Trick for bluing small parts

jim rozen · Apr 16, 2017

I had lost a small screw from a hardinge indexing toolpost (long story, but it's still somewhere on my basement floor) and took the time to make a new one this weekend.

But the originals are blacked and I felt queasy about putting a bare steel one in place of the original. There's a bit in "Trustee from the Toolroom" about a trick to blue small bits like this.
Damned if it didn't work perfectly.

Basically a small tin dish full of sand, held over the kitchen stove. Buried the screw in the
sand and kept turning it back and forth with some forceps while the tin of sand got hotter and hotter.
Took about three minutes before the part developed a deep blue finish. I had de-greased the part
before doing this, and dropped it oil after it had cooled.

I used to use Brownell's Oxpho cold blue for this. Not any more.

Monarchist · Apr 16, 2017

jim rozen said:
I had lost a small screw from a hardinge indexing toolpost (long story, but it's still somewhere on my basement floor) and took the time to make a new one this weekend.

But the originals are blacked and I felt queasy about putting a bare steel one in place of the original. There's a bit in "Trustee from the Toolroom" about a trick to blue small bits like this.
Damned if it didn't work perfectly.

Basically a small tin dish full of sand, held over the kitchen stove. Buried the screw in the
sand and kept turning it back and forth with some forceps while the tin of sand got hotter and hotter.
Took about three minutes before the part developed a deep blue finish. I had de-greased the part
before doing this, and dropped it oil after it had cooled.

I used to use Brownell's Oxpho cold blue for this. Not any more.

Small plate of Monel perched atop a "Fisher" burner. (Bunsen on steroids, basically).

Whether tempering or drawing a passel of punch-pins for die-sets, or just colourizing tiny screwdriver handles, watch carefully, then just tip the plate about 45 degrees and let them roll or slide off into the adjacent quench.

No sand needed. No stirring of it. LP gas will do fine. Beats holding a torch to do 'onesies' all to Hell and gone.

Monel. Neat stuff.

Spyderedge · Apr 16, 2017

Heat bluing is common in the gunsmith world, and you get a much clearer blue than with chemicals.

Sent from my XT1053 using Tapatalk

conant · Apr 16, 2017

I have done this with oxy acetylene. You have to keep the flame at a controlled distance and be very careful not to overheat.
I forgot about The trustee from the tool room. I read it twice years ago. He was coloring small eggs that he made for a little girl.
The sand method sounds like a good one.
A very long time ago I read in an old Machinerys Handbook about a black oxide procedure. It used a couple different salt chemicals that you heated until they were liquefied then dropped your parts in removed with tongs or pliers after a few minutes. I did it outside with a Coleman stove. Rinsed with water when done to neutralize the salt, dried then dropped into oil. It worked very good.

9100 · Apr 16, 2017

Spyderedge said:
Heat bluing is common in the gunsmith world, and you get a much clearer blue than with chemicals.

Sent from my XT1053 using Tapatalk

So called fire blue goes back to the middle ages. It is just a controlled version of the same oxidizing process that makes blue chips and blue tool bits when you grind on them too hard.

Bill

L Vanice · Apr 17, 2017

I learned heat bluing of small parts in the context of watch repair. The traditional way is to place a screw, etc. on a little sheet metal pan full of brass filings and lathe chips and heat over an alcohol lamp. Brass lathe chips in a watch shop are similar in size to filings. Brass conducts heat much better than sand. You can expect to find a container of brass filings in an old watch shop.

Long ago, I made a little screw bluer that used low voltage electricity flowing through the screw. It worked fine, but was trickier to get an even color than the pan and alcohol lamp.

Larry

conant · Apr 17, 2017

I have a lot of brass chips saved for the recycling yard.

I am going to hang onto some. Yes brass conducts very well.
I wonder if aluminum shavings would work?

Marty Feldman · Apr 17, 2017

I have done a bit of heat bluing. The results have been a bit spotty, presumably owing to the fact that I haven't really understood what I was doing, and never took the time to run systematic trials to explore variables. One thing I would appreciate learning is which metals/alloys lend themselves very well, only so-so, and downright poorly to heat bluing.

-Marty-

maynah · Apr 17, 2017

The one down side to coloring like this is it's not very durable.
If you handle the part much it will rub off fairly easily.
You can also make a part look like it's color case hardened by moving a torch around on steel to get straw, blues, greens, etc. A coat of lacquer makes it last longer, but it's still a poor substitute.

conant · Apr 17, 2017

I have done the color case with a torch also. Looks pretty darn good actually.
Definitely not the real deal like you say.

Limy Sami · Apr 17, 2017

maynah said:
The one down side to coloring like this is it's not very durable.
If you handle the part much it will rub off fairly easily.
You can also make a part look like it's color case hardened by moving a torch around on steel to get straw, blues, greens, etc. A coat of lacquer makes it last longer, but it's still a poor substitute.

Have you tried oil blueing? ......IME quite a bit more durable, I find used diesel engine oil gives a nice finish .......and yes I know the pitfalls,(the H&S freaks on the board love that one

) but if you use your loaf you'll have no problems.

JST · Apr 17, 2017

Oil bluing is a new one on me..... I know about oiling of rust bluing and other black oxide treatments.

What is oil bluing?

Limy Sami · Apr 17, 2017

JST said:
Oil bluing is a new one on me..... I know about oiling of rust bluing and other black oxide treatments.

What is oil bluing?

How I was shown and has worked for me for over 45 years.

Basically clean then heat the part until it is past the blue but before the scale forms and drop it in mineral oil,

The higher the polish you put on first, the better the shine when it's done.

An aside 'a few years back I was making a glorified stand off out of ex 1''dia 12 L 14 for a client in lots of anything up to 100off.
I won't get involved in plating - period, but he was pushed for a batch and didn't have time for the platers, did I have any suggestions - I showed him something oil blued / blacked off the back of the bench - he said that'll do him fine, and was paying 20$ a batch minimum charge and could I help him for that?

Nice little extra tickle - especially when the wood stove was going, ..................I lost count of the number of extra $20 I had out of him

Dave D · Apr 18, 2017

I know Limi Samy's technique as a "Japan finish". We used motor oil and it makes a cheap and realtively durable satin black finish. I always assumed (maybe incorrectly) that black twist drill bits were finished this way.

Dave

L Vanice · Apr 18, 2017

Dave D said:
I know Limi Samy's technique as a "Japan finish". We used motor oil and it makes a cheap and realtively durable satin black finish. I always assumed (maybe incorrectly) that black twist drill bits were finished this way.

Dave

Japanning was done with a paint or varnish type product. No heat or oil was involved, unless it was heated to get rapid drying on metal parts. It started in Europe in the 1600's as imitations of the costly Japanese lacquerware then beginning to be imported.

In the 1950's, I bought "Japan colors" and "Japan drier" and taught myself how to refinish old chairs and tinware in the mid-19th century style. Japan colors leave a flat finish. You coat them with varnish to make it semigloss or glossy. The chair technique involved making an imitation rosewood finish with a ground coat of deep red, then a coat of black that was roughly wiped while wet. Then the varnish was applied. Gold and silver stencilling was applied to the varnish after it got tacky. Then a final varnish coat to keep the stencil bronze powders from tarnishing. They looked like real Hitchcock chairs when I was done.

You can still get Japan colors. Ronan Superfine Japan Colors

Larry

JST · Apr 19, 2017

Limy Sami said:
How I was shown and has worked for me for over 45 years.

Basically clean then heat the part until it is past the blue but before the scale forms and drop it in mineral oil,

The higher the polish you put on first, the better the shine when it's done.....

Does that cook the oil onto the part somehow?

I assume it is considerably more durable as far as rust than oiled black oxide?

99Panhard · Apr 19, 2017

The Springfield Armory blued internal lock parts by heating and dipping in whale oil. The best, iridescent blue finish I've seen was done by dropping a highly polished part (usually springs) in melted potassium nitrate. Because of it's melting point, this was also a good way to temper them in the 18th and early 19th centuries.

SouthBendModel34 · Apr 19, 2017

Black Japan Finish Available from "Liberty on the Hudson" Paint Co.

If you want to apply black (only) japanning to a tool or machine, here's a purveyor of a NO BAKE formula which is indistinguishable (except perhaps by chemical analysis) from the original japanning on old Stanley tools such as their Bailey planes:

Liberty On The Hudson

(Note: I have no pecuniary interest in Liberty Paint Co.)

Japanning contains asphaltum. It can be made at home by dissolving a busted-up chunk of roofing asphalt in a suitable solvent and adding japan drier. I can't recall the exact formula, and it may not be critical, but if a member could post a known-good formula, that might be a worthwhile contribution to this thread.

John Ruth
Who uses a rattle can of gloss black Krylon to "japan" things.

Dave D · Apr 19, 2017

Larry, I already knew about the difference between a Japan finish (metal only) and Japanning (usually wood) but since they both basically mean to make something black (or at least darker) the terms are likely related although very different processes.

Dave

Ciszewski · Apr 19, 2017

JST said:
Does that cook the oil onto the part somehow?

I assume it is considerably more durable as far as rust than oiled black oxide?

Hello JST
I'd call it oil quench blackening.

Trick for bluing small parts

Diamond

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Titanium

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Titanium

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