Importr's How To: Swap a tricompax Navitimer dial

[importr]

Hi. We all know how its a fairly easy mod to replace our replica dials with that of the genuine. Luckily the rep makers often create the same size dials which enable us collectors to enhance our reps further, but one or two watches require a little bit more attention than just a straight swap.

"WHY BOTHER SWAPPING THE DIAL?"

The rep dial, fine as it is, but lacks the sheen and reflectivity of the genuine. The difference in sharpness, font weight and logo etc. can also be noticeable when compared side by side.

For this guide, we will concentrate on trimming and fitting the genuine dial of a 3,6,9 (tricompax) Navitimer into a 3,6,9 replica. With particular emphasis on the difference between a standard 7750 with 6,9,12 layout subdials.

First of all, what tools and parts do you need? (You'll see that I will use a mixture of my own photos. However, the technique/concept is still the same)

1) a genuine dial. Notice how the black (arabic) rep dial lacks the tiny lip outside the scale rule markings?

2) a replica watch - a 3,6,9 Navitimer. I'd advise a 3,6,9 Navitimer. We'll go into detail 'why?' later

3) a digital caliper

4) assortment of fine hand files, sandpaper

5) a dremel-style tool with fine sanding disc

6) horology tools - case opener, screwdrivers, movement holder, hands lifter, tweezers, rodico or blu tac, case blower

Now that you've got all the kit, let's get started!! This is what I did. You may have your own ways to do things:

Remove movement. This is a topic well documented by others. If you need to know how, please take a look around the forum

Refit the crown. Set the date slowly so that it has just clicked over to the next number. This will make the midnight switchover more accurate.

To remove the dial, first locate the tiny dial post clips, which will be at the 7 o'clock and 1 o'clock positions. Push the "toe" of the clip inside the movement.

This will free each post, enabling easy removal of the rep dial.

6,9,12 asian 7750's on the left, tricompax 3,6,9 asian 7750's on the right

Now would be the time to swap datewheels if such a thing existed for the tricompax Navi.

Measure the diameter of the replica dial using the calipers. It should be 31.43mm.

Now measure the diameter of the genuine dial. It should be 32.65mm.

You may also notice that the genuine dial is very slightly thicker than the rep. This would make the finished item sit very slightly higher

This first measurement is what you be aiming for when trimming the gen dial down. You will remove 1.22mm from the diameter, thats just 0.61mm off the edge of the dial.

I started off by wearing latex gloves so as not to scratch the gen dial. Use the hand file to remove the tiny lip mentioned earlier.

The dial is very hard....brass, i think. It will take a while, but you have to be very, very methodical with each pass of the file.

Otherwise you may scratch it!!!

Periodically check the diameter using the caliper. Keep rotating the dial while you are filing, keeping it as circular as possible. You dont want something that resembles Fred Flintstones' wheels!

Now that you reached 0.5mm of filing, its time to switch to the dremel. The aim here is the let the dremel slowly spin the dial, while you hold it in the centre using finger and thumb. This is to get a smoother uniform and circular edge.

Do not use too much pressure!! Or the dial will go out of round and will become egg shaped!

Trail fit the dial on its own into the rep case. You see that it will rub on the bezel scale rule. If so, keep sanding/filing where it rubs.

Check the diameter. By now you should be close to 31.43mm. Finish the job with the sandpaper (on the back of a ruler or wood) lightly scuffing across the edge. Remove the burrs.

Ok - now that the diameter is near-as-dammit. Trial fit again. It should be snug but not tight to the bezel scale rule...that is if you still want to rotate the bezel?

Time to re-fit it to the movement! Wahooo!

Clean off the dial with rodico/blu tac. Blow out the case, make sure there are no ugly fibres or dust on the scale rule and crystal.

Use the eye loupe to check!!

Refit the hands. Remember that earlier, the date change was set to exactly midnight

Check the dial, hands and case for dust!!!

Remove the crown, refit the whole thing into the case. Test the operation of the hands, date, chrono etc.

Secure the movement, grease gaskets etc and retighten caseback.

Now you will see that the date window is marginally outboard. This is because the dial was made for the ETA 7753. The date wheel is marginally bigger that the 7750 and therefore the asian 7750!

The ETA 7753 should fit into the rep case ok, but its thickness I'm unsure of.

The rep 7750 tricompax is thicker than the rep 7750 due to the extra transfer gears and plate. The datewheel became sunken because of this.

Now, I mentioned that you should use a tricompax rep case for this conversion. The reason being, the rep 7750 tricompax is thicker than the 7750 (6,9,12).

I fitted a 7750 into a tricompax case, and the dial was sunken. Not by a little, but a lot!!

Also, the crown was quite stiff to operate in this guise. I think is is possible that the tricompax case has lower crown and pusher drillings than for the 7750 (6,9,12). The caseback also is difficult to fit because it touches the movement ring.

If you used a 7750 case and fitted a tricompax movement and dial, I'm sure it would protrude further out from the bezel scale rule!

I've never had a problem with fitting (other than trimming) 7750 (6,9,12) dials into 7750 cases.

So, hopefully this has cleared up any unanswered questions. Hopefully you may have found this to be useful too!

Cheers

[yodap]

Very informative tuto, thanks for your effort!

Greetz.

[knmwt15000]

dude that's sweet.

I don't suppose when you did it you thought to take a pic of the topside of the a7753 without the dial...? would like to see.

[hackR]

I -

simply superb!...well done!!...

i may have to hire you for this someday...

all the best -- R

[importr]

dude that's sweet.

I don't suppose when you did it you thought to take a pic of the topside of the a7753 without the dial...? would like to see.

OP Edited

[RWG Technical]

Well done, great pictorial.

Thanks for this.

RG

[Toadtorrent]

Very interesting...thanks for posting this.

[andreww]

Great watch, but why didn't you swap datewheels? I know the single digit dates would be wrong, but at least all the others would be correct.

[importr]

Thanks for the comments guys

Andreww; I've not switched an asian tricompax datewheel before; but what kind of DW would I swap it for? The ETA 7750 date @ 4.5?

hmmm....thats got me thinking