Jump to content

Advice on turning down thin pivots

margolisd
 Share

Recommended Posts

margolisd WRT Addict

margolisd

Posted
Posted

Hi guys. Any thoughts on best approach to turning down a thin pivot (.14mm) on the lathe after replacing? Thinnest pivot wire I have is .33. I’ve plugged it fine but keep braking it when trying to turn it down with the graver when it gets close. It is tempered blue steel and I’ve not softened it. Should I stick at it or change approach?

I’ve read that maybe I should abandon the graver entirely and use a sapphire stone? But they’re super expensive so wanted to ask if anyone had any advice. Perhaps on a good brand of sapphire stone that’s not over priced Burgeon.

The pivot is also quite long (long story, it is an adapted ETA part that has to connect with a power indicator module). Are there lathe accessorIes that support long pivots whilst they’re being worked on? Or should I just put the graver rest underneath it and stone it?

Link to comment
Share on other sites
JGrainger WRT Addict

JGrainger

Posted
Posted

It should be possible to turn pivot steel but pressing it in may add a bit of hardness to the end. If I was struggling with this then I'd try rotating the graver to an angle so the cutting edge is at 45 degrees, with the tip above the work and the other end below the work. doing this will create a bit of an uneven surface on the work but should allow the material to be reduced in diameter so that the abrasive / burnishing tools have less to do.. starting from the least supported end. Ideally you'll need some sort of optical aid for this and something to be able to hold up to it as a reference diameter while working. A jacot drum is ideal for resting the pivot on for the latter stages of finishing but any stable and located (so it can't be knocked and run into the work) support or the toolrest might work if the height is spot on.

Link to comment
Share on other sites
nickelsilver Distinguished Member

nickelsilver

Posted
Posted

Are you using steel or carbide gravers? Either will work, but both need to be sharpened perfectly. It should be no problem to turn to 0.08mm or smaller. I leave about 0.01mm and finish in the Jacot.

Check your gravers and keep practicing. How long is "quite long"?

Link to comment
Share on other sites
 Share
Go to topic listing


  • Recently Browsing

    • No registered users viewing this page.

  • Topics

  • Posts

    • rjenkinsgb
      Any tips to correct a sloppy error?

      By rjenkinsgb · Posted

      Two pins or screwdrivers angled out slightly, pressing through from the barrel centre from the opposite side so they contact just clear of the hole in the lid? eg. Strap pin driver needles or similar.
    • Geotex
      Any tips to correct a sloppy error?

      By Geotex · Posted

      That's a good idea - shrinking down the nut and wrench size from the old casebook trick!
    • GuyMontag
      Movement holder made with 3D printer

      By GuyMontag · Posted

      I missed this earlier. The dial isn't going into the holder, it should sit proud of it. This is what I am currently using which I print for each different movement.    
    • Neverenoughwatches
      Setting lever spring

      By Neverenoughwatches · Posted

      I didn't think pulling to set position would work harden the spring, in that position it is stressed where the arm starts. By work hardening i meant rapid polishing at that point, a bit like polishing a pivot work hardens as it compresses the steel. I doubt polishing by hand would achieve much in that respect though. Its finished, arm polished up mostly at the join to the bridge's main body. I'm ok with it, the screw holes aren't great as i had to open them up by redrilling and positioning it was difficult, I'm not much use with a loupe, opening up with a file might be a better option for me or i could just use the correct drill size 😅. And the detent is way too deep, i had to guess that with the stem release out of position and sat on top, but i only took one measure and went for it, no slowly slowly catch your monkey 😅. First go I'm happy , well sort of, it works and thats a big thing for me, next one will have a bit more finesse.  Anyone thats interested, after filing, i used a 2000 grade home made diamond  micro file and then 20 micron film, the film is much better than wet and dry, more stable to use and doesn't shed cheap grade grit everywhere , then auto polish on a sponge pad.
    • RichardHarris123
      Setting lever spring

      By RichardHarris123 · Posted

      I'm assuming that every time you set the watch you are work hardening the detent spring, maximum hardening is  where it meets the plate due to maximum deflection.   That's why it snaps there.  The Young's modulus may be the same but after it's reached its maximum yeid strength it breaks.  My mechanic engineering is very rusty, correct me if I'm wrong. 
×
×
  • Create New...