New DTI “Glass”

[William ChithamParticipant @williamchitham75949]

I picked up this DTI at a jumble back in February. It was a bit sticky and the pointers were out of phase so I didn't pay much for it. I dismantled and reassembled it and works fine now but the plastic "glass" is yellowed and loose enough to pop out without much encouragement. Any thoughts about replacing the glass? I'm thinking maybe 1mm acrylic which seems readily available but I don't know if that is oil resistant.

[William ChithamParticipant @williamchitham75949]

[Former MemberParticipant @formermember19781]

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[Former MemberParticipant @formermember19781]

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[Pete RimmerParticipant @peterimmer30576]

An Etalon dial gauge is definitely worthy of repair.

I would make a new crystal from a welding mask lens cover. You can pick the screen covers up for peanuts as they are disposable and you'll get a few tries at it.

 

Edited By Pete Rimmer on 30/03/2020 18:27:32

[V8EngParticipant @v8eng]

You do not say what size this but it may be worth looking at Pocket Watch crystals/glasses, up to 50mm seem readily available, possibly some larger sizes as well.

Try an online search or on Ebay Amazon etc.

Edited By V8Eng on 30/03/2020 18:58:36

[Clive FosterParticipant @clivefoster55965]

Watch crystals are available in a wide range of sizes from around 1/2" to 2" (ish) diameter. Good chance that you will find something to fit.

Need to look carefully at the retainer to decide what thickness is appropriate and whether the glass shold be flat or domed in greater or lesser degree.

Clive

V8Eng types faster.  Google search should bring up some size tables.

Edited By Clive Foster on 30/03/2020 18:58:44

[old martParticipant @oldmart]

I would try the 1mm acrylic, after all, it is a precision instrument, not something to splash oil all over.

[William ChithamParticipant @williamchitham75949]

Thanks for all the suggestions, looks like I could have bought a watch crystal to fit but I wanted to try making one and it turned out pretty well, an improvement on the original anyway.

If anyone is interested I put some photos of the process in an album. In brief I turned a wooden male form; balanced a 1mm acrylic blank on top; heated with a hot air gun till floppy; pressed down over the form with a plywood "washer"; put the acrylic wrapped form back in the lathe and "parted off". It took a few attempts to learn to read the state of the hot acrylic and it was tricky to cut accurately to a diameter but I managed to get a good snug fit in the bezel eventually and only used one A4 sized piece of material.

[V8EngParticipant @v8eng]

Well done! That looks good and it’s nice to see the end product of a question on here.

Edited By V8Eng on 11/04/2020 15:07:49

[Michael GilliganParticipant @michaelgilligan61133]

Excellent looking result, William

… and nicely illustrated : Thanks

MichaelG

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