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Adding Stem Tube Threads to a 3646 or California Dial Case

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This section will deal with how to upgrade the Crown on your 3646 Case. To do this I will drill the Case and add threads to accept a new Stem Tube and "Onion" Type 3646 Crown.

The Stem Tube I will use is 4mm and the thread pitch is 0.35mm

First start by drilling the case. The recommended size is 3.4mm but I am using a 3.6mm drill bit (slightly larger). This will make the threading process a little easier. Using a 3.6 drill bit is adequate, the threads may not be quite as deep but they are perfectly strong. The stem I am about to fit is not heavy duty so it does not require any real strength other than to hold itself in place. I will later Tap (thread) the 3646 Case using an M4 (4mm) Tap with a 0.35mm thread pitch.

Tapping the Case: Its important that the "thread pitch" you make in the case is the same as the thread pitch on the stem tube. The hole in the case is now 3.6mm and I will start the threading process using a M4 Tap with a 0.35mm Thread Pitch (easy to buy on the internet).

To make the threads I will use a set of Three Taps. Tap 1 is the Starter (a fine weak thread). Tap 2 is an intermediate thread (a little deeper) and Tap 3 is a Full Depth Thread.

  1. Use the "Starter" Tap 1 the make the first few "light threads". I prefer to make a few starter threads to "at least" half way into the hole in the case. Make sure you apply pressure to the Tap so that the threads dont slip, the Tap needs to constantly cut new threads. Remove the Tap from the case
  2. Next take Tap 2 (Intermediate Tap) This will re-cut the previous threads you have made with Tap 1 (starter tap). Once this Tap is half way through the Case there is usually enough strength to proceed with this Tap so that it goes right through the Case.
  3. If you look at Tap 2 the threads start light and continue to full deep threads. Therefore there is no need to finish the case off using Tap 3 once Tap 2 has gone through the Case.
Set of 3 Taps but I only used Tap 1 and Tap 2

Now its time to try the Stem Tube and see how it fits.

The next stage is to Solder the Stem into the Case. The Authentic 3646 Cases were soldered in the same way. This wasn't to make the Stem strong, it was instead to make it water-tight when diving under pressure and also to stop it turning when you unscrew the Crown.

Before we start to Solder, REMEMBER to remove the small rubber o'ring from inside the Stem Tube. If you dont it will melt when you start to solder.

Type of Flux & Solder: To do this I would strongly advise using the very best flux and solder (there is a kit available on the Vintage Watch Parts website). The correct flux makes a big difference between the work being fairly easy and difficult. Dont try doing this work with cheap flux, and always us "fine" solder. You do NOT want to get solder on the Stem Tube Threads.

First apply the Flux around the Stem Tube (inside of the Case). Next use a "Flame" (Gas Blowtorch - NOT electric) and heat the flux, the flux will go black, next, try and touch the solder to the case it should melt on contact. As soon as you have some solder on the case add a little flux to the solder, the solder should easily flow. In fact the solder should "Sweat" inside the case and into the threads, sometimes it can be visible on the outside of the Case (stem tube area) this means the solder has fully sweated through the case. Its not always possible to do this so dont worry if you cannot.

Tip: What does it mean if you add solder to the case and it doesn't flow but stays in a large ball or blob of molten solder. Often it means your Case is TOO HOT. Cool with flux and it should flow like water.

Next, run solder around the top edge of the Stem Tube to form a nice seal. Be careful not to get solder on the threads. This is why I say you must use fine solder and good flux.

Once Soldered you should clean the Case by polishing. Remember to put the rubber o'ring back inside the Stem Tube

Below is a comparison between Crowns. The Old Crown is larger and more common on modern Panerai Watches. The 3646 Onion Crown is just like the Vintage Crown. Its not always important to have the correct 3646 Crown because during the late 1940's (and early 1950's) there was a parts shortage and it is very common to see authentic 3646 Watches with Rolex Crowns fitted.

One final upgrade - The owner of this watch wanted Lead O'rings fitted under the Bezel and to the Case Back. Lead o'rings were used as seals on the authentic watches but many didn't survive over the years or were lost.

Making the 6152 Water-Tight

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There are three areas to seal A) The Case Back B) The Stem Tube and Crown C) The Plexi

How it was done
The threaded Stem Tube was soldered to the case and cleaned (many authentic cases were soldered as the stem-tube threads would leak under pressure).

Below: Make sure all your parts clean before soldering. Once you have screwed the stem tube into the case heat the area up and run a little solder around the threads or between Case and Stem Tube. Make sure you use the best quality flux you can find it makes soldering so much easier.

Below: Clean the excess solder and try to make it look like its part of the case (its better not to have too much solder).

Below: After cleaning the Stem Tube is aged in a little acid (you can also do this by placing the case in a bag with a "boiled egg" it will age the brass or bronze (yes it works!)

Plexi: The Plexi was sealed using a rubberized adhesive (I am told authentic Vintage Panerai's used a glue to seal and didn't use an o'ring)

Case Back: Case Back is sealed with an o'ring
The Crown applies a good amount of pressure to the Crown O'ring (important at depth)
There is no Two Piece Bezel with this case so there is nothing else to seal.

Building the Modern Vintage MV #2

What is a Modern Vintage? The modern vintage (MV) is a watch that is built using old techniques that are uncommon nowadays. Often this includes case shaping by hand, soldering joints, the type of processes that are not usually found on watches today.

This section shows how to personalize a 3646 type watch and build a Modern Vintage with a lot of attention on how to build a very personalized dial.

This build will start by using the 3646 California Dial Case. This type of case is very sleek about 47mm in diameter and very comfortable to wear.

You can add any picture to a watch dial: Below I have used an image from an artist friend of mine, but it could have been almost any image, even a photograph of a son, daughter, car, building, dog, drawing or painting....anything

Case Shaping: This process is already documented on this website so if you haven't seen or are not sure how to shape and solder a 3646 Case then click on the following link How to Shape and Solder the 3646 Case

Dial: The focal point of this watch will be the dial and below you will see how to take the artwork, then print using a standard computer and finally to place the transparent print onto a dial.

All that is required is a simple computer printer, normal white paper, clear acrylic varnish (spray) and some clear resin.

To begin:
Lets start by making the dial. Below is a 37mm diameter Brass Plate thats 1mm thick. The centre hole has been drilled for the Hour and Minute Hands and also a second hole has been drilled that will sit below 12 o'clock and act as a marker.

The Dial Feet: The holes for the dial feet were made by placing the Brass Backing Plate onto the movement the marking and drilling 1mm holes, these must be precise.

Copper Dial Feet: 1mm copper wire was used to make the dial feet, push through the hole then solder and file to shape. Finally test the fit if you look at the last image there is a small gap between the Brass Dial Plate and the Bezel. This gap is important as the thickness of the dial is about to increase.


Polish the Brass backing Plate: I want a gold coloured dial finish so below I have polished the Brass Backing Plate to a high shine, most of this plate will be visible on the finished dial.

How to get your image onto the Dial

  • Find an image on your PC, (any image you like)
  • Use a standard printer and print the image onto standard paper
  • Spray the image with 5 or 6 coats of clear acryilic varnish and leave to dry
  • Cut the image to size
  • Soak the image in warm water
  • Rub the back of the image (paper) with your finger
  • Keep rubbing until all the paper is removed (it takes time)
  • You should be left with a clear printed sheet of acrylic

How to fix the image onto your dial:
Lay the clear image you have made onto the surface of the dial (brass plate)

  • Smooth Finish: For a smooth finish "lightly" spray the dial with acrylic spray and lay the image you have made. This will leave a nice flat image
  • Textured Finish: Brush acrylic varnish and apply "plenty so that its thickly covered". Then add the image you have made. Thick acrylic will cause the image transfer to wrinkle, it will texture the surface as it drys. Only do this if you want a textured finish.

Adding the Lume Marker: Below I have mixed some luminous powder with 2 part epoxy glue, then added a little colour. This mixture is placed in the hole that I drilled so that it will be below 12 o'clock.


Textured Dial: Here we see that the surface of the dial is textured which is caused by too much acrylic varnish being applied to the dial (this is what I want).

  • Heavy Texturing: Leave the wrinkles as they are
  • Light Texturing: Pop the wrinkles with a pin and allow the air to escape then  press the wrinkles flat. I will use this method on the dial I am making.

Adding The Resin: add a small amount of thin tape to the edge of the dial so that when the resin is poured onto the dial it doesn't run off and instead leaves a thick coat about 1mm thick. Mix good quality clear acrylic resin (available online) and pour.


The Meniscus Problem: This is the curved upper surface that forms around the edge of the resin. It means the dial surface isn't totally flat. Below you can see the edges shown in the red arrows curve upwards.

  • Method A) Rub the dial on a flat sheet of P400 wet and dry paper until flat, then pour another coat of resin on the dial without any tape around the sides or edges
  • Method B) Rub the dial on a flat sheet of P400 wet and dry paper until flat, then polish the dial using "Displex" (google it, its available online) this is the method I used .


What your dial should now look like:

Adding the Hands: I have used Blue hands and applied a Beige Lume so that it blends with the dial (white lume was too bold).

Close-up of the dial: Below you can see the textured surface of the dial. If you look very carefully I have left behind a very small amount of paper when I made the acrylic transfer on the dial. This has created another unique texture, its very fine (almost totally transparent) and its a lovely texture to add. But remember it needs to be super fine to work properly. To do this you need to check to see if any paper is left on your transfer, fine amounts of paper are only visible when the transfer is dry and may not be visible when wet.

Also I haven't tried to make the dial flawless, artwork often has some of the artist's own flaws within, its what makes his/her work personal. I didn't want to make this dial appear to be a factory dial. Sometimes flaws can add to the overall finish of the work. The best way to leave any flaws are on the transfer, the resin should always be flawless.

Another feature that I left was the small copper dial feet, I decided not to hide these tiny dots by covering them with the transfer and instead to leave them visible on the dial, they are not easy to see but there are two 1mm copper dots at 1 o'clock  and 7 o'clock.

The movement: I used the reliable fast beat 6497

The finished watch:

6152 Case Project – Polishing & Ageing.

How to build the 6152 step-by-step using the Nightwatch 6152 Case:

This section shows how to polish and age the case

Click Here to see Larger Step-by-Step Images

Paper is all you need: You can use an industrial polisher to finish your case but this will give a "brand new shine" depending on which grade of buffing wheel you use. Below I will finish this case using only wet and dry grit paper. When done correctly it will give a low-level shine as you would expect on a watch that is over 50 year old

Below: Start by rubbing the case with P400 wet and dry

Below: This image shows a case thats been polished using a machine. This is fine but it does look too new.

Below: When you polish the case you will start to see any errors you have made. Get them all out.

Below: The case has had P400 wet and dry and now its had P1200 wet and dry (a very fine grade paper). I usually rub the p1200 on itself  (rub 2 surfaces of p1200 together) to make it even finer. Then rub the case, you will find that the paper on its own will polish the case to a nice level (not too shiny).

Below: Polished with only paper

Ageing the Case Further using acid and making it look 50 years old

I have separated these stages as some people will not have acid or prefer not to work with it. Acid will add very fast aging to the case. Here is how its done.

Below: The case is being prepared with P1200 wet and dry. You can skip this process as shown above if you have already polished your case with p1200, simply dont polish the case too much and make it too shiny

Below: Make the case shiny but not too shiny (a little dull)

Below: This is what the finish should look like before acid

Below: The case has been dipped into hydrochloric acid for around 5 minutes (test first with a piece of stainless steel as acid come in different strengths).

Below: 5 minutes later

Below: later the case will be lightly polished in places, this image shows the case not polished straight after acid.

Below: Now its time to polish some areas with a cloth to remove some of the acid ageing. Do not used wet and dry paper.

Below: The inside of the case is nicely aged and is left as it it.


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