Basic hollow-grinding technique

[SharpByCoop]

Guys,

Now that I have my KMG-1 grinder in operation, I have started to practice. I bought a 4' length of 1"x1/8" steel from the Home Depot, and cut out a few 6" 'blades'. Marked and divided the edges to have a reference. 8" wheel, 80 grit at medium speed (1750rpm straight) I have Johnny Stout's video on hollow grinding, but believe me, he sure made it look easy. I'm not quite as ready.

I did manage a few nice bevels and am getting better, but before I start practicing bad habits I need to ask these ~simple~` questions.

I got better results by removing the work rest and doing it freehand. Do I just need more practice? What do the majority of grinders use? I couldn't figure out how to rotate the bevel with the table in the way.

Once I got a 'groove' started, can I go back and forth in this groove, or should I just limit myself to one-directional passes. I got better results with staying in there, but occasionally I'd flinch when it got too hot and lose what I gained. (no gloves)

I got the best upper grind line when I turned the knife over (top edge up). Practice more, or is this OK?

I find it hard to not go get a higher upper bevel at the plunge (?) area. Obviously I need to practice.

Don's CD mentions a number of guys using wooden push sticks. Johnny used one too. Lovelesss' book does it freehand. I found it tough to not burn myself, but actually remove metal. What do you use?

That's plenty for now....

Give me a few days and I'll post pics. I'm not there yet.

Coop

[Bob Sigmon]

Hey Coop,

No real help here but, I've been practicing too. It's not too easy, is it! Most maker say it is best to free hand. If you use gloves/push sticks, some say it is easy to get the blade too hot. Fingers will tell you when to dunk the blade in the water bucket.

I've got my scrap bucket started. I hope that it doesn't get too full.

It sounds like you have good start on it. I'm gonna try your method on the grind line cause I'm having trouble keeping it straight.

Good Luck,

Bob Sigmon

[Don Cowles]

Coop, my technique is evolved from my own experience, and might not work for everyone, but here is what I do:

• grind edge up
• initial bevels on work table
• all other work freehand
• no push stick

I have customized my work table by cutting it down to a 2" width. This permits rocking the blade to follow the edge contour, although I have found I do that very little. What I do do a lot is rotate or twist the blade against the wheel on its long axis to get a true distal taper.

Mike's counsel about keeping your arms locked in to your sides is solid gold. Let your body provide the movement, not your hands.

Grinding in both directions works fine for me.

I hollow ground 7 blades last Saturday; one of them is scrap (ground through the middle. It happens, and even if you are very careful (too careful?), it even happens on very rare/expensive damascus. Have the grace to chuck it, and factor that experience into the cost of your blades.

Good luck, and holler if you have more questions.

[SharpByCoop]

Here's my better ones!

Thanks for the tips. They're all noted. Yeah, I found the harder I held it and rotated my body instead of my arms, the better it looked.

Yup, I found I'm better suited on one side than the other. That's rust you see from the dunk and cool. I tried an upper bevel for the heck of it, on one.



Maybe tonight I'll cut out a couple more and then try it with the rest. Maybe Bob's suggestion of using wood would give me lots of practice at what angles to hold. Maybe I'll use the workrest tonight. Maybe I'll make a push block with a step and hold the blade with ViseGrips. Maybe some time before you guys stop laughing....

Maybe I'll surprise us all ! And then, maybe not.

Wait till I try flat grinding--which is my preference for some styles, but I'm not going to limit myself.

Coop

[Bob Warner]

Like Don, I grind edge up. I grind with my weak hand first. If I grind with my good hand (Right) I can't seem to match it with the left hand on the other side of the blade. If I grind with my weak hand and get what I want I have the ability to match it well with my right hand. I just don't have the left hand control I wish I did.

I use a small rest when profiling, freehand the rest of the time. I don't wear gloves, EVER. I have had them cause me injuries because of my having a bad grip on the blade and the grinder grabbing the blade out of my hand. I grind bare handed for control and safety.

You will experience heat but over a time you will get used to it. When grinding a hollow, (depending on how you hold the blade) you can get hit with sparks. I support the blade (Spine,) with my index finger and push on the blade with my thumb. This puts your finger right in line with sparks coming off the blade. You can get a little pile of grinding dust (HOT grinding dust) that builds up on your finger. You also have your thumb right in front of the belt, the HOTTEST place to be. Over time you will get a callouses there and it won't bother you anymore. Just have your water bucket close.

Many people grind by holding the tang and grinding but I have trouble controlling the tip of the blade from the tang end. I have to get my grubby fingers on the part of the blade being ground.

I grind in both directions like Don and have no problems with it. I cut a bevel on the edge to keep from stripping my belt, then start to grind a little ways into the blade. After I get a hollow started I push the edge of the knife towards the wheel to get the hollow wider and get the edge close to where I want it. Then I push the spine in to widen the hollow to the width I want for that blade. Lighten up the pressure and even everything out. Check your plunge cuts and make sure they are very close. Go to smaller grit and redo everything, cleaning up any small mistakes. Just progress down in grits to a finished blade. Keep the blade moving or you will get the 2" disease.

[Jamey Saunders]

Coop,

By no means am I an expert, but here's how I grind blades:

When I first started, I used a wet rag over the end of my thumb to keep from burning myself. I have found, however, that I have better control and feel by not using the rag. I don't use gloves or a push-stick either.

Like the others, I do the majority of my profiling with the tool rest in place. I remove the tool rest and freehand my bevels.

As for getting the plunge cut too deep and higher than the rest of the grind line, you have to keep in mind to keep the blade parallel to the face of the wheel as you look down on it. Having the blade a few degrees off of parallel will cause the plunge to be higher than the rest of the grind. I agree that this is the harder part of the blade.

I also think I do the same thing that Don does: When grinding toward the tip, I do not rotate the handle down, but rather toward me to taper the blade toward the tip. I always (with very few exceptions, such as upswept blades) keep the main cutting edge level.

I agree that practicing on wood would help. I wish I had been given that advice when I started. Grinding on wood would help you develop the "feel" of grinding, because it would be so easy to remove too much. The main problem I have is trying to go too fast. I get impatient and want the blade ground NOW! I have to tell myself to slow down. Just take off a little at a time. I only grind from the plunge to the tip (in one direction) unless I'm finishing.

Keep practicing. The samples you posted really look great for a beginner.

[cactusforge]

Coop, All or the above is very good advise. I do all my grinding
freehand, hollow and flat, I use a push stick but it is mora for support than for pressure. The only time I use gloves is on very
corse grit belts. I use a vise grip on most blades, on very small
blades 3" or less I make a double ended blade so I have a built
in handle, then cut it in half. Gib

[GANNMADE]

COOP ,I'M NOT SETUP FOR HOLLOW GRINDING ,BUT I DO
ALL MY FLAT GRINDING EDGE UP.I ALSO GRIND BAREHANDED.AS I CAN TELL YOUR IN GOOD SHAPE .

[Osprey Guy]

Jim-
Once I get started I only hope my first grinds look as good...

At the rate you pick up on new skillsets, you'll have this mastered before I can even get a grinder up and running...

Dennis

Yeah Baby!

[Kelly Carlson]

Very good first attempts, Coop.
The rest is PRACTICE.
I don't use a tool rest for hollow grinding, but do use one when flat grinding small folder blades.
I do use a push stick for profiling and initial grinds before hardening, but stick to bare hands after hardening.
A bucket of water on a low table just under the whell catches dust and sparks, and also serves as a convenient cooling dunk after each pass on the wheel.
For small folder blades, I needed something better than the blade to hold onto, and fashioned a few holders from scrap steel which engage the blade at the pivot pin hole, which I drill after profiling. Another approach is to make double ended blades and use one as the holder - good for most steels, but not always practical for expensive damascus.

[Frank Niro]

Hey Jim maybe you are doing better than you think for the time you have put in. What I'm saying here is that I'm sure almost everyone will tell you it can be a long slow learning process and it looks like you got off to a very good start. Frank.

[Bob Warner]

It is also a good idea to change the water as the grits get finer. When grinding with a 60 grit belt the "Dust" is large. When you get to 600 grit and dunk your blade to cool it down, you can pick up some 60 grit dust and scratch your blade pretty deep.

[mike koller]

Jim,
...make sure your grinder is at a comfortable height for you,your arms should be near 90 degrees when locked to your sides.

Also,practice taking a blabe all the way through to finish, as noted earlier it is easy to get them too thin in the coarser grits.

Have fun!!!

OH!!! One more thing....If you have a disc sander make sure the spine is nice and square. If it isn't and you true it up on a blade that you have already ground you may be suprised how even you did manage to get the top of the grinds.

[Gary Mulkey]

Coop,

Nice job for your first attempts. Here's a tip that I learned from someone here on the forums. I had trouble at first when I tried to line up the plunge cuts on each side as I was rough grinding toward the tip of the blade. I later learned to round off the edges of my grinder wheel and dull the edges of a 120 grit J-flex belt. Then do the plunge cuts by grinding toward the tang . This way you can match the two plunge cuts perfectly.

Gary

[Will]

Coop, I cant' add much to what has been said, I grind free hand edge up, flat and hollow.

The only thing I do diferntly is that I have a small jig( two pieces of o-1 bolted to gether over the blade to keep the pluges even) and I use a blade grinding magnet to hold the blade while rough grinding. When I go to 220 and abouve I just hold it with my hand and slow the belt down.