Affixing Standoffs

karbomusic · January 18, 2015, 03:13:46 PM

I had seen a thread from many moons ago discussing mounting standoffs in pedals and issues with epoxy etc. I saw this after I had used epoxy on a few builds only to see it simply fall away a few weeks later (even if had pre-roughened the surfaces). To help remedy this, I began drilling a 4x4 array of tiny holes about about 1/2 way through the inside of the casing as well as a few on the standoff. I would then make sure the epoxy filled the holes (and the bottom mm or two of the internal threads of the standoffs. I didn't really know how much it would help.

Working on a build today as I started wiring my PCB into the box... oh no, I had inadvertently attached standoffs that were too short a few days earlier (I had used the above method). That means I have to replace them. It took a set of pliers and a lot of force to get them out where previously I could have snapped them out with a hard squeeze with my thumb. I assume it could still break down over extended periods of time (?) but this is definitely better than what I had.

bloxstompboxes · January 18, 2015, 04:02:25 PM

Recently, I began using velcro on the back of the board to the backside of the pots. Seems to work well unless I have a lot of wiring that can't be routed around the pots and not in between the two. What kind of epoxy have you been using? I noticed when I was recently looking for a solution that there are many kinds with different strengths.

davent · January 18, 2015, 04:43:51 PM

So far so good with JB Weld. I glue aluminum standoffs down initially with a thin film of JB, let it set, then i go back and 'volcano' JB Weld around the standoff so there's a good area of glue surrounding it.

(Nylon washers atop the aluminum standoffs.)
dave

armdnrdy · January 18, 2015, 04:47:07 PM

#1 for the JB Weld.

smallbearelec · January 18, 2015, 05:19:41 PM

J. B.Weld is good, and I carry it. Still better is an enclosure that has studs molded or machined into it:

I know it's expensive; add up the cost of the studs and the cost of your time (that you could be using for other jobs) doing the gluing and see what the comparison looks like.

I'm aware that the Bare Box #1 is too small for some builds; #2, more like a "125-BB", is in the development stage and will be available this year. It will have similar features including a battery door and a "well" for the pots. Call me obsessive...since I started building this way, I have never used another stud.

karbomusic · January 18, 2015, 06:01:51 PM

Yea, I'm speaking of JB Weld.

Any of you testing the real strength? I think roughing up the surface isn't going to last that long. At least the one's I have tested.

bloxstompboxes · January 18, 2015, 06:17:32 PM

Out of the expoxies I looked at, some were not compatible with nylon for those using nylon standoffs. But, I think all were compatible with aluminum. They were different strengths though. I would be curious to know the adhesion differences, including strength between JB Weld and the epoxies. How long does the weld take to cure/dry?

bloxstompboxes · January 18, 2015, 07:02:14 PM

Ahhh, now I see you were talking about the JB Weld epoxy. Nevermind. lol.

trixdropd · January 18, 2015, 07:18:51 PM

Quote from: smallbearelec on January 18, 2015, 05:19:41 PM
J. B.Weld is good, and I carry it. Still better is an enclosure that has studs molded or machined into it:

I know it's expensive; add up the cost of the studs and the cost of your time (that you could be using for other jobs) doing the gluing and see what the comparison looks like.

I'm aware that the Bare Box #1 is too small for some builds; #2, more like a "125-BB", is in the development stage and will be available this year. It will have similar features including a battery door and a "well" for the pots. Call me obsessive...since I started building this way, I have never used another stud.

Steve, I'd likely use the barebox more if it wasn't predrilled. I do have one of your boxes and it is great, but I prefer to make my own pcb's with jacks onboard.

glops · January 19, 2015, 01:49:39 AM

Quote from: karbomusic on January 18, 2015, 03:13:46 PM
I had seen a thread from many moons ago discussing mounting standoffs in pedals and issues with epoxy etc. I saw this after I had used epoxy on a few builds only to see it simply fall away a few weeks later (even if had pre-roughened the surfaces). To help remedy this, I began drilling a 4x4 array of tiny holes about about 1/2 way through the inside of the casing as well as a few on the standoff. I would then make sure the epoxy filled the holes (and the bottom mm or two of the internal threads of the standoffs. I didn't really know how much it would help.

Working on a build today as I started wiring my PCB into the box... oh no, I had inadvertently attached standoffs that were too short a few days earlier (I had used the above method). That means I have to replace them. It took a set of pliers and a lot of force to get them out where previously I could have snapped them out with a hard squeeze with my thumb. I assume it could still break down over extended periods of time (?) but this is definitely better than what I had.

I've been using a tap for a good while, that way I can have a threaded hole and just screw a metal standoff with male threading right into the enclosure. Nice and sturdy!

amptramp · January 19, 2015, 07:34:37 AM

It may not apply to every style of build, but if you use small pots and large knobs, you can hide a screw under the flange of the knob so that it goes through the case but cannot be seen when the knob is in place. No epoxy required.

jefe · January 19, 2015, 09:49:01 AM

I've had good luck with JB Weld & aluminum standoffs. I don't just scuff the enclosure with sandpaper, I deeply score a crosshatch pattern with a dull utility knife where I want to mount the standoffs. Like davent, I "volcano" the JB Weld up around the standoffs. And be sure to get some up inside the I.D. of the standoff too. The JB takes a good 24 hours to cure. I've got pedals that have lasted about 5 years now without the standoffs falling off.

Now if we could just get people to include standoff mounting holes in their PCBs, that would be great.

upspoon12 · January 19, 2015, 10:10:47 AM

am i the only one that uses good old fashioned super glue? seems to work awesome for me

garcho · January 19, 2015, 10:11:56 AM

+1 for mounting holes. Just consider it a component and make room on yer boards.

I glue cheap cork or just cardboard on the bottom plate so if the stand offs fail, the PCB probably won't short. Not a solution, though.

karbomusic · January 19, 2015, 11:12:22 AM

Quote from: jefe on January 19, 2015, 09:49:01 AM
I've had good luck with JB Weld & aluminum standoffs. I don't just scuff the enclosure with sandpaper, I deeply score a crosshatch pattern with a dull utility knife where I want to mount the standoffs.

Nice, I used to do exactly that but I've had a couple break loose over time; not sure why now though. Normally I don't care that much when they are mine but some I sell hence the current overkill.

Quote
Like davent, I "volcano" the JB Weld up around the standoffs. And be sure to get some up inside the I.D. of the standoff too. The JB takes a good 24 hours to cure. I've got pedals that have lasted about 5 years now without the standoffs falling off.

I volcano it. Based on some replies I may be being over protective but the worry is 20 years where one day it could be in a band van @ 120 F one week and -10 F the next.

Quote
Now if we could just get people to include standoff mounting holes in their PCBs, that would be great.

Hehe agreed, I design holes into mine (the ones I etch myself) for that same reason. Not sure if you can see one of the holes in the top left of this pic.

Anyway, I found some old pics of when I first started using this method for anyone interested...

The array of tiny holes...

Posts with some cuts and a couple holes in the bottom to hold even more JB Weld.

And finally mounted except I started volcanoing after I did this build (It's a few months old)... It runs half way up the posts in current builds.

jefe · January 19, 2015, 12:44:18 PM

Yeah, I suppose something like temperature extremes could mess with JB Weld, but like I said, so far so good after 5 years and moderate transport to & from rehearsals & gigs.

There are other pedals where I just said "screw it, I'm gonna show my standoff screws". Doesn't look that bad as far as I'm concerned.

karbomusic · January 19, 2015, 12:53:49 PM

^Nice, I may go to tapping and screwing in standoffs at some point myself. I'd like to use standoffs that have the screw on the standoff possibly, thinking out loud.

davent · January 19, 2015, 08:58:44 PM

I've done the screw through the top and sides to hold things as well and.... for that added protection i use a piece of recycled transparent packaging as a shield under the pcb.

Greenmachine · January 20, 2015, 01:01:20 AM

I think countersunk standoff screws look really cool myself.

greaser_au · January 20, 2015, 04:47:44 AM

Epoxy is a 'filler' adhesive (as opposed to anerobic adhesives like cyanoacrylate (super/crazy glue)) - for best results it needs a keyed surface (e.g. scratches/holes) to increase the surface area of the bond, and the surfaces must be ***CLEAN***! The other important thing is that the glue joint is only as good as the substrate surfaces - if gluing onto paint and the paint falls off because the underlying surface isn't properly prepared...

Certain materials like nylon or polyethylene do not bond well (and some not at all-e.g. PTFE) , because of their slippery or soft surface.

Another useful 'secret' with filler adhesives is to use something 'sharp' to break the surface tension - initially scrape some of the mixed epoxy on to all surfaces to be bonded (e.g. with the edge of a toothpick/spatula/popstick) , then build the fillet up as normal.

The edge meniscus of the 'puddle' of glue should look like that of a good solder joint (that is meet the substrate at something less than 90 degrees) - that way you know it is glued and not just a blob on the surface.

david

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Affixing Standoffs