A Little Help With Grinds

colu41 · May 3, 2015

So I've done some grinds by hand but mainly I used a homemade jig. I decided to put that to the side since I've moved my sander back into the garage. Learning to grind by hand is so much more convenient than having to clamp in a jig and get the angles right and all that. Especially with after HT finishing.
But I have a small problem that I can't seem to figure out. With one hand grinding, I get this

A nice, straight grind that tapers up.
Where with my other hand, here:

Im getting a slight dip after the plunge, then the taper to the top. I thought I was pulling the blade too straight but when I was fooling around today with a full flat I'm doing, I just couldn't figure it out.

Any tips?

Maelstrom78 · May 3, 2015

Either you are angling the blade somewhat on the "smiley" face side or you just need to spend more time on the belt at the bottom of the dip.

i4Marc · May 3, 2015

Grind your least confident side first. Once you have gotten that where you are pleased with it you can match it with your most confident side. The dip you see in the second photo is where you need more pressure. Remember, keep your elbows at your side and use your legs to shuttle your upper body back and forth. The less parts you have moving the more consistent your grinds. Keep your knees slightly bent. You will be able to move side to side more smoothly. When grinding the side of the blade seen in the second picture, hold the tang in your right hand. Your right hand thumb shifts up or down to direct pressure towards the top ( the cutting edge as you grind edge up) or towards the bottom (spine as you grind edge up). Your left hand thumb supports and steadies the blade as you press the blade into the belt. Your left thumb also shifts up or down (or side to side) to direct pressure to where you want material removed. If you have a dip, as pictured, place your left thumb in that position on the blade as you grind. Gently lay the blade against the belt until the bevel lays flat against the belt carefully slide it over towards the plunge (you don't need to go all the way to the plunge) to start your pull. As you begin your pull towards the dip, add pressure with your left thumb as you pass the dip. You should remove more material there and the grind line should go up. Don't press hard. Do a little at a time and visually check the progress. If your edge is already as thin as you want it and don't want to remove any more material there use your left thumb to add pressure slightly more to the center or spine . You will remove material in that direction while leaving the edge thickness as is. When you get the line raised then make a couple of even pulls to blend everything into a smooth line.

cdunn · May 3, 2015

When this happens with me, I find that keeping my elbows tucked at the sides of my body, as they should be, I am unconsciously rotating
my whole body, which causes the arch effect. I try to, while keeping my elbows planted or tucked to the sides of body, pull my hands, holding the knife blank, across the face of the wheel while maintaining my forearms on level plane. Once a hollow begins to form, you can kind of feel
when the wheel drops into this hollow on subequent passes. Then you can adjust by tilting or putting upward pressure on the blank as you
pull it across the face of the wheel to control the shape of the hollow. The reply above by Marc gives a great description more in detail. Free hand hollow grinding is an individual ability and can only improve with practice by the individual. This is a summary of my thoughts in answering the above question, it may be meaningless to some but has worked for me for a long time.

S.Alexander · May 3, 2015

Another thing that has helped me with freehand grinding is the use of a push stick. When I don't use the push stick and the steel starts to heat up, I have the tendency to pull my hand away. This can contribute to a wavy grind.

HSC /// · May 4, 2015

S.Alexander said:
Another thing that has helped me with freehand grinding is the use of a push stick. When I don't use the push stick and the steel starts to heat up, I have the tendency to pull my hand away. This can contribute to a wavy grind.

+1 on the pushstick
UHMW plastic works well for a pushstick

colu41 · May 4, 2015

S.Alexander said:
Another thing that has helped me with freehand grinding is the use of a push stick. When I don't use the push stick and the steel starts to heat up, I have the tendency to pull my hand away. This can contribute to a wavy grind.

I find myself doing that pretty often. I'll have to try it out.

colu41 · May 4, 2015

I was thinking about this, this morning. And your absolutely right about the blade getting hot. My right hand slightly more rough than my left from work and whatnot. So can stand the heat a little better. But I noticed when I switched sides, I was flinching way too much.

Any special ways to make a push stick? Or just a chunk of wood?.
I was thinking a piece of wood with a nice tacky piece rubber at the end to hold the blade nice and sturdy but, then theres a possibility of it melting.

i4Marc · May 4, 2015

I don't think you want your push stick to be "tacky". The UHMW plastic probably works well because it is the opposite of tacky. It lets you draw the blade across the belt smoothly without drag from the push stick. This is of course if you're working on the tool rest. I don't think it will help if you are grinding unsupported.

Drew Riley · May 4, 2015

Looks like your you're putting more pressure on the side/corner of the belt when grinding at the ricasso on the side of the second picture. Also, it's possible that your blade had a slight bend in it, so that the convex side would be your first pic, and the convex side the second.

S.Alexander · May 4, 2015

I have been using a scrap piece of wood with about a 70° angle on the face. I don't use the work rest because it seems to get in the way.

J. Rosa · May 4, 2015

knife to a gunfight said:
Looks like your you're putting more pressure on the side/corner of the belt when grinding at the ricasso on the side of the second picture.

This^. To me it looks like you are bringing the blade in at a slightly off angle when starting the grind and the combination of that with your hand pressure is creating that dip and the wavy grind line. To clean it up I'd recommend not starting your passes at the plunge because it may be difficult to keep the blade straight when trying to place the blade flat on a moving belt. Instead start your pass by placing the center of the blade flat on the platen with the finger applying pressure also centered on the moving belt and then sweep toward the plunge and then back out toward the tip. In doing passes like this remember, it's a flat grind and you're only working with 2" of surface area. The more consistent you can make those 2" go across the area you're grinding in pressure, speed, and coverage, the more even your grind lines and blended flatness of the blade.

colu41 · May 4, 2015

Thanks guys. I will definitely have to whip up some kind of push stick. I have an ongoing thread on building my first 2 x 72. I think it will make life a little easier once I finally decide on that.

cdunn · May 4, 2015

On the subject of push stick, i use thick paper towels, still folded, and very tightly roll them into roll about 11/4" in diameter and about 4"long. Then tape it with masking tape. Wet it by dipping it in cooling bucket and use blade blank to mold the end for use. Advantages to me: not grinding fingers, dipping occasionally keeps hand cooler and cools blank to a degree, if you touch it to wheel accidentally, hands are not shaken, so you maintain control, cheap, quick and easy to make.

Matt Rochester · May 5, 2015

The good thing with no push stick is you will know if it it gets too hot. The bad thing is, you will know when it gets too hot! After burning my fingers over and over, I have started using one. I use mostly 1/8" stock. I take a piece of wood and make a 1/16" to 3/16" ledge on the end to hold the knife. Works well and keeps my tips cool!