Thread: Chisel Hardness Study, the first step.

Thanks, heat to orange/yellow and quench. Mineral oil works well too, cheaper than olive oil at the farm supply.

I want to expand the maker range in a couple of directions. First I want to pick up a set of those Japanese Funmatsu Nezumi chisels. I understand that the proprietor of the Tools From Japan webstore is in some difficulty at the moment however. I also want to add a Stanley set since they've possibly made more chisels distributed in NA than any other mark.

I plan to try to improve the under-performers in my test set, right now I'm thinking of cryo treating, less trouble than pulling the handles and re-heating them. We'll see.

I have found that a night in the deep freezer often does new production chisels some good.. It's not supposed to work - but does often enough..... It's not proper cryo - but I already have it here free... At worst - it does nothing... So there's no real downside..

Oh, and if you only torch harden the last inch or so - it has no effect on the handle. You can also clamp the chisel for tempering the end of the chisel in the fry pot (not the whole thing) - which usually doesn't hurt the handle either.

But usually I am making a new handle anyway - so off with it's head.

I've seen a small effect at -80 ^oC on 1095 spring steel, 0.5 to 0.75 HRC overnight. At -196 ^oC (LN₂) 1095 gains about 4% in hardness with a 2 hour soak. My welding supply place sells LN₂, only real problem is that you need a Dewar flask to put it in.

LN2... Welding supply you say...

I have been wanting to try that for some time now...

Easy peasy. Just get yourself a small styrofoam cooler to do the treatment in and you're set. Just don't put any body parts in that you value or they'll freeze almost instantly. Little splashes don't matter.

This is what you need to carry it: https://www.ebay.com/itm/10-L-Liquid...kAAOSw~gRViLg9

Warning, don't put the Dewar into the passenger compartment of your vehicle or any other closed space or you could suffocate yourself.

Showing my ignorance here. I thought a Dewar flask was one of these:

dewars-scotch-175l-400x440.jpg

I was wondering why "Dewars". Why not not Johnny Walker or Glen Livet?

I only know it as a vacuum flask . Will an ordinary vacuum flask do the same job or there insufficient security or the lid will not stand the temperature?

Regards
Paul

Originally Posted by Bushmiller

I was wondering why "Dewars". Why not not Johnny Walker or Glen Livet?

Invented by James Dewar in 1892.

Originally Posted by Bushmiller

I only know it as a vacuum flask . Will an ordinary vacuum flask do the same job or there insufficient security or the lid will not stand the temperature?

Regards
Paul

Best to get a purpose built unit. My impression is that you'll need it because the fillers won't work with your lunchbox style thermos.

The unit I linked above is surprisingly cheap at just over $200. I bought one about 8 years ago, 10l capacity, and it was around $500 delivered.

Be very careful if you try this, you can get seriously hurt if you make a mistake.

Originally Posted by Bushmiller

Will an ordinary vacuum flask do the same job or there insufficient security or the lid will not stand the temperature?

I've posted this before but cannot find it so here it goes again,

Back in the early 1990's I was lecturing a group of first time physics students in a 350 seat lecture theatre.
There was nominally 250 students in the class but only about half would turn up for lectures.
It was at 6pm at night and to pique their interest I always did a few demos part way through 2 hour lecture which they liked.

The topic for that evening was thermodynamics so a organised a few bits and pieces including some liquid nitrogen to show the student what happens when you put various materials in liquid nitrogen. The techo who provided the gear organised a partially filled 20L Liq N2 dewar on a safety stand on wheels but as the lecture was on the other side of campus I did not want to drag that dewar across campus so I looked around for a 2L SS thermos which we have used for this purpose before. I could not find the SS thermos so I grabbed a thermos with plastic housing outer and a double walled glass inner.

BIG MISTAKE - DO NOT DO THIS.

I transferred 2L of Liq N2 to the glass thermos and carried it across campus did the lecture and the demonstration mid way through the lecture - all good. At the end of the lecture I still had ~500 mL of Liquid N2 left in the thermos so I tipped the thermos upside down to tip the Liq N2 over the lecture theatre stage. I tipped the thermos sort of to my side with the bottom of the thermos facing the students.

When the thermos was tipped over the thing exploded in my hand and it blew the the plastic bottom off the thermos and fine grains of crushed glass came shooting out through the rear end like a firework out and showered the front couple of rows of lecture theatre seats. It was quite spectacular, a loud BANG! follow by silvered glass twinkling as it came down and I got a standing ovation. Fortunately these students were slack so they all had sat towards the back of the lecture theatre. Luckily no one was injured although some students did tell me the following week that the sound rang in their ears for some time afterwards.

Later I worked out what happened. Liquid N2 is cold enough to condense oxygen out of the atmosphere. As the outside of the inner glass part of the thermos got colder and colder it eventually started to condense a few mL of oxygen which accumulated as liquid in between the bottom of the plastic housing of the thermos and the glass thermos. Then when I tipped the whole thermos over the liquid Oxygen would have run down the inside of the plastic housing onto warm plastic up near the top and turned rapidly from a liquid to a gas. This would have been more than enough to cause the explosion and shatter the glass internal part of the thermos.

The lesson here is
a) not to use glass at all
b) not to use any multiple walled container unless it fully filled with sublation like styrofoam etc and is strong enough to with stand this effect - this means steel or similar vessel.

So you can use an thin walled SS thermos (for temporary transfer - not transport) provided it consists of just the double walled SS part of the thermos.

After that we purchased a set of half a dozen 2, 3 and 5L SS thermos and threw out all the glass ones.

Here in Australia filling and transport from any commercial supplier of Liq N2 has to be performed with certified containers. If you turn up with a SS thermos they wont fill it.

Bob's comment reminds me that I forgot to mention that you should also use appropriate personal protective equipment consisting of splash goggles (not just safety glasses), cryo-gloves and protection for exposed body parts.

There are more and less professional places. One of my vendors won't sell LN₂ to you if you're driving a vehicle lacking outdoor storage. The other would probably fill any container you present if you ask.

To reiterate - do not use LN₂ in an enclosed space, it displaces oxygen and can kill you faster than you can realize. See https://www.wired.com/2009/03/march-...st-fatalities/

In college physics......

You sat up front with the Theoretical guys so you could catch what they said and wrote before they erased it....

You sat much farther back when the Experimental physicists lectured - so they wouldn't catch you on fire, electrocute you, or some such....

I am just saying - your students knew you.

Originally Posted by BobL

I've posted this before but cannot find it so here it goes again,

Back in the early 1990's I was lecturing a group of first time physics students in a 350 seat lecture theatre.
There was nominally 250 students in the class but only about half would turn up for lectures.
It was at 6pm at night and to pique their interest I always did a few demos part way through 2 hour lecture which they liked.

The topic for that evening was thermodynamics so a organised a few bits and pieces including some liquid nitrogen to show the student what happens when you put various materials in liquid nitrogen. The techo who provided the gear organised a partially filled 20L Liq N2 dewar on a safety stand on wheels but as the lecture was on the other side of campus I did not want to drag that dewar across campus so I looked around for a 2L SS thermos which we have used for this purpose before. I could not find the SS thermos so I grabbed a thermos with plastic housing outer and a double walled glass inner.

BIG MISTAKE - DO NOT DO THIS.

I transferred 2L of Liq N2 to the glass thermos and carried it across campus did the lecture and the demonstration mid way through the lecture - all good. At the end of the lecture I still had ~500 mL of Liquid N2 left in the thermos so I tipped the thermos upside down to tip the Liq N2 over the lecture theatre stage. I tipped the thermos sort of to my side with the bottom of the thermos facing the students.

When the thermos was tipped over the thing exploded in my hand and it blew the the plastic bottom off the thermos and fine grains of crushed glass came shooting out through the rear end like a firework out and showered the front couple of rows of lecture theatre seats. It was quite spectacular, a loud BANG! follow by silvered glass twinkling as it came down and I got a standing ovation. Fortunately these students were slack so they all had sat towards the back of the lecture theatre. Luckily no one was injured although some students did tell me the following week that the sound rang in their ears for some time afterwards.

Later I worked out what happened. Liquid N2 is cold enough to condense oxygen out of the atmosphere. As the outside of the inner glass part of the thermos got colder and colder it eventually started to condense a few mL of oxygen which accumulated as liquid in between the bottom of the plastic housing of the thermos and the glass thermos. Then when I tipped the whole thermos over the liquid Oxygen would have run down the inside of the plastic housing onto warm plastic up near the top and turned rapidly from a liquid to a gas. This would have been more than enough to cause the explosion and shatter the glass internal part of the thermos.

The lesson here is
a) not to use glass at all
b) not to use any multiple walled container unless it fully filled with sublation like styrofoam etc and is strong enough to with stand this effect - this means steel or similar vessel.

So you can use an thin walled SS thermos (for temporary transfer - not transport) provided it consists of just the double walled SS part of the thermos.

After that we purchased a set of half a dozen 2, 3 and 5L SS thermos and threw out all the glass ones.

Here in Australia filling and transport from any commercial supplier of Liq N2 has to be performed with certified containers. If you turn up with a SS thermos they wont fill it.

Sharpness testing results 021718a_Page_111.jpg

Sharpness testing results 021718a_Page_112.jpg

Sharpness testing results 021718a_Page_120.jpg

Sharpness testing results 021718a_Page_118.jpg

Sharpness testing results 021718a_Page_119.jpg

No apparent correlation of hardness and edge retention.

Sharpness testing results 021718a_Page_115.jpg

Sharpness testing results 021718a_Page_116.jpg

And not much correlation if any of included angle and edge retention.

Sharpness testing results 021718a_Page_113.jpg

Sharpness testing results 021718a_Page_114.jpg

But at least I finally have identified a couple of sets of British chisels that perform well.

Originally Posted by truckjohn

In college physics......

You sat up front with the Theoretical guys so you could catch what they said and wrote before they erased it....

You sat much farther back when the Experimental physicists lectured - so they wouldn't catch you on fire, electrocute you, or some such....

I am just saying - your students knew you.

If only I could believe they were that smart. 95% of the students were from other faculties and had to do one semester of what was basically high school physics. Very few of them wanted to be there which is why only about half of them turned up. These day with all the lecture notes on line the lecturers are lucky to see 1/4 of the class after week 2 of semester.

Bob

Does that sound the death knell for face to face lectures in the future?

Rob

Sorry. I promise no more digressions.

Back on topic. Are you at a stage where you are going to embark on chisel making but if not, how much further will you need to test and investigate existing brands? I am rather interested in seeing a new chisel maker emerge.

Regards
Paul