Fastening the lid onto Hammond 1444 series enclosures - diyAudio
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Old 18th July 2008, 04:35 PM   #1
mihalis is offline mihalis  United States
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Default Fastening the lid onto Hammond 1444 series enclosures

Hi all,
I am currently putting together my first chip amp according to Peter Daniel's excellent kit and instructions. I'm using a Hammond 1444 series enclosure, made of sheet aluminum, as pictured here:
http://www.hammondmfg.com/dwg21.htm
The bottom plate has cutouts for screws as you can see. But after putting most of the necessary holes in the enclosure for the amp, I realized I had no idea how I would fasten it on when I'm done.

I can't simply use bolts because there is no way to hold both sides to tighten them when the lid is on. The other options include tapping, which I've never done before, or using self-drilling self-tapping screws, as an engineer friend advised. Assuming there isn't a better option than those, and given the thickness of 0.04 inches of the enclosure material, what would you recommend as the maximum thread spacing?

I've seen pictures on this forum of others who have used these enclosures with apparent success, but wasn't able to deduce from any of them how they got past this issue. Thanks for any advice you can offer.
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Old 18th July 2008, 07:00 PM   #2
MartyM is offline MartyM  United States
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Hi, in a case like yours, I've used a number of methods, be it for my personal electronics projects or really tough car audio installation projects:

(These all use items/parts that are very common)
1. If you have a decent cordless drill, how about #6 or #8 self-tapping screws. You can buy small inexpensive packs at Lowe's & Home Depot.

2. You could predrill the holes for machine screws and try that directly or also add the included nuts to the other side by using a suitable substance that will solidly hold them in place, such as:
-J B Weld
-Other strong off-the-shelf strong hardening putty

I've done that myself.

...I won't recommend epoxies for your metal enclosure, although I've used it for holding the nuts in other plastic projects.

Sometimes I also get L, flat, and other brackets and fasteners from Lowe's & Home Depot. With those and the screws you can build almost anything!
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Old 19th July 2008, 06:20 AM   #3
Nordic is offline Nordic  South Africa
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That looks thin enough for ordinary sheet metal screws, I would not bother tapping.... allthough it is pretty easy to tap... A thin piece like that can be tapped in 10 seconds useing a cordless drill.
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Old 23rd July 2008, 06:45 PM   #4
mihalis is offline mihalis  United States
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Thanks for your ideas. By the way, I emailed Hammond as well, and they said self-tapping screws were the recommended method. He also said the material is "way too thin for tapping."

I am a bit confused by this--how much difference is there between tapping and what the self-tapping screws do? I guess it's that when the screw itself does the tapping there is less room for error. But my main concern is, does this mean it's dangerous to ever take the screws out and put them back in again?

Also, I don't quite understand what the method is to use machine screws directly. Does some degree of tapping take place there as well, or what holds them in? How do I decide what size hole to drill?

Fastening on the nuts sounds like a good backup method if I screw up one of the other ones.
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Old 23rd July 2008, 07:02 PM   #5
MartyM is offline MartyM  United States
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Normally when you "tap" metal for screws, you use a tool that creates a thread in the target metal (for example normally a finer thread).

Self-tapping scews (the kind I use, anyway) only really drill a hole, and have an end on them like a simple drill bit. Just the same as you'd have to do if you had regular sheet metal screws-you'd have to drill a hole close to the size of the scew's diameter then insert the screw.

What I meant by the use of machine screws was fastening the nuts on the opposite surface so they'd remain in place. In my case, most projects I have I don't have to do that-I can hold the nuts in place when tightening them down. I assumed you didn't have that option.

If you use self-tapping screws, just don't overtighten them because with power tools you can easily 'strip' the hole out larger than it should be.

If you've never used self-tapping screws, this can be a really useful thing to have around for projects, so maybe now's a good opportunity to get familiar with them!
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Old 23rd July 2008, 08:05 PM   #6
mihalis is offline mihalis  United States
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Thanks Marty, I think I understand now. You're correct, I don't have the option of holding the nuts in place while tightening them.

I think what I'll do is try self-tapping screws, and if something goes wrong with those I'll just attach the nuts on the other side and do it that way.

Thanks a lot for your advice!
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