Bolting 2 plates together but keeping them insulated.

[Deactivated-1]

I need to bolt to plates together, they have an insulating spacer between them, but I need to insulate the screws somehow.
what would be the best solution?
using plastic screws
drilling the threaded holes, epoxying them and tapping them
drilling the screw head part plate and epoxying that

or something else entirely?
I dont need to torque the plates much at all, but I'd like to have it robust anyway.

[TimFox]

I would suggest insulated shoulder washers, with normal bolts and nuts.
Traditionally, these are made of hard fiber, but nylon and Teflon are available.
They also exist made of ceramic, which are good for high temperatures, but may be brittle.

[bdunham7]

I need to bolt to plates together, they have an insulating spacer between them, but I need to insulate the screws somehow.
what would be the best solution?
using plastic screws
drilling the threaded holes, epoxying them and tapping them
drilling the screw head part plate and epoxying that

or something else entirely?
I dont need to torque the plates much at all, but I'd like to have it robust anyway.

Nylon screws and nuts may work for very light duty uses, but the more rugged method is to use nylon shoulder washers to center and insulate the bolt from both plates.  Depending on the plate thickness and the general stack-up and design, you may use just one per plate or put one on each side.

https://www.digikey.com/en/products/detail/keystone-electronics/3054/16013?s=N4IgTCBcDaIDoBcAEBmAbAWhQBgKwBYMA5AERAF0BfIA

[Benta]

Plenty of nylon shouldered bushings available as TO-3, TO-220, TO-247... mounting kits. Cheap too. Normally for M3 bolts.

[ajb]

Yep, shoulder washers, or if you need a larger fastener than you can find a suitable shoulder washer for, a regular plastic spacer on the shank of the bolt and a plastic or fiber washer on each side would do. If the OD of the plastic spacer is close to or larger than the OD of the head/nut then you might want metal washers on top of the insulating ones to spread the clamping forces out past the spacer. For heavy loads, you'd want to use heavy structural washers rather than plain flat washers.

Be aware that plastics can flow under compressive loads, so you may not be able to rely on bolt tension alone to keep the fastening secure with plastic washers.  In those cases you probably want a nylon insert or deformed thread locknut to keep it from coming loose, and/or Belleville washers to maintain tension.  It all depends on the materials, environment, and geometry involved.

This all assumes a dry environment, though, if this will be outdoors or otherwise exposed to water then you might need to take extra precautions to ensure that water can't get into the fastening and form an internal conductive part, or can't bead up across the insulating washers

[jonpaul]

Spaces dimensions eg 1mm, 10 cm ?

We use double threaded porcelaine or nylon spacers, that have screw holes.

Keystone, Brooklyn NY, best supplier

jon

[AndyBeez]

Is capacitance across the plates important? Have you thought about using adhesive to bond the plates to the insulator?

[AndyBeez]

It depends on the mechanical loading on the plates? Double sided carpet tape is pretty sticky stuff.

[inse]

If the plates are supposed to be the electrodes of the capacitor microphone, then sticky tape is no solution.

[bdunham7]

but what about using epoxy as an insulating "insert" for the threaded holes? would it be too brittle to tap a thread into?

Certain epoxies can be drilled and tapped (JB Weld) but then you have to worry about their actual electrical characteristics.  Some of them may not be good insulators.

[mikeselectricstuff]

I need to bolt to plates together, they have an insulating spacer between them, but I need to insulate the screws somehow.
what would be the best solution?
using plastic screws
drilling the threaded holes, epoxying them and tapping them
drilling the screw head part plate and epoxying that

or something else entirely?
I dont need to torque the plates much at all, but I'd like to have it robust anyway.

Nylon rivets instead of screws

[vk6zgo]

An alternative would be to edge clamp the plates using insulated clamps, where the metal bolts are through the insulating material.
It would obviously be more complex mechanically, but would solve the bolting problem elegantly.

[CatalinaWOW]

If you are really pressed for space or concerned about aesthetics it is possible to install non-conducting islands in your plates.  Not cheap or standard, but possible.

[jbb]

I may be excommunicated from the forum for this, but… how about some quality double sided tape (eg something from the 3M ‘VHB’ range)?
+ No need to drill holes (which can be quite frustrating with copper sheets)
- Nearly impossible to undo cleanly