Using standoffs to mount PC boards

[Kearns892]

I like to use standoffs when possible myself, and I was considering going with the counter sink method as it seems the best long term solution. The only problem was i couldn't find a countersink small enough for the standoffs I typically use (3mm screws). It seems most countersinks are made for larger wood screws. Maybe I just don't know where to look.

Anyways, let us know what you decide to do.

[davent]

Use the footswitch to hold a plate of 1/16"aluminum or acrylic against the bottom/top(?) of the enclosure, a false bottom if you will. Countersink  holes in the plate for the standoff screws. Your pcb is mounted to the standoffs- attached to the plate and the footswitch (or pots, switches whatever is already drilled through) holds the whole thing securely in the enclosure. No holes through the top of the enclosure, no sticky pads to loose grip and no glue joints to let go.

When i've used standoffs i've gone the JB Weld/aluminum standoffs route with no problems so far.

dave

[JKowalski]

I like etching aluminum face plates for the fronts of my pedals. This allows me to countersink all sorts of holes in the top of the enclosure, then cover them up later with the plate.

The plate is attached to the enclosure by the nuts of the foot switch and potentiometers.

[trjones1]

I guess I don't mind a more utilitarian look because I just let the standoff mounting screws stick out the front of the pedal.  It works a lot better for me than mounting the standoffs with epoxy.  I've used JB Weld for that before and I found it surprisingly easy to rip the standoffs off the epoxy. 

I also use board mounted pots on some of my pedals and I've never had any problems with reliability.  I'm not some big builder, but I've probably made 15-20 pedals that are out in the world with bands (not to mention the dozens of ones I've made for myself) and I've never had one come back with a problem related to the board mounted pots.

[jefe]

Use the footswitch to hold a plate of 1/16"aluminum or acrylic against the bottom/top(?) of the enclosure, a false bottom if you will. Countersink  holes in the plate for the standoff screws. Your pcb is mounted to the standoffs- attached to the plate and the footswitch (or pots, switches whatever is already drilled through) holds the whole thing securely in the enclosure. No holes through the top of the enclosure, no sticky pads to loose grip and no glue joints to let go.

When i've used standoffs i've gone the JB Weld/aluminum standoffs route with no problems so far.

dave

It's been a long time, but thank you for the idea, Dave. Finally got around to implementing it. An added bonus when using this method is that your pots sit a bit lower, so your knobs don't sit up quite as high. TS808 using tonepad's layout:

[digi2t]

The only problem was i couldn't find a countersink small enough for the standoffs I typically use (3mm screws).

You can use 3mm button head, allen cap screws. Yes, they will show, if you go through the top, but they are fairly discrete due to their low profile dome head. That's what I use, with plastic, or aluminum stand-offs. I prefer to have the heads show, and know that the board is well secured, than use adhesives. I find that adhesives dry over time, or if the surface is not prepared properly, can let go given a good bump.

I do all my work on vero, and I always plan 2 mounting holes in opposite corners for my stand-offs. Case in point;


I can live with a little less beauty, for a bit more piece of mind.

[StereoKills]

Also, you could consider using standoffs with a male threaded end and tap the plastic. Voila, standoff screws right into the plastic by itself.

[jefe]

Also, you could consider using standoffs with a male threaded end and tap the plastic. Voila, standoff screws right into the plastic by itself.

Not a bad idea - I think I'd want to use a thicker piece of plastic for that, mine is around 1/8" thick.

Side note: I should probably point out that I used a higher grade material for this, not sure, but I think it's Lexan. Dont' buy the cheap plexiglass from Home Depot, go for their "best". The cheap stuff doesn't work, it shatters when you try to drill holes in it.

[DavenPaget]

Also, you could consider using standoffs with a male threaded end and tap the plastic. Voila, standoff screws right into the plastic by itself.

Not a bad idea - I think I'd want to use a thicker piece of plastic for that, mine is around 1/8" thick.

Side note: I should probably point out that I used a higher grade material for this, not sure, but I think it's Lexan. Dont' buy the cheap plexiglass from Home Depot, go for their "best". The cheap stuff doesn't work, it shatters when you try to drill holes in it.

Or my friend suggested i went near a industrial area , they throw entire sheets like it's nothing . (Acrylic of course , not sure about Plexi , because i still can't tell the difference between plexi and acrylic )

[davent]

I'm pretty sure Plexiglas^® is simply a trade/brand/Company name for acrylic products like Lexan^® is a trade name for polycarbonate products.

[jefe]

I think you're right, Dave.

[joegagan]

working on a bunch of old mxr pedals with crumbled foam on the inside taught me to never trust sticky tape or foams unless forced to do so. since i was the designer, i got to say what went into my pedals. i use real metal standoffs, with 3/4" spacing from the 'floor' of pedal. my plastic faceplate was designed to hide the screws, which were countersunk into the enclosure so they would be flush. i know those boards will still be exactly where we installed them 100 yrs from now. can you confidently say that about your 3M adhesives?

likewise, the feet we used had real screws drilled into the bottom plates. just like the old days.

the tonepad mouting holes in the pic on the previous page look problematic. they are too close to component pads on the board. you need more room around the mounting hole for standard size standoffs and nuts. i know because one of the bronto holes was a little too close, and it was further away than the tonepad holes are.

[Greenmachine]

I use metal standoffs in most every build now.  I get a big warm fuzzy feeling when I look at how stable and solid that board is inside the enclosure.  I also sometimes use the standoff as a ground via contact with copper trace to reduce offboard wiring; however, I can't say if this is best practice or not.  So far I haven't noticed any extra hum from multiple ground points - don't typically exceed three chassis grounds; in/out jacks and then a standoff ground.

[joegagan]

I like to use standoffs when possible myself, and I was considering going with the counter sink method as it seems the best long term solution. The only problem was i couldn't find a countersink small enough for the standoffs I typically use (3mm screws). It seems most countersinks are made for larger wood screws. Maybe I just don't know where to look.

Anyways, let us know what you decide to do.

a normal countersinking bit can be made to work for even very small holes, you simply have to know when to stop. when we did production, this was done on a drill press, the depth was entirely up to the operator, since the countersink bit was 5 times larger then the beveled hole we needed. there were a few errors, but once you get the hang of it it works fine. the thru hole was drilled first, then countersunk second. also, since we were covering the hole with a cover, a too-deep countersink wasn't really a problem.

[joegagan]

even the pedals that didn't get a faceplate looked ok, we had the boxes powdercoated locally after the drilling and mounting of standoffs ( this is preferable to reduce the rick of scratching the finish by machining after powdercoat).

you can  see the screws but since they are blue they kinda blend in...



note that on some units, we used nylon nuts because the component pads were a little too close for comfort: