Omega 752 Day wheel fault

[hofnerpres]

Just finished another Omega 752 166.036 with no drama one I'd figured out how to sync the day with the date wheel position. Got the dial on and adjusted the hands - all done - double check since this a one piece case. Oh great - the day wheel has popped up and clearly the operating lever has slid under and we are stuffed. Now - unlike previous dials I'm looking at a nasty 1 mm thick plastic spacer ring which holds the dial away from sitting on top of the day ring - hence the lack of any retention. That would explain the mangled copper washer that was sitting under there during disassembly. Looks like a small but 1 mm thick spacing washer needs to be under here in order to retain that wheel. No mention on the Parts Data. Are we looking at a factory adaption here to allow a proper fit in the one piece case ? It's the drop in and twist type fitting. Omega did use different styles of day wheels for this movement - some where flat and some had a built in small centre which gave better support. This ring has that upstanding steel centre bush. You can see it is a smaller diameter than the dial centre hole so it is of no use for stopping things from popping up and disengaging. Am I missing something or has the previous repairer just lost the washer and fiited a bodge ? Pics below.

[JohnR725]

11 hours ago, hofnerpres said:

Omega did use different styles of day wheels for this movement - some where flat and some had a built in small centre which gave better support.

one of the problems with the watch companies are they upgrade and change things. The problem is the tech sheets magically do not change to reflect the changes. Sometimes the changes are in the case of Omega in the general instruction sheet that covers a whole bunch of similar calibers. But typically these type of documentation is never find themselves outside of well Swatch group. For instance for the Omega 751 and 752  they have this the old versus the new.

or you might have things such as this

 

 

 

[hofnerpres]

 John - Your reply is excellent as usual. I remember whilst working at a car manufacturers headquarters how the various part numbers would be continually superseded as changes and modifications would change over the life of a particular model. This was often to improve a weak design or a part which the warranty department were getting tired of paying out for replacement. So the problem is now fixed. I placed a tiny ball of Rodico at the side of the offending day wheel post and replaced the dial. Took off the dial again and noted what the flattened Plasticine had to say. It said the unwanted air gap was a little less than the wheel central tube which measured at 0.5 mm. So we need a small spacing washer at say 0.45 mm thickness. The central hole needed to be 2.00 mm in diameter in order to clear the central tube. A rummage amongst  the radio control model parts bins produced something close enough but a shade thick at 18 thou ( I'm an old imperial guy ). No fancy lathes available but you only need a good quality diamond nail file. Just hold it down with a finger and slide up and down for a few minutes whilst turning it around 90 degrees occasionally so that a wedge shape does not result. Clean it well and try it -  beware - if you err on the thick side because you're bored and your finger is getting sore a trap lays in wait. The day and date will now change nicely but there is pressure on the hour wheel it sits upon. This will show up as an amplitude drop and can go unnoticed. If it's a one piece case you will not be pleased at ripping it all apart again so make sure it's checked before you replace the hands etc. I ended up at 15 thou but I expect the next one will be slightly different so use the Rodico trick to see what your missing spacer needs to be. Omega produced so many different cases it's little wonder they had to play around with spacers I expect this strange plastic ring was to get the stem aligned to the case tube. Also not sure how they expected the extended wheel tube to control end shake when the dial hole was a larger diameter. What it does do is provided an secure location for any spacers - good idea. Despite this niggle and the usual replacement of the dog bone shaped pivot which holds the large auto driving gear ( Part 550-1438 ) it has been an easy ride - what a lovely quality piece of engineering which runs very cleanly. There are rumours that this part was produced with a ruby insert - is that so ?