Thread: Grinding razors

One of these days my pot of money is going to be full (*) and I want to start learning to re-grind razors, and sometime later to grind new razors from tool steel.
Before I buy anything I want get a better idea of what I need.

Can I use a belt sander to grind and re-grind razors or do I need a stone?
If I need a stone, do I need a high RPM stone for dry-grinding, or a low RPM stone for wet grinding?
If I go with a low RPM wet grinder, what disc size is best?
Any and all tips and information are appreciated.

(*) I have a habit of removing all my 1 and 2 euro coins from my wallet and the end of the week and tossing them into a metal whisky bottle gift box. I have been doing this for 5 years now. It is almost full and when it is I want to spend the money on something that wouldn't normally buy out of the household budget.
I have no idea how much there is, but I am pretty sure it will be more than enough to also buy something expensive for the missus so that I avoid an argument about the need for a grinding setup

I'll be interested to hear what the experts have to say on this as well. The posts I've read and videos I've seen on razor manufacturing lead me to believe grinding is done with belt sanders, and edges are created with stones. There is a video of the manufacturing process at TI somewhere on a website if you haven't seen it. A search here might turn it up.

I know that you can rig up a belt sander for grinding blades, but I'm not sure where you can get the jig or how much it costs. A cheap source of "blanks" are old files as they have the right width/thickness and are made of very hard steel.

Starting with a flat bar of your favorite steel, you have to remove everything that doesn't look like a razor.

That can be accomplished with what ever method, belt, disk, files, chisels, stone wheels you choose. This part of the process does not make any difference. Really, just use the tools you have and get good with them until you can afford better tools that do the job more effectively. You can abrade away material to your heart's content at whatever speed you wish. Grinders will heat up the steel and turn it all sorts of colors, but by that time it will be too hot to hold anyway.

Once the blade has been heat treated, then grinding can dictate a different approach. You don't want to get the blade hot enough to temper away the hardness of the blade.

Wet grinding addresses the problem of heat generated during abrasion and helps to protect the investment put into the heat treatment. You can use a belt grinder running at a slower speed, aka variable speed. But, have a bucket of water handy and work with your bare hands so you can feel the moment that the steel is warming up and cool it right away.

Files are good steel for the most part, IF they are old ones like Nicholson or Black Diamond. Some of the new files are case hardened mild steel and should be approached cautiously. Grinding a blade from a hardened old file will be more work since you have to grind away hard steel and you have to attend to the heat problem if you don't want to lose that hardness. It will take longer in terms of time invested.

Originally Posted by Mike Blue

Starting with a flat bar of your favorite steel, you have to remove everything that doesn't look like a razor.

Got it.

Originally Posted by Mike Blue

That can be accomplished with what ever method, belt, disk, files, chisels, stone wheels you choose. This part of the process does not make any difference. Really, just use the tools you have and get good with them until you can afford better tools that do the job more effectively. You can abrade away material to your heart's content at whatever speed you wish. Grinders will heat up the steel and turn it all sorts of colors, but by that time it will be too hot to hold anyway.

Does that mean that I don't have to care about steel temperature until I get to the heat treating stage?

Originally Posted by Mike Blue

Once the blade has been heat treated, then grinding can dictate a different approach. You don't want to get the blade hot enough to temper away the hardness of the blade.

Maybe a naive question, but why would I grind AFTER the heat treatment if I can do everything before hat treatment?

Originally Posted by Mike Blue

Wet grinding addresses the problem of heat generated during abrasion and helps to protect the investment put into the heat treatment. You can use a belt grinder running at a slower speed, aka variable speed. But, have a bucket of water handy and work with your bare hands so you can feel the moment that the steel is warming up and cool it right away.

What is the significance of diameter of the grinding stone? If I use an 10" diameter stone, won't that mean that I am limited in the grind to something between half hollow and quarter hollow?
Not that I have the desire to jump into full hollows before I know what I am doing, but how are full hollows ground then?

I think you do a rough grind to get the general shape, heat treat, and then do finish grinding because the steel may warp in the heat treating process. I could imagine thin steel warping more easily and being harder to fix

read this: http://custom.straightedgerazors.com/?Making_the_blades

Why not ask Bill Ellis. He sells a DVD on restoring razors. I haven't got it but it is said to be good.

That's a good idea even though I wouldn't turn my nose at Mike's advice either.. Mike has tons of experience with working with metal, especially with blades.

Originally Posted by Bruno

Got it. Does that mean that I don't have to care about steel temperature until I get to the heat treating stage?

Sorry to take so long to get back to this. I am hip deep in teaching a Nordic knife class this week.

You don't have to worry much about the temperature of the steel before heat treatment. Likely even if you have a grinder that could produce temperatures hot enough to affect the steel, you could not hold on to it at those temperatures.

Maybe a naive question, but why would I grind AFTER the heat treatment if I can do everything before hat treatment?

As was noted, rough grinding to shape, then final grinding and polishing after heat treatment are the general rules. Depending on how you heat the blade directs how much grinding afterward. Examples, a coal fire or gas fire will burn the outer skin (decarburization, scaling) and that rough surface has to be ground away to make polishing easier. A salt, or lead bath, as in Thiers, there is no oxygen and the blade could conceivably be ground, even polished before heat treatment. Without oxygen there is no decarb and all that has to be done then is to buff away any minor oxides on the surface.

What is the significance of diameter of the grinding stone? If I use an 10" diameter stone, won't that mean that I am limited in the grind to something between half hollow and quarter hollow?
Not that I have the desire to jump into full hollows before I know what I am doing, but how are full hollows ground then?

It's the radius of the wheel that guides the depth of the hollow. A larger wheel has a much more shallow curve to the hollow than a smaller wheel. I'm no expert on hollow grinding razors so I'll defer to anyone with greater experience here, but of the hollow ground blades in my rotations, there appears to be several different diameter of wheels applied to the blades before finishing. I'd have to watch the shop process to know exactly how that all fits together.

Of the razors I've finished, I use a 12 inch wheel and try to grind in one go with a single radius from the spine to edge. But, I have a 12 inch wheel and that makes more sense than using a four or five inch one and having to move the blade up and down to have a very tight radius at the spine and essentially a flat ground blade at the edge. That's what I consider a full hollow grind, but I may not be applying correct nomenclature to razors.

Your questions are good ones. Nobody wants to gamble on success when they can study things up front and reduce the potential for errors. Still, someday you're going to have to put metal to abrasive. If you could visit someone's shop and spend some time with some hands on guidance, it'll improve your odds of success and confidence. Plus you may get to play with several different methods before settling on the one that's best for you in your shop.

Thanks Mike.

I know that the only way to learn is to actualy do it, just like with honing razors or making scales (or anything). But it is nice to know some basic things before actually doing something. For one thing, it saves money os tool steel and useless tools