Should I anneal first?

Machine Shop
#1

My idea is to anneal a piece of rod and then do the machining. I know this would be unusual, but I’m working with tiny parts.

I need to make a half dozen brass pins like this.

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As for the type of brass - I dunno. I plan to use 1/32" hobby brass and just turn down the two ends because the center diameter can be within a few thousandths.

I will need to peen the ends to assemble the final item. I will have better success with the peening if I have annealed (I can’t really wail on these with a monster hammer. :smirk: ) Each overall piece is less than 0.1" long and I think my torch will toss them around the workbench if I try to anneal them afterwards.

Any thoughts?

P.S. No - I don’t intend to use the Colchester to turn this.

#2

If you at all expect the piece to hold it’s shape & dimension you do need to anneal it so that during the process of peening over the heads you deform the center as little as possible. Made from brass - there’s pretty much zero chance the dimensions you are cutting this to will hold - so if it’s a critical dimensional you don’t want to peen it - You might form one head for aesthetics - then use a press to form the other after softening the end with a torch if possible so you have some measurable control over the pressure and brass pin deformation is minimized.

Better to use a bolt with a collar/spacer in place - then a nut - then a SLIGHT peen to set the the bolt into nut so it cannot come off and you might be able to hold the dimension without too much compression.

If this is being done for aesthetics, you could use a brass bolt.

#3

These pins become swivel-connectors (sorta like hinges).

Did you happen to notice that this is less than 1/32" diameter? ( I ask this because the smallest threading dies I have are 00-90 UNF and that’s too big. 000 dies are rare and expensive and I don’t think I can turn a bolt 0.023" in diameter).

#4

If this is problematic to machine, it could be done via jewelry methods if the right sizes are available (tiny is possible). This is essentially a hinge pin in jewelry. And in sterling, it’d be easy to peen. Can start with dead-soft, or anneal half-hard easy enough.

You’d combine wire, then fit inside close fitting shorter tube. Solder. (Then maybe trim to true up dimensions instead of finessing placement of tube perfectly ahead). Voila. Check Rio Grande Jewelers supply for materials. Might be more way selection in sterling silver versus brass metals.

MIGHT be a tube cutter in Jewelry. Have to check. Would make things easier.

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#5

If you have to anneal afterwards, try using a stand with a screen on it and maybe make a small copper sheet box to hold them, Theh use the torch under it to head the copper and the brass

#6

Tubing! Interesting suggestion! I have some Albion tubing that precisely slip-fits together. I have to ponder that.

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#7

How are you machining something that small? I think that would even be too small for my Unimat micro-lathe.

#8

Well … I do expect to have trouble machining it. Like you said … micro tools. Turning on the Taig. Length is going to be the problem - I don’t have an X-axis dial indicator set-up.

#9

Re length
If you could get it close, could you hand file or sand the metal to precise length?

I’ve shaped steel tool iron for repousse tools on sandpaper, so a softer metal would work

For keeping the round, if you sand in a figure-8 shape it’d keep that.

In a different life, when grinding for attaching ends to a fiber optic cable, to keep it precisely vertical, then resulting in end precisely at right angle (the ground with that figure 8 motion to keep round in end) there was a little disk holder jig thingy that the cable inserted into and was much easier to grasp and manipulate. All had to be perfect or connection no bueno.

The point being if you decided to file length to precise length, maybe it wouldn’t be hard to drill a hole in something and make a little holder to hold the teensy bit perfectly vertical for you while sanding to exactly the length you need

Sandpapers…you can get exquisitely fine sanding papers with jewelry stuff. Jewelry department might have. Or I could loan you some of what I have.

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#10

Anneal the metal first. Then it will be soft for machining and stable dimensionally as you’ll already have relieved the internal stresses. I believe brass is like copper, it can;t be heat treated to increase hardness but can be work hardened.

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#11

Brass (and copper) are the opposite of iron in that heating and then quickly quenching the brass in water will keep the metal soft. Quenching hot tool steel makes it hard: quenching hot brass of copper keeps it soft.

Make sure the brass is clean so as not to introduce oxides into the surface when heating. Heat the brass until the metal starts to show a blackened color, then quench quickly in water. You may need to again clean the surface before working, though if you are milling off the surface, this might not be necessary.

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#12

@nausser915 - do we have any torch-safe containers in which I could anneal some tiny pieces? (think of a dozen pieces each smaller than a grain of rice)

Trying to turn annealed brass 0.025" diameter is a lot like trying to turn Silly Putty.

#13

I wonder if a shallow copper bowl would work? I think I could raise
a small one of make a edged pan,

If you think that would work, I will try to make one for you
sometime this week, I have an eye exam on Tue
and if I get injections, not likely, I will be out the rest
of that day, I should be able to get to the space on
Wed on later, I am trying to register for the shakepo class on Sat

The first part of the next week is out for me, Then I should have
a bread from doctors

#14

Not sure of anything off hand, but I’m sure you can find something. Maybe you can use pyrex and anneal in an oven low and slow?

#15

That’s an interesting proposition. I’ll have to read up on that. I don’t know what the annealing temp is for brass - I just always default to using the torch. Thanks for the suggestion.

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#16

From a site on annealing brass ammunition:

The higher the annealing temperature, the shorter the time required to anneal. The grain structure of the brass begins to change - indicating the start of annealing - at just under 500 degrees Fahrenheit. At 600 degrees F, brass will anneal in one hour. At 800 degrees F, brass will take only a few seconds to anneal.

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#17

I know you can anneal brass, but I think it is like copper in that it can only be work hardened/wrought. So it may be a one way trip. Basically you’re looking at about 600F, that’s high for an oven, 550F is typically the max. Not sure of cool down rate and steps.

I would not use copper as suggested to put it on, you need something inert, like the Pyrex, not sure how the copper and brass may interact at that high of a temp.

#18

So, I did anneal the parts before the machining (using a torch). Wow. It was like trying to turn (uncured) polymer clay. Sheesh.

I have all the parts made, but I’m struggling with assembly. I have put it aside for now while the frustration subsides. My husband has been very afraid to go into the workshop.

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