Attaching insulated bus bar to metal box

Chris Bryant wrote:
What about blunted screws

Great minds...

Just wanted to report that after reading the instruction on the bus bar again :) - it says "#10 sheet metal OR 10-32 self-tapping screws".

Existing bulges and "bulbs" from rivets of the DIN rail at the back of the box result in clearance from the trailer wall about 2 mm - slightly over 1/16".

3/8" self-tapping screw in 1/4" thick insulator + 1/16" aluminum will protrude at the back by exactly 1/16". Bingo!

A blob of Goop won't hurt too.

PS: Still curious about those 3 extra holes in the back, see my last photo.

What about blunted screws- it really only needs a small bit of actual thread. You should be able to grind a few down to under the standoff depth.

Great minds think alike. I thought about rivets this morning, but there are problems.

Insulator (nut in the hole is explained below):


Click For Full-Size Image.

Hole in the "foot" (left on the photo) is 0.206" as per drawing. 3/16" rivet needs a hole 0.204", good enough.

Here is the problem: rivet in plastic needs a washer. Then total material thickness will be 0.3825", and rivet head 0.39". Hole from the top is 0.375". Ops - need a thin rivet 5/32" with 0.33" head.

Now, plan B: Hex nut #10 has OD 0.375", I put it easily in the hole from the top (right on the photo) and with some effort I can push it all the way in. Machine screw from the back, nut in the hole (as on the photo), 1/4" clearance from the nut to metal bus bar. And glue under the insulator.

There is already one screw head on the back of the box - photo below.

Or plan A: rivet 5/32"=0.16" in 0.2" hole. And glue.

Q 1: What do you guys think, A or B?

(Why not just glue - because the insulator foot is hollow, it rests on thin perimeter wall with 2 tiny pegs).

Back of the box:


Click For Full-Size Image.

Red circle are pre-drilled holes for insulated bus bar - for tapping screws and 2 pegs. See the head of Ground lug screw above? Box mounting screws are recessed so there are "bulges" on the back, but the screw head still sticks out beyond those bulges.

Q 2: If I use bolts and nuts, what if I file the heads off by about 1/3, making them lower profile?

Q 3: There are 3 more holes in the back - what are those for?

Q 4: With insulated bus there are included 4 machine screws #10-32, half-inch long. They are not set screws. Have no clue what those are for, but this is how I came to Plan B. What are they for?

BruceMc wrote:
Depending on the strength of the material, 1/16th inch aluminum will probably hold those 2 #10 screws just fine.

I haven't discarded this plan yet, this is what manufacturer recommends. It's just odd that insulator tapping screws will penetrate the plywood wall behind.

Depending on the strength of the material, 1/16th inch aluminum will probably hold those 2 #10 screws just fine.
I'd try it by drilling pilot holes that are just a tad smaller than the screw shank, then running the screws in. Tighten until snug.
If you think that is insufficient, then add Mex's goop with those screws. You get the advantage of holding the buss bar brackets in place while the goop does its job.

MEXICOWANDERER wrote:
Had awful luck trying to pop rivet plastic.

You use a backup washer, so the plastic is compressed. That's how most of the stuff is built in the first place.

Adhesive is fine, though I would screw the thing in while the adhesive cured. I prefer mechanical attachment.

Had awful luck trying to pop rivet plastic. The GOOP proved to be as strong and durable as a 10X32 machine screw. Have to set bushings in small puddles of GOOP. Simple, fast, easy, cheap, no drilling for bolts and best of all, permanent. Connect bar to both ends pedestals before GOOPing entire pedestals/bar unit as 1 piece. Holes in plastic pedestals a bonus. Pinholes drilled in box make the adhesive connection bulletproof. Don't spare the GOOP, those puddles have to be substantial to work best.

I would pop rivet from the back.

Techwriter: I hope some my cables will be thinner. A breaker with gauge 10 panel-controller wire, a breaker with gauge 6 controller-battery wire, a breaker with gauge 8 loads wire. No breaker #4 (yet). This for Pos bus. Neg bus will have wires in/out, but needs no breaker. Will see. In the worst case, will not install Neg bus in box.

Westend - let's see if I understand. Yes, screws heads from the back (if I do it this way) could prevent the box from resting flat on the wall. There is Ground lug on the photo - it is attached from the back, and its head does push the box off the wall. The box has 4 recessed holes for mounting screws - see the photo in the 1st post. So there are 4 bulges on the back, so the box is resting on those bulges, with a little clearance from the wall. Still, darn head screw of the Ground lug pushes the box off the wall. Will have to file the head off a little.

No, box is not mounted yet.

Mex: Yes, I thought of gluing. Yes, there are tiny stubs-pegs on the back of those insulators, and there are pre-drilled holes in the box for those pegs:

See drawing at the bottom

Why drilling the insulator? - look at the diagram in the link, the "sole" of insulator is mostly hollow already. Ebonite dielectric plastic, smells like it.

One of the worrisome things, to me, would be the screws pushing the box forward.

Do you have this box still on the bench or is it mounted already?