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Discussion Starter · #1 ·
I finally started following my TimeZone School Level 1 course to disassemble an HMT movement. The HMT 0231 is very similar to the Fontainemelon calibre 97 (FM97). The big difference (actually fatal :-() was that the screw holding down the ratchet wheel on top of the mainspring barrel was a left-hand thread.

The school instructions say the screw on the ratchet wheel is a normal right-handed. (turn screw counter clockwise to remove)

Why would the HMT copy of an FM97 be different?

(or am I just confused?)

P.S. I wimped out on removing the trishock assemblies.
 

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Discussion Starter · #4 ·
Just remembered that I'd seen a thread a long time ago about about tearing down a HMT. Googled and found it.

Review: HMT Sona | Watch Guy

He also snapped the same barrel screw that I did. Although he actually knew which way he was supposed to turn it. The posting also confirms Roland's post - both crown and ratchet are left hand.

wus thread by wilderbeast

https://www.watchuseek.com/f71/teardown-hmt-sona-635140.html

I'm pleased with the Time Zone School lessons and I've got a couple more donor HMT's to hone my skills.
 
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