a7750 21.6 --> 7750 upgrade question: large chrono hand fit?

[hackR]

hi guys...

i am working on a Navitimer Fighter project using the old skool fighter rep with low beat 7750 movement...have just swapped all the hands over to the eta 7750 with no problems...but am having trouble with the large chrono hand fitting...been working under a loop, and the chrono hand's tube is fine...from my eye, the eta 7750 center post seems to be wider than than a7750 hand tube...it could just be my eye - but like i said, i am working under a magnified loop...anyways, wondering if there's any difference between the center posts on these two movements...

any other advice would help...perhaps i just need to apply more pressure to get it on...but i'm having a helluva time getting the female opening on the hand tube on the movement post to even apply pressure...

any help is appreciated...

thx...R

[Justasgood]

You need to broach the hand.

[Watchmeister]

I am surprised to hear that the ETA movement pinion looks broader than the hand tube. The old A7740 movements could easily take gen hands and the newer one had a thicker post and so it required "opening" the hand tubes.

[hackR]

i was surprised, too...but from viewing with a loop, the eta7750 movements pinion does look wider in diameter than the chrono hand tube...i have tried to get the tube opening on the pinion, but it simply will not "bite" onto the top in order to press it on...the old a7750 low beat's other hands fit with no problem whatsoever...weird...the hand is packed up and will head to Mike for broaching...argh...

[Rolexman]

Maybe a 28.800 chrono second wheel was used as replacement part? A left over or hybrid?

[hackR]

the watch is a v1 old skool Navi Fighter, so the hand has to be for the low beat...but you never know...