WARNING: Yet More Metal Working Content - Tool Blackening

Cold bluing or cold blackening seems to be an accepted method of
protecting steel parts in the shop. Add on a sealant or keep the part
oiled and supposedly it will resist rust and corrosion indefinitely.
I have done cold bluing in the ancient past using the gunsmith supplies.
When I was a kid I stripped and refinished and old Sears .22 rifle,
and I built 4 different black powder kit guns that came in the white.
The quantity in gunsmith supplies is rather stingy. The amount in a
bottle is enough to do a fair to good job on one complete firearm and
maybe do some touch up work if you know how to make it blend. Two guns
if you don't make any mistakes.
More recently I've started making tools in my own shop. Many were
intended to be a single use or short run tool. Long reach clamp to hold
a slide bar in a mold until it could be match machined and clamped in
other ways. Long reach tool holder for deep milling. Half round tool
for work stop in the spindle and work positioning. Lots of stuff
really. Mostly I have left them in the white (fine for carbide tools
and some I've made in stainless) because they were made to do a single
job. I didn't throw them away, but I didn't plan for them to be likely
to see future use. It turns out nearly all of them have been much more
useful than I originally planned. I need to blacken and oil them I think.
Not wanting to go with a stingy little bottle from a gunsmith supply I
looked at McMaster and MSC. They both stock some form of steel tool
black. It seems expensive, but its a larger quantity than your local
retail bottle of gun blue. How long does it really last? Is the
"sealant" in some of those kits better than just oiling the part? Is it
just oil? I don't mind spending the money. I just want to know its
worth it.
Reply to
Bob La Londe
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I wonder the same. There appear to be something like 3 classes of bluing.
1) the room temperature selnium stuff, like Hoppe's gun blue. Works fine to make parts dark. Durability is questionable. The stuff is heavy metal toxic so beware and wear gloves. You can't wash it out of your body once absorbed. It's more of a coating of a dark selniumcompound than real oxide layer.
2) high temperature oxide kits, seems to require some weird solutions and you the seal it all with some snake-oil like sealant. Kits come with and require special cleaning steps. Expensive
3) low temperature kits that don't need the 300F solutions or whatever they are. Same special cleaners and magic sealant involved. Expensive
THe last bottle of Hoppes I bought was $3.79, I really don't care if I have to reapply it to stuff. Coat with your favorite rust preventer oil and you're golden.
EPI (epi.com) makes sample kits of #2 and #3. Haven't tried them yet though.
None of it will be as durable as real steam oxide coating you'd get on even cheap chinese tools, but it's all better than metal that gets rusty fingerprints when you handle it.
to prevent rust, my favorites are LPS-2 and even better, gun-coat from Fluoramics. It has some additives with an affinity for iron, so the protection is superior to a smear of some random lubricating oils. Any TRUE corrosion inhibitor should have those extra ingredients.
Reply to
Cydrome Leader
Cold bluing or cold blackening seems to be an accepted method of protecting steel parts in the shop. Add on a sealant or keep the part oiled and supposedly it will resist rust and corrosion indefinitely.
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I was surprised by how long a knurled sawmill adjusting knob I made from 12L14 and blackened by boiling in sodium thiosulfate (photographer's hypo) lasted without rusting.
Reply to
Jim Wilkins

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