "BAD!" - I'm going to sharpen the swedges on both of the two big knives I'm currently making.

What I did on the swedge is what I'm going to do with the main bevel: I flat ground it first, on my 4 x 36 Sears belt sander, then I ran a groove the length of the swedge with a Dremel tool and a cylinder sanding bit. Then I just moved up to a 3/8" electric drill and a 1" x 1" cylindrical sanding bit - Voila!

Have a happy day guys!

"No me saques sin razon, no me embaines sin honor"
Catherine or Aragon to Henry VIII

Gene

[Jonesy]

I don't know any knifemakers who use a bench grinder(stones) to make knives start to finish. I have seen water misters set up on belt grinders but the guy was grinding a couple hundred blades in one setting.

Most of the grinders (stone) I have seen with water drip were for cutter grinding. I have one.

For what its worth I would rather have a belt break than a stone fly apart. Making a knife isn't about speed.

Be careful and GOOD LUCK!

[cordless101]

Hi, I just ground a blade with two hollow grinds on it, on a bench grinder to start with then switched to belt grinder to finish it. 01 steel 1/4" X 2". Put a hollow grind on the top and on the blade. Just started it good with the bench grinder, cause my Jet 1 X 42 only has a three inch wheel.

Kinda tuff finishing it, but got it ok finally. First blade I ground through of course...

I have a knife sharpener with a 10" wet wheel at 70 RPM, I'll try that to hollow grind the one I'm starting now. Seems like it would take forever though. Gonna start it on the bench grinder with an 8" wheel.

This hollow grinding is tuff work. Think I just have to go slower, trying too hard to get things done NOW. Everyone keeps saying to take your time and go slow. Hard to do though.

Charlie

P.S. Sure glad this thread is here now. Couldn't have come at a better time, just as I was looking for a hollow grinding thread.

[Ray Rogers]

A few years back Terry Hearn told me he grinds nearly all of his blades on an ancient 5 HP bench grinder that has 10" wheels that are 2" wide. He said it saves him a fortune on belts.

So, I went looking for a grinder like that because I feel like I spend too much on 60 grit belts. The closest I could get would cost about $1500 and that was a bit much for something that I was pretty sure wasn't going to work for me anyway.

Instead, I had a brainstorm - maybe more of a mental breeze - and I bought a 10" wheel that was 1.5" wide (the closest I coud get) in 36 grit. Then I used it to replace the 8" contact wheel on my Grizzly belt grinder. Pretty cool, I thought. I can still use the belts and I get a 10" wheel to boot or I can remove the belt and grind on the stone directly. The Grizzly, BTW, is a 1725 rpm motor so that's about as slow as any motor you're likely to find.

It still seems like agreat idea but it didn't grind worth a hoot for me. Way too hot and much to slow. Maybe it has something to do with the way the stone is dressed, I don't know.

Or maybe that Ol' Boy was jes pullin' my leg....

[Terry Hearn]

Ok Ray, you got me in on this one Weren't pulling your leg at all. I do most of my basic grinding on that big ole hard rock grinder. That is what I learned on and still use today. I have used most every kind of belt grinder out there and still go back to the hard rock for hollow grinding and removing micarta and brass. It will remove steel and micarta like nobodys business if you don't push it hard, just let it ride on the wheel. However you will have to dress the wheel on a regular basis to keep the build up out. I never had much of a heat problem though, no more than using a belt but I do keep a bucket of soapy water right by it to keep it cooled down.

[Bob Sigmon]

This is my first attempt at a hollow ground knife.

I was inspired by Gene, who is making some knives for his son and daughter.



ATS34 7" Blade. . 8" hollow ground . . false edge . . handle to be determined

Thanks for all the tips and clues!

Bob Sigmon

[Gene]

WOW, WOW, WOW, BOB!

I can see I've taken up the wrong hobby!

I'm gonna trash what I've got of my two knifes and take up underwater basket weaving!

How am I ever going to do that well!

That's magnificient!

Gene