Some MBK case tube info...

[automatico]

This is from a message I sent to 'bobandshawn'  12-13-17 pertaining to his post about MBK case tubes in the General Discussion section:

 

I have 4 MBK cases made in the last 5 to 7 years and they all have the correct oem spec threads in the case (3.0mm x .35mm). 

'The Catch' (there is always a catch with replica parts)...the MBK case tube gasket seat cut in the case was not oem spec on any of the cases so they either have to me machined to spec or an alternate gasket used.  I used an alternate gasket because it was easier and I do not plan to put the watches in water. 

The MBK cases are 5512, 5513 and two 1680...they are all absolutely identical except for reference numbers, all have dial window openings made for 26.0mm 5512/13 dials and need to be cut a little bit bigger if a 26.5mm 1680 spec dial is used so it will not be shielded by the reflector (rehaut) because it can shave the outer tips of the minute markers off.

 

Q...What is the fix to make an oem spec gasket seat?

A...Cut the gasket seat in a milling machine or drill press to spec with the appropriate cutter bit.  I have a milling machine and cutter but never took the time to machine any of the cases.  I looked for the cutter in order to give the size but could not find it right away.  As usual.

note:  I finally found the end mill, it is 4.0mm and the base of the oem spec case tube (ST) is 3.9mm where the gasket seats against the tube.

 

I do not remember what the alternate gasket size was but it came from a miniature O ring assortment.  What you need to be careful about is to make sure the gasket is not cut or squeezed too much when the case tube is tightened down.  I use case tubes from Star Time as they are high quality and oem spec. 

 

Something else...another member sent his case to me a while back (not an MBK case) to have an Athaya 'no dot' 7mm replica crown and tube set fitted.  The threads in the case were oem spec (3.0mm x .35mm) but the Athaya tube was not oem spec at all (where it screwed into the case) so we ordered three aftmkt  'no dot' case tubes from WSO990.  The WSO case tubes were oem spec except ('The Catch' again!) the threads on the tube where it screws into the case were the correct pitch and depth but the outside diameter was a hair too big to screw into the case without the chance of binding or breaking.

 

Q...What is the fix?

A...Polish the OD of the threads down with Simichrome polish using a stiff 1 inch buff wheel on a Dremel tool, it did not take very much.

Q...So...What's 'The Catch'?

A...The Athaya crown fits the WSO990 case tube just fine after polishing the tube but the 'telescope' clutch in the crown was not sealed to the crown cap and the crown cap gasket did not do its job and allowed water to flood the case.  Imho aftmkt crowns are not always good to use if you plan to get the watch wet.  Case tubes are an exception and many of the current aftmkt tubes are as good or superior to oem, especially aftmkt stainless 5.3mm case tubes compared to oem nickel silver tubes...imho.

 

Also...the 'no dot' Athaya crown will not work with a standard 'three dot' modern type triplock case tube even after 'serious modification' because the 'three dot' tube is a lot taller.  I have not tried to shorten one at the top but after you cut the top down to the threads, the base of the tube below the threads will still be too tall because of the space needed to cut a gasket groove on the lower part of the tube for the 'dust and grit' gasket.

 

A genuine 7mm 'no dot' case tube should have worked just fine with the Athaya crown but like the cutter bit, I could not find one at the time.  Still have not found them.

[bobandshawn]

More great info!!!

 

B

[Nanuq]

Outstanding writeup!!!