Seiko 7A38 - by the numbers

Gentlemen,

I recently purchased a badly "esteemed" 7a38-7070. The previous owner had the case drilled for fixed bars, holding a cheap folded links bracelet. 

I´m planning to make sleeves for the holes from spring bars.

Right now I need a new set of hands (plus gaskets and glass), since the originals are corroded and lume is history. I am not a purist and I will consider alternative hands. Does anyone knows the hole sizes of the hands?

Thank you.

hi there luso

 sub hand size is 0.20mm and the second sweep hand is 0.20mm. As for the other hands sorry no idea, but some other of the seiko model hands are interchangeable. look at the forms on here they have very handy information. Thanks to Seiko7A38 , Sir Alan and Others well written  and with brilliant photographs that I have found extremely educational. 

ric

Hi, Pedro.

Sorry for the late reply - I've been out all day. Off the top of my head, hole sizes for the hour and minute hands are 1.5mm and 0.9mm.

As you've probably gathered from your earlier enquiry on SCWF, both the early style 'polished edge' hands and the later white-painted hands, as on your 7A38-7070 (also used on the stainless 7A38-7270) are obsolete and no longer available as spare parts from Seiko.

There was a topic about them in the 'Tech Tips and Tinkering section, over a year ago:

http://www.seiko7a38.com/apps/forums/topics/show/7357640-reluming-hands-specifically-obsolete-nla-7a38-hands

Thanks for your replies, friends.

I would say that the proper course of action should find a compatible set of hands. I wonder if a set from later chronograph modules are compatible with these early movements. Is there a way to find out the dimensions of the hands holes?

And now I know why I can´t find a decent watch: 7a38 has them all!

Let's say I have 'a few', Pedro. 

But not many spare pairs of original Seiko stainless or white painted hands, unfortunately. 

In fact, I gave my last pair of 'polished edge' hands to Simon, to help improve his 7A38-7070. They weren't new and slightly tarnished, but the lume was better than his. I've got a couple of 7A38 re-build projects on hold, awaiting better hands (if they ever materialize). 

If you're not averse to using 'aftermarket parts', you might want to consider trying Cousins' p/n H34302 hands (I haven't yet myself).

See: http://www.cousinsuk.com/catalog/watch-parts/hands-watch and scroll down the page to:

 (They're style B in this illustration. Maybe a bit short @ 12mm.)

I can't remember the holes sizes, but I can tell you 7T32 Hour and Minute hands won't fit a 7A38 (too small), but Sweep Second does.

That´s a start, 7a38. I will try some of those. And I´m glad you told us that 7t32 won´t fit as I was going to try a set. Thank you once again, mate!

hi there, I was going to find some fine drills and have a go at drilling the hands out. they odd ones I've picked up. just another idea, I'll be looking into.

ric

I wouldn't recommend that Ric, even twisting the drill very slowly, manually in a pin vice. 

The correct technique for increasing the hole size in watch hands is called broaching.

There's plenty of information on the 'Net, if you search Google: http://www.google.co.uk/search?q=broaching+watch+hands

Including this old thread on WatchuSeek: http://forums.watchuseek.com/f6/broaching-hands-how-can-i-go-about-334484.html

Incidentally, when you come to fit NOS Seiko hands (first time out of the packet) of the correct size, they may need a gentle 'easing'. 

I've had to do it a couple of times myself, when fitting NOS Sweep second and Chrono sub-dial hands. Used a suitable sized needle. 

Because although, as you stated, the hands are nominally 0.20mm hole size, measure the spindles and you'll find they're 0.21mm Ø.