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skridlov

Measuring missing screw sizes

Question

I have a large, unsorted, quantity of potentially useful watch screws of all sizes and types. Unsorted... I also encounter many missing screws. How to reconcile this problem? Is there any kind of mandrel (similar to the Bergeon hand hole sizing tool) which can be used to identify the size of screw holes? - case screws are the most common culprits it seems. I realise this begs the question of thread pitch but it would be nice to have somewhere to start. Then I might one day attempt the sysyphus-ian task of sizing some of the screw pile.

How do others deal with this?

Roy

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Often see the plates on Tradera that has lots of different holes in them. 

But you can measure them with a caliper. Sizes are usually 

0,65

0,70

0,75

0,80

0,85

0,90 

So they are often pretty easy to recognize. 

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Well, if you want to know the size of a hole, the easy way to do it is with a pin gauge. They come in a set, little cylinders of known size, You see which one goes in the hole, and that is your size. For the screws, as @rogart63 says, measure with a caliper.  Vintage pin gauge sets made for watchmaking show up on the bay every once in a while.

When I'm sorting an unidentified set of something,  I just start dividing into big/little, or short/long, or something like that, and keep dividing until each size is in  its own little group. If I then want to know an actual size I will compare against a known example. If I want to know thread pitch, for example, I might hold a screw up to a tap to see if the threads are similar.

Not hard, just tedious. I have to be in the right mood to tackle some of my junk piles :-)

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Thanks! I have the Bergeon and WIT hand sizing tools, calipers and a micrometer so I obviously need something in addition! Measuring sub-1mm holes with calipers looks like an exercise in frustration to me. The pin gauge (I was thinking "mandrel" as in ring sizing) sounds invaluable when dealing with lots of wounded and cannibalised movements. Odd that these tools don't seem made any longer. There are a couple of USA based horological tool specialists who may well have this tool.

Roy

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Pin gauge sets are still made, just not specifically for watchmakers any more. The most common sets you will find will be with larger sizes that a machinist would find useful. If you want to see what a watchmaker's set looked like,  search for -

Watchmakers Swartchild's Cylindrical Metric Jewel Gauge No. 51836 

This set was sold for measuring jewel holes, but you can get an idea of what they look like, and the larger sizes are certainly useful for screw holes.

 

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I've just located what looks like an interesting supplier in, wait for it, Guangdong. Requesting a sample set now. 

Roy

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What watches do you usually work one?

For Amercian made  watches pre 1950 try and find yourself a copy of the 'Illustrated Manual of Amercian Watch Movements' by the E & J Swigart Co.

They turn up regulary on ebay US and it lists all the screw sizes used in Elgin and Waltham movements plus some other American movements which is very useful for working up what size screw you need for these watches.

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I have a lot of very elderly Swiss watches and a lesser number of US brands. At present, as a novice, I'm sticking to those that are relatively easy to fix or else have such low value that the outcome doesn't matter.

However I just located a supplier who is prepared to make up a boxed set of pins in whatever sizes I need. All the sets I see on the bay contain a vast range of sizes, the majority of which don't have much relevance to watch movements. I'm going to order a sample set, which may be of interest to people here. What would be very useful would be a suggestion about the most generally useful range. Someone here has already posted a suggestion about screw sizes but  I may as well order a set containing a representative selection.

I'd appreciate a suggestion as to a modest set of useful metric (for the moment) sizes. If I get it made up it will be an easy matter to repeat or anyone who needs it.

Roy

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I'd appreciate a suggestion as to a modest set of useful metric (for the moment) sizes. If I get it made up it will be an easy matter to repeat or anyone who needs it.

Roy

This is great! I don't have a set for watches for the very reasons you mention.  How big of a set are you looking at?  When I get home tonight I can put together a range of (metric) sizes that I think would be useful. I'd like to get down to jewel hole sizes, do you know how small your supplier goes?

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This is great! I don't have a set for watches for the very reasons you mention.  How big of a set are you looking at?  When I get home tonight I can put together a range of (metric) sizes that I think would be useful. I'd like to get down to jewel hole sizes, do you know how small your supplier goes?

I've lost the original information but as I recall VERY small and "Diameter tolerance: ±0.001mm". I'll mail him now and ask. What I really need is an estimate of the range and spread of useful sizes. Most seem to be sub-1mm but they will assemble a set to spec and box it. Suggestions of sizes please. I'd be happy to re-order once I've checked it out and maybe buy a few for resale (not a commercially motivated idea!!!)

Roy

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Ok, since I'm at work, I grabbed one of our copies of  Machinery's Handbook, and looked up the Unified Miniature Thread series. This series consolidated the American and Metric screw sizes in 1955. At least the ones used in instruments and watches. I also looked up what was included in the Swartchild pin set.

All in mm -

Swartchild 

.07 - .19 in .01 increments

.20 - .40 in .05 increments

Unified

 .30 - .55 in .05 increments

.60 - 1.10 in .10 increments

1.20 and 1.40 

So, consolidated it is

0.07 - 0.19 in 0.01 increments, 13 sizes

0.20 - 0.55 in 0.05 increments, 8 sizes

0.60 - 1.10 in 0.10 increments, 6 sizes

1.20 - 1.40 in 0.20 increments, 2 sizes

All together that's 29 pins, not a large set. That will take you out of the instrument and watch sizes into the standard sizes. Maybe add a few larger sizes in 0.20 increments, and, depending on how small they go, a few smaller in 0.01 increments to fill out the set.

Does this help?

 

Edited by dadistic

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Whoops! It just occurred to me that if you are using a pin to measure a threaded hole, you are actually measuring the minor diameter of the thread, so the 0.30 pin won't go in a UMT size 0.30 threaded hole. The minor diameter is smaller. 

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Ah, nothing horological is simple. First, I was thinking metric only as I haven't got many American movements.Secondly, the issue of thread inner and outer measurements had occurred to me (no experience of machining at all) but I figure that the lesser dimension, outer female thread, will be close enough to establish what is presumably(?) a relatively consistent set of sizes.

Or I could be entirely wrong about all of this..

Where does this leave us?

Roy

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This is what I get for trying to do this at work in my spare moments, confusion!

This is the Internal Thread Min. Minor Diameter for the UNM (not UMT) miniature thread series -

0.217,0.256,0.296,0.346,0.370,0.420,0.444,0.518,0.592,0.666,0.740,0.840,0.940,1.088

So, a series of "go" (plus) pins might run like this -

0.22 - 1.10 in 0.02 increments.

There is for example -

M0MMP - plus .22 to 1.50  in .02 increments for a total of 65 pieces from Meyer Gage that cost about US $100.

 

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I must be exceptionally dense today - maybe it's the heat? The set you list above are all imperial, are they not? But the parts I'm dealing with all seem to be metric, ignoring the USA made stuff which I have yet to do much with, although there must be a hundred pieces of that origin here. The shipped prices of pin sets (ignoring the imperial/metric conundrum) here in UK is pretty fierce, particularly shipping from USA (again, ignoring...) There's the sterling exchange rate to consider these days too. 

Quandry...

Roy

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hang in there Roy!  you don't need to know it all,  deligate the job to a watchmaker and then you will know.  for example;  there is more to screws and nuts than just SIZE.  several types of FITS   (thread clearance - tight or loose) - etc..  cheers vin

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Just to throw another spanner in the works I believe that both Elgin and Waltham made there own threads that did not comply with any other standard so watch repairers had to buy the screws and dies / taps directly from Waltham or Elgin.

This is why on the odd occasion when you see Waltham or Elgin taps appear for sale they go for large sums of money as they are now so rare

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Yes, Waltham and Elgin were making screws long before there was anything like a standard screw size. It wasn't just a marketing thing!

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The set you list above are all imperial, are they not?

Quandry...

Roy

Nope. They are metric. That's the neat thing about the Unified Miniature Thread screw series, metric and imperial are the same. But they really are metric screws with the pitch sometimes shown as inch dimensions.

If you can find a UK supplier you will be ahead of the game.

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Now I'm lost in the maze. I understand, to some degree,  the issues involved but let me reiterate what I'm thinking here. I have lots and lots of interesting but in the main not very valuable watches and movements - hundreds. I am encountering missing screws on a daily basis. Trying to fit screws chosen from a box of many hundreds of unsorted screws is an exercise in frustration (although occasionally successful.) Being able to prod a sequence of wires into the 'oles until I find a reasonable fit seems to me like a distinct improvement over fiddling with tweezers (someone will now tell me why this is not so, I expect...) Depth is slightly less of a problem to estimate. Or isn't.

As for variations in thread pitch etc, all accepted. The fact remains that I'm an amateur, working not wholly unsuccessfully, on not very valuable pieces. I'm learning and I know where the limits of my ability currently lie - or at least I'm regularly reminded of the limits. When something's worth more than the risk of attempting it myself I get someone competent to sort it out. 

I've had an interest and a small collection of watches for decades and In the relatively short time I've been attempting this demanding work I've had some reasonable results - dozens of minor repairs and part swaps. I don't overestimate my abilities but in a long life this isn't the first time I've attempted something new and difficult. It helps that, frustrating though this work can be, I enjoy it.

Nobody has yet convinced me that it's pointless using pin gauges, limitations notwithstanding. I've found a supplier that can make up sets to order at a reasonable price. I'd like to think that a couple of dozen would probably cover at least 80% of my requirements - but maybe not.

If someone would give me a list comprising min/max sizes and the intervals between for a couple of dozen pins, I'll order a sample set and report back. If it proves successful and there's a demand I can buy some more adding only a small amount for the handling, and offer them to anyone who would like a set.

By way of complete contrast a beautiful little silver travel clock a mate and I bought jointly made my day yesterday. I'd requested information about the movement from the very high end watchmaker who owns the brand. They came back to me wanting to buy it for their museum...

Roy

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