Polishing with a Boley of Lorch Schmidt screw-head polishing set.

[Endeavor]

I recently bought a Lorch Schmidt polishing set and after some TLC, I'm very pleased with it. The set is not 100% complete, but for polishing screw-heads it is.

I also found an very instructional & educative video on YouTube "Grumpy's Watch restauration" in which he explains how the tool works, which diamond paste sizes to use on which lapping wheel; the steel, the brass & the wooden and how to clean them.

In the video he uses different diamond paste grit sizes, starting with coarse (max #14 µm) slowly working down to the very fine (#0.25 µm). To avoid cross-contamination of a coarser grit with a finer grit, he cleans the equipment (disk & screw) very thoroughly.

To summarize his grit-sizes / lapping wheel recommendations:

Steel lapping wheel: grit #14 µm down to #7µm (For scratch-, burr-removal and surface flattening)

Brass lapping wheel:  grit #5 µm down to #2µm (For fine polishing)

Wooden lapping wheel: grit #1µm down to #0.25µm (For final- or black-polishing)

I started doing the polishing the way he does it in the video and, like he says in the video, the initial grit #14 (meant for the most demanding screws) on the steel lapping wheel is very aggressive indeed.

Having done the first screw, what I noticed was that between each step the thoroughly cleaning of the disk and screw takes a lot of time, lots of paper and lots cleaning fluid. Thinking about it, and to get more "mileage" out of a paste charged disk, it would be nice to have more spindles and/or more lapping disk, each charged with a different grit size. This also to avoid the laborious task of cleaning. Most likely none of those two options come up often for sale and most likely not cheap either.

Instead of using all different grit sizes, I tried to use one grit-size on each lapping wheel. As mentioned, grit #14µm is very aggressive and I found that grit #7µm on the steel lapping wheel works very well and very fast too.

For the brass lapping wheel I tried grit #3.5µm and for the wooden lapping wheel grit #0.5µm. Obviously with a grit #3.5,  it takes longer to polish away the groves made by the grit #7, and to polish the grit #3.5 groves away with the grit #0.5µm (Cleaning the screw and the collet thoroughly between the steps!!), but it is "infinitive" faster than using all the intermediate grit sizes with all the cleaning required. It also saves a lot of paper and cleaning agents.

Tip: to see if all the previous scores are removed by the grit-size in use, I hold the spindle still and just rotate the lapping wheel back-&-forth a few rotations. If under magnification all the grooves, over the whole surface, are in the same direction, you can proceed to a finer grit.

I leave the lapping disk, in my case charged with oil-based diamond paste, charged with the diamond paste ready for the next screw. This saves a lot of (here in Europe expensive) paste too. In the evening, to avoid the drying out of the paste, I clean all the disk and the tools. Obviously, if you notice cross-contamination, you have to clean all the disk and re-charge them with fresh paste.

I didn't have the grit #0.25µm paste (it's on order), but the grit #0.5 µm paste gives already a (for me sufficient) fantastic mirror finish .

Any constructive comments or idea's are very welcome

 

Edited May 11, 2023 by Endeavor

[nickelsilver]

It doesn't make sense to use different grits on the same lap. Cleaning will get it off the surface, but the grit embeds in the lap, at least it is supposed to, so there will be the last one embedded unless the surface of the lap is machined off. 3 grits is plenty, rough / medium / fine; the fine one would be around 1 micron or less (but not too much less), the others as desired, but rough not more than 20 micron.

 

You can use 3m self adhesive lapping film on the rough and medium and it works quite well, but best to finish with paste on the wood wheel; the lapping film can impart a slightly curved surface, while the paste ensures a very flat surface. Also, the fine grits of paper load up extremely quickly and the metal particles in the paper then impart scratches.

 

The surface of the laps should be roughed up a bit with a file, like a 2 cut, just scratching somewhat radial lines on the surface. This allows extra paste a place to go, and breaks up the surface making the process go faster. A big mistake folks make, especially for the last final finish process is to have a very smooth lap. The grains of the paste can roll up together there causing head-scratching scratches. Most issues of not being able to obtain a true mirror finish are due to the lap surface being too smooth, or too much paste (there should be the thinnest film possible).

 

You can see the surface of the tin block (analogous to your wood lap) in this post:

 

Of course, if a lap becomes imbedded with a coarser grit by accident, that will cause scratches, and will require resurfacing the lap.

[JohnR725]

6 minutes ago, nickelsilver said:

It doesn't make sense to use different grits on the same lap. Cleaning will get it off the surface, but the grit embeds in the lap, at least it is supposed to,

yes the video that was a bit peculiar. Because I was under the impression you charge the lap and it embeds itself into the lap where it can't really be removed not without resurfacing.

7 minutes ago, nickelsilver said:

3m self adhesive lapping film

I have a fiber optics polishing film upgrade or replacement kit. I believe there's four different sizes a film I'd have to go and find it look. Then I have a roll of 3 µ pink colored with no backing like maybe mylar something. What I find interesting is the 3 µ is almost like a universal film for polishing and even knocking small burrs off the bottom of ratchet wheels for instance. It actually seems to polish better than the finer grits in the fiber optics kit? So I'm curious if you've noticed that that maybe there's a limit of how far you can go with the film and it just doesn't work or maybe it's a technique thing. I do know that back see have a special lubrication for the films maybe I need to use that. But no matter what I find I love my 3 µ film for quick polishes on things or just smoothing stuff off

[nickelsilver]

14 minutes ago, JohnR725 said:

yes the video that was a bit peculiar. Because I was under the impression you charge the lap and it embeds itself into the lap where it can't really be removed not without resurfacing.

I have a fiber optics polishing film upgrade or replacement kit. I believe there's four different sizes a film I'd have to go and find it look. Then I have a roll of 3 µ pink colored with no backing like maybe mylar something. What I find interesting is the 3 µ is almost like a universal film for polishing and even knocking small burrs off the bottom of ratchet wheels for instance. It actually seems to polish better than the finer grits in the fiber optics kit? So I'm curious if you've noticed that that maybe there's a limit of how far you can go with the film and it just doesn't work or maybe it's a technique thing. I do know that back see have a special lubrication for the films maybe I need to use that. But no matter what I find I love my 3 µ film for quick polishes on things or just smoothing stuff off

I use 20, 12, 3, and 1 micron "everyday", sometimes 30 micron for flattening large parts on a thick glass backer, and sometimes 9 micron between the 12 and 3. A typical job might be altering a chronograph hammer for correct contact with the chrono runner and freedom at the minute counter, so: file the offending face, remove file marks with 20, then smooth with 12, then first polish with 3 (and often this is better than "factory"), then a few licks with the 1 micron. The surface looks properly polished with the 1 micron, but larger surfaces you pretty much always see scratches. Similar process when beveling a part.

 

But yes, the pink 3 micron is great stuff! Way more robust than the (green) 1 micron, and 9/10 times the finish is plenty good for functionality. For handwork I cut little strips and use them on backers like in the photo- a couple are old steel pivot burnishers, a couple of shop made (just filed up) steel rods, and one burnisher I glued some Plexy to for polishing with paste freehand.

 

For screws or other parts to be flat polished, I skip the 3 micron, I find I end up rounding things more and it's faster to go straight from 12 micron to final finishing.

 

 

 

 

Edited May 11, 2023 by nickelsilver

[Endeavor]

Interesting point about the embedded diamond particles in the lapping disk. The set I have is 2nd, 3rd or ∞-hand and only the universe knows what has been on these lapping disk.

I just did another set of screws and grit #7 on the steel, grit #3.5 on the brass and grit #0.5 seems to work very fine. It would be nice if I could erase the lapping disks histories and start with virgin disks.

Without having a lathe, is there another way to properly clean / re-surface these disk? I do have glass-plates to assure flatness, but were to treat them with without introducing another problem?

BTW, I spotted my spelling mistake, all the wrongly "grid" are changed to "grit"

Edited May 11, 2023 by Endeavor

[nickelsilver]

There's no easy way to resurface, even with a lathe you need to get it chucked so the face is running perfectly true (harder than it sounds, even with a high-end chuck). Any abrasive method risks embedding that abrasive. The 3M lapping films are very good about retaining their grit but it just takes a grain or two to embed and ruin things.

 

Sounds risky, but in reality careful filing can do the job. With a clean file, hold the lap in one hand file in the other, and just slowly file the face. Clean the lap and file often, to get rid of the contaminated filings, file across the face, changing direction all the time. Be regular about it, like put a mark on the outside of the lap, and go through a certain number of strokes while turning the lap after each stroke, ending up at the mark. Start again 90 degrees (or whatever) from the mark, do the full turn, repeat. There is a possibility of throwing the face out of true, but you would really have to try. Maybe after several refacing efforts it could be wobbly?

 

Holding the lap in your hand helps keep the file in full contact. Also, not all files are super flat- check your file with a straight edge. A 2 or 0 cut would work well, 6"- 8" length, double cut (single cut is harder to control).

[Endeavor]

Thank you for

51 minutes ago, nickelsilver said:

a clean file

Thank you for your suggestion. I was also thinking that a file is (probably) the only which doesn't shed off abrasive particles.

During polishing another screw (lots of time to think ) I realized that my disk actually do work pretty well and whether it would be worth to re-surface them? It seems that every disk does its job and the end result is pretty darn good.

If I, from now on onward, were to consistently use the same grits, #7 on the steel, #3.5 on the brass and #0.5 on the wooden lapping wheel, the results will stay (hopefully) the same as they are now.

My current thoughts are to leave the disk until I notice that there is a coarser "embedded" particle problem, which currently doesn't seem to be the case.

The polishing of the screw-heads is a lot of work, but I've to say, my Great Grandfathers pocket-watch starts to look nicer and nicer ........ I'm sure he would be proud

Edited May 11, 2023 by Endeavor

[nickelsilver]

Yes, if you are getting good results now then "don't fix what isn't broken" !

 

The most potentially problematic is the finest lap, which in your case is wood (they are sometimes tin or zinc), so the easiest to address. Using diamond, in theory, even if you have some higher grit particles embedded they should eventually wear down to nothing.

 

I don't really use my screwhead lathe ever since I switched to a tripod 20some years ago, but sometimes it's just the tool for a given part. I did these earlier this year, the tip of the skinny part (they're about 9mm overall length) was called out "flat polish" on the print. The most practical way to address that was to drop them into one of the little brass collets of the screwhead lathe from the backside, so just the tip poked out. Worked great!

 

 

 

Edited May 11, 2023 by nickelsilver

[Canadianwatchmaker]

Hello, I have been using a screw head polisher for some time, I use the same paste on all three discs, but when going from the one disc to the next, it is very important to clean the screw really well before using the next disc. Also some screw head files would be good to fresh in up the screw head slots. Hope this helps

[Endeavor]

10 hours ago, Canadianwatchmaker said:

Also some screw head files would be good to fresh in up the screw head slots

Nice to hear that you are using the same grits and it seems to, at least for me, work well.

What kind(s) of files are you using? Can you take some pictures, give specification and how to use them? I tried one screw-slot with a 2.4mm square needle file (cut 6) but I found it very hard to keep the file in line with the slot (parallel, flush & true with the slot), hence the slot became further "open" at both ends ...... I stopped doing it

Edited May 12, 2023 by Endeavor

[Canadianwatchmaker]

I will try and post some pictures of the files soon. Yes, you are right, if the files are not held straight, or to much pressure is put on it, the slots will open up first at the ends. I did that in the begining also. The screw and file have to be held straight. I will try to post some pictures. 

[Endeavor]

On 5/12/2023 at 3:41 PM, Canadianwatchmaker said:

I will try and post some pictures of the files soon.

Hope you will find some time

 

Edited May 15, 2023 by Endeavor