fallout

Countersinking screws in a par-metal 12 series chassis..
« on: March 23, 2010, 11:10:06 AM »
So i'm in the process of finishing up my mnats 1176 project and am trying to figure out how i'm going to mount the pushbutton PCBs..

My idea was to use a par-metal 12 series chassis which has the double front panel. My plan was to countersink screws in the 'inner' front panel and attach them
to the pushbutton PCBs with small homemade L-brackets. These screws would be hidden behind the actual front panel.

So here's my question.. Are the par-metal chassis too thin to effectively countersink screws? I think the 2nd front panel with the lip is only .06" thick, which isnt much. Even if it is just enough to hold the the PCB in place, I could always put another bracket behind the PCBs for added support as I've seen someone else do on the forum. Or would i be better off just drilling the holes for the screws as normal then use flat head screws and tighten them until they bend the aluminum a bit?

Thoughts? Thanks!

-jay
« Last Edit: March 23, 2010, 11:19:43 AM by fallout »


dissonantstring

Re: Countersinking screws in a par-metal 12 series chassis..
« Reply #1 on: March 23, 2010, 12:25:41 PM »
hi jay,
first, good to see you around again.  i've still got your melcore DOAs running in my gear. :)

i know you haven't been around for a while and not aware of all the stuff available to the forum now.
so if you haven't done anything to your panels or chassis yet save 'em and get mike's (hairball audio) 1176 case in the White Market.  it will save you all the headaches.  

for my mnats 1176 rev.D i used the par-metal 12 series with the inner support panel to mount the pushbuttons and it was very difficult to get both front and inner panels aligned with the pushbuttons.  i actually ended up spacing out the inner panel with about a 2mm gap so i could use a regular button head screw.  this made pots tough to thread through the front panel.  the hairball cases will be much easier and is what i plan to use on my next build.

if you have already started working on the panels and there's no turning back then do a search as i believe there were ideas about mounting screws to the inside of the front panel with JB Weld or something.  seemed like some elegant ideas in those threads.

another idea i had (or maybe i got it from somewhere) might be to drill a hole slightly smaller than the screw size through the inner panel and thread it for a set screw.  use a set screw with the largest diameter that will work with your L-bracket mounting hole. apply a little JB Weld, loctite or crazy glue to the set screw and screw it in and let the chemical bond set.  you might want to test this on scrap metal first.  i've never tried this but it seems like it would work fairly well.

hope this babble helps.
kind regards,
grant

regularjohn

Re: Countersinking screws in a par-metal 12 series chassis..
« Reply #2 on: March 23, 2010, 01:13:31 PM »
+1 on the JB weld.  I've built two 1176's with it.

Basically just get any screw that's long enough to reach the pushbutton chassis that'll fit through the hole in the chassis (I think it's 4-40 size IIRC), and that's got a flat top.  Use the JB weld to secure it to the panel.  Then just use a pair of nuts on the screw to hold the pushbutton chassis in place. 

I've yet to have any of the "welds" fail after lots and lots of pushing.
SATANOSCILLATEMYMETALLICSONATAS

fallout

Re: Countersinking screws in a par-metal 12 series chassis..
« Reply #3 on: March 23, 2010, 01:16:16 PM »
Hey Grant.. Nice to see you around as well and glad those Melcor's are getting a workout..

You're right, there are so many new projects that my head is spinning. I'm just trying clear my bench of all the unfinished projects before I tackle any of this new stuff.

Thanks for pointing me in the right direction for the case. I havent even purchased the par-metal enclosure yet so looks like I'm just going to grab the Hairball one and call it a day. Looks way more elegant than anything i could cobble up in my basement.

Thanks again and glad to be back!

-jay

That JB weld stuff looks like pretty good stuff as well! Regularjohn, do you have any pics of the inside of your 1176 chassis?

Re: Countersinking screws in a par-metal 12 series chassis..
« Reply #4 on: March 23, 2010, 10:00:11 PM »
There's also a special flathead screw-type for using with thin sheetstock that keeps the head from bottoming out. It's called an undercut screw:

http://www.mcmaster.com/library/20050706/91771A103L.GIF



 

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