Bolting 2 plates together but keeping them insulated. - Page 1
Forum section: electronics / projects

author: Deactivated-1
author_rank: Frequent Contributor
timestamp: October 01, 2022, 05:19:27 pm
content: 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 screwsdrilling the threaded holes, epoxying them and tapping themdrilling the screw head part plate and epoxying thator something else entirely?I dont need to torque the plates much at all, but I'd like to have it robust anyway.

author: TimFox
author_rank: Super Contributor
timestamp: October 01, 2022, 05:25:10 pm
content: 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.

author: bdunham7
author_rank: Super Contributor
timestamp: October 01, 2022, 05:25:46 pm
content: Quote from: ELS122 on October 01, 2022, 05:19:27 pmNylon 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

author: Benta
author_rank: Super Contributor
timestamp: October 01, 2022, 06:32:03 pm
content: Plenty of nylon shouldered bushings available as TO-3, TO-220, TO-247... mounting kits. Cheap too. Normally for M3 bolts.

author: ajb
author_rank: Super Contributor
timestamp: October 01, 2022, 08:49:50 pm
content: 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

author: jonpaul
author_rank: Super Contributor
timestamp: October 01, 2022, 09:15:22 pm
content: Spaces dimensions eg 1mm, 10 cm ?We use double threaded porcelaine or nylon spacers, that have screw holes.Keystone, Brooklyn NY, best supplierjon

author: AndyBeez
author_rank: Frequent Contributor
timestamp: October 01, 2022, 09:54:53 pm
content: Is capacitance across the plates important? Have you thought about using adhesive to bond the plates to the insulator?

author: AndyBeez
author_rank: Frequent Contributor
timestamp: October 01, 2022, 10:29:30 pm
content: It depends on the mechanical loading on the plates? Double sided carpet tape is pretty sticky stuff.

author: inse
author_rank: Super Contributor
timestamp: October 02, 2022, 02:24:16 pm
content: If the plates are supposed to be the electrodes of the capacitor microphone, then sticky tape is no solution.

author: bdunham7
author_rank: Super Contributor
timestamp: October 02, 2022, 02:31:43 pm
content: Quote from: ELS122 on October 01, 2022, 09:28:13 pmCertain 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.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: October 02, 2022, 02:46:04 pm
content: Quote from: ELS122 on October 01, 2022, 05:19:27 pmNylon rivets instead of screws

author: vk6zgo
author_rank: Super Contributor
timestamp: October 02, 2022, 03:29:07 pm
content: 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.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: October 02, 2022, 04:12:57 pm
content: 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.

author: jbb
author_rank: Super Contributor
timestamp: October 02, 2022, 09:38:28 pm
content: 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