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Old 08-06-2017, 07:25 PM   #1
Gordon
 
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Default Dial indicator

What can be done to replace the crystal on dial indicators? I have a large Lufkin dial indicator with the crystal missing and a small General indicator set with a badly discolored loose crystal. There are places which repair indicators but prices seem to be in the $70 to $100 range which is more than my home work shop can justify. In looking for how to instructions it seems that a special press is required.

Where do I purchase replacement crystals and how do I install them?


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Old 08-07-2017, 02:32 AM   #2
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Gordon,
I had a very good friend give me a replacement crystal for my Verdict indicator.

It was just a matter of being gentle and with little pressure, the crystal just 'clicked' into place from the front of the indicator..
I suppose if you were into repairs, a little tool could be used, but for just one, I don't think it would be required.

John


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Old 08-07-2017, 10:57 AM   #3
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A watchmaker would possibly be able to help you with a watch crystal up to about 40 mm diameter. They come in steps of 0.1mm A larger crystal can easily be machined up out of a thin sheet of perspex or other rigid clear plastic sheet. The lid of a small display box or other similar object can be cannibalized as a material source. 1000grit or 2500grit and then metal polish will give you a pretty good finish.
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Old 08-07-2017, 04:04 PM   #4
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As for fixing the glass/crystal that wasn't quite the correct size to the body of my Mercer DTI, a watchmaker acquaintance of mine used 'horological super glue' to secure it.
'What's the difference between that and ordinary super glue?' I asked. He replied that I wouldn't be able to see his stuff, and he was correct.
So there's a suggestion if you can find a suitable glass/crystal.

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Old 08-07-2017, 05:33 PM   #5
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As a poor apprentice my go to fix for a damaged/cracked dial lens was to make a new one from a slip cover from a welding helmet. Trace out slightly larger than you need then carefully grind to size. I would usually finish grind the lens on the diamond wheel. Cheap fix, worked great!
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Old 08-08-2017, 12:06 PM   #6
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I have at least partially solved the problem. The General Indicator set had a yellowed lens which would not stay in. I put the lens in hot water and put it in the indicator with a weight on top. Now the lens is grey clouded but still visible and stays in place. I looked for a lens for the Lufkin and Long Island Indicator Co says no parts are available and it is not worth fixing. I tried putting in a flat lens made from a welding lens but the center pivot is too high and will not work unless the lens is crowned. The option is probably to glue a flat lens to the outside. In any case it is probably no better than a cheap import which can be purchase for $10-$15. Just hate to dump stuff like that.
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Old 08-09-2017, 05:23 AM   #7
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YOu can make a flat disc of thin perspex or plastic into a domed crystal by cutting it a little bit oversized then pressing it into the bezel using a domed tool. Hold the bezel in the lathe chuck and the domed tool (piece of wood etc turned to shape) in the tailstock and use the tailstock feed as a light press. As the domed tool bends the flat perspex into a dome, the OD gets smaller until it pops into the bezel. If you get the size right, the perspex retains the dome shape once it is in place.

You may have to sand the edge of the perspex at an angle so it pops into place in the groove in the bezel, depending on how the bezel is made.
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Old 08-09-2017, 06:38 AM   #8
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Watch crystals, acrylic and glass, are readily available up to 50mm both flat and domed. They're not expensive either. Dirt cheap, in fact. They're sold by pretty much all horological supply shops. Cousins UK, Esslinger in the States, Jules Borel... the list goes on.

Watch crystals (when they are glued) are typically glued with UV curing adhesives, but epoxies are also used. The UV curing crystal glue is handy stuff. The way you use it is that you apply a generous amount of it on the mounting surfaces, then you cure it under a UV light for less than 30 seconds so it goes slightly hard, but not all the way, then you scrape off the excess and finally cure it under the light for a minute or two. If done properly, the seam is almost invisible.
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Old 08-12-2017, 04:56 PM   #9
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I got the Lufkin indicator repaired. I ordered a crystal for a watch. I needed 52 mm and that cost me $7 + $3 shipping. It fit and I glued it in with super glue and it worked well.

Thanks for the input.
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Old 08-12-2017, 11:32 PM   #10
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That was quick! Honestly I would have never thought about watch parts, but it makes sense now as they would be mass produced.


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Originally Posted by Gordon View Post
I got the Lufkin indicator repaired. I ordered a crystal for a watch. I needed 52 mm and that cost me $7 + $3 shipping. It fit and I glued it in with super glue and it worked well.

Thanks for the input.


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