Aluminum casing concerns

[gates_2]

I've finally gotten around to ordering some aluminum to case up my firstwatt F2 clone. The heatsinks I used have a 3/8" aluminum plate from with the fins extrude. Each sink is 12" long, so I figured I'd build the case around the heatsinks.


First, I ordered a 1/4" thick 16" x 5.375" plate for the front, a thinner sheet for the back(.09" thickness) and a top and bottom sheet (top is .04 bottom is .05)
All of it is 6061-T6 aluminum.


..yes...I want this to be built like a tank


My thinking is to drill through and tap holes through the front plate into the cross section of the heatsinks. considering the thickness of the heatsink is 3/8", will this be OK? Or will I have to worry about fracturing the metal? Can a hand drill handle this?


For the bottom(cross section 16" x 12") I'm concerned about the weight of the transformer(320VA- its pretty hefty!). Will the .05" thick sheet be sufficient? If not, I ordered some extra .25 x 2" bars to reinforce the bottom.(i'm thinking about having the trafo directly supported by one of these running across the length of the bottom.)


Unfortunately, I only have a power drill(decent) and a cheap Chinese-made dremel that cost $5 from harbor freight

As such, I'm thinking about just having the 4 screw holes in the front, with perhaps one hole for a LED(a "power amp" layout). For the rear, the sheet is much thinner, so should be easier, right? I've failed to gain access to a machine shop, and am worried about the $$ involved about taking the project to a commercial place. Unless there is someone in the area who has a drill press and such

I apologize for my lack of knowledge, I've never done any metalwork before, but I do need to get this amp finished one of these days!

 

[amb]

Consider buying a table-top drill press. Harbor Freight has some perfectly usable ones for around $50. It will make your job a whole lot easier and less likely to mess up. It's very difficult to hold a portable drill perfectly perpendicular to the surface you're drilling. Lubricate the bit with oil when you drill the heavy, thick stuff.

0.05" is too thin to properly support a big transformer. Definitely reinforce with something.

 

[Listen2this1]

Things to remember when drilling into any metal that you are needing to look good after drilling. I always cover the area in a masking or I prefer blue painters tape. Always use a punch of some sorts to mark the spot before drilling, so the bit will not walk. I also agree with Amb that if you are going to do this more in the future I would put some money into drill press. Try to clamp when possible, If you cant get cutting oil, WD-40 will work.

I hope this will help.

 

[luvdunhill]

The F2 is a nice amp! I just ordered the newly released F4 PCBs and am planning on doing a fully balanced configuration with dual mono power supply!

 

[gates_2]

Yes, I was quite amazed when i first hooked up my k1000's with it, thats why i want to finish this and be happy!

I don't know if i can go out and buy a tabletop drill press- I'm a student and I have to move around often. I have already gotten so much stuff for all my diy work, it could be a problem

 

[gates_2]

Got the aluminum in today.

2 questions:

1- what size screws should i use, keeping in mind that the screw will be going through the faceplate and into the side of the heatsink(dimensions above)

2- how can i get rid of the scratches and imperfections in the aluminum. Should i use some type of polish? Or sandpaper first?

 

[Listen2this1]

I would use a bolt nut combo instead of screws. This way if you need to change aheat sink out you can re-attach it, screws can strip out in aluminum pretty easy. As for the scratches, try to cover the aluminum in tape until you are done drilling. If you end up scratching it you can depending on the depth of the scratch. you can use sandpaper that is real fine probably 320-400 wet sand paper. Good luck