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17th Jun 2019, 3:28 pm | #1 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 14,005
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Refixing meter glass.
I've got a 1940s-era milliammeter made by General Electric - the glass has come detached from the bakelite casing.
In the past I would have reattached it using "Durofix" but my remaining tube of this has gone hard in the decade and a half since I bought it, and Durofix doesn't appear to still be available (banned because of its high aromatic-solvent content?). What to use ?? - I'm reluctant to use modern superglue as I fear it may set too 'hard' and increase the risk of the 70-odd-year-old piece of glass cracking. |
17th Jun 2019, 3:44 pm | #2 |
Octode
Join Date: Dec 2010
Location: St Ives, Cambridgeshire, UK.
Posts: 1,180
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Re: Refixing meter glass.
I used black Roof & Gutter sealant on an AVO once. Not too expensive at a couple quid a tube.
Andrew
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Invisible airwaves crackle with life. Or they should do. BVWS Member |
17th Jun 2019, 3:53 pm | #3 |
Dekatron
Join Date: Aug 2016
Location: Colchester, Essex, UK.
Posts: 4,107
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Re: Refixing meter glass.
Araldite. There's two grades of curing, the red packaged one takes minutes, the blue takes hours. I usually use the red unless it's a fiddly job.
Even if you apply a little too much and it smurges onto the front of the glass, it doesn't set rock hard so can be scraped off when semi-cured quite easily. I have only ever had one glass crack, and i think that was because i applied Araldite around the EDGE of the glass as well as the front face. This appeared to set up stress when it cured. I would say that if you ever have to remove an araldited glass though, it does put up a fight. For this reason i tend to use quite small amounts, blobbed on at strategic points. On the rare occasions i use superglue, it is when the glass feels secure, but viewed from inside the meter the contact area of the old glue doesn't seem large enough. In this case the wick effect of cyanoacrylic is an advantage. The one proviso is waiting until the glue is utterly dry before reassembling the meter, as it can creep across dirt or fingerprints on the surface of the glass and fog it. (Cure- acetone based nail varnish remover) I recall that Micheal recommends making up a black putty so that glass can be removed easily in future if required. I have never tried this approach. Dave |
17th Jun 2019, 4:19 pm | #4 |
Moderator
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
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Re: Refixing meter glass.
Clear silicone sealant worked fine me.
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Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
17th Jun 2019, 4:42 pm | #5 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 14,005
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Re: Refixing meter glass.
Thanks for the suggestions! I've gone with clear silicone (a variety that's supposed to be mould-resistant). Will see how well it's worked in a day or so once it's cured and the vinegary smell has dissipated.
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17th Jun 2019, 8:22 pm | #6 |
Dekatron
Join Date: Aug 2016
Location: Colchester, Essex, UK.
Posts: 4,107
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Re: Refixing meter glass.
That should work; and I don't know why it hasn't crossed my mind before. Once the acetic acid has dispersed it should be inert.
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18th Jun 2019, 12:30 am | #7 |
Nonode
Join Date: Dec 2012
Location: Stockport, Greater Manchester, UK.
Posts: 2,113
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Re: Refixing meter glass.
Durofix was aiui a cyclohexane contact adhesive and these are still universally available. I keep a tube in stock at all times, either Uhu or Wickes High Strength Contact Adhesive
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- Julian It's good here Last edited by Julesomega; 18th Jun 2019 at 12:36 am. |
18th Jun 2019, 12:47 am | #8 |
Dekatron
Join Date: Apr 2012
Location: Worksop, Nottinghamshire, UK.
Posts: 5,554
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Re: Refixing meter glass.
PVC pipe glue is quite good on quite a few things.
The problem is that it is a bit smelly. I had some left over after fixing a drain. |
18th Jun 2019, 1:18 am | #9 |
No Longer a Member
Join Date: Oct 2016
Location: Maroochydore, Queensland, Australia.
Posts: 2,679
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Re: Refixing meter glass.
I use non-acid cure black silicone rubber for this task. It takes a long time to set at least 24Hrs. It is important to make sure it is applied everywhere to get a seal, or dust and atmospheric contaminants can enter around the perimeter where the glass is not perfectly approximated to the housing surfaces. Excess is easily wiped off the class with a lint free cloth soaked with some meths.
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18th Jun 2019, 1:19 am | #10 |
Banned
Join Date: Jun 2015
Location: Mareeba, North Queensland, Australia
Posts: 2,704
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Re: Refixing meter glass.
I use roof and gutter silicon sealant too. It does not contain the smelly acetic acid. I have wondered whether it would eat the varnish off the very sensitive enamel used on the coil.
Joe |
18th Jun 2019, 9:15 am | #11 |
Moderator
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
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Re: Refixing meter glass.
I thought PVC pipe glue (cement) was a solvent? It dissolves the mating surfaces effectively welding them together when they resolidify. It won't have much effect on glass.
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Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
18th Jun 2019, 9:52 am | #12 |
Octode
Join Date: Jul 2004
Location: Dundee, UK.
Posts: 1,813
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Re: Refixing meter glass.
There is a grade of Araldite specifically for bonding glass.
https://www.go-araldite.com/products...l-2-x15ml-tube PMM |
18th Jun 2019, 10:05 am | #13 |
Octode
Join Date: Feb 2007
Location: Ely, Cambridgeshire, UK.
Posts: 1,976
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Re: Refixing meter glass.
I use RTV silicone 732 as its black and works very well
plus we use it at work |
18th Jun 2019, 11:51 am | #14 |
Pentode
Join Date: Mar 2007
Location: Croydon, London, UK.
Posts: 111
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Re: Refixing meter glass.
Putty mixed with a little oil based black paint, looks similar to original and glass can be easily cleaned afterwards with white spirit.
If glass ever gets broken can be easily replaced. mike |
19th Jun 2019, 1:19 pm | #15 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 14,005
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Re: Refixing meter glass.
All back together now, and working just fine.
Speaking to someone else who fixed a similar meter I'm glad I didn't use superglue: on his one the superglue 'crept' across the interface between the glass and the meter-case until it found the set-zero adjuster (which lives between the glass and the case) with predictable and unsalvageable end-results. |
24th Jun 2019, 11:22 am | #16 | |
Octode
Join Date: Jan 2012
Location: Wimbledon, London, UK.
Posts: 1,465
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Re: Refixing meter glass.
Quote:
Colin. |
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