Drill Holes Through a Switch

[vidarr]

I am rebuilding a lab still and need to remount the switches. There are no places to buy the proper sized bolts to fasten the switch where I live and ordering online and shipping is ridiculously expensive. I have bolts that are a tiny bit bigger than the mounting holes. Anyone know if it is possible to increase the size of the holes of the switch without damaging the internals of the switch? These switches are $50 USD EACH (there are three), so I cannot mess this up.

Thank You!

[Mad Axeman]

We use those microswitches on equipment and having seen the inside of failed switches I would say no, you can't open up the hole. The switch you've shown looks really rusty and I'm surprised it's still working. If you must re-use them then use smaller diameter bolts and washers/nuts. Why are they so expensive where you are? In the UK RS components sell them for around £15 and if you shop around you can get them cheaper.

[jpanhalt]

The holes look threaded.  If so, are they imperial or metric?  If imperial, they are probably 6-32 or 8-32.  Although the fit is not perfect, it is said that M3.5x0.6 and and M4x0.7 will fit those sizes, respectively.  If that fails, you could drill to the max diameter of the thread* and use a smaller metric bolt.  Since you do not know how thick the walls are, I would be cautious using the bolt you show given the cost of a new switch. A few thousandths (inches) oversize will probably be safe.

If the wall is breached will it damage the switch?  I don't know, but judging from the corrosion on the lever, I suspect that would not be a good idea.

*Outer (major) diameter of those imperial sizes are readily available.

[vidarr]

Thank you for confirming that. I'll have to find another solution. The cost is because I live in an area of Brazil where everything is shipped in (taxed heavy) and very expensive. When you buy screws and nails, etc, they count them to sell them. I bought 400 screws once --each one hand counted. $0.25 USD each.

[jpanhalt]

How critical is the positioning of the switch?  I have used small width "zip ties" that loop through both holes.  A bit of hot melt glue between the switch and back plate would keep it from wiggling too much (or epoxy).  I have mounted servos that way.  If you go that approach, be sure to roughen the surfaces before assembling.

[Gregg]

Several times I have made my own rivets from copper wire for similar installations.  Assuming you have some copper wire, you can drill a hole in a piece of scrap metal or even hardwood that is suitably thicker than the desired length and form a head on one end; a process called upsetting in the metal working world.  The upsetting process can also increase the diameter of the rivet near the head end. The head end should probably go on the switch side and the other end through the base and peened over while suitably backing up the other end. 
If the end opposite the switch isn't easily accessible, make the rivet long, fold over the end and apply some solder to keep it tight.

[Kleinstein]

The switches look corroded bad and normally I would consider to replace them.  Microswitches are not that expensive normally, unless a special type or high power.

For smaller screws - mybe find some old scrap parts to take appart - may still be a slight challange to find sufficiently long ones.
As a makeshift fix, a wire or zip tie could work - I would not expect the switches to last anyway with that much corrosion.

[Psi]

They look like they're made of bakelite.
If so they will likely shatter the second they see a drill bit in their immediate proximity.

Bakelite is quite brittle and seems to get more brittle as it ages.

Sometimes just doing the screw terminals up tight will cause the entire switch to fracture into two pieces

[jpanhalt]

Bakelite is workable.  You just have to treat it right.  You can drill glass.  One of the important things about certain materials including bakelite, other plastics (acrylic and polycarbonate),and even brass is to keep the drill from "hogging in."  That is, the drill grabs and tends  to pull itself into the material.  The solution is th "dubb off" the cutting edge so you get a scraping action rather than a digging action.  One might also want to use water as a lubricant on the plastics. 

See here at about 2:50:
[plain]https://www.youtube.com/watch?v=8Ri6poVpQM8[/plain]

I dislike YT but that should give the idea.  I dubb on a a fine grinding wheel.  It's easier to get a nice shearing edge that way.

[Haenk]

Drilling is not a good idea, there is likely not a lot of material to take away from. And it seems they are properly sealed, so don't mess with it.
The zip ties are a proper way to fix them, judging from their position, there is no load on them, so the zip ties will work fine.
Another solution would be just a cable - loop through both holes and tighten by rotating. Considering the corrosive surroundings, that's probably best done with stainless wire like welding filler or (easier to source, I guess) thick copper wire. Don't use iron wire (which we call "Tüddeldraht" or "Blumendraht" in Germany)