What straight razor/Kamisori dimensions for a 4" contact wheel?

[JG Custom Metal Works]

I was supposed to get a 5" contact wheel today but the guy sent me a 4" instead. Would the hollow it would make be too drastic to make a decent straight razor/kamisori? If not, what would be the optimal thickness and width for a design being ground with that contact wheel size? I've done a good amount of research before starting this thread but was unable to find anything in regards to using a 4" wheel, with a certain stock thickness/width, in particular.

I like the idea of grinding it like in this video:

https://www.youtube.com/watch?v=2fAXTWUrzMo


Any help you guys can offer would be greatly appreciated.

 

[razormaker]

Maybe this will help you decide. For a 6/8 razor I use a 6" wheel and get what is considered a half hollow grind. For a 7/8 razor I also use the 6" wheel and get a 3/4 hollow grind. My 6/8 blanks are .220 in thickness and my 7/8 blanks are .250 in thickness. Your wheel size will be more of a factor in your depth of hollow grind.

I hope this helps.

 

[JG Custom Metal Works]

I'm just trying to decide what would be the optimal steel thickness and width for use with this 5" contact wheel. In regards to the depth of the hollow, I'm not sure what is considered a standard with straight razors. I don't want to do anything to extreme. Just a well proportioned straight razor. I more or less just need an opinion as to what would be a good thickness/width to use with my 5" wheel. Specifically for grinding one using the method in the video I posted above.

Well, it turns out the guy who I bought the wheel from sent me a 4" wheel, not a 5" wheel. Apparently he thought it was a 5". So am I screwed? Is it possible to make a decent straight razor with that deep of a hollow?

 

[razormaker]

A 4" wheel will do a pretty deep hollow grind on a 6/8 blade. I would still try to find some steel not more than .210 thick for that. You can also leave more reveal along the top of the spine and keep it from getting too deep. You will find that there is no one size fits all method for this. Expect a learning curve if you try to get a thin, hollow ground blade.

Good luck and post some pics of your progress please.

 

[jdm61]

So would the 4 inch wheel with a little reveal work on a 6/8 made with this new .196 AEB-L stock that Alpha has?

A 4" wheel will do a pretty deep hollow grind on a 6/8 blade. I would still try to find some steel not more than .210 thick for that. You can also leave more reveal along the top of the spine and keep it from getting too deep. You will find that there is no one size fits all method for this. Expect a learning curve if you try to get a thin, hollow ground blade.

Good luck and post some pics of your progress please.

 

[razormaker]

So would the 4 inch wheel with a little reveal work on a 6/8 made with this new .196 AEB-L stock that Alpha has?

I would try it. Keep in mind, the thinner your steel is, the harder it will be to maintain the angle necessary to hone the razor properly. I know there is a math formula, W X D, to get the proper angle, I don't know the numbers though.

 

[jdm61]

No more than 1 to 4 thickness to width at the top of the grind appears to be the simplified formula.

I would try it. Keep in mind, the thinner your steel is, the harder it will be to maintain the angle necessary to hone the razor properly. I know there is a math formula, W X D, to get the proper angle, I don't know the numbers though.

 

[JG Custom Metal Works]

Please forgive my ignorance in regards to this subject, I'm new to straight razors AND hollow grinding. When initiating the grind on the blank razor, do I start the grind at the lowest point of the blade(where the edge will be)? Or, do I start a little above? I ruined a blank the other day starting too high up on the bevel.

What would be, in your opinion, the optimal steel thickness for grinding with a 4" wheel?

Thanks a bunch for the help gents, I appreciate it.

 

[razormaker]

Please forgive my ignorance in regards to this subject, I'm new to straight razors AND hollow grinding. When initiating the grind on the blank razor, do I start the grind at the lowest point of the blade(where the edge will be)? Or, do I start a little above? I ruined a blank the other day starting too high up on the bevel.

What would be, in your opinion, the optimal steel thickness for grinding with a 4" wheel?

Thanks a bunch for the help gents, I appreciate it.

I will try to impart some experience I gleaned from my mistake pile.

Although steel thickness is important, the width or height of the blade you are grinding is more important. A 4" wheel will do a good job on a 5/8 or 6/8 razor. Keep in mind, none of them will be a one pass grind. Meaning, you will have to roll the hollow grind from top to bottom to make a razor. A 4" wheel has such a small radius that it will not create a hollow grind that has good dimensions. That being said, if you want to try a 6/8 razor, you will need steel in the .200 thickness range. Try some Aldo Bruno 52100 in the .187 thickness. It arrives at .205 but requires some cleaning up.

Start your rough grind from the cutting edge of the blade. This is the bottom of the blade but is oriented up when grinding. Work your way to the top or spine of the blade. The reverse is true when finish grinding. Take care to keep the cutting edge centered and leave at least a good 1/16th on the cutting edge. Too thin and it will warp bad when heat treating. Do all of your shaping of the handle and top spine before heat treat, grinding to around 220 grit. Don't forget to drill the hole for the pin.

The grinding method in your video is great for rough grinding but when you get to the finish, get your fingers on that blade. A piece of steel only a few thousands thick will burn in an instant. You will want instant temp reports that only your fingertips can provide.

I hope this helps.