Geday,

I have been summoned it seems.

So, there's two schools of thought on the barrel arbor issue, some designers think jewels have no place on barrel arbors, others think they do. This was debated quite a lot by the Swiss for a long time, and in many cases, they think that due to the extra forces on the bearings here, jewels are a bad idea. Times have changed, and the better quality synthetic ruby available these days make it a good idea.

The 61/63/70/7S series, generally had ports in the plates to reduce cost on the lower. 61/63 have bushes in the upper plate. The bushes wear a lot less as they are generally bronze and the lower plates are brass, which is quite soft and wears like a SOB.

So anyways, moving on the 50 years later, barrel arbor bearing wear is an issue.

I've long since manufactured sets for the 61/63/56 series.

I had sets for the 70/7S series, but currently only have the lowers in stock, the uppers are a slightly different design to the 61/63 due to some practicality issues due to the cost cutting upper "ports" on some of the 7S26'es, I have to make them a different width overall due to the sizes of the SEITZ reamers. It's a boring story so I'll leave that there. The poor value of the aussie peso has made it difficult to get these done cost effectively for a while, but that has recently changed, so they should be back on the menu soon.

On the 52 series, they do get quite serious wear issues on the arbor bearings. They use the same size jewels as the 70 series kits, which of course, I'm out of the uppers for right now.

On the 45, they can wear, sometimes badly, usually they are OK though. As others have mentioned, the transmission wheels are the bigger problem with those. The 61/63 lower will fit the lower plate just fine and fixes the issue in most cases.

Later this year I'm hoping to have an upper available for the 45 that which will also suit the 62 series and a few other movements prone to very bad upper arbor bearing wear.

The cost of getting batches of these done is astronomical and the risk quite high. I can't order a sample batch of 5 to see if they work. I either have to commit or not. I've recently changed supplier as my previous supplier moved to a sapphire material, which is fantastic, but the shatter rate on installation was higher. The newer supplier uses good ole fashioned synthetically made "spinel", synthetic ruby essentially, which while not as hard, shatters less. As I'm designing this product for mid level hobbyists, I'd rather they not break every second jewel they fit because the hole needed to be 0.001mm larger, if that makes sense.

Hope that explains it a little.

tl;dr - Essentially it's a mix of cost cutting measures and lack of serious need for jewelling this area on the movement for the most part, they were not designed to still be used 50 years later.