Concave grind radii questions

I hope radii is the plural of radius.

Grinders most often are talked about needed an 8" or 10" contact wheel for hollow grinding. I decided to take a cheap compass and draw some circles out on stiff cardboard; 1", 2", 3", 4", 6", 8", 10". I cut out the profile of each of these and used them as a gauge, placing each in the hollows of some of my single concave straights. Every one of them appears to fit perfectly in either a 2" radius or a 3" radius.

I did notice that the 10" radius touches the top of the spine and the very edge of the razor.

Question: Is the 10" contact wheel in grinding used only to remove the outer portion of the billet quickly and the 2" or 3" used for the actual hollow grinding on a single concave razor?

I was excited to see the 2" and 3" wheels fit so perfectly in the hollows. I'll probably use the grinder I'm going to build for restoration long before I get into making my own blades. I now have visions of 2"&3" contact wheels putting a beautiful satin or mirror finish on single concave razors in not time flat.

Chris L

If you are going to do restoration work, I'd think you would need many different sizes of wheels to be able to do many different razors.

But that is speculation.

I have a cheap low cost low rpm wet grinder which I fitted with rubber and then sandpaper. it is 4" diameter.
What I found was that the wheel doesn't have to fit. It only has to be smaller in diameter.
As long as it is smaller you can work different areas of the concavity without touching the dge or the spine, and get good results.

At first I thought the overlaps would be visible, but they are not.

I do not know if the archives are still available but search for
Razor Central Arthur Boone. Then read the segment 32-37.

RazorCentral - Home of the straight razor

BTW, I have my grinder at home now so stop by any time.

Hope this helps,:)

Most of the custom makers are using 8" wheels, which let you do a heavy grinds. On a 6/8, it's close to a wedge; on a 7/8 it's more like a half hollow.

There are only one or two people doing full hollows, and it sounds like that is what you were measuring. For full hollows, a smaller wheel is necessary, anywhere from 2" to 4". The reason you hear so much talk about 8" wheels is because heavier grinds seem more popular for customs, and because vintage full hollows don't have enough meat in them to allow you to do a proper regrind.

A 2" wheel should fit up into the upper hollow portion of a lot of vintage razors. The tricky part, though, is walking the wheel out onto the lower part of the blade, which is usually flat. Keeping this even is difficult, but I'll bet it's quite doable with practice.

It's easier to get a really good grind on quarter and half hollow blades, because the contact wheel just rides in the groove. You don't have to extend the grind out towards the edge. It's really easy to mess up when doing that.

Make sense? If you can get the hang of this, it's an excellent skill to have. I need to work on it one of these days...

Josh