Chassis Fabrication

[Wittgenstein]

I'm looking to start making my own custom chassis for future projects and I would appreciate any help that you could give. Do you use steel or aluminium? What thickness? Any tips or tricks that I should know of? Do you know of any really good how-to guides, besides the basic ones I keep finding?

For my last build I purchased a chromed chassis that I was really pleased with, but I am having a hard time justifing the money. Besides saving a few bucks, I am mostly interested in doing it myself for the experience and knowledge. I have most of the tools I should need for a basic chassis, but any help that you or anyone else could give would be much appreciated. My latest project is a 5F1 Champ, which I found plans for here. I would like to keep it small (8.75" L x 4.112" W x 2.625" H), and I plan on using a switched pot (as seen in drawings). For about $30 I can pick up a Mojo aluminum chassis with only the transfomer cut out, but I'm reluctant to use aluminium, due to it's conductive properties.

[Chuck H]

What's wrong with aluminums conductive properties??? Do you mean it's EM shielding properties?

I use aluminum when I fabricate because it's SOOOO much easier than steel to punch and cut. That said, I have never had a problem with ground connections or shielding. But none of my fabricated amps are over ten years old. Still, don't be afraid of aluminum. One nicety you might enjoy is that with some work it can be polished to a chrome like shine. Of course it will dull a little with age, it's not chrome after all. but it does keep most of it's shine and is a fraction of the cost of chroming (which is getting real expensive and even hard to source).
One considerations for aluminum would be to use enclosed type trandsformers. Any EM shielding will be handled that way. Though I have used open frame trannies on aluminum chassis without issue.

[J M Fahey]

I make my own chassis and use 1.5 or 2mm aluminum exclusively.
Relatively easy to work with, and does not rust all by itself.
Of course I have shears, a folding press and punching presses with all kinds of dies, both round and rectangular, slits for pot sliders, etc.
You don't need to actually have these at home, but access to them , maybe at a friendly sheet metal shop.
Amps I made over 40 years ago are still living happily in their aluminum chassis.
Sheet iron ones, which I had professionally made, are hunks of rust by now.
In a home environement you may have the aluminum cut and bent to size for a basic U or C shape chassis, add end reinforcements to make it rigid, and make all holes with a drill press and an assortment of bits or even better, a stepped Unibit, not only for the convenience but because when one step makes the actual cut, the next higher "cleans" the burr it makes.
On aluminum your relatively expensive Unibits will last forever, not so much on iron.
Remember to lubricate with a drop or two of Kerosene.
For tube sockets you can use Greenlee punches (best) or "cup" hole saws.
For transformer cutouts you can drill a starting hole and cut what you like with a nibbler.
You will *sure* have a lot of hand strength after that !!
I mean, after it stops aching, he he.
Good luck.

[mooreamps]

I have only one steel chassis ; for my 813 project. That's because to handle the extra weight of the 1 KV power transformer and other stuff.. Else, I would tend to agree with the others and use aluminum for all other projects....

-g

[Chuck H]

+1
Steel is best for strength. If you need to support a bowling ball sized PT I would go with steel
I once had a couple of custom aluminum chassis made that were actually too thick to mount Alpha pots on. They didn't need to be that thick for strength but it's how the fabricator did them. The gauge of the aluminum plus the thickness of the face plate was greater than the thread barrel on the pots! I had to omit rear lock washers and cut bigger holes in the face plate so the nuts would flush on the chassis itself. Point is there are complications with making aluminum thicker for added strenth.

[J M Fahey]

Yes. *Real* problem is what tools you have available.
For iron real macho presses are needed, plus suitable dies.
Another problem is that sheet metal is perforated while flat, and bent only after that, which implies a certain minimum quantityto compensate setup time.
Actual punching is very fast.
When I had my metal corners set of dies made, just "testing and adjusting" produced about 800 "second grade" ones.
Each actual production lot was about 5000, about 40 "knocks" a minute .
I'm mumbling about make a "standard" tube amplifier; the same basic chassis would do for a Bassman, Plexi, AC50 and a couple more; in that case it would justify having 50 or 100 made, in iron and by a commercial shop, for a *very* reasonable price.
But in one-offs or small 2 to 5 quantities, it doesn't pay.
That $30 chassis mentioned above sounds very reasonable to me.