# Can brass be "re-hardened"?



## wigginsn (Jan 9, 2008)

Long shot, kinda hoping someone may have trick up their sleeve..

I've been fiddling around with hard soldering some small bits of K & S brass together, size is 1/8" x 0.032" or 0.064". Of course its typically red hot or close to it as I solder (Easiflo45 & Silfos 15). The brass once cooled is annealed and quite soft. Not a huge issue with the .064 but the .032 parts are easily bent.











Is there something I can do to either retain some of the strength, or reharden it after the parts are finished? Obviously can't take it back up past the melting point or it'll fall apart!


Cheers
Neil


----------



## SteveC (Jan 2, 2008)

Neil

No expert or tricks here, but as far as I understand it most copper alloys like brass only get more brittle/hard by working it into the basic shapes (e.g. rolling, hammering, or drawing it). The only suggestion that I can come up with is when making small parts where the annealing will cause a problem in the finished item. Would be to start with a basic shape as close to the finished item and then figure out the sequence of steps of machining the basic shape into the item you desire. This might also include machining separate parts and then using a strictly mechanical means (sans high temperature soldering/brazing) to assemble them into the finished item. The other possibility I believe would be to get into casting of brass, that way you would have as much control as possible on the rough item and then only need to finish out the item to its completed state.

Have you considered dropping back to soft-soldering, instead of the silver/hard-soldering? Because while I don't know all the specifics of each brass alloy, however, from my experience in hand loading cartridge brass where you anneal the cartridge neck. As I remember it, changes in the grain structure of the brass starts to take place at around 490° F., and the silver/hard soldering fillers melt somewhere above 840° F., which means you're stuck with the annealing problem.

You might try posing the question on the Live Steam forum where you've got a lot of individuals that have a great deal of experience with silver/hard-soldering.


----------



## Michael Glavin (Jan 2, 2009)

Neil, 

It’s not plausible; in order to harden brass you have to work harden it, this means you have to literally compress the brass by hammering, roll forming or the like. As Steve suggested consider a low temp solder. We use on occasion a low temp solder in the refrigeration industry, if I recall it requires around 450*F and is quite strong. 

Michael


----------



## SteveC (Jan 2, 2008)

Neil

I remember someone talking about a heat sink compound in a previous topic, but as yet I've not located it. I don't know if the following is the specific product the individual was referring to, or if something similar is available in New Zealand. Additionally, I have no personal experience with this type product, but maybe it might help in localizing the heat and control just how much of the part gets annealed.

Heat-Block by; Alvin Products[/b]

The other thing I wanted to mention is that there are two parts to the annealing process, temperature and time, and while temperature is always mentioned time rarely is. The reason I bring this up is it may provide a method to resolve the problem.

Reflecting once again on my past experience with cartridge brass and hand reloading. While using the annealing of the neck of an expended cartridge, to extend the usable life expectancy of the cartridge and also improving the tightness of your groups. The one thing you don't want to do is extend that annealing to the body of the cartridge, because at best you'll ruin the cartridge for its intended use and turn it into just plain scrap, or in the worst case cause destruction of the firearm and likely cause severe bodily injury to the individual firing it.

Most individuals, unless they're involved in the commercial manufacture of ammunition or are really into hand reloading of same. Are unaware that the hardness of the brass in a cartridge varies from the neck to the body to the base, because each has a differing job to perform. Which pretty much mimics your needs in this instance.

So, in an attempt to offset the natural excellent thermal transfer properties of the brass.
[*] The length of time it takes to bring the actual area involved in the hard/silver-soldering up to temperature needs to be as short as possible.
[*] The source of the heat needs to be as concentrated as possible, thus keeping the area directly heated as small as possible.
[*] And the heat source must be capable of providing the required BTU's.
[/list] The above leads me to suggest maybe one of the small mini/micro torches used in jewelry work might be a partial resolution to the problem and a viable investment. While I provide the following information as an example of what I'm speaking of I'd recommend you buying it locally so you wind up with connections that match what's required in New Zealand. Additionally, which version of torch used; i.e. air-fuel or Oxy-fuel would be best suited I'm not sure, although I do know that Oxy-Acetylene will create a temperature hot enough to burn the brass.









Smith - Little Torch[/b]

Another bit of information that may prove useful is, it's much easier to observe temperature change in brass that has a highly polished surface (i.e. loss of shine and color change), which is a good indication of how far the annealing has progressed in the particular part.

Hope something in the above is found to be of help.
Steve


----------



## Totalwrecker (Feb 26, 2009)

Battern's Self Pickling Flux, when torch coated (apply and dry with soft flame until an even white coat covers it) will preserve the temper in gold alloys. Can't speak for brass. 

It's a yellow green liquid found at jewelry supply. There are many knock offs of it. Those I've tried seem as good. 

The flux is great for karat gold and sterling silver solders.... 

John


----------



## wigginsn (Jan 9, 2008)

Thanks guys, 

I wish I had machine tools - maybe one day but its not on the financial horizon yet, so playing around with different solders & fluxes looks like the go. I've got two torches, one small propane one that can't quite get the parts to temp all at the same time, and another butane beast that scorches the bricks and has the bits glowing crimson in a few seconds.. 

I might make up a final part and do some tests to destruction this weekend just to see how soft the annealed brass really is. I'm making up the valve gear for a loco and been treating it with kid gloves so far but what the heck - its all in the name of science.. 

Cheers 
Neil


----------



## SE18 (Feb 21, 2008)

This might be a stupid idea, but can you fill the brass tube with something? Maybe fine sand and seal the other end with epoxy and do a stress test.


----------



## Nutz-n-Bolts (Aug 12, 2010)

What about resistance soldering? Would the heat just be localized at the joint ?


----------



## Dwight Ennis (Jan 2, 2008)

One option to consider would be to always (or at least as often as possible) use a mechanical connection to provide most of the strength of the joint. In your photo above, threading the joint area either 00-90 (0.0470) or 0-80 (0.0600) would work. Then you wouldn't need to silver braze the connection with the accompanying heat and resulting annealing, and could soft-solder the connection for added strength. I might also recommend *Stay-Brite silver bearing solder* for such work. It melts at around the same temperature as 60/40 tin/lead (430F), but is far stronger, and can be used with a normal soldering iron. Added to the strength of threaded joints, it should prove more than adequate for the purpose shown in your photo. It might prove adequate all by itself without threading the joint.


I used Stay-Brite to assemble most of the major components in #21 (shown in my sig photo). Since it's a live steam locomotive, it gets a lot of handling. Some of the parts are also screwed together (wherever possible) but some are not. Nothing has come apart yet.










Micro-Mark sells the 00-90 and 0-80 taps and dies.


----------



## SE18 (Feb 21, 2008)

It looks like the entire piece could be crafted from a small steel bar (very small) without any power tools except maybe a dremel and drill press. (hacksaw, file, sandpaper etc). It would take a bit of time but


----------



## Totalwrecker (Feb 26, 2009)

A jeweler's saw, a dozen (for me, a gross for you) new blades, some beeswax and a lots and lots of practice and you could saw them out of brass stock. Never cut over your line and file to final. 
Tip; use a light grip and guide the downstroke, more to keep blade straight than to force the cut. Beeswax is sticky and clings to the blades as it melts to clear the teeth and lube the stock. 

If you have a high speed hand tool, you could also try sanding them to shape, but it generates bad dust and heat. At jewelry supply stores (and other places, I think) they have mandrels with snap on sanding discs, a square gromet makes them spin. 

John 

I know post a picture;


















There ae a variety of grits and media made by 3m.

JC


----------



## bnsfconductor (Jan 3, 2008)

I kind of had the same question too! I recently annealed some .010" brass to bend into a plow shape, and it is quite soft. When I started to plow with it the other day I noticed some bending. On the other side of the plow I didn't heat it quite as much, so it's much harder. I guess my question got answered too. I'll probably take a piece of .015" brass and form a new plow shape, and not allow it to heat up quite as much.
Thanks for answering my question too..
Craig


----------



## wigginsn (Jan 9, 2008)

Ha ha, I looked at the jewellers saws in the hobby shop last week John and thought - Naw.. thats too much work! There's 14 parts in each set of valve gear (excl parts of parts like the clevis's on the rods in the pic), x 4, plus stuff ups = callouses on my callouses already. Cutting and filing these by hand from brass sheet stock is enough for me. I've another plan to nickel plate the right bits for the bright steel look but still has to come together (in a cheap fashion). I chose brass over steel for ease of cutting & filing Dave.

Never knew about the Stay-Brite solder - thanks Dwight, will look for a local source. Glad you got good results. Not sure what you mean about "threading the joint" though? Where abouts do you mean?

There's going to be a bushing in the clevis held by an M1 thread (.040) but attaching the clevis to the .032 stock is the where the hard soldering heat annealed the rod. Here's a 1000 word shortcut of what I'm planing for the LH rod in the top pic - is the threaded part where you meant?












Cheers
Neil


----------



## Dwight Ennis (Jan 2, 2008)

Never knew about the Stay-Brite solder - thanks Dwight, will look for a local source. Glad you got good results. Not sure what you mean about "threading the joint" though? Where abouts do you mean? I'm talking about where the rod meets the clevis. From your drawing above, it looks like you're using a butt-joint and completely relying on the silver braze to hold the 0.032 x 1/8 bar to the clevis. That explains why you need the strength og silver brazing. However, as I said before, relying on solder or brazing to supply 100% of joint strength is usually a bad idea.

If you were to notch the end of the bar as shown here...










then you can thread the protrusion 00-90 (start the die normally to start the threads, then reverse the die and use the backside to get as much threading as possible). Then drill a #61 hole centered in the adjoining side of the clevis (u-shaped part) and tap it 00-90 as well (use cutting oil to thread the parts btw - Tap Magic works well, and it will aid greatly in threading such small parts). Clean both parts in Acetone to get rid of the cutting oil. Flux both threads and screw the two parts together. Using a normal soldering iron, solder the joint with Stay-Brite. File off any part of the threaded rod that protrudes inside the clevis.

You could also use a torch to do the soldering if you applied the heat judiciously so as not to get things too hot so as to anneal the metal (what you're trying to avoid).

Alternatively, you could try eliminating the threading and drill the hole a couple of thousandths larger than the protrusion. You don't want it too sloppy, but you need two or three thoudsandths so the solder can flow into the joint. That wouldn't be quite as strong as the threaded joint, but for such small parts the difference might be negligable. It doesn't appear that the parts are load-bearing, and they only need be strong enough for cosmetic purposes and to hold together.

The same applies to the larger parts originally mentioned, though I'd go 0-80 for those.

Here's a link to *small taps and dies* from Micro-Mark and a link to a supplier of *0.032 dia. Stay-Brite and flux*.


----------



## Totalwrecker (Feb 26, 2009)

An alternative to Dwiight's idea would be to drill and tap the rod and clevis then run a screw in to fix the two together. Solder and then remove the screw head. This way you would have soldered threads holding the two together.... 

John


----------



## Ken101Ward (Jan 1, 2010)

As Dwight stated, if the parts are not load-bearing and they only need be strong enough for cosmetic purposes, maybe threading the 
parts and using a suitable epoxy might work. This way you can eliminating heat from the situation altogether.


----------



## Mr Ron (Sep 23, 2009)

How about using the drilled hole in the clevis and shrink fit the rod? A lot less work than soldering or threading. You can freeze the rod with dry ice and heat the clevis slightly and press the two together. Drill the thru holes for the pins after assembly. You will need a jig to hold everything together in perfect alignment.


----------



## Mr Ron (Sep 23, 2009)

I've used "crazy glue" to hold small parts together, but a mechanical joint is always needed.


----------



## Mr Ron (Sep 23, 2009)

Another method is to cast an epoxy resin around the end of the rod and file the casting to the finished shape. Brass filled epoxy resins are available as are stainless steel and aluminum filled resins. I'll bet even J.B. Weld would work.


----------



## wigginsn (Jan 9, 2008)

Gotcha - thanks.

This stuff is purely cosmetic, unless there's a bind in the valve gear then loads are small and timing (tolerances) are not critical.


First shot at this part - the Union Link. Its the smallest part so everything should be easier than this one











Had a lot of trouble lining the parts up straight, any kind of uneven heating bent it out of shape before I even applied the solder. You can see the slight bend that developed as I hard soldered the second clevis. Screwing or clearance fitting it together first & low temp solder is going to solve a lot of probs - thanks again.


Cheers
Neil


----------

