Finishing and refinishing an AP ROO or RO case - need for a tutorial?

[Jurgenk]

As with many of the OCD types on this board, I find that keeping my AP watches in as near mint condition as possible is a challenging task.
Swirls gradually creep into polished edges, and even with the most care to avoid doorknobs, seatbelt latches, and door frames, an occasional little ding can appear.
Avoiding contact with abrasive surfaces and impacts is the best policy, and wearing partly concealed under a shirtsleeve is very helpful in this regard.
However, when things do happen, I've found that careful refinishing can be helpful.

We've all seen the results of careless refinishing, occasionally on reps and frankens, but more commonly on older / vintage AP ROOs or ROs on sale on eBay or C24 that have been refinished by other than AP, or have been refinished too many times.
One must be especially careful with refinishing AP models to use the utmost in restraint, and to protect sharp edges to preserve the geometry and character of the case-- AP itself will limit itself to two refinishes for this reason.

Every polished and brushed face has a sharp edge or crease that should not be softened, and every brushed surface reflects a precise degree of coarseness/grit that must be calibrated to contrast with adjoining surfaces. Moreover, special brushing tools and techniques must be used to retain the "holographic" effect on curved brushed surfaces that result from the random pattern of ultrafine gouges that scatter light at many distinct angles as you rotate the brushed surface.

I've been compiling and testing grits/particle sizes for micromesh and diamond abrasive tools for accomplishing the above, and simple tricks for preserving geometry and transitions.
Would this be helpful, and would other modders be willing to share tips of the trade?

 

[GingerBubba]

I'd love to know!!

Subscribed!

 

[BIONONE]

Beside the fact i‘m not familiar with watchmaking and the expertise that comes with it - i have to say that a good insight into the craftmanship of people like you and other respectable modders is always an interesting and of course a valuable addition to the forum.

I‘d love to read a bit about this topic in a pictured manner that provides an even more interesting aspect.

 

[Jurgenk]

Lets start with the original finish. For example, this is a Domi modified Franken SS Rubber Clad JF case that is essentially mint and unrefinished. Two observations: JF does a really nice job with replicating AP techniques for case finishing, and Domi does an amazing job of protecting these finishes despite the crazy machining/lathe work and beadblasting to which he subjects these cases. Even edges of the back of the shaved mid case are properly refinished. Note that there is a shaved Noob caseback that mates nicely with the JF mid case but shows more brushed edgework than the JF caseback even when shaved to the same 1.7-1.8 mm thickness.

The takeaways here include that the lug surfaces and plots have carefully calibrated differences in brushing grit, and the case sides and lugs have a holographic effect in their brushing pattern that if compromised ruin the character of the case. Also note the straight parallel lines that define the polished corners of the lugs— these are the most challenging parts of the case to refinish and protect without softening the sharp creases, yet the polished edges are the most prone to accumulating swirls. These details are what you should strive to recreate in any refinishing attempt.

 

[slaughterer62]

I am very curious where this thread is going. There are a few videos of RO mid-cases getting milled at the AP factory which you might want to link to and comment on. Good topic, but I have no time to make detailed contributions.

 

[Jurgenk]

Thanks slaughterer62 and BIONONE, would appreciate your expert input on this. Basically the idea here is to try to replicate the result of what’s accomplished using professional tools (lathes and polishing wheels as in this link from AP) with tools and materials that are available to most casual hobbyists.

LINK: the making of an AP RO case
https://youtu.be/zn0UHZuOEeY

 

[slaughterer62]

If you have a way of matching the quality of an AP factory finish with hobby equipment I will be very impressed and I would think this would be of great benefit to forum members. Please continue with your endeavor.

 

[BIONONE]

Some of the following videos show the refinishing of some cases - the outcome is often impressive from this watchmaking lab. (Cannot link them directly but they can be seen by everyone)

https://www.instagram.com/p/BhHT29zhWlb/?utm_source=ig_share_sheet&igshid=1g2gwwez76aeh

https://www.instagram.com/p/BfyqMMTh4Kb/?utm_source=ig_share_sheet&igshid=1xqzivm4ui8ig

https://www.instagram.com/p/BeI27lIgJP6/?utm_source=ig_share_sheet&igshid=1vncz29hr8rn5

https://www.instagram.com/p/Bccvn98AEG7/?utm_source=ig_share_sheet&igshid=1xtd9iwnoxxu6

 

[Jurgenk]

That’s really impressive work from the Italian watch finishing shop. Crevoisier is the real deal. That level of salvage is definitely beyond the limits of a hobbyist, even with all of that equipment at ones disposal. One of the biggest challenges is trying to replicate the effect of a feathered brushed finish that is obtained by rotating the sides or lugs of a midcase against a spinning abrasive belt.

 

[Woundup]

I appreciate this thread Jurgenk as I would like to be able to take care of very minor blemishes myself without the need for specialized equipment. I would always defer to our modders for anything more than minor but if I can learn how to configure a set up that would allow for accurate and straight brushing to remove hairline scratches with a dremmel or something similar I'll give it a try.

 

[slaughterer62]

Forget the Dremel, get a Kemet lapping machine.
https://www.kemet.co.uk/products/fl...MI2tO3yJ6t4QIVi0PTCh2rUgdWEAAYASAAEgLckPD_BwE

 

[Jurgenk]

So while the Dremel is a fine tool for many kinds of work on small parts, I haven't gotten much mileage from it in watch refinishing. Most of what I've been able to do at home without a belt driven machine, lapping machine, or lathe, would best be described as manual slow lapping while taking care to mask creases and sharp areas that need to be protected, and using aids to maintain a precise angulation and direction. And experimenting with different types of abrasives and particle sizes, and those with or without cushioned backing depending on the effect being sought. It's a dangerous thing though as slaughterer62 acknowledges in his interview part 1, that these kinds of experiments can initially be fun and gratifying but can spiral into OCDs. If you haven't read the interview yet, it makes for great reading.

https://forum.replica-watch.info/for...terer62-part-1

When I have a bit more time I will try to do a pictorial describing in more detail.

 

[slaughterer62]

Thanks for the hyperlink to my interview: it made me think I need to put part 2 up soon. I will play along with contributions if you start the tutorial. Most of the refinish work I do is pro bono charity work, so I lose no money adding advice here and there. Plus, I would really like to see photos of your "manual slow lapping."

 

[Jurgenk]

Okay, in the interest of seeing part 2 of the interview with slaughterer62, I will post my informal guide to refinishing in a few installments. One tool I found to be incredibly useful for giving flat and curved surfaces the correct “lapped” appearance is actually a knife sharpening stone. These come in a wide variety of grits and with different quality material. I have used for the purpose of this tutorial a combination whetstone that has 600 and 1500 grit surfaces made of corundum aka aluminum oxide. This whetstone is less than $20:

Let’s tackle the most common issue, dings in the bezel. For minor dings you can just sand the flat surface. If the polished sides are affected you can polish them too— I would do that first, because the sanding should come last to maintain a sharp transition between the polished edge and the sanded front. Sanding the bezel should only take off minimal metal as you don’t want to lose the sunken profile of your bezel screws. Also it should be done using a very flat abrasive surface. If you’ve acquired an AP ROO that has been improperly finished you’ll notice that perfectly flat surfaces such as the bezel face are actually uneven, due to the application of sandpaper by hand, typically. Shown here is a stainless bezel that doesn’t have much in the way of nicks or dings, but was improperly finished and shows its uneven surfaces when viewed at certain angles.

The remedy for this is to simply pass this bezel in very even and straight strokes over the 600 grit surface of your stone. If you are worried about scratching you can mask the polished edges with tape. If you don’t trust yourself to make straight strokes you can use a straight surface next to the stone to maintain position. At first the refinishing will tend to exaggerate the unevenness of the flat surface. You should refinish just enough to take out the peaks and valleys, and eliminate the top part of your dings. The finished result should look like this:

The next challenging issue is how to refinish the polished edges of the lugs, and take out dings from the polished or brushed edges of the lugs, yet maintain a sharp transition between all of these surfaces and the mid-case front. I’ll come back to address this next.

 

[Jurgenk]

Okay, so that was a bit easy and fairly intuitive. What about dings to the brushed portion of the lugs on an offshore? Here the goal is to maintain a visual contrast with the plots, which are sanded linearly to a finish of 1000 grit or so, as opposed to the lapped surface of the lugs that has a deep almost holographic quality to it, and should be 600 grit in finish.

Note not only the contrast in coarseness between plots and brushed lug surface, but also the texture of brushing of the lugs, which is “lapped” and multidimensional.

The sanded surface on the plots can be easily be recreated, and scratches removed, by passing the plots (remove them from the watch and strap/ bracelet first) across a norton softouch sanding sponge, which is basically sandpaper on a thin layer of sponge backing, just being careful to make perfectly straight lines with your sanding by using a straight edge if needed. This material should not be used for parts of the case requiring flat or lapped finishes or else you’ll end up with results like the bezel above due to differential pressure. Use 1000 grit for this step.

The lapped surface of the lugs can be disrupted by careless application of sandpaper. Here is a case that was refinished with sandpaper, and while it looks okay from a distance, close inspection reveals that the lugs have the same sanded uniform grain texture as the plots. This is not the right look.

The proper lapped appearance must be generated by passing the the case over an abrasive material and not vice versa. The multidimensionality comes from varying the angle of the case as it passes over the abrasive material. To do this properly, you need to disassemble the entire watch so that you can rework the midcase by itself. You then pass the lugs across the 600 grit surface of the whetstone in very straight motions while modulating the angle of the mid case carefully during the each pass across the stone. Watch the angle carefully to avoid ruining the sharp transition to the front of the mid case, as well as the transition at the bottom of the lugs. The angle changes and motion across the stone need to be performed smoothly to avoid chatter marks. This whetstone is fairly forgiving in that it will take many passes to remove material, and chatter marks from movements that are not smooth can be removed with 1 or 2 smooth passss. You’ll notice that if previous hand sanding left peaks and valleys due to differential pressure, it will take a while to get rid of theses peaks and valleys, but the straight surface will be far better. As for the bezel, only remove enough metal to get rid of your scratches and dings, and eliminate the peaks and valleys, while attaining a lapped appearance by changing angle. The result should look like this:

Once you’ve fixed the lugs, any imperfections at the transition to the front of the mid case can be removed by straight sanding the front of the mid case using the same 600 grit whetstone surface. I‘ve found that the stock JF mid case can be a little warped and may need some effort to be flattened. This treatment removes nicks, scratches and dings from both front and brushed portion of lugs and maintains the lapped appearance of the latter, as well as the sharp crease at the transition.

Next I will cover polishing the lug edges.

 

[Tompa]

You are the master


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[Jurgenk]

Very kind Tompa, actually just a lot of trial and error here I’m afraid.

To get the lug ends re-polished after accumulating mild hairlines from wear, I have used a variety of different tools.

The best approach has been to carefully mask the polished lug area with scotch tape, cut precisely to follow the curve of the lug ends, and stopping just before the crease where the lug meets the front of the case.

You can get better exposure by removing the strap here, if you like.

There are two polishing methods here.
If you can discipline yourself not to use excessive force, a high grit (12,000, 15,000 or higher) polishing stick with micromesh abrasive works well here. These are sold as coated boards that look like emery boards, but have a very soft backing made for polishing applications. You have to be careful not to use much force or you will ruin the sharp edges of your polished ends.

The sticks look like this:

If you need a little more force, you can use 3M Lapping Microfinishing Film Aluminum Oxide with pressure sensitive adhesive backing, which you can get in a variety grits including 1 Micron (14,000 Grit) and 0.3 Micron (60,000 Grit).

You need to make a custom tool using a small hard object with a perfectly flat surface, that you can fit between your index finger and thumb. I had a 0.5 x 1 x 0.25 inch aluminum block that was perfectly flat on all sides. You cut off just enough lapping film to cover a flat surface. Start with the 14,000 grit to get the minor imperfections leveled. You then approach the polished edge with light pressure, and rub down the polished edge. You’ll feel some slight resistance as you engage the whole flat surface of the polished lug, and you’ll leave some metal marks on the lapping film. Try not to go over the same area of the lapping film twice, as the microabraded particles that are released can scratch on later approaches. The 14,000 grit will leave linear marks, though fine. You’ll repeat with the 60,000 grit film, using fresh surface with each pass, until you get a mirror like finish such as this:

Between the whetstone refinishing and the masking of edges, your polishing should leave a perfectly smooth and shiny lug surface, without any haze from the whetstone work, and without blurring the sharp margin left by the whetstone.

I like the 60,000 grit lapping film because it is quite gentle and would take a lot of force to cause your edges to get rounded. You should still make sure that your little sanding block is engaged to meet the polished edge perfectly face on, so that you don’t inadvertently lose the sharply defined surface as you polish. This is how you approximate the action of a lapping machine used for polishing which would also give you a flat surface.

Incidentally this lapping film is perfect for polishing the heads of bezel screws and caseback screws. Use a larger sheet of material that is not coated with pressure sensitive adhesive. Lay it on a flat surface and run the heads of the bolts across without retracing on the lapping film twice. Make sure the heads of the bolts are perfectly flat and maintain even pressure as you glide across the film. 2-3 passes over lapping film across the length of a lapping sheet (8x11.5 inch) is usually enough to remove hairlines. Start with 1 micron and progress to 0.3. If your caseback screws are more damaged from careless screwdriver technique (always use thin plastic film to engage caseback screws) you’ll need lower grit to take out that damage...

Next, refinished mid-case sides...

 

[tosoboso]

This thread guide is a pleasure to read. Thank you OP

 

[Tompa]

Wow Jurgenk. Amazing


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[Jurgenk]

Thanks for the kind feedback tosoboso and Tompa. Just want to caution, just as true refinishing with lathe/lapping machines are limited to 3 or so applications, before case geometry is altered, there are a limited number of times you can put the case through this treatment before losing proportions, although I would propose hand refinishing is generally more conservative. So if you’re going to take these steps to refinish, do them decisively while taking the minimum amount of metal, and try to get a good amount of gentle wear and wrist time before you do it again. It won’t do to repeat this every few months or you will have a caricature of a case after a year. If you’re trying to make a daily beater look like a safe queen, even your gen AP ROO would not come out right after a short while — a quick scan of the lower priced early 2000s AP ROOs on eBay is proof of this. This OCD is a difficult thing to bear for people like us who love the AP finishing. Gerald Genta played a cruel joke on us when he dashed off the first Royal Oak prototype, reportedly in minutes. The beauty of 316 steel turned in this fashion is so transient, the material is so soft. Would it have killed him to use 904L?