preacher62 Posted January 4, 2014 Report Share Posted January 4, 2014 Gentlemen and ladies, I recently picked up an old school MBK 1680 from another member. It was advertised as having a gen crown. The tube (clearly not a gen tube) is worn out so I ordered and have received a 703 tube. After further examination of the crown I found that it looks like (from the outside) the gen 703 crown on my 16610 but it does not have the skirt on the inside that slips down on the large o-ring on the case tube. What crown might this be...if it is gen. Additionally, it will not screw down on the new 703 tube. This is a red flag to me. Would another Rolex 7mm crown have different threads to screw down on the tube? I thought that had not changed. (Me thinks it might be the original MBK crown.) One sure fix for my problem is to order a gen 703 crown to go with the new 703 tube. Is this a real bad gig (on a 1680) or have 702 crowns and tubes been replaced with 703s. Many of the 1680s on eBay look like they have 703 setups. Thanks a million! M Quote Link to comment Share on other sites More sharing options...
vlydog Posted January 4, 2014 Report Share Posted January 4, 2014 I would go with the gen 703 crown. If one were to service their 1680 with RSC , the original crown would be replaced with the current service replacement part. Quote Link to comment Share on other sites More sharing options...
preacher62 Posted January 5, 2014 Author Report Share Posted January 5, 2014 I would go with the gen 703 crown. If one were to service their 1680 with RSC , the original crown would be replaced with the current service replacement part. Okay! This is good. That's what I wanted to hear. Thanks for the speedy reply! Do you know if the MBK 1680 case will have to be drilled and tapped? Quote Link to comment Share on other sites More sharing options...
automatico Posted January 6, 2014 Report Share Posted January 6, 2014 "Do you know if the MBK 1680 case will have to be drilled and tapped?" The cases should already be tapped for oem spec rolex case tubes...3.0mm x .35mm. I have two later MBK 1680 cases and both will accept oem spec case tubes of the modern type (for 703 crowns). Many builders use a genuine spec aftmkt case tube and a genuine crown with good results. I used a tube and crown from TC in one and they also worked fine. The tubes and crowns that came in the watches are similar to TC parts but I do not know if they are exactly the same or not. I knew TC parts were good so I changed them out. Iirc, the one spot that may give trouble on some MBK cases is where the case tube gasket contacts the case...some cases may not be properly machined to accept an oem spec gasket but both of mine did. My watches were purchased directly from the 'watch nazi' at MBK about 2 years ago. Quote Link to comment Share on other sites More sharing options...
preacher62 Posted January 6, 2014 Author Report Share Posted January 6, 2014 Thanks auto. That's what I was hoping for. I have the drill and tap and have done it a couple of times but I do not have a drill press so it is frightening to do it freehand. It's much easier to just run the tap through there and clean up the threads. Quote Link to comment Share on other sites More sharing options...
Nanuq Posted January 6, 2014 Report Share Posted January 6, 2014 My early MBW 1665 case was threaded for a gen tube but the tube wouldn't seat fully; its lip ended up proud of the case a smidgen. I reamed the tube opening slightly then chased the threads again and that did it, the tube would then screw in until it seated completely. Quote Link to comment Share on other sites More sharing options...
preacher62 Posted January 6, 2014 Author Report Share Posted January 6, 2014 I was wondering about beveling. It seems that when we retrofit a gen tube to a rep 16610 case, we need to bevel the entrance to the drilling because the gen tube seat is beveled where it meets the case. Can this be done with a drill bit or is a special beveling bit necessary to make a smooth cut? Quote Link to comment Share on other sites More sharing options...
mymanmatt Posted January 6, 2014 Report Share Posted January 6, 2014 That is correct. Im pretty sure you will need to tapper the entrance of the hole in the case for the tube to go in far enough so the crown will fit almost flush with the case Quote Link to comment Share on other sites More sharing options...
Nanuq Posted January 7, 2014 Report Share Posted January 7, 2014 Preacher, you can do the beveling by hand. With my old MBW I just removed the old tube, I found the biggest drill bit that would fit between the CGs, and chucked it up in my DeWalt. I held the case in one hand, held the drill in the other, eyeballed it and gave 'er a whirl. I didn't remove much metal and tried a test fit. I repeated it a couple times until I was happy, then I put some Loctite on the tube threads and screwed it in. Then I put the crown on the tube and screwed it all down tight. Quote Link to comment Share on other sites More sharing options...
preacher62 Posted January 7, 2014 Author Report Share Posted January 7, 2014 Thanks, Nanuq! I will do that. I think this might be my last build. Thanks to this forum, I have built two DJs from gen cases and parts, a 1016, using JMBs stuff, 1655, 1675 El Cornino, 5513, and an MBK 16610, that has morphed over time, with TCs Superlumed dial, hands, DWO and V3 bracelet with V4 clasp. I would love to launch into a 'tona project, but I do not think that I have "The Right Stuff" for that. I might just work on the others. Quote Link to comment Share on other sites More sharing options...
mcotter Posted January 7, 2014 Report Share Posted January 7, 2014 As long as we're talking about crowns & tubes...Not having removed a tube before I'm facing it soon w/ an incoming modern GMT which I'm removing the crownguards on. How will I know if it's threaded or forcefit? The 3sided file has been suggested, I assume left hand threads? Thanks in advance for the wisdom, sorry for the elementary question....Best, mcotter Quote Link to comment Share on other sites More sharing options...
automatico Posted January 7, 2014 Report Share Posted January 7, 2014 "How will I know if it's threaded or force fit? The 3 sided file has been suggested, I assume left hand threads?" Look inside the case where the case tube is mounted and you should see threads on threaded cases and no threads on cases with pressed in tubes. Nearly all will have threaded cases/tubes. Some cases will have case tubes and crowns same as oem and some will have the wrong sizes...6.0mm crown on 1675, 7.0mm crown on modern GMT (using a submariner case) etc. Most case tubes can be removed with a file or something similar and if you use a modern type oem spec tube in the case, try to find a rolex type spline wrench for installation to avoid damage with a file etc. There are a LOT of things to know about case tubes and crowns so it is a good idea to study up on them before you jump in. Case tube threads are standard... righty tighty lefty loosey Quote Link to comment Share on other sites More sharing options...
preacher62 Posted January 7, 2014 Author Report Share Posted January 7, 2014 There is a case tube tool (with multiple bits) on eBay for about $34. I know nothing of the quality but I will know soon. Quote Link to comment Share on other sites More sharing options...
mcotter Posted January 7, 2014 Report Share Posted January 7, 2014 Auto & Preacher, I knew that much wisdom would follow my question, I appreciate your response's. It's such a joy having this wonderful resource..... My best, mcotter Quote Link to comment Share on other sites More sharing options...
preacher62 Posted January 7, 2014 Author Report Share Posted January 7, 2014 @mcotter - The way this hobby is going one needs a line of credit at the bank. I paid $117 for a tube a crown, but that is not the worst thing. The worst thing is that I thought it was a good deal. What is going on with me? I will have more money in this piece and all the rest combined. Sad...sad! M Quote Link to comment Share on other sites More sharing options...
preacher62 Posted January 10, 2014 Author Report Share Posted January 10, 2014 Well, now I am in a quandary. I have received the Rolex 703 tube and crown and they are beautiful. I ran my tap (3mm X .35, the one I have used several times) through the MBK 1680 case and it runs through just fine, but the tube will not screw in. It goes about 1 to 1.5 turns and then locks up tight. I have also a WSO 703 tube that I tried and...same thing. When I lay the tap down beside the tubes, they appear to be a different thread size from the tap. Anybody got any words of wisdom before I drill this out and epoxy it in there. Quote Link to comment Share on other sites More sharing options...
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