Fusing brass to steel, issues with pin holes

[john.k]

I dont see how the OP could overheat to zinc volitalization temp.......this is near white heat ,and generally leaves a copper coloured braze.............incidentally,overheated braze also adversely affects steel,and makes the steel very brittle and weak.............this effect is well known in the bicycle industry from the 1890s.onward....................anyhoo,he says the brass is leaded,so lead volitalization is more likely...............Ive also had problems brazing with petroleum gas ,it contains a greasy residue ,and braze that wont flow flashes all over when the flame is shielded from the work.

 

[john.k]

Another snippet from the 1890s.......braze on the low side of the joint ,the brass is drawn upward into the clearance for a solid joint..........brass added on the high side will trap air in the joint,and be unsatisfactory............bicycle making 101.

 

[L Vanice]

Mention of vacuum reminded me that jewelry casting by the lost wax process is done with vacuum to eliminate air bubbles on the wax pattern in the wet investment and then during casting to encourage flow of molten metal into the mold.

Which in turn reminded me that I never had a porosity issue in the gold castings I did (without vacuum; just using the old centrifugal machines). So I got to thinking if, instead of using machinable brass rod, the balance had an outer rim of low karat (high copper content) gold, would that fuse to steel? American Watch Co. (Waltham) used gold jewel settings and train wheels in their high grade movements, though I cannot recall if the they had gold balance wheel rims.

A large budget project could justify a tiny bit of gold in the works.

Larry

 

[Scottl]

Yes, it's Gazeley's book! One paragraph. Definitely gets hardened afterwards.

Boric acid is soluble in alcohol, borax in water. Boric in alcohol is getting me close, but not there yet.



No inert oven, unfortunately. But these things have been made for a few hundred years, so while I'm sure it would help, it must be possible without.

I wonder if you could do what some gunsmiths do to eliminate scale. Wrap the part in brown craft paper with an over-wrap of stainless steel foil. As the the paper chars it absorbs oxygen and the tightly crimped foil keeps it airtight.

 

[John MacArthur]

Daniels does specify "yellow brass", not free-cutting. I assume this would be 260 or cartridge brass. He also recommends leaving a tiny air gap at the outside of the groove when making and installing the brass ring; this allows the air to escape as the brass slumps into the groove. He also says that "this by no means ensures success". FWIW
Johnny

 

[Screwmachine]

Daniels does specify "yellow brass", not free-cutting. I assume this would be 260 or cartridge brass. He also recommends leaving a tiny air gap at the outside of the groove when making and installing the brass ring; this allows the air to escape as the brass slumps into the groove. He also says that "this by no means ensures success". FWIW
Johnny

I can't believe I forgot that Daniels had a section on this.

I'm not looking at it right now, but I'm pretty sure Daniels "Watchmaking" has a section on just this procedure.
Johnny

And you mentioned it before. He does give a lot more info than Gazeley. Now to source some non-leaded brass...

Edit- none of my usual suppliers have anything without lead, ordered some 260 from McMaster. Man I wish we had something similar here.

 

[jim rozen]

It's not lead.

Vapor pressures of the Chemical Elements, vapor pressure of metals and halogens from -150 degrees C to 3500 degrees C including lead, aluminum, zinc, iodine, copper, indium, iodine, magnesium, selenium, lithium, iron, sodium and gallium

vapor pressure chart, zinc vapor pressure, lithium vapor pressure, vapor pressure of aluminum, indium vapor pressure, vapor pressure of gold, sulfur vapor pressure,

www.powerstream.com

Lower graph shows Zn has about 10e4 higher vapor pressure than lead.

 

[memphisjed]

Lower graph shows Zn has about 10e4 higher vapor pressure than lead.

Zinc is always the issue. Reason number 759 I really hate working with brass.

 

[john.k]

I used to love the bronze shop horror stories..........getting bronze needles in the washing at home .

 

[L Vanice]

I can't believe I forgot that Daniels had a section on this.

And you mentioned it before. He does give a lot more info than Gazeley. Now to source some non-leaded brass...

Edit- none of my usual suppliers have anything without lead, ordered some 260 from McMaster. Man I wish we had something similar here.

Brass that is not meant to be machined (sheet brass, but not engraving brass) and tubing will probably be lead-free. Round, square and hex rods will probably have lead. As was mentioned, cartridge brass is made from lead-free sheet. I have made a few things from fired cartridges, which come in many sizes, but probably not the size you want. I think leaded brass is a 20th century invention, so the 19th century watchmakers would not have had to worry about it or mention it in the old books. Daniels would have known to specify what he used.

Larry

 

[MrStretch]

Adding small amounts of lead and tin to brass to make it more free cutting is old. Clockmakers of yore used something called "best brass" which was 69/29 copper/zinc with 1% of lead and tin.
Just out of curiosity, has the op looked at the copper/iron phase diagram and considered some sort of cementation? Do you have access to a heat treat oven?

 

[DanielG]

This question sucked up way too much time. I was curious about the bimetallic balance wheel; it does look cool, and away to google I went. I found an interesting blog by a watchmaking student and spent way too much time reading it. Here's his brief post on making one:

Bi-Metallic Balance: Fusion — Nathan Bobinchak

Thermally fusing brass and steel is the first and most important step.

www.bobinchak.com

Ah, the internet, such an interesting way to get lost and waste time.