Leaderboard

For these old chronos with a printed ring as tension ring and no parts available, I often use a "generic" (quotes because randomly enough a few Omega crystals have fit the bill in the past) armored crystal which I modify. As luck would have it the usual tension ring for a given outside diameter is often smaller than the printed ring. I make a friction chuck out of plastic in the lathe that will just allow the crystal to snap into, backwards, then turn the inside to fit the original ring. Takes about 15 mins start to finish if you are accustomed to latge work.

Maybe a Sternkreuz ATCH? Take a look at their data sheets.

Inner diameter is slightly larger then 31.1. But i glued the inner ring with a small dap of crystal glue. Hasn't come of yet . This one i had was 33,3 but i used the 33,2 already. BTW it was a evertite . And it's 4 mm high on the spot.

Rather expensive.

Unrealized that just after I posted. IQ at 59. Sent from my iPhone using Tapatalk Pro

Will do, I've ordered a donor 1320 movement. I managed to clean all the old parts except the minute wheel which is a tad rusty (but may work). The calendar date ring is garbage, as is the calendar retainer plate. although could be used in a pinch. If the part was extremely rare, I would have sent the date ring to a dial specialist to reprint - hopefully the 1320 ring matches. The stem was broken so thats no good. The crown yoke is de-chromed - so will need replacement. A lot of the parts suprisingly survived. The base plate is really all I need to survive. Will post pics soonish. Waiting on a soldering iron to touch up the circuit board.

The PTA or Pultra's are beautiful lathes. they were made by Smart Brown who made top notch tool makers lathe, same caliber as a 10ee or Hardninge HLV. I've a 10mm PTA, next size up, with all the accouterments and love it. I struggled with urethane belt joining for a long time. The challenge is perfect alignment so you have vibration free operation and secondly there is a cure time so it should held perfectly in position for up to 30 minutes. Sans cure is why the break and the small the size the more challenging a strong perfect joint is - that comes from a conversation with a belt manufacturing when I finally asked for help. Eventually I made the following fixture and its hard not get perfect joints. Basically 4 cold rolled steel bars with holes drilled as shown and dowel pins in reamed holes to insure alignment. First you clamp both sides of the belting with say 1/8" protruding. Slip a hot knife between the halves, get the belt good and gooey, pull the knife and clamp the to sides together. Leave for half an hour, trim with nail clippers and you have a perfect belt. It works so well I had a belt manufacturer ask to quote making them for them for resell (didn't bother).