Seiko 7A38 - by the numbers

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Forum Home > Parts Info, Tech Tips and Tinkering > Sand Blasting & general Case Re-Finishing (Topic Moved & Re-Named)

donwatch
Member
Posts: 520

Has anyone tried using this method to restore  a factory finish? If so what type of media used ?  :/

March 1, 2014 at 12:52 PM Flag Quote & Reply

Rob Benham
Member
Posts: 229


Don, you mentioned the finish on your fine 7000, I've had a bash at doing that surface.  This was the first go. :(


It was impossible to draw the Dremel's abrasive mop in straight lines. 


I made a board with a straight edge, and drew the case over 400 grit wet and dry.   Not a good photo, but it was a major improvement.  Using a mop with stainless polish (green) I softened the cuts.  Perhaps too much.   Top right done, bottom as was - more or less. 



Conclusion:  I think it's doable, but only with a proper jig that will allow the tilting as one reaches the ends.  The fine striations are perfect in some places, which gives hope of finding a very satisfactory solution. 




March 1, 2014 at 5:07 PM Flag Quote & Reply

donwatch
Member
Posts: 520

Looks good--I have had some sucess----But the dull area under the 7000 and the dull of the RAF has me wondering how they do that flat dull finish

March 1, 2014 at 5:16 PM Flag Quote & Reply

Rob Benham
Member
Posts: 229

Fixing the Dremel with the cutting mop and drawing the case along is still fraught with dangers.  The edges became ill defined!   I was able to restore those to mirror finish with green polish.  (Phew!)  I really thought I'd finally runined the case.

.

My feeling is, that if a case is fair, probably better to leave it alone.  Once into the cutting, one is committed. 


March 1, 2014 at 5:17 PM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 9333

@ Don. As far as I know, the only 7A that has anything like a 'blasted' finish are the 7A28-7120 RAF Gen. 1's.

If you're talking about the matte lower part of your 7A38-7000 case I think you'll find that's an anodized coating.

An example of a 'sand blasted' 7A38 Franken here: http://www.seiko7a38.com/apps/forums/topics/show/12123975


PS - In case you wondered where it's gone, I'm going to move your topic to the Tech Tips / Tinkering section. ;)


March 1, 2014 at 5:21 PM Flag Quote & Reply

Rob Benham
Member
Posts: 229

One of several watches to turn up this week is a 7A38-7020 Number: 413443; One of those with a dodecagonal bezel. A bezel that has been stripped of the gold finish while leaving the rivets gold, It's a design that I'm not fond of, but the light grey face on this is very clean and attractive. It's very clean inside despite the case having taken a beating. The top surface of the case has also been abraded, so it's an ideal candidate to practice my surface striation cutting on. The bezel is quite a different matter. All I can think of doing for the moment is polishing the base metal to a brilliant shine and advising any purchaser of the fact. As mentioned before, I've polished handles on my lathe with jeweler's rouge to chrome brightness and the steel stays free from rust for years. I've just recalled a thread about one that had been stripped and the rivets left in gold, and wondered if this was one and the same. (Mine was from an American collector from whom I've purchased three.) I have no real need to know if it's the same, just wondered.


March 14, 2014 at 3:20 AM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 9333

Rob.

Stripping the remaining worn gold plating from the dodecagonal (always makes me think of a thruppenny bit) bezels of two-tone Seiko 7A38-7020's (and gold-dialed 7A38-702A's and -702H's) and polishing them, leaving the gold dummy rivets is probably one of THE most common bodges inflicted on Seiko 7A38's. Some watch botchers do it better than others. I've even done it myself occasionally. 




There are a couple of typical examples in this thread: http://www.seiko7a38.com/apps/forums/topics/show/7451104-page=2

Another one, done reasonably well in this other thread: http://www.seiko7a38.com/apps/forums/topics/show/7588308-page=2

Notice what I wrote there ? :|

Perhaps I should start another thread just to flag up all the two-tone 7A38-7020's, -702A's and -702H's that I see with this 'botch'. :roll:


March 14, 2014 at 4:24 PM Flag Quote & Reply

donwatch
Member
Posts: 520

This is the way Seiko should have done this bezel in the first place. Keeping that -THIN- plate safe in the recessed area. Like they did on the band. :/  I like this look and see no issue with doing it---> BUT-- if sold, full disclosure. :| Just my opinion. :roll:

March 14, 2014 at 9:45 PM Flag Quote & Reply

Rob Benham
Member
Posts: 229

Yes, that one is magnificent compared to mine, but at today's prices I paid for a very clean movement and the case comes free. 

I noticed that in one of your links the gold part of the band was worn through, leaving jagged metal - albeit at a very small scale.  It's an odd failure of design, IMHO.

.

I've been hours following the missing aircraft saga on PPRuNe.org   In my 14 years on that forum I've never seen anything like 5,000,000 hits on a thread.  The most bewildering mystery in aviation in my 50 years in the game.

My bench time is being divided with refurbing a bathroom.  No wonder I'm confused.

.

The matt finish on my 7A38-7000 has gone unnoticed since 1985.  Just never really thought about it.  I'll resist all temptation to polish it . . . probably. :roll:


March 15, 2014 at 12:31 AM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 9333

Let's face it Rob, even if it weren't for the Malaysia Airlines debacle / disaster, you'd still find some reason to take the thread 

As It started off as simply a question about Sand Blasting by Don, I've edited the title once more to cover scope of the current posts.


March 15, 2014 at 6:47 AM Flag Quote & Reply

7ARCool
Member
Posts: 168

Hi Don, I am intending to experiment with Sand/Bead blasting myself.

I recently spoke with a guy who has a small workshop locally where he sand/bead blasts and polishes items from one-off to multiple jobs.

He explained that sand blasting gives a fine textured matt finish due to the sand being sharp, and bead blasting gives a softer darker finish due to the beads being spherical.

For best results an item should be sand blasted then bead blasted.

I have access to a compressor and am looking into various kits, I will obviously need to build some type of enclosure as the work is extremely messy!

I  will update my results, but they may be a while due to too many projects.


March 15, 2014 at 9:27 AM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 9333

My turn to make an  post in one of your threads for a change, Rob. Well actually it was Don's, but what the heck. :P


Stripping the remaining worn gold plating from the dodecagonal (always makes me think of a thruppenny bit) bezels ....


The old thruppenny bit:




New Pound coin announced in today's budget.




Good to see it's got plenty of 'dummy rivets' around the edge. Should make it harder to forge. :lol:


March 19, 2014 at 7:14 AM Flag Quote & Reply

Rob Benham
Member
Posts: 229

Gosh, I'd give a couple of quid for one of those. :o

March 20, 2014 at 2:27 AM Flag Quote & Reply

Arpie
Member
Posts: 202

Many months ago I purchased a 7A38-7070 but the case has lost its dull matte finish as it was polished during the years. Moreover, when I tried to pry off the bezel I made some scratch as well.


So this was the situation:









I always wanted to do an experiment with the sand blasted finish so I thought I will give it a try. I called my brother in Hungary, he had the facility to sand blast small things like a watch. Luckily I was about to go back Hungary for holiday so I took the watch with me to play a bit 8)


I didn't have so much time to find the best blasting media, so I purchased some fine copper and steel powder. My brother had some fine sand as well.

In order to hide the big scratches we started with the fine sand. Here is the result:



Then we tried even a more fine sand just to achive more softer-smoother finish, here it is:




I'm not saying that it's perfect, actually it is very far from even the original factory finish. Even though I like the result it is slightly darker than the original finish due to the rough surface.

So the next turn was the copper powder. As I didn't have as much powder as I should have we cheated a bit. I mixed the copper powder with plain flour. The result was slightly odd. The copper particules sticked on the case and gave a goldish-copperish color....which I didn't really like. Therefore I mixed the steel powder with the plain flour and applied that on the case. Here is the result:




Much more smoother than it was before. It is still not the same as the factory finish but who cares.

I should have tried another blasting media too but I didn't have time and patience......and I didn't have the source for the blasting media :(

August 5, 2014 at 5:49 PM Flag Quote & Reply

Arpie
Member
Posts: 202

It is time to re-assemble the watch.

Couple of better shots about the final surface treatment:







And the completed watch:





And a wristshot:



As you can see I was a lazy bastard because i didn't remove any of the pushers. They could be a point of an argument but sooner or later they will be polished too due to the usage.

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

Arpie
Member
Posts: 202

Let me share some comparison shots as well.


You can see an original factory finished 7A28-7040 against my sand blasted 7A38-7070. The differnece is clearly visible: the 7A38 is slightly darker and has more matte-dull finish due to the blasting media was still too big. (we are talking about microns here)







As fas as I'm concerned I'm quite happy with the result.....considering the time and money I spent on this project. Obviously there is always a way to get closer to the original finish. Probably I should have tried another media like glass bead or aluinium powder.....maybe later. :)

August 5, 2014 at 6:05 PM Flag Quote & Reply

Sir Alan
Member
Posts: 451

I really like that - nice work.

August 5, 2014 at 6:09 PM Flag Quote & Reply

Arpie
Member
Posts: 202

Many thanks Simon! :)

August 5, 2014 at 6:14 PM Flag Quote & Reply

Phil
Member
Posts: 148

Just browsing through old posts and I like this one, great finish Arpie, I think I prefer the darker one :D. It's good to tinker well done that man

September 10, 2015 at 3:42 PM Flag Quote & Reply

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