Seiko Barrel Arbor Jewel Set (70/7S Series)

This kit is designed to solve the notorious barrel arbor wear issue that is common across the most popular SEIKO 70 and 7S series movements. The barrel arbor first wears an oval hole in the main movement plate, which tilts the barrel and wears an oval hole in the top. This causes the circumference of the barrel to touch the plates and the 4th wheel.

 

After repairing the issue, the movement's life is extended to indefinite if regularly serviced. In many cases, the amplitude is often around 5-10 degrees higher as an additional benefit.

 

The jewels are designed to be fitted with the correct horological tools e.g. SEITZ or similar jeweling tool.

 

We offer NO GUARANTEE against breakage. If the correct procedures and methods are used, with the correct tools, the risk of breakage is none to minimal. We will assume you're a professional or have experience in this sort of work previously. It is not a job that is easy for a beginner watch hobbyist.

 

The bottom arbor needs to be reamed with the 1.59mm jeweling reamer. We suggest doing this in stages to help keep the hole central. You will also need to ream the calendar plate as the jewel protrudes slightly through the calendar side of the plate. This is simply so we could make one jewel suitable for several calibre lines to keep the cost down.

 

The upper jewel cannot be fitted without additional work to the plates. The top plate will need to be carefully reamed out to 2.59mm. We suggest doing this through stages, as it helps to keep the hole central. The goal of the design was a "one size fits all" solution to the entire 70 series derived calibres. The earlier 70 series movements usually have a bush which can be pressed out and then the plate reamed. Earlier 7S series movements often just have a port in the plate, which will need to be reamed in stages. As we don't know which variant you are installing the jewel in, this was the best solution to cover the entire range. There is no 2.49mm reamer in the SEITZ range, so we went up to 2.59mm.

 

The 7S26C, 4R36 variants etc, already have a jewel in the mainplate, so you do not need this kit for them. Due to that jewel, they tend to have less wear issues at this point in time.

 

The wear usually presents as: