Glass Cutting - Yes, it is electronics related  - Page 1
Forum section: electronics / repair

author: edpalmer42
author_rank: Super Contributor
timestamp: August 04, 2016, 10:11:35 pm
content: tl;dr Any ideas on carefully cutting open the glass enclosure in the picture?I bought a nice looking quartz oscillator. It has a good name and looked like it had some 'play value'. Maybe it would be useful, maybe I'd learn something. But it didn't work.I took it apart and found the problem. See the picture below. How hard would you have to hit it to break the quartz disk away from its mounting??So now, instead of a Bliley BG61A-5 vacuum-sealed, low aging (1e-10 per day), space-rated crystal, I have a small, sad paperweight.So since the crystal is junk, I might as well play with it. I'd like to open it up and see if I can resolder the crystal back into the mounts. Yes, it will probably degrade it - it may never work again. So what?But I've never done any glass cutting, never mind cutting on a round tube where I have to preserve both pieces. I've looked at a few videos on Youtube that involved flames or hot and cold water, but those are a little too traumatic for this application. I have a pile of vacuum tubes that are similar in size that I can practice on.So any suggestions on how to proceed? Glass cutter? Dremel?Ed

author: tautech
author_rank: Super Contributor
timestamp: August 04, 2016, 11:36:53 pm
content: I seem to remember reading about using a hot nichrome wire for cutting glass bottles, easy enough to set up something for some experimental trials.

author: BradC
author_rank: Super Contributor
timestamp: August 05, 2016, 02:09:41 am
content: Quote from: tautech on August 04, 2016, 11:36:53 pmI used to do it with coathanger wire and a set of jump leads. Wrap the wire firmly against the glass, put a hundred amps or so through it until it glows between dull and cherry red (ie stop before it melts) and plunge the whole shebang into a bucket of water. Agricultural, but a nice way to convert empty jim beam bottles into guitar slides. The cut edges can be quickly fire-polished with a standard propane blowtorch although I started getting much nicer results when I got an oxy.

author: edpalmer42
author_rank: Super Contributor
timestamp: August 05, 2016, 02:28:36 am
content: Yes, I am concerned about contamination. No matter what I do there will be a lot of contamination compared to now, but I'd like to keep it as clean as possible. Flooding it with water just doesn't seem like a good idea, but I might have to do it.Ed

author: nukie
author_rank: Frequent Contributor
timestamp: August 05, 2016, 04:01:02 am
content: Dremel plus diamond cut off bit and lots of cooling

author: CatalinaWOW
author_rank: Super Contributor
timestamp: August 05, 2016, 05:10:00 am
content: A set of rollers to let you roll your tube as you scribe it with a sharp carbide point or a glass cutters wheel is the way to go. Making sure the surface is clean before you start will help avoid skips in the scribe. Practice on your tubes until you get the feel. You can use the hot wire or a simple physical shock to finish the break. Again, practice. When you get it right it will be easy, but be prepared for quite a bit of frustration on the road. Both the pressure applied when scribing and the shock have an upper and lower limit, but I can't help with numbers, it is just something that experience gives you.There will definitely be a lot of glass shards (fraction of millimeter size). They will get sucked in and distributed as the outer air fills the presumed vacuum in your part. Hopefully they won't harm things too much and maybe you can even achieve some cleaning before you attempt to reseal this.That is another whole project, much more difficult, and something I can't provide any meaningful advice on.

author: pickle9000
author_rank: Super Contributor
timestamp: August 05, 2016, 05:28:19 am
content: I have done it with a wet saw, you know for tile cutting. Cuts nice but would be completely covered with debris. I was interested in the glass tubes and not the innards.

author: TerraHertz
author_rank: Super Contributor
timestamp: August 05, 2016, 12:35:02 pm
content: I've used the hot nichrome wire technique to cut thin glass tubes neatly, for instance from fluoro light tubes. Works fine.As others mentioned, scribe a fine neat line around the tube, then wrap a taught nichrome wire once around the tube right on the scribe line. Apply current to wire. If you got it right there will be a faint 'tink' after a few moments, and a clean cut. No need for any water.A good way to hold the wire, is to make a kind of springy bow, with insulated ends and the wire stung across them. With enough slack that you can loop it around the tube with the wire tensioned by the bow. It HAS to make even contact with the glass all round, so the wire better be free of kinks. You can make it nice and straight by hand drawing (stretching) the wire out a bit.To scribe the line around a tube, take a piece of tough paper and wrap it tightly around the tube. When it's straight the end edge will line up with itself. Tape it in place and use the paper edge as a guide. Anything that can score glass will work. Fine sharp-edged file for instance. Or diamond tip glass cutter. The scribe line is the most critical part - it has to be even and straight all the way round. Roller wheel glass cutters won't work on a glass cylinder by hand - you can't apply the force evenly enough. Might work with some kind of roller jig.That picture of the failed crystal... I'm wondering how the solder joins worked. The crystal disk has gold plating on both sides, and usually there are some kind of clips that contact the plating, one per side. In that one, were the mounts soldered to the flat faces of the gold plating on each edge?Maybe it just failed due to fatigue from the oscillation warping? Perhaps over driven?In any case, I doubt you can solder back to the gold plating, if it didn't already come right off the crystal.Also it was probably in a vacuum.Glass enclosed crystals are pretty. The one below is (I think) from 1966. 5.0000MHz

author: wraper
author_rank: Unknown
timestamp: August 05, 2016, 12:46:17 pm
content: Quote from: TerraHertz on August 05, 2016, 12:35:02 pmOverdriven by dropping from something like 1 meter height.It's dead Jim,even if there is any possibility to restore the connection, it will be useless because will be nowhere near to the spec and $0.5 cheapo crystal will work order of magnitude better.

author: Aodhan145
author_rank: Frequent Contributor
timestamp: August 05, 2016, 12:55:47 pm
content: First few seconds of the video is the easiest way to cut glass there is.

author: Seekonk
author_rank: Super Contributor
timestamp: August 05, 2016, 01:08:00 pm
content: Just touch an ice cube to it after heating. it will crack.

author: edpalmer42
author_rank: Super Contributor
timestamp: August 05, 2016, 03:19:27 pm
content: Quote from: TerraHertz on August 05, 2016, 12:35:02 pmThe gold plating on each side goes right to one edge - opposite sides go to opposite edges. I can't tell if the plating went down opposite edges or not - it doesn't now! The solder joint was then made between the support and the plated surface. There is no mechanical clip. If there had been, I probably wouldn't be in this situation!And yes, it is in a vacuum. There's no way I can fix the crystal, replace the envelope and redraw the vacuum so I'm just going to do my best at resealing it. This is more of an experiment than a repair.Ed

author: Cubdriver
author_rank: Unknown
timestamp: August 05, 2016, 03:30:52 pm
content: I didn't see it mentioned, but when you scribe the cut line, do it onlyonce. It will be very light, but resist the temptation to go over it again to make it 'better'. Doing so will not make it better, it will likely bugger up the cut.-Pat

author: DenzilPenberthy
author_rank: Frequent Contributor
timestamp: August 05, 2016, 03:32:22 pm
content: No need to score all the way round the tube. See option 3 here:http://www.ilpi.com/glassblowing/tutorial_cutting.html