Thread: Hollow Grinding help?

Nicko, at this point you need to take the advice of the other guys and purchase a shave ready straight razor from the SRP Classifieds, a strop, brush & soap and learn how to use them. You will need exposure to both wedge grinds ( single concave) and german grinds ( bi-concave).
Then you need to learn how to hone. After you have used & honed 10-20 different razors and read most of the posts by the various razor makers and watched various hollow grinding videos then you will be ready to start grinding straight razors. I do not want to rain on your parade or discourage you but the fact is that a number of knife makers have thought that they could easily grind a straight razor. They all found that it was not easy. The guys here on SRP are willing to help but you first must start with the basics. There is no cookbook recipe to learn this. Ya just gotta start by shaving with straight razors.

I wish you well

What a good write up Holygates! I can see you spent a lot of study time and I really liked reading the heat treating stuff. I liken steel to glass it can be tempered in many ways and nearly always has some stress in it somewhere.

Do you know if O1 is a steel that slowly improves with age? I learnt this the other day. Some steels (not all) change their crystalline structure over time and they improve. Mercedes used to leave their engine blocks and some components outside to de stress over a couple of years.

Thanks for taking the time to do a write up!

Originally Posted by Nicko

...I liken steel to glass it can be tempered in many ways and nearly always has some stress in it somewhere.

Do you know if O1 is a steel that slowly improves with age? I learnt this the other day. Some steels (not all) change their crystalline structure over time and they improve. Mercedes used to leave their engine blocks and some components outside to de stress over a couple of years.

I'd like to know what resources you're getting that information from. It will make it much much easier for me to give you an answer.

Hey Mike my dad told me that info. He is a fitter and turner and worked at the Australian mint for a long time. He then trained as a silversmith and made titanium jewelry for a long time also. He hasn't got a shop set up now and is a busy guy so I only get to call him now and then. I don't know where he heard about that but you know what steel trades are like, if something's interesting word gets passed around.

Nick

Originally Posted by Nicko

What a good write up Holygates! I can see you spent a lot of study time and I really liked reading the heat treating stuff. I liken steel to glass it can be tempered in many ways and nearly always has some stress in it somewhere.

Do you know if O1 is a steel that slowly improves with age? I learnt this the other day. Some steels (not all) change their crystalline structure over time and they improve. Mercedes used to leave their engine blocks and some components outside to de stress over a couple of years.

Thanks for taking the time to do a write up!

I am a Toolmaker by trade. We would make all our tools whenever there was a slow period. Sine bars, precision grinding vices, angle plate etc. They were always made out of a carbon steel & case hardened for it was the most stable after heattreating. We would often place the blanks on the roof of the shop for years to "season" the material. Now I'm not sure if and anything was happening to them, but thats what I was told to do. Urban Legend? Perhaps, but who could argue with the boss. Who was straight "OLD SCHOOL"

Originally Posted by Nicko

...Some steels (not all) change their crystalline structure over time and they improve. Mercedes used to leave their engine blocks and some components outside to de stress over a couple of years....

Interesting stuff. Maraging steels must be aged to restore some of their properties, and Robert Mushet patented a 'self-hardening' steel in 1868 which was air hardening - I suppose it was an early tungsten-steel alloy that produced a very hard steel, though, rather than improving with age.

I recall another steel that was produced by Mushet in the 1850s especially with train tracks in mind - the more it was subject to stress, the harder it got. Heavily trafficked lengths of track had to renewed every six months at the time - after years Mushet's length of track, placed in one of the heaviest trafficked parts of the line was still as good as new. It lasted an incredible 16 years, and although the train company promised to deliver it as an exhibit, it was unceremoniously scrapped when finally lifted.

As far as ageing goes, it appears that strength and rigidity are improved at the expense of plasticity and toughness, which may or may not be a desirable thing as far as razor steel is concerned - Mike Blue would know the answer to that one!

I guess that the answer to most things can be found by extensive research - ie reading books, particularly scholarly articles - and forming your own opinions then experimenting to confirm the validity of your theories, rather than by reading the opinions of others. It's a proven, old-school approach though - not much favoured in this must-have-it-now day and age.

Regards,
Neil

Originally Posted by Neil Miller

Interesting stuff. Maraging steels ...

...- the more it (rail steel) was subject to stress, the harder it got.

...It's a proven, old-school approach though - not much favoured in this must-have-it-now day and age.

Regards,
Neil

There are legendary tales of the Frankish steels being able to withstand a Russian winter when other steels would fracture in the cold. The reason is more likely very clean steel and optimum heat treatment. That's even more amazing since none of the concepts we bandy about were known at the time. It was simply luck and the moment to moment awareness of a keen smith. Some of those blades were more sought after than wootz, another remarkable material resulting from the luck of a local ore source and near religious attention to repetition in processing.

There are legends of old blades being reported to lose hardness, or becoming more brittle over time (several generations of time not a year or two). Probably that is best explained by crystalline changes due to improper heat treatment. But a blade that became more brittle would be harder right? If you believed that a blade that was easier to break must be harder, then it's true. If the blade breaks because of larger fracture planes and inclusions then it's not. It's very relative. The legends, do not mention the steel improving with time.

Both of the steels Neil mentions are special cases developed for those characteristics. The maraging process is really a reference to the long heat treatment (aging) process that sets up the structure of the alloy. Interestingly enough the alloy does not depend on carbon like other steels do but moreso on the alloys like nickel.

The rail steels contain manganese and are designed to work-harden at the surface. An old railroad blacksmith, who honestly hated talking about 35 years of on the job stuff, was a treasure for knowledge and pure talent. His explanation (old school) was the surface hardness allowed the train to roll easier and the un-hardened body of the rail remained tough. Nothing like a broken rail to give the engineer a bad day. I have no problem with old-school stuff, but it makes me dig even deeper into the books so that I know for myself where the common ground is between OS and NS. And what is true and what is legend.

A good deal of this stuff leads to confusion between the old school types and the present day metallurgists. Some of this kind of thing is riding the edge between truth and superstition, or nothing more than a coincidence that it happened the way it did. Trying to repeat the process means nothing more then, than attempting to repeat a coincidence, not a repetitive process that will work every time. I know smiths who will leave steel out in the weather to rust and weld successfully every time. Other smiths can't weld until all that rusty skin is ground completely clean. Some like a little flux some like a lot. Mostly success is based only on the variable known as confidence.

O-1, if heat treated correctly the first time, would probably not change in a detectable way for several lifetimes. The only way to know is as Neil suggests, study then make some blades.

Thanks for the input! Very interesting getting different takes.
I wish I had several lifetimes to test this. I think if steel is like a crystal it might change overtime but that may only be when it's heated and therefore allowing the state to change. I know concrete is in a constant hardening state and most of the action starts in the first 28 days after it poured. If a blade was treated with a hard edge and a tempered spine then there would be a constant internal stress? Anyways we could probably discuss it forever just thought I would see if there is a Definate answer.

Yes. Some forms of iron-carbide crystals are more stable than others. The differential heat treatment you describe does have different stresses at the edge than the spine, that's what gives a longer blade the classic curved edge. But it can occur in short blades too. It depends on the type of steel. A steel that is low hardenability will have a measurable change from straight when quenched. A through hardening steel will not change much at all. It also depends on the type of quench, whether oil or water, faster or slower. It also depends on the temperatures of both heat and quench and the amount of time involved in the various parts of the process.

No there is no defined answer as it depends on so many variables. Most places that sell steel will give you a spec sheet that specifies times and temperatures, but even they will give a range rather than a specific recipe.

That's what makes steel so fascinating. When you think you know something, you find uncertainty. It's great training for remaining flexible.

Whiskey and wine improve with age. Steel, when properly heat treated is as good as it will ever get.

It goes something like this; Back in the day Fe and Al alloys would indeed get better with age. This is why MB let their blocks sit for years to season. Also why hot rodders use to like to build a “seasoned” block. We did eventually learn to get the HT correct and the stability problems all but went away. Just as true with tool steels as with cast iron.

Nicko,
Do your research on blade geometry. Buy one and learn to use it. Get some O1 and go to town.

I see little reason to shave or hone with dozens of blades. It would, however, shorten your learning curve. You will need to use the ones you create. Get them into the hands of someone else and get feed back. Then use them some more. I suspect that every successful maker, large or small, can use a straight very handily.

The higher your skill in metal working trades the shorter your learning curve is likely to be.

Jump in with both feet the waters fine. The worst that can happen is you scrap a chunk of metal. The best is you learn something about yourself.

Jeff