Thread: Will belt grinder work to hollow grind blades? Thanks guys.

Will this belt grinder, sigh I failed with my title.


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Im having a hard time finding people talking about grinders for razors. Does the lack of speed adjustment eliminate this option?

Search for belt grinders and you will find quite a few threads of DIY grinders, that will give you an idea what to aim for.

Yes and no

It will be no problem for the rough phase of the work, hogging out a blade before heat treatment.
But after HT, it's a different story. Especially with higher grit belts where healt build-up is a real problem. If you run a high grit belt at 3600 FPM and put a razor to it, the thin parts of the blade will heat up almost instantly to temper ruining termperatures.

For knives, this problem is more manageable, so it is not unreasonable to call it a knife belt grinder. Knives are a lot heavier, so there is more mass to act as a heatsink. Knives are typically also not hollow ground, which means the surface contact area is a lot smaller. The smaller surface means less heat buildup. Those 2 things combined are why knives are not as sensitive to the problem, and the reverse is why this grinder is not suitable for high grit polishing razors.

Originally Posted by Bruno

Yes and no

It will be no problem for the rough phase of the work, hogging out a blade before heat treatment.
But after HT, it's a different story. Especially with higher grit belts where healt build-up is a real problem. If you run a high grit belt at 3600 FPM and put a razor to it, the thin parts of the blade will heat up almost instantly to temper ruining termperatures.

For knives, this problem is more manageable, so it is not unreasonable to call it a knife belt grinder. Knives are a lot heavier, so there is more mass to act as a heatsink. Knives are typically also not hollow ground, which means the surface contact area is a lot smaller. The smaller surface means less heat buildup. Those 2 things combined are why knives are not as sensitive to the problem, and the reverse is why this grinder is not suitable for high grit polishing razors.

Thanks so much, this was exactly the type of specific response I was hoping for. Can I trouble you to tell me what you think the best for the money belt grinder is? Most other things have been fairly easy for me to research but this one evades me. Thanks!

Some people make their own belt grinder. I am not one of those people
I bought my grinder in germany, simply because of shipping cost. Good grinders weigh a ton, so you have to buy on your own continent / landmass. For western europe that is this one:
Bandschleifer Modell 2-S

For the US, I would go with KMG. It's practically the industry standard, and they're solid and dependable. Here too I would go with the variable speed drive instead of the pulley system. It's a bit more expensive, but with the ability to change the speed with the turn of a button will make your life just so much easier.
Beaumont Metal Works : Variable Speed Packages : KMG Belt Grinder Parts Knife Knives Industrial Commercial Metal Belt Grinders Sander USA

Still, this is quite expensive. The only real alternative is to build your own.

Thanks again for taking the time to help me. I had seen people mention the KMG but wasnt sure there wasnt a better beginner option. Looks like I know what I gotta do after seeing if building one is something I wanna take on. One last question, will the three speed option work well enough, or is the $500 upgrade more than a convenience option?

In terms of 'will it work', yes, the 2 speed option will work well enough.

The main reason I think varispeed is the best buy (if you can afford it) is that I work on various projects at the same time, and sometimes I just need to quickly remove some metal, or quickly just polish an edge, etc. Since you need different speeds for each, switching between jobs is as easy as switching between belts. If you have a pulley system, it takes a bit more time. That is all.

Also, with a variable speed set up, you can have any speed, not just the ones the pulleys allow. I have variable speed, and would not be satisfied with anything else. Yes, it's more expensive, but well worth it.

If I had the extra money I would probably go for a KMG variable speed myself. But I don't, so I made my own with step pulleys and honestly yes it takes more time to switch things, but with a limited amount of cash it will be a long time before I make the jump to a $1.5k+ machine. I'm sure using a nice KMG would be a world of difference, but honestly my home-made one lets me easily do a lot, it's smooth, gives me the speeds I need and I really have no complaints with it. Plus I saved myself a grand or more...

oh... and 3700 SFPM is way to fast for razors, and the vast majority of knives. I hollow grind 90% of my knives and while the cross-section is thicker than razors, I still like to stay in the 1800 SFPM ball park.

Originally Posted by wynndow

oh... and 3700 SFPM is way to fast for razors, and the vast majority of knives. I hollow grind 90% of my knives and while the cross-section is thicker than razors, I still like to stay in the 1800 SFPM ball park.

Im sorry but alot of this is really new to me. Is this the measure of speed that the belt is moving? Can you elaborate more? I would be left obliged.