Heat hardening?

[Steve CrowParticipant @stevecrow46066]

In "Watchmaking", George Daniels describes how he hardens a tourbillon bridge by placing it in a box turned from a copper disc before heating.

My question is, why copper?

Is there any reason I can't use brass or mild steel for that matter?

Cheers

Steve

[Steve CrowParticipant @stevecrow46066]

[jaCK HobsonParticipant @jackhobson50760]

Copper has the best thermal conductivity so better for even heat. I think you could get acceptable results with other materials. Dimensional stability during quench could help.

Steffen Pahlow https://www.youtube.com/watch?v=nT2oVtc5wh4 seems to use sandwich of steel parts held together with binding wire.

https://watchmaking.weebly.com/tourbillon-bridge.html just wraps in binding wire – I would be surprised if the dimensional stability of the wire contributed to reducing warping. Daniels uses binding wire approach for other things – helps retain heat for really small items like pivots and holds borax to reduce scale.

 

Edited By jaCK Hobson on 20/03/2019 18:19:55

[John ReeseParticipant @johnreese12848]

Check out Clicksping's You Tube videos. He wraps his parts in fine iron wire and coats it with a paste of boric acid and denatured alcohol before hardening. That prevents scale formation during hardening. Cliclspring uses a pan of brass chips when tempering small pieces. That assures even temperature around the parts. Steffen Palhow's method using a copper plate is ideal for flat parts. If tempered using an open flame there would likely be some temperature differences in the part resulting non-uniform color. The tempering to a specific color could also be done in a controlled temperature oven provided the parts were left in long enough to reach uniform temperature throughout.

[Michael GilliganParticipant @michaelgilligan61133]

Thanks to 'Google Books' there is no need for me to dig-out my copy of 'Watchmaking'

The description is on p312, but the additional text on p318 is important: Daniels [ever the perfectionist] describes a process which is pretty-much certain to work … any deviation from this carries risk ['though, of course, you may get away with it].

 

MichaelG.

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https://books.google.co.uk/books?id=ZWq8c0xvGxsC&pg=PA318&lpg=PA318&dq=george+daniels+watchmaking+tourbillon+bridge+copper+box&source=bl&ots=P1v5cRgFW2&sig=ACfU3U2YIMYQNbiculM5H8g2d9199CEupg&hl=en&sa=X&ved=2ahUKEwjjvOT7ypHhAhVNOBoKHRvaDqoQ6AEwC3oECAkQAQ#v=onepage&q=george%20daniels%20watchmaking%20tourbillon%20bridge%20copper%20box&f=false

Edited By Michael Gilligan on 20/03/2019 20:56:50

[John ReeseParticipant @johnreese12848]

The modern equivalent to enclosing the work in a copper box for hardening is the use of stainless steel foil to wrap the part.

[Steve CrowParticipant @stevecrow46066]

Thank you all. I've used the iron wire binding method before.

The reason I ask is that a brass one would double up as a blueing tray for brass chips.

Can I just add that I'm not making a tourbillon bridge!

[Maurice Cox 1Participant @mauricecox1]

I once read a book by a retired blacksmith, who said that watchmakers, casehardened items by putting the parts in an old shoe, packed with salt and horses hoof clippings! I have no idea if it should or did work, but I bet it smelled wonderful !!

Maurice

[John HaineParticipant @johnhaine32865]

Great descriptions of case hardening in Lautard's Machinists Bedside Readers, parts put in small clay flowerpots with bonemeal and other stuff. Smelt like a charnel house he says! This to produce nicely patterned parts for gun making.

[John ReeseParticipant @johnreese12848]

Posted by Maurice on 21/03/2019 18:30:12:

I once read a book by a retired blacksmith, who said that watchmakers, casehardened items by putting the parts in an old shoe, packed with salt and horses hoof clippings! I have no idea if it should or did work, but I bet it smelled wonderful !!

Maurice

One of the old case hardening methods was to place the part in an airtight box surrounded by bone charcoal or charred leather, followed by prolonged heating, quenching, and tempering.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Steve Crow on 21/03/2019 17:12:26:

Can I just add that I'm not making a tourbillon bridge!

.

You certainly can, Steve … It might ease my inferiority complex.

MichaelG.

[jaCK HobsonParticipant @jackhobson50760]

Posted by Steve Crow on 21/03/2019 17:12:26:

a brass one would double up as a blueing tray for brass chips.

I'm confident you could use a copper one for blueing.

[Steve CrowParticipant @stevecrow46066]

Posted by jaCK Hobson on 22/03/2019 08:54:52:

Posted by Steve Crow on 21/03/2019 17:12:26:

a brass one would double up as a blueing tray for brass chips.

I'm confident you could use a copper one for blueing.

The reason I want to use brass is it needs to be 1 1/2" OD and I have some scrap of that size.

[IanTParticipant @iant]

Posted by John Reese on 21/03/2019 00:38:22:

The modern equivalent to enclosing the work in a copper box for hardening is the use of stainless steel foil to wrap the part.

A slight drift off topic I'm afraid. I once wrapped a part in kitchen foil before annealing it in the incinerator overnight (thinking it would be easier to clean up after). Of course the aluminium foil melted and made things even worse…

IanT

[Ian S CParticipant @iansc]

If you heat brass to hardening temp for steel, it will melt, copper takes a bit more temperature. I often use brass for brazed steel joints.

Ian S C

[Steve CrowParticipant @stevecrow46066]

Posted by Ian S C on 25/03/2019 11:02:05:

If you heat brass to hardening temp for steel, it will melt, copper takes a bit more temperature. I often use brass for brazed steel joints.

Ian S C

Thank you Ian. Back to the drawing board.

[Author]

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