A good way to free up a sticky or frozen rotary switch is to heat the shaft of it up with a hair dryer or heat gun and apply a little bit of penetrating oil where the shaft goes into the bushing; the heat drives expanded air out, and when the shaft cools a vacuum is formed and sucks the penetrating oil in between the shaft and bushing. I had a Dynaco PAS3 preamp with a completely frozen rotary input-selector switch (with at least 4 or 5 switch wafers); repeated applications of heat and penetrating oil, plus visegrip leverage, freed it, and I didn't have to disassemble anything.
It appears that you used JB Kwik which is a fast cure epoxy (also note that it's black). JB Weld slow cure epoxy (which is gray) takes an hour or so to even begin to start to think about curing (😉) and in the time that it remains liquid it will flow down into the voids under its own weight, displacing trapped air. If you have a hot air pencil that can be set to a low temperature/low pressure, you can also use that to help blow and flow the apoxy into the voids; the heat will temporatily thin the epoxy but then accelerates the curing process.
Very nice job! I've done similar repair/reinforcement in the past, but I've never been impressed with so-called "plastic fusion" epoxies, which typically don't fuse to the types of soft plastics that are most likely to require repair, have a softer, rubbery consistency when cured, and stink to high heaven from MEK or whatever solvents it contains. The plastic fusion glues also seem go bad in storage more quickly than ordinary epoxy glues, even if the tube/dispenser is unopened, because the solvents manage to leak their way out (a sealed metal tube is probably more trustworthy than a clear plastic dual syringe dispenser). An ordinary slow cure epoxy would work best: JB Weld, Devcon 2-ton etc. If somebody doesn't have access to a milling machine for grinding notches into the metal insert, a Dremel tool equipped with a carborundum grinding or cutting bit will rough up or grind slits/notches into the sides of the insert and remove sufficient anodizing for the glue to bond to it (an ordinary file would work if that's all you have on hand). At the very least, however most people will find it difficult to do this without use a drill press; getting the insert perfectly perpendicular and concentric before the glue sets is the hard part, and It's very helpful to be able to remove the center of the plastic knob cleanly and concisely with a drill press versus doing it by hand with the Dremel tool. PS, I have a video about using epoxy and other adhesives (UV-curing glues, specialty CA/"Super" glues, etc) on my channel. I have been using epoxy glues for about 55 years and therefore It amazes me how many people have never used epoxy; I am a volunteer with the local Repair Cafe group and it surprised me thst many of the other volunteer repair people ( "fixers") had never used an epoxy glue either, so I've been instructing them. By the way, if ordinary epoxy glue is a little bit old and starts to gel and thicken, you can sometimes soften and liquifiy it sufficiently to use by putting it in the microwave for 5 seconds at a time, or dunking it in a cup of really hot water. Obviously you can only "nuke" it if it's in a plastic bottle or tube because a metal tube would spark and arc; and I only do it with a clear epoxy because grey or black JB Weld containing powdered steel might also react in the microwave. Metal squeeze tubes of epoxy would need to be dumked in hot water to liquify the glue more, but in truth I've never experiencedJB world sitting around here unused for long enough to start curing or gelling on it's own inside the tube!
Another thing to try , I picked up a Heathkit HM-102 that needed a good cleaning. I had a bottle of plastic headlight polish and used that to clean up the paint. Did a very nice job. I was careful cleaning the lettering with nice results. FWIW Carl AB1ZI
AES has some brass inserts that I used to make a replacement thumb wheel on a Heathkit tube tester. That took a bit of manual work to get the hole size just right in the 3-D printed part. Bottom line: metal insert plus the right adhesive for the win.
I did think about doing that, but two problems - mounting the switch in the mill vise would be very difficult, so I'd have to disassemble the switch to remove the shaft temporarily, which is a bit dicey. And two - the set screws in the collars are very short, so I'd have to replace them with longer ones to handle the extra distance to reach the flats. And they are an oddball size. Fortunately, I think the grip will be plenty strong now even without a flat on the shaft.
What a nice gift of showing how to do this love this channel and really beneficial really enjoy you channel appreciate you time and effort and kindness too 73s wb7qxu
A good way to free up a sticky or frozen rotary switch is to heat the shaft of it up with a hair dryer or heat gun and apply a little bit of penetrating oil where the shaft goes into the bushing; the heat drives expanded air out, and when the shaft cools a vacuum is formed and sucks the penetrating oil in between the shaft and bushing. I had a Dynaco PAS3 preamp with a completely frozen rotary input-selector switch (with at least 4 or 5 switch wafers); repeated applications of heat and penetrating oil, plus visegrip leverage, freed it, and I didn't have to disassemble anything.
It appears that you used JB Kwik which is a fast cure epoxy (also note that it's black). JB Weld slow cure epoxy (which is gray) takes an hour or so to even begin to start to think about curing (😉) and in the time that it remains liquid it will flow down into the voids under its own weight, displacing trapped air. If you have a hot air pencil that can be set to a low temperature/low pressure, you can also use that to help blow and flow the apoxy into the voids; the heat will temporatily thin the epoxy but then accelerates the curing process.
Very nice job! I've done similar repair/reinforcement in the past, but I've never been impressed with so-called "plastic fusion" epoxies, which typically don't fuse to the types of soft plastics that are most likely to require repair, have a softer, rubbery consistency when cured, and stink to high heaven from MEK or whatever solvents it contains. The plastic fusion glues also seem go bad in storage more quickly than ordinary epoxy glues, even if the tube/dispenser is unopened, because the solvents manage to leak their way out (a sealed metal tube is probably more trustworthy than a clear plastic dual syringe dispenser). An ordinary slow cure epoxy would work best: JB Weld, Devcon 2-ton etc. If somebody doesn't have access to a milling machine for grinding notches into the metal insert, a Dremel tool equipped with a carborundum grinding or cutting bit will rough up or grind slits/notches into the sides of the insert and remove sufficient anodizing for the glue to bond to it (an ordinary file would work if that's all you have on hand). At the very least, however most people will find it difficult to do this without use a drill press; getting the insert perfectly perpendicular and concentric before the glue sets is the hard part, and It's very helpful to be able to remove the center of the plastic knob cleanly and concisely with a drill press versus doing it by hand with the Dremel tool.
PS, I have a video about using epoxy and other adhesives (UV-curing glues, specialty CA/"Super" glues, etc) on my channel. I have been using epoxy glues for about 55 years and therefore It amazes me how many people have never used epoxy; I am a volunteer with the local Repair Cafe group and it surprised me thst many of the other volunteer repair people ( "fixers") had never used an epoxy glue either, so I've been instructing them. By the way, if ordinary epoxy glue is a little bit old and starts to gel and thicken, you can sometimes soften and liquifiy it sufficiently to use by putting it in the microwave for 5 seconds at a time, or dunking it in a cup of really hot water. Obviously you can only "nuke" it if it's in a plastic bottle or tube because a metal tube would spark and arc; and I only do it with a clear epoxy because grey or black JB Weld containing powdered steel might also react in the microwave. Metal squeeze tubes of epoxy would need to be dumked in hot water to liquify the glue more, but in truth I've never experiencedJB world sitting around here unused for long enough to start curing or gelling on it's own inside the tube!
Another thing to try , I picked up a Heathkit HM-102 that needed a good cleaning. I had a bottle of plastic headlight polish and used that to clean up the paint. Did a very nice job. I was careful cleaning the lettering with nice results. FWIW Carl AB1ZI
Thanks for the info!
AES has some brass inserts that I used to make a replacement thumb wheel on a Heathkit tube tester. That took a bit of manual work to get the hole size just right in the 3-D printed part. Bottom line: metal insert plus the right adhesive for the win.
Great tip! Thx
Thanks Darren
👍👍👍👍👍
Since you have a mill why didn't you cut a flat on the shaft? I'm genuinely curious.
I did think about doing that, but two problems - mounting the switch in the mill vise would be very difficult, so I'd have to disassemble the switch to remove the shaft temporarily, which is a bit dicey. And two - the set screws in the collars are very short, so I'd have to replace them with longer ones to handle the extra distance to reach the flats. And they are an oddball size. Fortunately, I think the grip will be plenty strong now even without a flat on the shaft.
What a nice gift of showing how to do this love this channel and really beneficial really enjoy you channel appreciate you time and effort and kindness too 73s wb7qxu