Blade "proofing"


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weaponhead
March 9, 2014, 09:18 AM
So......after my debacle with the "broke knife in the washer machine," I am wondering if there is low cost, easy non-destructive way to test a blade for latent detects. Supposedly maker Fred Perrin suggested "gently" throwing a blade a few times......

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MuffinMaster
March 9, 2014, 05:16 PM
I THINK all ways to check if the steel is serviceable for your expect use would involve either metal removal in some part or physical stress test of some sort that will break the knife if it is not serviceable. I would expect a top quality knife maker to be working with certified metals and not seconds or drops. Bridge builders follow strict rules on collecting all the certs for a job. There is an old saying in that business. It goes something like "If you replace secondary steel with certified steel you loose money but if you replace certified steel with secondary steel you loose the business". I am guessing knife makers do not worry on that level.
I'll tell though if it can not survive a washing machine well ..... hahaha .... sorry .....

There is a scene in "Paul" (comedy about an alien) where a character draws a large sword and it snaps off at the hilt inside the sheath. So I guess you could see if it passes the quick draw and not snaps off test.

SlamFire1
March 9, 2014, 06:09 PM
I heard that washing machines are tough on knives. Try the spin cycle! :evil:


Really, just use the knife. Cutlery steel is very hard stuff, any twisting, bending, could break any knife blade. But if it makes you feel better, cut something, whittle, pare an apple. If it holds up, then apples are in danger.

jerkface11
March 9, 2014, 06:47 PM
http://www.magnaflux.com/Products/PenetrantInspection/ZygloFluorescent/ZygloKits/ZygloZA70Kit/tabid/121/
There you that will show you any micro fractures.

buck1032
March 9, 2014, 07:50 PM
Magnaflux will not work, so an Eddy Current (NDI) inspection would be in order. Other than some sort of NDI I do not know.

The magnaflux link is for a liquid penetrant inspection kit. That is designed for inspecting discontinuities on a metals surface. Not a sub surface defect. For sub surface one would need an eddy current, mag-particle or x-ray inspection.

T.R.
March 9, 2014, 08:17 PM
Rockwell hardness testing has been around for nearly a century. A hardened tiny steel ball is driven by an instrument into the blade. Depth of "dent mark" determines hardness on the Rockwell scale. Many stainless steel knives are tempered to 58.

Stainless steel is a nickel based alloy which makes long lasting cutlery. The most expensive steels are alloyed with elements which are hard to spell and pronounce!

TR

jerkface11
March 9, 2014, 08:23 PM
The knife he had break looked like it had a partial fracture that finished breaking in the washer. So magma flux would have caught it. I doubt he wants to shell out the money for the equipment needed to check for subsurface defects.

ugaarguy
March 9, 2014, 08:32 PM
Stainless steel is a nickel based alloy which makes long lasting cutlery.
Actually it's chrome, not nickel that makes a steel stainless. In fact, several of the most common premium stainless knife steels don't contain any nickel.

Another misconception is that higher hardness equals a tougher blade. If a blade is heat treated to too high a hardness (varies depending on the alloy) it will actually be brittle. A properly heat treated blade should be hard but still able to withstand impact and light twisting / bending.

rcmodel
March 9, 2014, 09:43 PM
I actually think Magnafluxing would have found the existing flaw in the 'Washing machine Knife'

It's very nature allows a magnetic field to pass through the part and the magnetic powder on the other side will show up is an irregular field pattern on the off side.

Perhaps the crack could or should have been seen before it failed with a closer inspection?
Or perhaps final grinding and polishing closed up any visible surface crack you could see with the naked eye?

At any rate, none-destructive testing of a knife blade with Magnaflux would cost more then the knife cost.

Myself?
Every knife I ever made, or rebuilt was clamped in a wood vice and flexed sideways as far as I felt it should be able to stand without breaking.
I never ever broke one doing it.

But like I said in the Washing Machine tread, I broke a few Bucks at the tang joint just cracking the plastic handle off with a hammer to get it off so I could put a nicer handle on.

See photo below:

They never would have withstood the vice flex test if I had spent a week customizing them.
So best they broke immediately breaking the plastic handle off.

rc

hso
March 9, 2014, 10:59 PM
easy non-destructive way to test a blade for latent detects

"easy" has so many meanings.

X-ray is easy if you know someone with the equipment.

A gentle lateral stress test is something that anyone can do, but you would want a face shield and throat protector in case the blade did fail. It is non-destructive if the knife has no defect, but quite destructive if it does. Still, you'd rather find out in a more controlled environment than the field.

buck1032
March 10, 2014, 06:43 PM
The knife he had break looked like it had a partial fracture that finished breaking in the washer. So magma flux would have caught it. I doubt he wants to shell out the money for the equipment needed to check for subsurface defects.
If there were surface discontinuities you would be correct. It seems I missed something along the way and missed that nugget of info. With that said, one can perform a rudimentary liquid penetrant inspection like what was done on the rail roads in the 1800's. Soak the suspect item in used oil for a few days. Dry wipe it then sprinkle talcum powder. The powder acts as the developer and will draw out any oil remaining in the subject piece.

jerkface11
March 10, 2014, 06:55 PM
In his other thread he posted a pic of the broken blade. And it looked like it had been broken most of the way through for awhile.

MuffinMaster
March 10, 2014, 08:59 PM
"As with all Buck Knives, comes with Buck's 4-Ever Unconditional Lifetime Warranty"

Is this warranty any good?

weaponhead
March 11, 2014, 06:19 PM
I sent it back to Buck - I am confident they will stand by their warranty.

Coyote3855
March 21, 2014, 05:01 PM
He posted in another thread that Buck replaced the knife and gave him 25% off on his next purchase. Buck warranty is solid. I've owned Bucks for 55 years, only had two repaired under the guarantee. One was stupidity on my part. They fixed it anyway and paid shipping both ways. But that was 50 years ago.

Coyote3855
March 21, 2014, 05:02 PM
And for the OP, I don't stress test my knives, but I always carry at least two.

Big Shrek
March 28, 2014, 12:33 AM
Am I the only one thinking, "What the heck was his knife doing in the washing machine??"

:evil:

rcmodel
March 28, 2014, 12:57 AM
Are you the only man who has never ever forgot to clean out all his pockets before throwing them in the laundry?

It was his wife's fault for not checking his pockets before washing clothes!
MmmmmKaaaaa!

rc

Radagast
March 28, 2014, 08:15 AM
Obviously its the next step in Youtube Hard Use testing. Baton through firewood. Shave aluminum plate. Stab stainless steel sheet. Spine whacks with a mallet. Open cans. Cut down saplings. Carve V8 big blocks from raw forgings. Fission uranium. Fuse Hydrogen. Clean out the washing machine lint filter.

I'm glad to hear Buck stand by their product instead of treating it as a disposable item.

hartcreek
March 28, 2014, 08:19 AM
I just do not buy new knives. I go to thrift shops and second hand stores. I figure that if the knife has lasted for at least fifty years it was never used or the steel is hard enough.

conw
March 29, 2014, 01:02 AM
I just do not buy new knives. I go to thrift shops and second hand stores. I figure that if the knife has lasted for at least fifty years it was never used or the steel is hard enough.

Seems kind of extreme unless you have other reasons ;)

rcmodel
March 29, 2014, 01:13 AM
I see his point though.

The sharpest, and easiest to sharpen knives are the old WWII and earlier carbon steel ones.

The new exotic knife-snob steels are hell to sharpen, and don't stay sharp enough longer for all the effort sharpening them.

The very sharpest, and easiest to sharpen knife I currently own is a 1916 vintage Marbles Woodcraft.

And I have some WWII Ka-Bar & Case stuff. that isn't far behind.

They put modern super steel knives to shame when it comes to stay sharp, and easy to sharpen.

Rc

hartcreek
March 29, 2014, 04:21 AM
I have a 1936 PAL hunting knife that is so hard I had to purchase one of those multi stone kits just to sharpen it. When was the last time at a store you could find a good trout cleaning knife? I have six or seven camco, sabre some just say made in germany fish knives. Never payed more then $5 a piece for them. If you watch places such as Sportsmans Guide you can get bulk deals. I picked up a dozen of those WW2 Marlin spike knives for $30.

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