Burning my edges

D

Don Nguyen

Joined
Oct 4, 2011
Messages
1,043
In the past I have only rough ground my knives at 36 and hand sanded the rest. Since I make kitchen knives, most of my shaping is done post-HT. The grinders I've been using are 3450 RPM with 10" drive wheel, single speed, severely dished platen. If I try to use higher grit belts, even just 120, it only grinds on the edges of the platen.

Today I was trying out the Trizact Gator belts, and they were working pretty well, but I ended up burning the edges on two of my knives, which I was nearing completion :(

I was being suuuper careful not to overheat the blade, but even then I still burned.

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I was really hoping to finish these no problem and sell them to fund for my own grinder, but now I'm going to have to wait. Maybe I should've been patient and just hand finished them; it goes so slowly though because I haven't been able to afford good paper, and the last knife took like 20 hours just to get to a clean 400.

Not much I can do now. Today was the last day I had access to a grinder for a while (school set-up). Just had to ramble for a bit.
 
You definately need to use slower belt speed with finer grits. I don't know what type of grinder you have? Any way to add a pulley and belt system to it.?
 
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It's an old Wilton grinder at school. Direct drive, no modifications allowed. It definitely made it worse that since the platen was dished, it was only grinding on two very small spots rather than a larger, more even surface area.

It's now a thing of the past, and I'll soon be working on my own grinder sometime soon.

I was really, really upset about it yesterday. I spent 8 hours at the grinder expecting to practically finish the blades on the last day I have access to all the equipment, only to burn both of them (maybe I should've learned my lesson with the first one). I've cooled down now, and since summer just opened up I'm no longer in a rush.
 
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Aside from the insane belt speed, here are two other pieces of advice:

1. Use new belts for post HT blades. Dull belts will create more friction and remove less metal. They are the main reason blades heat up in my shop
2. Dip in water every pass. Make sure you don't use gloves, and dunk the blade when it starts to get warm. Not hot, but warm. Yes, it slows down the process but it is much faster than starting over.
 
Jason, thanks for the tips. I tried to makeshift dress the gator belt, but it didn't provide too drastic a change. The belt was fairly new though... Also ground without gloves and dipped practically every chance I could. I think maybe with a knife this thin, that grinder isn't suitable for higher grits.



For future reference though, I heard that the gator belts were supposed to be run fast and without water. I'm drying the blade after each dip, but concerning speed, what is optimum?
 
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