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Help Cutting Threads on Stem

jdrichard

By jdrichard
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jdrichard Distinguished Member

jdrichard

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I am making a watch stem and am at the final step of cutting the threads. So I have a Swiss (probably Chinese) die plate and clamped the part in my lathe. The die did not cut the material AT ALL. So the stem is made of blue steel. Do I need to soften the blue steel before i cut the thread? I also just bought another die plate just in cast the one I have is dull.

 

 

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jdm Distinguished Member

jdm

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26 minutes ago, jdrichard said:

I am making a watch stem and am at the final step of cutting the threads. So I have a Swiss (probably Chinese) die plate and clamped the part in my lathe. The die did not cut the material AT ALL. So the stem is made of blue steel. Do I need to soften the blue steel before i cut the thread?

I do this with blue pivot steel. First annealing the steel to make it easier to turn and cut the thread.

https://www.watchrepairlessons.com/2011/07/17/vintage-rotary-repair-making-a-new-winder-stem/

 

 

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jdrichard Distinguished Member

jdrichard

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I think you'll need more heat than that. A small butane torch should do the trick....

What colour do I need the steel to get and do I just let it cool down at its own pace. Then once I cut the threads, do I reheat it to blue and quench it quickly in water. I think I only need to do the threaded area of the stem, correct. Have never done this before.


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measuretwice WRT Addict

measuretwice

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Annealing requires you to hold at the critical temp for a minute or two (for small parts) then a slow cool for a full anneal.  Overnight in ashes is ideal, shorter may work but for a full anneal it needs a very slow cool, so I've always done the box of ashes thing.  To heat treat it again, heat to critical temp (1450), hold for a bit then quench in appropriate fluid (will depend on the steel).  After quenching, heat to the desired tempering temp to 'let the steel down" - this reduces the hardness a bit but also reduces the brittleness.  The following colour chart is based being viewed in sunlight, ie they'll all seem brighter with the lights out.  The right temp is often called bright cherry red, which I always thought was a poor description given the ripe ones are lot darker than you want the steel

http://www.stormthecastle.com/blacksmithing/images/color-of-steel/forging-and-tempering-colors.jpg

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khunter WRT Addict

khunter

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12 hours ago, jdrichard said:


What colour do I need the steel to get and do I just let it cool down at its own pace. Then once I cut the threads, do I reheat it to blue and quench it quickly in water. I think I only need to do the threaded area of the stem, correct. Have never done this before.


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I'm not an expert in this by far but red hot at least for both annealing and hardening, let cool for anneal and quench for hardening. The exact temperature depends on the material, and that's the hard part. There's a ton of information on the web about it, YouTube especially. I have a feeling your die may be at fault also, if it's anything like my die plate (again probably chinese) it's not good for much besides re-threading a buggered thread. Finding actual quality dies for our work seems to be one of the very hardest things to come by. Sorry I can't be of more help. 

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rodabod Distinguished Member

rodabod

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 Cherry red for a couple of minutes should do it. Taper the very end of the stem so that it can reach into the die plate. 

Turn the stem by hand whilst it’s clamped in a lathe collet. Use an empty tailstock to push against the die plate so that it’s perfectly perpendicular to the stem. 

Harden the stem to straw (or whatever hardness you prefer) and then polish. 

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measuretwice WRT Addict

measuretwice

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see post above.....a slow cool means a slow cool - like overnight.  less will work, but a complete anneal is hours and hours of ramp down.  Just heating it up and letting it air cool is essentially air quenching it.   Google O1 heat treat cycles and note the ramp times.  Heat it up bright red, hold it there and drop it in a box of ashes is how I do it

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measuretwice WRT Addict

measuretwice

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edit window closed and I miss a bit....I'm giving the way to anneal carbon steel.  A shorter, simpler cycle might anneal it enough, but the point is if its not working its because you are either not getting it to the critical temperature, or more likely its not being cooled slowly enough.  A BIG advantage to to doing a full normalizing (think slow and full anneal) is that the stresses are removed.  Without that, there is an increased chance of cracking at the stress riser (ie bottom of the V thread) when you do the quench to heat treat after machining

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rodabod Distinguished Member

rodabod

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The metric HSS set I suggested recently in the other tap and die set is great. It’s the 31 piece set which comes under various brands. Don’t bother with the shitty Indian die plates. Though a Martin Swiss die plate should work well if you can find one. 

For annealing small parts like this, you need to keep heating as you cool it down to bring the temp down gradually. I found that you don’t need to do that for long - say one minute of gradual cooling. 

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jdrichard Distinguished Member

jdrichard

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Bargain! I paid £40 odd in the UK. Mine was branded Tool Station or something like that. It’s  a nice quality piece of kit. 

Same manufacturer in china. Check out aliexpress app and buy from them first, free shipping as well, mist of the time.


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teegee Watch Enthusiast

teegee

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On 1/29/2018 at 8:32 PM, rodabod said:

This is the set which I was describing:

https://m.ebay.ca/itm/31pcs-High-speed-steel-Tap-and-Die-set-metric-Model-Making-Watchmaker-Tool-SH1/192333554846?hash=item2cc7f9249e:g:TkAAAOSwG0hZ4XaO

I've had the same set for years. Pretty much hit-and-miss when it comes to quality. I've bought a few separate dies and taps for the smallest three sizes, also on ebay. Even though more expensive, these were not necessarily any better, sigh.

 

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jdrichard Distinguished Member

jdrichard

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I've had the same set for years. Pretty much hit-and-miss when it comes to quality. I've bought a few separate dies and taps for the smallest three sizes, also on ebay. Even though more expensive, these were not necessarily any better, sigh.
 

Just need to find a reasonable priced professional tap and die set for us watch guys

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