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Forum Home > Parts Info, Tech Tips and Tinkering > Strange request for 7a28 'Alien' pushers

Ross McS
Member
Posts: 24

I've just bought a 7a28-7009 in shocking condition, but I'm hopeful that I can get it restored & replated without too much difficulty.


The watch I bought doesn't have either of the two plastic pushers, but from what I can see from photos, the design is reasonably simple. I was planning on having the pushers turned from SS rod at a local CNC company, and can get the plastics made in ABS in any colour (red, yellow, black) - I was wondering if replacement pushers would be sought after if I made a few extras?


I was also wondering if anybody had a spare pusher, regardless of condition, that I could either borrow for a day or two (I'll cover all postage costs etc.), or that they could fully measure? I'm an Industrial designer by trade, so making new parts to the correct dimensions & finish shouldn't be too challenging!

August 1, 2014 at 1:50 PM Flag Quote & Reply

Ross McS
Member
Posts: 24

I figured this was a bit of a long shot! I'm working on an initial design - I think I can probably figure out all of the dimensions, but any pointers on the pusher rod length or diameter would be appreciated! I think I've got the correct dimensions for the plastic part, I just need to model up the pusher housing to make sure the offset is correct:



One last question... does anybody know what the correct plating is for a 7a28-7009? I've read in numerous places that it's ion beam / PVD - although the appearance and durability looks more like black chrome / passivated zinc plating. I'm lucky enough to have a plating shop at work that can do just about any finish, but I'd like to stick to the original intended finish!

August 4, 2014 at 5:42 PM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 9333

Ross. It is indeed Black Chrome, (underneath) - as signified by the Seiko abbreviation BCRP.

However, I believe that over that it was then spray painted with matt black paint. Nothing more. See this thread (for lots more detail):

http://www.seiko7a38.com/apps/forums/topics/show/12473036-underneath-the-gold-and-other-unidentified-seiko-base-metal-coatings


August 4, 2014 at 5:58 PM Flag Quote & Reply

Sir Alan
Member
Posts: 451

Hi Ross, hopefully this will help:







this was from a 7A28-7009 that had two cracked pushers. I managed to source two new ones (which come with the pusher rod).

I can send this to you if it would help.


August 5, 2014 at 3:43 AM Flag Quote & Reply

Ross McS
Member
Posts: 24
Thanks for that - very useful! I wouldn't mould them, which opens up the possibility of a couple of design tweaks to avoid cracking. I'll drop you a PM shortly!
August 5, 2014 at 2:43 PM Flag Quote & Reply

Ross McS
Member
Posts: 24

Just a quick one - I've got the metalwork drawn up, but still searching for a supplier who can deal with reasonable MOQ's. I've prototyped the plastic pushers - they're just quick mock ups and not polished, but at least it proves the dimensions before spending any money.


Here is my shockingly bad condition 7a28-7000 with the first prototype pushers installed (I've got a new crystal waiting, and am going to get the watch refinished & plated in black chromium - although I still haven't had any luck in finding a strap remotely suitable!):




September 1, 2014 at 3:28 PM Flag Quote & Reply

Ross McS
Member
Posts: 24

Next update: a member has kindly sent a metal pusher for measuring, I'll draw up the CAD this weekend and see if we can get some produced.

On other news, I decided to strip back the coating on my watch - the yellow colour inside the case shows that it has had a chromate conversion ('chem film') coating with black passivation - aka black chromate, just as expected. I'm refinishing the bezel as it has a couple of small dents - and before it's replated, the case is going for an X-ray Fluorescence check to confirm the base material. I've heard horror stories of castings disolving in the wrong chemical solution, so better to be safe!!

Here's the case after a quick 180 grit Al-ox bead blast (I only did it lightly to show any scratches as I'll have to give it a final preparation prior to coating):


September 4, 2014 at 5:34 PM Flag Quote & Reply

Ross McS
Member
Posts: 24

Latest update (this is turning into more of a build thread than a request for pushers!):

The case is confirmed as stainless steel (not sure of which grade as it was just a quick test to ensure it wasn't anything horrible like a zinc casting!). It looks like the best option to keep the original finish will be something like a black zinc plating - just like 'black chrome' it is basically a base plating which is then black passivated. This is a very common & cheap finish for military connectors & hardware - so there are dozens of companies to do it in the UK, and adding a bracelet etc. doesn't really add cost due to it being plated in batches in tanks. PVD coating, on the other hand would cost a small fortune & each additional component incurs additional cost.


I hope to update the thread soon with details of pusher samples & the replated case. Disappointingly I can't find anything similar to the original bracelet, so I suspect I'll just plate one of the 'Feiko' bracelets for the time-being!

September 6, 2014 at 4:42 AM Flag Quote & Reply

Phil
Member
Posts: 148

Very interesting Ross, I am awaiting delivery of my 7A28-7110 SSAY078 and I will most likley be re-plating this, I would like to see your finished case and great job with the pushers

September 16, 2014 at 2:34 PM Flag Quote & Reply

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