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-   -   Chassis constrution and tapping holes (http://www.diyaudio.com/forums/solid-state/36811-chassis-constrution-tapping-holes.html)

s_c_leach 28th June 2004 12:45 AM

Chassis constrution and tapping holes
 
I am currently looking in to building an aluminium chassis for my project. For case I am thinking of using 4mm aluminium with 10mm bars holding everything in place.
I really want the case to have no bolts in the exterior (except for the base)
The question is, is it possible to tap 3-3.5mm holes in the aluminium and screw the bolts in from the interior? I have no experience tapping holes, so was just wondering if this is possible? and what problems this would cause?

Regards

Stephen

Magura 29th June 2004 02:38 AM

Nope, youll have too short thread if tapping in a 4mm sheet. Youll get an effective thread of 1.5 to 2mm wich isnt enough for keeping the whole thing together.

To use that approach youll need to make the chassis of min. 6mm sheet and preferably 8mm sheet. Then you can cut M4 which is much stronger than M3, and youll have a better chance not to break the tap as well.


Magura:)

Charles Hansen 29th June 2004 03:48 AM

To fasten from the inside requires what is called a "blind hole" (as opposed to the normal "through hole"). When tapping a blind hole in thin material, you will need a "bottoming tap". (Look at www.mscdirect.com for more taps than you will ever need.)

Magura is right, but even a bit conservative. In my experience, 8 mm is the *minimum* for tapping a blind hole with normal techniques. Of course with enough desire, time, and money you can do it in 6 mm, but this becomes *much* more difficult.

Magura 29th June 2004 04:13 AM

Quote:

Originally posted by Charles Hansen


Magura is right, but even a bit conservative. In my experience, 8 mm is the *minimum* for tapping a blind hole with normal techniques. Of course with enough desire, time, and money you can do it in 6 mm, but this becomes *much* more difficult.


Thats right as well.....its good to be reminded from time to time that good advice is taking the abilities of the person to recieve the advice into account.

I guess the best advice in a case like this one would be to forget about tapping....and glue the whole thing with epoxy instead.

Magura:)

zinsula 29th June 2004 06:57 AM

Another possibility would be Stud-Welding, but it will not be reasonable for a DIYer to buy such a welder. Maybe you'll find someone in your region who could do this job for you.

Saludos
Tino

Peter Daniel 29th June 2004 02:15 PM

Another possibility is using rivets (with shallow countersink). After brushing, they would be barely visible. It also make for a permanent chassis construction, something you might not really want.

Bricolo 29th June 2004 02:24 PM

I agree with Charles, unless you're experienced, I wouldn't advice tapping "blind holes" in less than 8mm

My gainclone's chassis is made of 6mm aluminium, I made "blind holes" on the side pannels, to fix the ICs
The deepth was just enough, but it was for M3 screws

djk 30th June 2004 10:17 AM

SAE made some nice looking gear with brushed 0.125" fronts, they used the welded stud method.

MK XXX
MK XXXI


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