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MBW/MBK Crown Tube replacement???


bobandshawn

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Hello fellow modders,

Have any of you replaced the crown on the MBW 5512/13??? I have a new gen crown to install but the threads don't fit the tube that's already installed. Does anyone know if the MBW tube thread (the case hole tap) will accept the gen tube threads? I'd hate to rip out the old one and start a mess...

 

Thanks,

Bob

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I don't remember, been a long time since I did anything to an MBW.  A lot of the reps used to use a smaller hole, maybe M2.5, if so it would need to be drilled.  If it is the right size then the hole would need to have a slight countersink drilled and the threads cleaned with a tap.

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It was a lot of years ago so my memory is rusty. I had a very early MBW 1665 and wanted to install a gen crown and tube.

IIRC, the tube came out of the case with a triangular file pressed in the opening to unscrew it. I used a tap to chase the threads and clean them up a bit, they were the same as my gen tube, and quite messy. I unscrewed the old crown from the stem and the new crown screwed right on. I did a test fit and decided the tube should be countersunk a little so I put a big drill bit in my Dewalt and opened up the tube thread a little. I added a bit of red Loctite, screwed the tube in, then screwed the crown onto the tube and cranked it down until the crown bottomed out against the case.

Perfect fit and it never leaked a drop. Total elapsed time, maybe 30 minutes.

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This is a great and useful  thread!!  I am sure many will be asking about this as time goes on and in my opinion should be part if the sticky once there has been a good contribution of information from various members. I suppose many of us would like to at some stage replace our replica crown and tubes with a genuine one.  Some of the forum members that have done it already on more than one occasion and are considering to do it again could take some photos or a footage of the steps involved and add it as a tutorial.  It would be great!!.  I have learnt a lot from the mod gurus here and I an sure many like myself would treasure this write up! 

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7 hours ago, Nanuq said:

It was a lot of years ago so my memory is rusty. I had a very early MBW 1665 and wanted to install a gen crown and tube.

IIRC, the tube came out of the case with a triangular file pressed in the opening to unscrew it. I used a tap to chase the threads and clean them up a bit, they were the same as my gen tube, and quite messy. I unscrewed the old crown from the stem and the new crown screwed right on. I did a test fit and decided the tube should be countersunk a little so I put a big drill bit in my Dewalt and opened up the tube thread a little. I added a bit of red Loctite, screwed the tube in, then screwed the crown onto the tube and cranked it down until the crown bottomed out against the case.

Perfect fit and it never leaked a drop. Total elapsed time, maybe 30 minutes.

 

This is best case scenario. The last time I tried to pull a tube from a Cartel case it ripped apart leaving part of the threads in the hole. Trying to clean up and re-thread was fruitless. I tried JB weld and it never held as expected. Eventually I just tossed the case. I was hoping the gen 703 would just thread onto the MBW tube - but sadly no. I think I may just hold off until it NEEDS to be fixed down the road. I'd hate to muck up a perfectly good looking/running watch for something so trivial...

 

B

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That is always a possibility when doing any kind of mods to this stuff.  You have to weigh the pros and cons and decide what you can live with.  When you do decide to remove the old tube you can use a small torch or big soldering iron to heat up the area around the tube before removing it.  The heat will help release any adhesive that might have been used when installing the tube.

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In the old days it used to be that the MBW tubes were slightly smaller than the gen tubes. Like jmb says, this would entail drilling the hole. I had read that a 2.65mm bit would get the right size hole and then you run the 3.0m x .35 tap thru there. 

I tried to just tap an MBW case one time and broke off the tap in the case- it was too tight a fit. Stilty than showed me how to use alum powder to melt out the tap in a pan w/ hot water and it didn't mess up the case (ss).

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20 hours ago, bobandshawn said:

 

This is best case scenario. The last time I tried to pull a tube from a Cartel case it ripped apart leaving part of the threads in the hole. Trying to clean up and re-thread was fruitless. I tried JB weld and it never held as expected. Eventually I just tossed the case. 

 

B

I have always use a thread extractor without any problems .  Sometimes a 3 sided file will also work, but I find that it isn't as easy as using the thread extractor

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14 hours ago, bobandshawn said:

You wouldn't happen to have a fraction or number drill size???

 

B

 
As I understand it, the outside of the threads is 3.0 mm. The inside is 2.65mm which happens to the pitch- ,35 less the Outer diameter  3.00mm in this case.


To drill a new case hole, you would use a 2.65 mm drill bit. The actual depth of the threads might be a little bit less to allow for installation.  As there will be threads on both sides of the case tube, the depth of the top of the thread to the bottom of the thread would be less than half of 0.35mm being less than 0.175mm. I recall I had this same problem.  Those that have done it recently can verify or dismiss my claim.  

 

In theory it seems simple, but you have to have a very accurate setup, good tools (and the mrs off your back) with a very steady hand as if you do not get it centred, you won't have enough fingers to cross to hope for luck.  It must be dead centre!!

 

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I have done a number of them and I can confirm that a 2.5mm hole is too small for the 3x.35 tap and you stand a good chance of snapping the tap
Trust me they can be a bugger to get out when broken


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