two heating questions and how do you test a blade?

[koyote]

Several questions at once:

annealing process-

Where I live ambient in the daytime ranges from the 50s to the 100s. I most recently tried out using my large charcoal grill for annealing with the following process.

use a lot of charcoal. Use a lot of lighter fluid. FLAME. wait until the coals are showing some white (1/3 to half white visible), put steel (saw blades in this case) in, close lid, wait 5 hours, burn finger, wait 3 more hours.

What this seems like it *should* accomplish is a reducing heat, hot enough for annealing, with a slow cool down. I did check at one point in the process and saw a soft glow in the steel.

From what I can tell, it worked, but I'm open to suggestions.....


Tempering-

I got a piece of advice on the phone the other day that's got me thinking. I was told that putting blades in an insulator (like between two oven mitts) after removing from the tempering oven (okay, I'm using a toaster oven with a "tempering oven" label on it so it will work better) and I'm thinking maybe just turning the oven off and letting it cool inside would work?


Hardness and knife testing!

Okay, this is probably the fun bit. What would constitute a generally effective, low investment, useful set of knife tests? I realize that the TYPE of knife is important and testing chopping through 12 2 inch branches isn't a USEFUL test of a 5 inch hiker's filet knife.

I've got a brass rod, so far that's it. It's useful to test the edge deflection, but where do you go from there?

Here's 3 knives for examples, which would probably require different tests:

1: The small outdoorsy filet knife

2: A 5 inch blade fine utility/skinner/hiking knife, with a thin blade and a fine edge, not a chopper, something to cut rope and trim marshmallow roasting sticks, whittle a bit, and skin a coon if you needed to, yknow?

3: A large bladed military utility bowie descendant- swimilar to a kabar or a sog government or some such, thick spined, 7 to 9 inch blade, heavy enough for chopping, with some combat properties.


Okay, edge deflection is good on the first two, maybe not the third (depends on the grind angle, I can see "sharp like a tree axe" on that).

The filet definitely needs a bend test, though maybe not 90 degrees, but it's part of the design purpose of a filet knife, right?

The ultralight hiker won't be whippy, but I could see a 30 degree bend and return, maybe? I don't really know.

The Iraq Dirk? it needs to not break if you drop it on a concrete floor from 20 feet up, or something, but I don't see a bend test being appropriate.

As far as edge holding, I imagine that you want to make it appropriate to the blade, but fast enough that you don't have to "waste" a day fishing or making camp. (though I don't see this as a waste of time......)

The heavier blade seems easiest, here- you limb a felled tree and see if it still cuts reasonably like it did before (paper test, cardboard test, avocado test?)

What abut the other two? slice paper thin sheets of frozen salmon, then cook it up with your eggs and add chives. Have a beer- oh, wait, the knife, right. test the shaving edge *before* the beer, right.

Bark a 5 foot walking stick and carve a simple head on it?

 

[Stacy E. Apelt - Bladesmith]

The annealing system described is more likely to ruin the steel and make it into mild steel. I wouldn't do it. I am sure it got soft, it just may never get hard. To anneal, bring it up to non-magnetic and place it in a bin of vermiculite, ashes, or wrap it in a roll of insuwool. Allow to cool as slow as possible (but not in the fire). There is no reason to keep it at critical temp for any length of time (and many reasons you don't want to !)

Placing the hot blade in an insulated wrap of insuwool or ashes is for annealing, not tempering. When you take the blade out of the oven from tempering, it does not matter how fast/slow it cools. Most just set it on a trivet and let it air cool. You can dunk it in cold water if you don't want to wait for it to cool. It will not harm the blade or warp it. Once the blade has dropped below 200F after the initial quench, and then been heated back up to tempering temp (e.g.350-400) you are not changing the structure or hardness by a quench to cool it.

I won't get into knife testing . Everyone has his/her own reasons for the how/why to test a knife.

I would recommend first becoming knowledgeable about the metallurgy and science of heat treating. Then you will know what is happening to the steel ,and how to control/influence it. Once you are capable of REPEATABLY producing a good quality blade with the desired parameters, then you are ready to test those blades to assure quality. Until then the best questions and tests are:
Is it evenly hardened?
Is it properly tempered?
Did I ruin the above two in finishing/grinding?

The way to test these for a new maker is the check the edge with a good file after quench and after temper. Then sharpen the blade and test it for cutting and edge retention. Cut up a bunch of cardboard boxes, slice up a broom handle, even chop through a 2X4. If the edge is still not chipped or bent, then the blade is OK. (Whether it will bend 90 degrees is not an issue with most knives.)

Later on you can start doing all sorts of tests, but first learn how to make a good blade.

Stacy

 

[Allan Molstad]

One problem I noticed when I use BBQ charcoal with no blower is that the heat is only in spots on the steel.
Some spots got too hot, some never did get hot enough.

I rigged up a hair blow dryer duct taped to a pipe and was able to use the BBQ charcoal to get the steel hot enough...(Lots of sparks , so it's fun to do at night)

I also learned to use ash to bury the knife in to anneal over night.

 

[koyote]

Good points. I "know" about leaving too long a heat on, but hadn't put it together with annealing yet. That's why I ask questions

Fortunately, I've got a ton of ashes around.

 

[koyote]

I won't get into knife testing . Everyone has his/her own reasons for the how/why to test a knife.

I would recommend first becoming knowledgeable about the metallurgy and science of heat treating. Then you will know what is happening to the steel ,and how to control/influence it. Once you are capable of REPEATABLY producing a good quality blade with the desired parameters, then you are ready to test those blades to assure quality. Until then the best questions and tests are:
Is it evenly hardened?
Is it properly tempered?
Did I ruin the above two in finishing/grinding?

The way to test these for a new maker is the check the edge with a good file after quench and after temper. Then sharpen the blade and test it for cutting and edge retention. Cut up a bunch of cardboard boxes, slice up a broom handle, even chop through a 2X4. If the edge is still not chipped or bent, then the blade is OK. (Whether it will bend 90 degrees is not an issue with most knives.)

Later on you can start doing all sorts of tests, but first learn how to make a good blade.

Stacy

Well, you *are* describing testing. So it's obviously important enough to worry about- though I think you are trying to say worry about production tests and not finished blade tests. I think.

I left out file testing because I counted that as a quench test, not a blade test, but I can see using it later in the process, too.

One thing is- learning how to make a good blade involves knowing what ya got. And a good blade for one thing won't be a good blade for another. A scalpel blade on a folder can be a lot glassier than a filet knife can afford to be.

This isn't purely a making issue, either- Production or custom, purchased blades can and may need to be tested, if for no other reason than to have a benchmark. How else can I know I've made a good blade.

I won't claim any of my first four knives have stellar heat treatments, but 2 of them pass the brass rod test and hold an edge pretty well, one is a total bust and soft, and the other chips on deflection, but sharpens up nice and is a 1.5 inch blade, so I won't call it a total bust- though I am sure I will in a year. But again- how do I *know* I can repeatedly produce a blade of quality n without testing?

And part of the question in detail comes down to- do people consider and use purpose relevant tests instead of one-size-fits-all type tests like using rope cutting for a santoku and a machete and thinking it measures the same thing. Or does it measure the same thing exactly? I don't see it, the edges are made differently for a reason, aren't they?

 

[Allan Molstad]

When you test a blade, try to have picked out a test that can be done again and again and again in the future on other blades of the same type.
This well help you to be able to tell if anything has caused your knives to change over time.

I think a worthless test is one where you could never do it again in the same way.
I think another important part of doing a blade test is having some way to record the force used against a knife.
It's pointless to just smack a knife against something hard unless you know how hard that smack was?

The question I always have when I see someone doing a cutting test is, "Whats really being tested?"
Is it the ability of the knife maker to sharpen a knife?
Is it the steel?
Is it the rope?

 

[jdm61]

When you test a blade, try to have picked out a test that can be done again and again and again in the future on other blades of the same type.
This well help you to be able to tell if anything has caused your knives to change over time.

I think a worthless test is one where you could never do it again in the same way.
I think another important part of doing a blade test is having some way to record the force used against a knife.
It's pointless to just smack a knife against something hard unless you know how hard that smack was?

The question I always have when I see someone doing a cutting test is, "Whats really being tested?"
Is it the ability of the knife maker to sharpen a knife?
Is it the steel?
Is it the rope?

With the caveat that if you smack it against something and it chips out the edge, then you probably need to think about tempering it at a higher temperature.

 

[Allan Molstad]

I just wish that there was a way to record the force of the smack???

It does no good at all to just take a knife and start wacking things with it, even if the edge chips how would you compare that to a future blade?

We need a controled smack, something that you can do again and again in the future so that you get some idea if the knife that chipped is normal or not normal?

 

[jdm61]

I think Mr. Cashen could tell you how to do that, but at great expense.....

 

[Allan Molstad]

I think...
Tests that are a lot of money to do are pointless.
Tests that can not be repeated in the very same way, are pointless
Tests that are not recorded are pointless.

I watch a lot of what are called "Knife test" videos on youtube, but they are worthless...There is no point to driving down a road and tossing a knife out being called a "test"...it's pointless because you could never in a million years do that test over in the same way.

Thats why I like the 90'bend test if done with a torque wrench...at least there is a number of foot lbs that can be recorded...and compared.
There used to be a topic that showed a guy at a Hammer-In showing some knives with different heat-treatments all lined up side by side.
Then some weights were added to each knife to compare the flex of each...
This is a great test because you can see results right away and the test of different knives is all with the same weights.

However in the one clip I saw the guy failed to keep going and add weight untill every knife failed so that the results could be recorded and compared with future kinves.
You have to test the knife until it fails,,,then you have an idea of the limits.
Knowing the limitations is key to knowing if you are getting better at making a knife, or only more fancy?

 

[koyote]

DO you have to test to failure? Maybe once in a while, but not all the time, obviously.

Do the tests have to be "extreme"? I mean, if I cut 50 paper thin slices off a frozen hunk of salmon and then crossscut 5 shims (I'm just looking in the kitchen and picking stuff here) with a filet knife and it still shaves, I can probably claim it holds an edge. That's repeatable, not a failure test, but gives you a known functionality of a knife that is mostly appropriate to the type of knife. do I need to hammer the blade into bone? Doesn't make sense to me, but maybe some people would say so.

 

[Allan Molstad]

DO you have to test to failure? Maybe once in a while, but not all the time, obviously.
.

It all depends on what you are seeking to learn???

Lets say I have tried real hard to make a fully-hard blade that will not want to bend under lots and lots of weight.
How do I know if Im on the right track with my Heat-treatments?

Far as I know , the best way would be to add more and more weight to a knife until you reach the moment the knife will fail.
You then can record this amount of weight and have the results around to compare years and years from now on future blades.

Lets think of a cutting test.
Lets say you cut 500 sheets of paper before you stopped when you got tired.
What does this number really tell us?.......
well,,I think it tells us very little.
Had you kept going until you could not cut any morew paper because the knife edge failed, Then you have a worthy result that can be recorded and compared in the future.,

How about a test where you bang the edge of the knife on a anvil....what does that tell us?
Does it mean anything much by itself?
I dont think so.
But if you can record the force of the blows into the anvil somehow, and then keep banging until the blade cracks you then have a test worth doing.
A test that can be compared when you do it on a different knife even years in the future.

These are tests that can help you rank your blades abilities in the future.

But if you wanted to sell a blade that you wish to test somehow to conferm it's normal?
Then a good test might be a etch test where you use acid to check on the Heat-treatment.
You could cut a few things to make sure the handle fit the hand under stress correctly.
You could try to flex the blade a little to make sure it did not come appart.

 

[koyote]

flexing and hand fitting are good, and a basic function test should, I think, be done on any knife.

So far I've got out of this:
file test after quench.
File test after some blade finishing
flex and usage tests for handle/fit/togetherness.
cut stuff to test edge (paper, which is a one size fits all thing that I can't quite trust tells me the same thing about all blades)

for destruction test, assumed not to be done on every knife-
weighted breakage and chipping tests.



But, in the spirit of open inquiry and not "just doin' it cuz all the old dudes did it"- does it make sense to test everything one way?

Also- I'm not sure that demonstrating that a given blade can flex n amount and return, and be usable, is worthless. Okay, it's nice to know what the preaking point or "set bend" points are, but if you know you've got enough for the purpose f the knife, you do know you've got enugh for the purpose of the knife.

 

[Allan Molstad]

does it make sense to test everything one way?

.

No it does not.
Each blade has a designed use in mind when it is made.
A blade that I make for fishing and cleaning fish is going to future of vastly different use than my hunter/user blades go to.

Thus if I were to want to judge my knife against another I had made I would want a type of test best aimed at the different designs of each knife.

HOWEVER, what you want to do is have a way to test a knife that can be recorded and compared to other knives of the same design in the future.

It's pointless to say "I banged it down once to check the edge" if you have no idea how much force was used against the knife,,,
It's also pointless in my view to walk around the back yard cutting tree branches and junk if you would be hard pressed years from now to remember what was cut, or how much effort it took?

A good test for a knife you make is one that can be recorded and used to compare future knives to.
I would not test a fishing knife the same way as a Hunter, but I would try to test all the fishing knives the same way so that I can learn if Im getting better at making them or not?

If you just want to check to make sure a knife you made can cut rope?...then cut some rope.
You dont have to cut miles of rope to learn if the knife can cut rope or not.
But, if you wish to put a knife to the test to see what it's limits are?..then you have to cut rope until it cant cut rope anymore.
The number of cuts can then be recorded and compared to other knives in the future or the past so that a bladesmith can learn how he is doing?