Thread: Blademeisters: Bellied Hollow?

here is what a 3 wheel grind would look like if you didnt smooth out the bumps

Besides being a manufacturing artifact, if you can call it that, does it add anything functional to the razor? I'm speaking of only one belly, left intentionally by a grinder.

Originally Posted by L R Harner

the "soft center" would be more from bad quench not from botched temper

some steels are shallow hardening (but still more then and 1/8 inch deep ) when done right
when you temper you may have the blade at 3-400f for 2 ours of more (that will evenly heat any blade you got )

i could grind and leave a belly but its more like a part way unfinished blade to me as i liek a nice smooth even grind from spine to edge

and yes its done by startign with say a 10 inch wheel then step doen to a 6 then 4 and 2 if you didnt clean up the bellies between the wheels you would have a ridge for each when that you "stepped" down to the bigger the difference in wheel size the wider the "speed bump" thats why the production houses have so many different wheel sizes

Butch, correct me if I'm off here but doesn't our food analogy depend on they type of tempering done? I'm going to use a hard boiled egg instead of cake, but it's the same idea. Hard on the outside ~60 HRC, lets ignore the brittle factor, and 'soft' on the inside ~25 HRC. This could be a botched tempering cycle/process, but it couldn't it also be the result of a martempering process. Almost like a low carbon steel that's been case hardened.

in the knife world if you have a soft core in steel less then 3/16 thick your hardening wrong(or making a quench line )
from quench the steel will be 65-67 hardness and brittle then a temper temp and soak of 400f gets you in the ball park of 59-62 depending on the alloy

martempering is quenchinng into molten salts at the temperture that you woudl temper at (think auto temper )

so that when your done with the quench its at the hardness you were shootign for (again 59-62 ) but it will he all the way through the steel

if any part of the quench is botched you will not have got full hardness in the blade and then as you temper you keep droppping hardness
lets say you drop 4 points of hardness in temper if when you harden the steel you get 60 and not 66 then your talking aobut a blade that will be 56 RC and not 62

on shallow hardening steels like any of the 10XX steels in thicker blades you might get everything right andd have that hard skin and soft core ( we are talking steels over 3/8 inch thickness tho ). to have that tho you have to have a really thick cross section and a quenchent thats not pullin gthe heat out the bar at a rate of speed needed to fully harden
inthe blades that you see quench line or temper line (thats a misnomer ) we use clay to disrupe the oil and keep it from interacting with the blade (slowing the quench in the places that the clay was on the blade )
causing the cool look of hardened and unhardened steel

Originally Posted by L R Harner

causing the cool look of hardened and unhardened steel

That is a cool look !

thanks but that blade is plane jane
i will try and get some more crazy action on the clay that was jsut a test

I love the way that using clay really dresses up a blade. The Japanese swordsmiths were experts at it. There you go Butch, giving me more ideas...

Originally Posted by bassguy

Besides being a manufacturing artifact, if you can call it that, does it add anything functional to the razor? I'm speaking of only one belly, left intentionally by a grinder.

Yes, it does. Much like the shape of an I-beam adds strength to the structural component of a building with less weight, less material.

You still get a very thin edge suitable for the razor to function, but you also have a portion of the blade acting as a stiffener to support the very thin razor edge so it won't fracture quite so easily.

Originally Posted by shooter74743

I love the way that using clay really dresses up a blade. The Japanese swordsmiths were experts at it. There you go Butch, giving me more ideas...

Japanese sword steels are very low hardenability steels and require a water quench to achieve that fine hamon (hardening line). An oil quench using clay will not produce the exceptional character of a water quench and tends to be a little more indistinct and muddier.

In a low hardenability steel, it is expected that only a portion of the steel will harden when quenched. That is entirely desirable and not an accident of manufacture or the heat treatment process. It is related to the hardening portion of the process and not the tempering. The low hardenability steels have a predictable depth of hardening that can be controlled simply by section thickness or heat treatment preparation, as in thermal cycling. This does not imply that it is limited by any particular section thickness, but there is an upper limit where the steel is thick enough to temper itself into a pearlite state from retained heat no matter how good your tools and your experience. The lower limit of this equation can be manipulated to where even a 1/16 th of an inch will not harden very well. It depends on the steel and how it's worked.

There are some 10xx steels that can be had as low hardenability steels, just as some 10xx steels like 1084 are notorious for being high hardenability steels. This is due to the inclusion of minor alloying elements, in this example, specifically manganese. The 1084 is a through-hardening steel. This makes it a good one for essentially fool proof heat treatment. Get it hot, quench it and it's hard all the way through. No thought required. This means that the industrial shops could afford heat treaters to work at minimum wage. Simple economic pressures really.

Other steels require more attention to initial temperature, rate of cooling, time to cool, martensite formation temperatures and so on until it gets a lot more complicated and not worth minimum wage anymore.

You guys & your knowledge of steels and how to work them amazes me. I am truely in awe. My first interest, true interest in steel, was from Japanese swords. I consider it an art & you guys are true razor artists. I'm still painting by number and am thankful you guys are here to offer an expert opinion.

I'm looking to start working on my next razor and the waterline/hamon would be of definate interest to me. I have two blanks left from the waterjet offer that Dave put out there for us in 1095...would it work for a hamon line or should I do it in another steel? If another steel, what would you guys recommend?