Proper way to mount binding posts in a metal front panel?

[ledtester]

I am mounting a pair of 5-way binding posts into a metal front panel, and I'm concerned about the shafts shorting with sides of the hole I've drilled.

For now I'm using heat shrink to insulate the first centimeter or so of the screw threads, but I was wondering what the standard solution is.

[RobertHolcombe]

There are similar style panel mount which are designed with isolation in mind

https://www.pomonaelectronics.com/sites/default/files/styles/product_image__500px_x_450px_/public/products/slideshows/2143.jpg?itok=aFdDx7yr

Or more commonly the individual panel mount jacks

 https://uk.farnell.com/productimages/standard/en_GB/1654713-40.jpg

[beanflying]

Not use the one you have. Most of the ones I use have a raised washer to keep it away from the metal. Even the very cheap and nasty ones.

The one on the right is Beryllium Copper and if you have to ask the price you don't need it

Your heatshrink is sort of OK but maybe look at an alternate.

Better - Make or 3D print some stepped washers then over drill your holes to suit.

[Ian.M]

A cheap and dirty way that's only suitable for low voltages is to put a close fitting O ring over the stud, slightly thicker than the panel and drill the hole to just clear the O ring OD, measured when its on the stud.   For high voltage work, you need proper insulating shoulder washers (aka: 'Top Hat' washers) with a bush long enough to provide enough creepage distance + a thick back washer to support the long bush.  I would be very reluctant to trust 3D printed ones a they really need to be a solid piece of plastic with no micro-voids or other defects.  Such washers are commercially available, but you may have difficulty finding them in the  flange and bore diameter combo you need.

[beanflying]

I would be very reluctant to trust 3D printed ones a they really need to be a solid piece of plastic with no micro-voids or other defects. 

So what you are saying is a void or 'Air Gap' is an issue or may be lower resistance than fully formed plastic, show me the data?

Typical 3D printing done properly has no defects on a well setup machine but like any manufacturing process including injection molding can have flaws done badly. Where it may lack a little is strength but PETG, Nylon or even Poly Carbonate will take care of that at a doddle.

O'Rings are simply WRONG!

[brucehoult]

O'Rings are simply WRONG!

What about rubber grommets?

Of course just getting the mounting posts that already come with insulation would be better.

[beanflying]

Please indicate to me the micro voids and defects on this 0.2mm thick single layer washer let alone using multiple layers that would be required for a stepped washer? I have even back lit it to make this easier.

What about rubber grommets?

Of course just getting the mounting posts that already come with insulation would be better.

Biggest issue with rubber is it rolls or gets pinched by nuts and washers and can roll out of the way completely under pressure.

[Ian.M]

A micro-void is fine till the combination of plasticiser migration, environmental contaminants and humidity leaves it with a somewhat conductive surface film.  There's also the risk of stress cracking starting at the void (or sharp interior corners).

Yes, O-rings are wrong (I did say 'cheap and dirty'), but for low voltages, they do the job - providing insulating gap filling - more reliably than sleeving the stud with heatshrink. . .

[beanflying]

If you use that logic then ALL plastics will get a somewhat conductive film not specific to 3d printing. As I said show me the void! It is extruded as a circular filament there is NO sharp interior corners on small 100% infill items like washers.

As to porous/trapped moisture or similar with modern 3D printing have a look at this.

https://youtu.be/WNvXFYG-C2s

[Brumby]

.... but I was wondering what the standard solution is.

The standard solution is that the insulating pieces that clamp against the panel have a raised section that sits in the hole through the panel.  The terminal/conductor/thread then passes through a smaller hole.

Something like this:


That set of terminals is the sort that could be used in a non-conducting panel - but if you want to use then in a metal panel, then you are going to have to provide something to keep the thread right away from the panel.

The O-ring idea is one approach - but I'd be more in favour of a plastic washer type solution.  If you can't find one, make one.  Find a plastic sheet about the same thickness as the panel and cut a disc from it.  Put a hole in the middle for the thread.  Drill the hole in the panel big enough for the washer to fit.  Assemble and done!

Check dimensions before committing.  You don't want the washer so big it will be visible and you don't want it thicker than the panel.

[Jeroen3]

Shorting to chassis is not a problem with proper binding posts. Stop buying that cheap stuff.
930103101 -  Binding Post, PKI 10 A Series

This one has plastic bushing in and around the hole on both sides.
Look for yourself in this this model.

[David Hess]

Binding posts intended for a metal panel include an insulating flange.  Hardware kits for some power packages like TO-220 also include an insulating washer with a flange to isolate the tab from the mounting hardware.

I like Ian.M's o-ring idea but have not used it myself.  I think o-rings would be more reliable than heat shrink tubing and as good if not better than a small insulating washer that fits inside the hole in the chassis.

[Gyro]

I've never seen terminals with absolutely no locating flanges. It will be very difficult to make them look straight unless you introduce some form of rigid insulating spacers - that probably rules out anything flexible (rubber).

@OP: You say 5-way binding posts, the ones you show are 2-way, any pictures of the actual ones? Is it a case of the end terminals having flanges and the intervening ones not? (You didn't trim them off so you could use smaller holes did out?  )


EDIT: You want someting like these, designed for the job... https://uk.rs-online.com/web/c/fasteners-fixings/spacers-standoffs/screw-insulators/

[Brumby]

The only problem with things like this: is the flange at one end.

There's no room for them without lifting one side off the panel, cutting the flange off or some other mechanical modification.

Edit: By cutting off the flange, you create the plastic washer I mentioned above.

[Nusa]

@OP: You say 5-way binding posts, the ones you show are 2-way, any pictures of the actual ones? Is it a case of the end terminals having flanges and the intervening ones not? (You didn't trim them off so you could use smaller holes did out?  )

Depends on how you choose to count the ways:
(From http://www.ietlabs.com/pdf/GR_Experimenters/1952/GenRad_Experimenter_June_1952.pdf )

[vk6zgo]

Over the years, I've seen a lot of such binding posts with moulded bits which are supposed to sit in the hole in the metal panel.
In all but a few cases, that part is either too long or too short to work properly, so you still end up trying to use "workarounds".
Usually, the best such terminals are ones salvaged from properly made equipment from HP, Marconi, or the like.

I would suggest cutting a rectangular hole in the panel, fitting some strong insulating material inside the equipment to cover that hole, & attaching the terminals to that.

[Gyro]

The only problem with things like this: is the flange at one end.

There's no room for them without lifting one side off the panel, cutting the flange off or some other mechanical modification.

Edit: By cutting off the flange, you create the plastic washer I mentioned above.

The idea is that they replace the rear plastic plate (if as shown in the OP photo). The nuts and washers then clamp down on the flanges. There are many sizes of bore and flange available.

[Brumby]

OK.  That could work ... but I'd be looking for some decent flanges then.