Thread: Hollow Grinding help?

Wow thanks guys! I am currently not shaving with a straight razor but am cocky enough to try making one.

I saw that dovo razor company are using watercooled stone wheels to grind after heat treat. I have gathered the finish grinding is to be done after the razor is mostly ground because to heat treat a thin edge would melt the razor and possibly warp the profile. But I am concerned that if I grind without the right method I will destroy the temper and as said above make a letter opener.

My friend next door has an Edwin jagger and I noticed on his the diameter of the hollow grind wheel is probably about a 5 inch wheel. I want to use a 10 inch wheel and that might cause me to need a wider piece of steel? So that the hollow grind is in far enough to not be in the way of the shaving process. I have however seen some fairly narrow blades razors with not much of a hollow at all. Maybe you don't need much of a cut away to shave?

They are fat pieces of steel they are using I am thinking 3mm or .125 in the old inch.

I will be using a CPM stainless and that might create some problems? But I am curious how those guys don't effect the temper especially as alot of steels need time to sort out the stresses that lay internally?

Nick

Originally Posted by Nicko

Wow thanks guys! I am currently not shaving with a straight razor but am cocky enough to try making one.

There's no faulting your courage. As has been suggested previously, some study time is strongly recommended. The price of learning on your own face drives the lessons directly home, but if you're not willing, then you need to hold in your hand, some razors and consider everything about the blades. They are not knives, nor chisels.

I saw that dovo razor company are using watercooled stone wheels to grind after heat treat. I have gathered the finish grinding is to be done after the razor is mostly ground because to heat treat a thin edge would melt the razor and possibly warp the profile. But I am concerned that if I grind without the right method I will destroy the temper and as said above make a letter opener.

Good observation about water-cooling. But Dovo is an industrial plant and has been making razors for years. It is entirely possible for the home shop to heat treat a razor after grinding, as many do here. But leave 20-40 thousandths inch edge before HT and carefully grind that away with repetitive cooling afterward. You won't melt the edge. You can ruin the heat treatment.

My friend next door has an Edwin jagger and I noticed on his the diameter of the hollow grind wheel is probably about a 5 inch wheel. I want to use a 10 inch wheel and that might cause me to need a wider piece of steel? So that the hollow grind is in far enough to not be in the way of the shaving process. I have however seen some fairly narrow blades razors with not much of a hollow at all. Maybe you don't need much of a cut away to shave?

A ten inch wheel is not too large. I use a 12 inch wheel and make a "near wedge" Your assumption that a wider piece of steel is needed is correct. The hollow grind exists for another reason and has little to do with shaving efficiency. More study.

They are fat pieces of steel they are using I am thinking 3mm or .125 in the old inch.

I'd suggest 5-6 mm and the reason is your study of the blade mentioned above. There is a specific ratio of spine width to blade width that is necessary. No, I won't say it, dig it up for yourself. It's not very well hidden, and your study is far more important to understanding this stuff, than just having the answers handed to you.

I will be using a CPM stainless and that might create some problems? But I am curious how those guys don't effect the temper especially as alot of steels need time to sort out the stresses that lay internally?

CPM steels have a solid reputation, depending on the alloy and the purpose of that alloy. Most of the development of CPM steels research has been into the perfection of tool steels meant to cut other steels (the M-series). If anything the CPM steels require more attention during the heat treatment process than the simple steels. The metal cutting tool steels will tolerate a lot of heat at working temperatures and not abrade as quickly. No human shaver could generate (or tolerate) that sort of heat while shaving.

There may be a high "cool factor" because you want to use an exotic steel, but there is no practical need for doing so when there are so many other better choices that are simpler (read less expensive and less complicated) to heat treat. They are also cheaper by the pound so if you screw one up grinding it, you don't feel as much pain there either.

Free steels from a scrap bucket are always problematic, unless you know exactly the provenance of the steel. Thinking it's one kind and heat treating wrong is a real possibility.

If you must use a CPM steel, start with CPM154 or the equivalent ATS34. For first practice razors I'd strongly recommend the under-rated O-1 or W-1. It'll be much more likely a successful learning curve all the way round.

Ditto everything in the previous posts. Underline everything in Mike's post. I have made 5 razors, so far, and based on what I have learned since, I am going to go back and redo the finish grind on all of them. A good start on the process would be to read Baldy's "Bastard" post and all the replies. Then watch all of Charlie Lewis's videos. Good luck, and post your progress.

I agree with all that has been said. I would get a razor and become familiar with using it first.

I think the best way to learn to grind is by grinding-> messing up -> learning from mistakes -> grind again. Every time I grind I learn a little more.

Charlie

If you really want to try grinding, think about practicing on some 1/4x 1 inch mild steel. You won't be able to shave with it, but you will learn a lot about the process of grinding.

Originally Posted by skipnord

If you really want to try grinding, think about practicing on some 1/4x 1 inch mild steel. You won't be able to shave with it, but you will learn a lot about the process of grinding.

I should have thought of this sooner than Skip did. It's probably the best advice yet. You'll solve Charlie's equation of learning from mistakes a lot cheaper than my suggestion.