7mm Crown & Case Tube

[alfa1]

This is in two parts, the first was originally posted by JimmyThree on TRC. It was this, which prompted me to do some further critical analysis, so the second part is mine.

It covers what has been discussed before, however, these random discussions were to me, lacking the necessary absolutes needed to allow completion of the proceedure with any degree of success.

Onward

Part I

A genuine or aftermarket submariner 7.0mm case tube can be installed in the case in order for a genuine crown to be used.

The 7.0mm submariner case tube has the same thread size where it screws into the case as the standard 6.0mm case tube used in older DJ, Exp I etc...3.0mm X .35mm and a standard thread tap for the Rolex case can be used to tap it out to the correct size if necessary. The 3.0mm X .35mm taps are available from most watch parts supply houses.

Many replicas have the case threaded for the smaller case tube thread size same as the 5.3mm crown and modern 6.0mm crowns...2.5mm X .25mm and if this is the size in your submariner watch case, the hole will have to be drilled out first with a number 36 (2.7mm) drill bit before threading the hole with the 3.0mm X .35mm tap. Be sure to drill the hole straight through the case and lubricate the bit with cutting oil or WD 40 etc.

After the hole has been bored, line the tap up straight and very carefully start cutting the threads in the case. Turn the tap about 1/2 turn at a time and back it up to dislodge the metal chips and lubricate the tap with thread cutting oil or WD 40 etc to help prevent galling and to carry the chips away from the threads.

After the hole has been tapped, clean the case in warm soapy water with an old toothbrush being sure to get all the metal chips out of the newly threaded hole (I hope you removed the movement before starting this project!!) and try the case tube for proper fit. Pipe cleaners are another way to clean the threads out.

Be advised that the 7.0mm submariner case tube does not fit up against the case same as the standard 6.0mm case tube. The standard genuine 6.0 case tube uses a silver sealing washer between the slightly tapered case tube and case for a gasket (I have never seen one of these gaskets on a replica) and the 7.0mm case tube uses a rubber O ring gasket that fits against a flat machined surface on the case. Machining the case is a bit more involved so I will leave it out and simply recommend anyone to seal the case tube O ring to the case with waterproof silicone grease. I have a miniature milling machine and cutter for cutting a flat on cases but if the case has enough area for the O ring to seal, I let it go as is.

Tips:

On cases with the correct 3.0mm X .35mm hole size...be sure to run the tap through it first (if you have one) or very carefully try the case tube for proper fit because sometimes the threads are not very good and they can ruin the case tube.

You can find good used genuine submariner crowns on eBay.

Practice cutting threads on a junk case or bore a few holes in a piece of stainless steel sheet and tap them for practice.

When cutting practice holes, it is easier to start out with a smaller bit first and work up to the # 36 bit.

Stainless steel is not easy to work with so a few practice runs are in order.

The #36 (.2.7mm) drill bit is a tiny bit larger that usual so the tap will not bind up when cutting threads in the hard steel case. It is better to have the threads a bit shallow than take a chance on breaking the tap off in the case.

When you buy a 7.0mm case tube, be sure to get all the rubber O ring gaskets including the one inside the crown cap and on the outside of the case tube.

You can use plastic based gasket sealer on the case tube threads to help seal the tube and hold the tube in place and keep it from backing out.

Case tube spline wrenches are available to make the job of inserting the case tube easier but you can usually get the tube screwed in by using the crown for a tube driver if you are careful.

Sometimes the crown will tighten down and unscrew the case tube after insertion so if you can get a case tube wrench it is money well spent.

There are old type and new type case tubes and wrenches so ask for new type replacement case tubes and wrenches so everything will work together.

Do not count on the tube to be water resistant without testing the empty case first.

Part II

Establishing dimensions and how minute they really are.

1 mm = .039370082"

2.60mm = .102362"

2.65mm = .104330"

2.70mm = .106299"

The following directly relates to the Installation of a Genuine or Very Good replica 7mm Trip-Loc Crown.

This is for edification and discussion only.

Rolex Trip-Loc 7mm Crown - Part No.24-703

Rolex Case Tube 7mm - Part No.24-7030

Generic - are generally refered to as 7mm crown or tube.

TAPS:

Tap size for the 7mm case tubes(specifically 24-7030) is 3.0mm x .35mm

proper drill size is 3.00mm (- .35mm) = '2.65mm'

(a little formula my industrial tool supplier showed me)

On minature threads such as these, it is imperative that major

and minor diameters are correct for desired lock up. You will

surely strip the case tube (or more catastrophically) the case,

when applying proper setting torque to improperly cut threads.

When working with 316, 440 or 904 stainless steel, either facing,

cutting or tapping, it is imperative that you use a cutting

fluid that is compatible with the parent metal, in this case

I prefer 'Tool Cool' or 'Tapmatic-plus1'

CASE TUBES:

The 6mm case tube wrench works on both 6mm and 7mm case tubes,

why they don't advertise them as such, really baffles me.

Keep in mind, all new case tubes in current Rolex' have the new

style case tubes (splines at the top) and, so will all of the

new generic case tubes.

If you see an advertisement for case tubes showing 'old and new'

make sure you get the new tube and tool. That is of course, unless

you have an endless supply of early genuine case tubes. Then the

early tool with splines in the lower body of the tube would be

correct.

CASE TUBE 'O' RING OPENING:

A stepped Spot face cutter is required to duplicate

the cavity in the tube bore of the case to capture the

outer 'o' ring that resides above the case tube threads.

First stage cuts the proper diameter for the 'o' ring,

(in some earlier Rolex' models a flat fabric seal was used)

the second, cuts the stop shoulder, which in turn determines

the desired amount of crush to the 'o' ring. This operation

is one more of the critical operations that help achieve its

resistance to water and pressure.

Because this machining operation is done to the case while on

a CNC machining center, You 'WILL NOT' be able to acquire this

cutting tool, it will have to be made by an industrial tool

supply house. Calculating its correct dimensions, is a story,

all by itself.

2mm SPRINGS BARS:

Geniune or very good aftermarket Spring Bars for the models we most covet,

1665,1680,1675,16800,16610 will measure:

center section: 2mm x 19.7mm*

depressable ends: 1.2mm in dia.*

extended overall length: 25.25/25.57mm (.994/1.006")*

You will, no doubt, see them advertised in all sizes and dimensions,

claiming to be what they are not. Use good judgement before making

your purchase and avoid dissapointment. There is plenty of good

information to be gleaned on this board as to where to acquire them

from the many capable and talented members.

Please keep in mind, the advertised dimensions are meant to show

relationship to an application. These dimensions may seem

cut and dry. In reality the spring bars do not have a true

2mm diameter main body, nor do the ends measure 1.2mm.

These measurements indicate the bore diameter in which they are to

be inserted, therefore, the true diameter of the respective part of

the spring bar will (should) measure:

ENDS-Diameter: 1.187/1.190mm (.0467/.0468")*

MAIN BODY-Diameter: 1.978/1.980mm (.0778/.0780")*

NOTE: *These dimensions acquired from 20 sample spring bars*

This differential allows for compliance in the bore,

just .0005" will make the difference between go and no-go.

[Edge]

Very informative and technical post. Much appreciated.

Chris

[the collector]

good info, thanks

[ubiquitous]

Excellent info and specifics! I see you've been doing quite a lot of studying on the matter, eh UB?

[alfa1]

You noticed!! Yes, I suppose I have

I hope it answers some of the questions many have had (or were unwilling to ask), regarding this change over.

Here are some illustrations, they say a picture is worth a thousand words. I hope these give a clearer understanding of how the crown and tube work together.

[lancelot]

Hey alfa1 great info, thanks for sharing with us

[Tribal]

Good Post..

Very informative.....

Great

RG Tribal

[abakan]

I actually found that 7mm tubes have smaller pitch than 0.35mm. I would say in the range of 0.25mm - 0.27mm with 3 mm diameter which is correct. Anyone would confirm that?