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A fast knife


one_rod

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I dropped my best work knife the other day.
Typically, it landed in a 4 metre deep tank of Chromic Acid, from where it cannot be recovered, in a couple of days it will have dissolved competely.

So I needed to make a new one, in time for the start of my shift next day.

I have some pretty exacting requirements for a working knife;

1, Big
2, Strong
3, Free

So, a quick look in the Outdoor Material Resource Storage Facility, (ok, it's the scrap metal bin....) turned up this.


worknifey.jpg

Front end sawn off, a piece of a big old file welded on, and 30 minutes work with the disk grinder.

worknifex.jpg

Heated and left to anneal overnight, HT'd with an oxy/gas torch next morning. 5 minutes with a flap disk to get the scale off and she's ready to go. Just have to be a bit more careful where I drop this one.


one_rod.

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  • 2 months later...

Sir, you have raised the bar for the rest of us.

With regard to chrome plating and galvo giving off fumes, I agree that the fumes given off would be dangerous, even fatal, but would it still be the case for a spanner as rusted as the one in the picture?
Surely the coating would be corroded away?

Any ideas? I ask so as not to (accidentally) kill myself. What if it was left in the fire (with the air off) whilst I went for lunch?

Does any one have any idea what kind of steel is in a spanner?

Thanks in advance!

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With regard to chrome plating and galvo giving off fumes, I agree that the fumes given off would be dangerous, even fatal, but would it still be the case for a spanner as rusted as the one in the picture?
Surely the coating would be corroded away?

!


My take on this is why take a chance? You only get one run at life here on earth.

Ralph
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1. Yes, zinc fumes are very dangerous. I have had mild "zinc fever" from arc welding on galvanized steel. I never want it again. Ever.

2. Hexavalent Chromium Trioxide (Chromic Acid), the raw chemical used in the chrome plating process is dangerous if inhaled, it causes lung cancer. Most other chromium compounds are harmless. Vapourised metal fume from chrome-bearing alloys is no more dangerous than that from any other steel. Forge welding chromium alloy steels presents no significant threat.

Chrome plated items have a tiny amount of chrome on them, typically only a few microgrammes. A slightly higher risk comes from the nickel which is deposited under the chrome. Nickel fume can cause an allergic reaction (called "Nickel Itch"). It's unpleasant but never fatal. If you need to weld chrome plated items grind the plate off from around the weld area first.

Most wrenches are made from chrome vanadium alloys. The chrome content is very low. Even arc welding, which causes much greater amounts of metal fume to be given off need no special precautions.

In industrial situations where a lot of stainless steels, which typically contain 18% or greater of chromium are being arc welded local fume extraction is normally used. This is more likely due to the nickel content of SS alloys rather than any danger from the chrome.


one-rod.

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Hmm, does that mean that the bright-finish wrenches are not galvanized, and that's just a tumbled finish or something on CrV steel? I can't really figure out to my satisfaction what that surfacing is. I'm pretty sure it's not galvy but it does look like some kind of plate...

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T-Gold,
bright finish wrenches are normally chrome plated, as this finish is a lot more durable than zinc.

Chrome plating is a finishing process and the actual amount of metal involved is tiny. It should not be confused with the fact that most modern wrenches are made from chrome / vanadium alloy.

In any case the chrome does not present any real threat.

If you can get hold of some dilute hydrochloric acid try putting some on any item you are not sure about. If it is zinc plated it will fizz, if it's chrome plated there will be no reaction at all. The best way to remove zinc plate is to pickle the item in acid.

The only practical method for removing chrome plate is to grind it off.



one_rod.

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  • 2 weeks later...

Just throw the wrench into the next brush fire you have :) you can't tell me that oak, maple, used motor oil, tires, etc. won't burn off that chrome and nickel! That's what I do with anything galvinized. More than enough ventilation, getting stock ready for use, and getting rid of that useless stuff around the house, all at the same time. :) Triple WHAMMY!!

Hillbillysmith

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  • 2 years later...

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