Help! Hollow Grinding!

go mike

go mike

Joined
Dec 5, 2008
Messages
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My grinder is finally finished (mostly... few things left) so I thought I'd give a wing at hollow grinding. First off, 60 grit belt, at 3500 sfm, it goes it goes pretty fast!

I took this up to 400 grit, but I'm having trouble holding the same exact position for the length of the blade, and then repeating it. I've uploaded a few pics of what I've done. Any suggestions on how to blend the lines at least?

hpim1841q.jpg

hpim1842u.jpg

hpim1843.jpg



Thanks for any advice.
 
If you are up to 400 grit already , you are doing it wrong. You should have that hollow grind well established before switching to the next grit , the finer grits are for scratch removal and refining the lines , not so much for removing material.

Get a nice hollow groove going and you will have a much easier time of staying in it...

it appears as though your angle and your pressure are not constant , that will come with practice , it kicks my butt on each knife still :)
 
ya when your done with the 60 grit you should have a nice crisp grind that is one pass and not a bunch of diffrent angles. i have a hallow grinding how to video on my web site, check it out and i thonk it will help you out.
 
Try it again and again and again. Someday it will just click and you will be the hollow grinding champion of the world. :)
 
Thanks for everyones answers. Josh Dabney gave me a very detailed explanation, and I watched Jarod's video on it and it made even more sense. I went back and REALLY locked in my elbows, and went back to 60 grit, and I think it turned out pretty nice.
hpim1845.jpg


I hope the dip in the grind height won't be too bad once I start finishing it.
 
I would get that blade flat again on both sides before I started grinding again. Then start back with the 60 grit belt. Your blanks looks rounded off. Pick up some mild steel to practice with first. It is cheap and you can trash it until you get the swing of it. Never give up. If I lay off a while, it takes some time to get my groove back. George Herron told me once that you will get the hang of it after you grind and finish 200 blades. He said to try to grind one or two every day to keep it in your head.
BB
 
its all about getting in that groove, i also like to pull the tang away from the wheel to do the point instead of trying to follow the curve of the edge, that way you have a nice straight grind and your point will be nice and stout.
 
i think you should try around 900 SFPM first ! Then go faster and faster if you really wanna hog off metal. Less likely to mess up real bad at a slower speed :D
 
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