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Resources for screw restoration


JohnC
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Hi all,

I am looking for recommendations of videos or book chapters on the topic of screwhead restoration. Encountering bruised or damaged screws is a given for any of the watches I work on. I try not to add to the damage, but I am increasingly annoyed at having to replace damaged screws back into a watch movement, regardless of who caused it! Any resources would be great. Many thanks.

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Most damage is caused by bad fitting screwdrivers. This is what I used to do with clock screws. Remove all the burr using various needle files, re-cut the slot using a slotting file. Polish the head in my lathe using various enemy sticks then burnish. If the screw needs bluing than that is carried out. Also with clocks if the bottom of the screw is showing that is also polished and burnished. You can do the same with watch screws the only difference is the scale. 

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14 hours ago, LittleWatchShop said:

I need some of these!

That's not difficult really. Cut and glue your favorite (some are better than others) waterproof emery paper on ice-cream wood sticks. 

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12 hours ago, oldhippy said:

Most damage is caused by bad fitting screwdrivers. This is what I used to do with clock screws. Remove all the burr using various needle files, re-cut the slot using a slotting file. Polish the head in my lathe using various enemy sticks then burnish. If the screw needs bluing than that is carried out. Also with clocks if the bottom of the screw is showing that is also polished and burnished. You can do the same with watch screws the only difference is the scale. 

Even with freshly sharpened screw driver heads I can sometimes still bruise the screw head. Does this mean you need to make sure the screw head is always the correct width size for each screw head slot? Meaning you may have to grind each screw driver head before use? I find that there is some variation in slot width thickness even amongst screws of the same head size (length).

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Always use a good fitting screwdriver. You should dress your screwdriver to make sure it's in the best possible condition the width of the blade is most important. If you have the right width it will not make any burrs to the head and the force you apply will unscrew with little effort, In some cases you might have to alter the blade, but don't worry it's not that often.  

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5 hours ago, JohnC said:

Thanks guys that's helpful. Yet another reason for me to start saving for a lathe. @watchweasol
that video is nuts. I hope to have that kind of equipment by the time I'm 95.

Yes Steffen Pahlow is at the top of his tree when it comes to watchmaking. He has a wonderful workshop and his set up is out of this world. You should watch all his videos he is the master. 

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4 hours ago, ifibrin said:

Even with freshly sharpened screw driver heads I can sometimes still bruise the screw head. Does this mean you need to make sure the screw head is always the correct width size for each screw head slot?

No. A small discrepancy in width is not that important, what it is instead is that a regular wedge shaped driver blade will not touch the bottom of the slot. If it does, it will easily cam out. We don't say that the driver is sharpened, we say it's dressed, I find that the latter term better reflects the care one exercises. Now, since there are screws of the same head diameter but different width slots, that can mean you have to keep two drivers, one with a wider tips and one with a narrower one. Check and further discuss this subject in the topic below

 

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There is an excellent explanation at this link:

https://watchesbysjx.com/2015/01/explained-the-fine-art-of-black-polishing-aka-speculaire.html

 

This pretty much exactly as I do it, including the slots and bevel around the head. I have a Lorch screw polishing lathe like Steffen's, and have done may hundreds of screws on it, but I find the tripod is faster and you can very easily adjust it to match the plane of the screw head rather than needing to grind away a possibly significant amount of metal to get it initially flat.

 

Polishing with hand held abrasives in a lathe will always give a slightly domed surface. On many old pieces, especially clocks, this is desired. On most high grade watches the screws are polished dead flat, and to get that requires a little more work- either a screw head lathe or a tripod. With the tripod you can also flat polish any flat part, simply glue them to a brass block that can be held in the tripod (I use superglue, a few minutes in acetone and they unglue).

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36 minutes ago, oldhippy said:

If your drivers have changeable blades no need to have two lots of screwdrivers just change the blades over. 

With a quality, ball bearing, EU made screwdriver costing just GPB 2.50, having many is not a big issue really. Of course one can fit the blade of his preference. Full discussion at:

 

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4 hours ago, jdm said:

No. A small discrepancy in width is not that important, what it is instead is that a regular wedge shaped driver blade will not touch the bottom of the slot. If it does, it will easily cam out.

 

Could you explain what cam-ing out means? Should a properly dressed screwdriver head touch the bottom of the slot? I attached a picture from the thread you mentioned.

2181E7F1-6E4A-4C2B-99C6-DADDC7D9214F.jpeg

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11 minutes ago, jdm said:

As mentioned before, it should not.

The reason being, you want the downward pressure from your index finger to result in a wedging action on both sides of the slot along the whole width of the screwdriver blade. This inhibits the blade from slipping sideways out of the slot, and distributes the turning force evenly, so the slot isn't damaged.

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3 hours ago, Klassiker said:

The reason being, you want the downward pressure from your index finger to result in a wedging action on both sides of the slot along the whole width of the screwdriver blade.

Which is also why the so called hollow shape in the picture by OH is not superior. The blade will contact evenly only if it's wide exactly as the slot. Whilst the wedge profile will be in full length contact with slots of different width, as long there is no interference to the bottom. 

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The above is important stuff, but I'd just like to revisit the original couple responses for a second.

Currently I don't have a lathe, but I have files and emery paper.

My immediate objective is not to achieve a high level of finish, but simply to clean up the most unsightly and damaged screws.

From my reading of the above, my guess at a procedure would be: 1) remove burrs using needle file or other small file. 2) re-cut screw slot using slotting file. 3) give the screw a light polish with emery paper.

Does anyone want to weigh in on this? I realize it's not ideal, but I feel like I need to start small here.

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Personally I prefer seeing damaged screw slots with what's left of the original finish rather than "shined up" screw heads if they are flat polished screws. If they are originally domed, even slightly, you can get them back to original with paper (probably best to do final finish with some polishing paste on a leather buff).

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20 minutes ago, JohnC said:

The above is important stuff, but I'd just like to revisit the original couple responses for a second.

Currently I don't have a lathe, but I have files and emery paper.

My immediate objective is not to achieve a high level of finish, but simply to clean up the most unsightly and damaged screws.

From my reading of the above, my guess at a procedure would be: 1) remove burrs using needle file or other small file. 2) re-cut screw slot using slotting file. 3) give the screw a light polish with emery paper.

Does anyone want to weigh in on this? I realize it's not ideal, but I feel like I need to start small here.

That is a good way to start. You will soon get the hang of things. Going back to black polishing you don't do that with clock screws as stated most are domed. 

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43 minutes ago, JohnC said:

@nickelsilverthanks. So are you saying to do nothing to flat, once-polished screws? Or clean up bruises but don't polish them?

For a flat polished screw, I prefer to see them with whatever is left of the original finish; when you start filing on them that itself raises burrs so it's all or nothing. I get really irritated when I see a buffstick job on formerly flat screws. That's just my opinion though.

 

 

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