Tap size on crown for Seiko Bellmatic

[Vich]

Just a query about the Seiko Bell-matic 4006-6011.

does anyone know whether the 4006 of Bellmatics has a variation regarding the tap size of the stem. I am curious as I now have two crowns neither of which is tap size 9 and both of the crowns were supposed to be a fit.  I was advised that the first crown had been supplied incorrectly and was refunded. However, I got a second crown reportedly to fit the 4006 series and it proved to be the wrong tap size as well.  I have the original stem and a NOS stem both of which are tap 9 so I am going to either grind down a tap or obtain an M1 .25 bottoming tap to re -tap the crowns to sort the matter but I am curious to know if any members have any info on this.

Cheers,

Vic

[clockboy]

This is the correct dimensions for the 4006. Which is tap 9

[Vich]

Thanks Clockboy,

I think we go to the same place for info, windingstems.com.  As in the pic you posted the important info is 354805 that gives only one size for the stem ie 100/1000 or 1mm  ie Tap 9.

It seems that there is a reference for the stems actually from Seiko but so far I have seen nothing from them that designates tap 9 to a crown for the 4006, the actual part number is 55M22NS1, however Boley have this reference as well:-

Brand    Seiko         Reference    6138-0020

Group                     Part No                 Description                 item no.

crystal                     340W14GN           Glas Mineral               XMD340811
                               340W14GN00       Glas                            XMD340811
            
crown                     55M22NS1                                               98455M22NS1
            
bottom gasket        DJ0160B                                                  984DJ0160B
            
others                     DJ0060B                Crown Seal                984DJ0060B01

I note that this is for the 6138-0020 which is one of the Seiko Chronos, I am tempted to seek out a crown for this model and if it is only a few quid take a punt to see if it is tap 9 and whether it fits the tube etc.  Cousins may have some dimensions in their catalogue.

Cheers,

Vic

[Vich]

Just noticed whilst browsing the Crowns in the Cousins catalogue that they have their own standard for crown sizing. All references refer to the hundredths of a millimetre that is to say for their purposes Tap 7 is .7 mm, tap 8 is .8 mm etc so if I was ordering from them I would have to ask for Tap 10 to get a 1 mm stem. This seems to go against the standard (rather annoying) convention whereby I would have normally ordered a Tap 9 crown - puzzling.

I sort of understand why they would do this but those of us that have the old standards in our head would have to be careful. Perhaps that has something to do with the original crown I got from them having the wrong thread.
I am now wondering whether I will be able to tap out that old crown to a greater size and if there is in fact enough metal. I suppose I will find out soon !
May work with the help of Loctite.
Cheers,
Vic