Electrical tape insulation for through hole - Page 1
Forum section: electronics / beginners

author: Stuartambient
author_rank: Regular Contributor
timestamp: August 10, 2016, 12:08:30 pm
content: I bought some binding posts to mount on an aluminum enclosure. It was tell from the picture and description if they were the insulated type. When they arrived though I found out they are not insulated.Tried finding some small grommets, the whole is around 1/4", but no luck.Here is what I'm wondering. What if I masked the edges of the hole with electrical tape. I have 3M Super 33+, rating is 600 V, though the temp rating is 220F, which seems a little low. This seem like a perfectly safe way to insulate?

author: Monkeh
author_rank: Super Contributor
timestamp: August 10, 2016, 12:12:06 pm
content: Your holes are too small. Drill them out to the size of the raised section. This will suffice to quite a few hundreds of volts.

author: RobertHolcombe
author_rank: Frequent Contributor
timestamp: August 10, 2016, 12:26:24 pm
content: Heatshrink would be a better solution than electrical tape if you do continue down that route.

author: Stuartambient
author_rank: Regular Contributor
timestamp: August 10, 2016, 12:41:02 pm
content: Quote from: Monkeh on August 10, 2016, 12:12:06 pmI didn't think of that one. My only concern is that the posts would shift around.Quote from: RobertHolcombe on August 10, 2016, 12:26:24 pmConsidered that as well. Two things though is 1) I have no idea of the rating on the heat shrink. I use it for passing 15+ amps so I guess it should be sufficient. Plus I could add two layers. 2) I was about to try it and wondered if my heat gun would melt the plastic material on the raised portion, so I held off.

author: Monkeh
author_rank: Super Contributor
timestamp: August 10, 2016, 12:43:51 pm
content: Quote from: Stuartambient on August 10, 2016, 12:41:02 pmThere should be a similar section on both sides of the assembly. A little torque and they'll go nowhere.If you're worried they'll shift around like that, neither tape nor heatshrink is acceptable: Pressure pierces both.

author: rob77
author_rank: Super Contributor
timestamp: August 10, 2016, 01:01:25 pm
content: Quote from: Monkeh on August 10, 2016, 12:43:51 pm+1and in addition you can use thick plastic washers with outer diameter of that raised section if your front panel is thicker than the height of the 2 raised sections combined.

author: Brumby
author_rank: Unknown
timestamp: August 10, 2016, 01:52:46 pm
content: The hole should be the same diameter as the raised section - as I have shown. There is likely a similar raised section on the back of the front plate.These raised sections are not very high - so the binding posts can be fitted to thin sheet metal panels and still have clamping force on the panel face which will keep them firm. (The raised sections should reach into the hole, but not touch each other leaving the surrounding face of the front and back pieces to make full contact with the panel.)Once both pieces are fitted with a firm amount of torque (nothing excessive please) then these raised sections will stay put - and you will have a reliable air gap clearance.Also ....pleasede-burr your holes better than that shown. If you don't, some of that metal could break off and give you a short.

author: Stuartambient
author_rank: Regular Contributor
timestamp: August 10, 2016, 03:39:31 pm
content: Quote from: Brumby on August 10, 2016, 01:52:46 pmOkay, I see what you are referring to now. Little nervous about getting the holes correct but we'll see. And yes, I will deburr.

author: Blastcap
author_rank: Regular Contributor
timestamp: August 10, 2016, 03:55:14 pm
content: They will, just make sure your holes spaced correctly.Then when mounting, you can feel it fall into place before tightening it completely.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 11, 2016, 01:20:46 am
content: Plenty of air clearance to withstand many kV.If you prefer, you can buy shoulder washers that fit snugly over the thread, centering it within the hole. You will need one for each side of the panel, the panel will have to be as thick as the shoulders are tall, and if you truly need a large clearance distance, you'll need one more piece of tube that fits snugly over the thread (inside the shoulder washers), or over the shoulder washers, or both. And some nice and goopy vacuum grease or silicone (non acid curing) to pack the hardware with, to eliminate most air space.With that, you'd be able to do over 10kV, which is more than the post-to-post gap will take. At that point, you should seriously consider HV type connectors with very deep insulating shrouds...Tim

author: Stuartambient
author_rank: Regular Contributor
timestamp: August 11, 2016, 12:51:26 pm
content: Quote from: T3sl4co1l on August 11, 2016, 01:20:46 amI considered shoulder washers. Ones I had on hand were the wrong size. As for HV connectors, they are too expensive for this project.Anyway, I did one set of posts and it seems to be fine. I wish the raised part was just raised just slight more. The raise is the thickness of the panel so I assume .04" panel thickness is common. Why I didn't think the raised part was actually a functional design or notice it bothers me some.

author: Stuartambient
author_rank: Regular Contributor
timestamp: August 11, 2016, 01:17:57 pm
content: I will also admit that I really haven't worked with aluminum enclosures enough. They seem to get scratched up really easily even after taping them up. I know aluminum is a soft metal and I've had easier and less messier times doing little jobs on computer cases so this another learning experience.