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Single Ended Triodes (SETs), the ultimate tube lovers dream.

RE: Aluminum plate thickness for amp project




Have no fear. You can do the machining yourself if you have just a few basic tools and some patience. It would be nice to have a drill press with a larger throat, but that's not necessary--you can use a hand drill if you're careful.

IME, the most useful drill bits you'll need are the ones in the attached photo. The one on the left is a stepped bit (aka uni-bit). Very useful for making clean holes up to the maximum size step (in the case of the bit pictured, that's 7/8 inch). The bit on the right is used for starting holes in metal without the bit wandering. Very handy if precision is important to you. (Regular drill bits like to 'wander' when first encountering metal, and your hole may not end up where you'd like it to be. More on that below.) Either of these bits can be used in a press or hand drill.

Other tools that are very useful are hole punches (Greenlee is one brand, there may be others). These make very clean holes (perfect for tube sockets) in metal. Punches aren't cheap, though. If you end up doing a lot of your own metal work, they're worth it. Maybe not so much if this is the only amp you're likely to build.

For the larger, irregularly shaped holes, a jigsaw with a metal cutting blade will get you close (leave your line!). Finish them with an appropriately sized metal file (stop when you get to your line! Aluminum files fairly easily). Your large round holes can be done the same way, BTW. You'd be surprised how close you can come to a perfect circle using this method and some care. Draw large circles with a compass. Compound shapes with straight edge and square, an inverted teacup, or whatever works.

You can cover the entire surface with adhesive backed paper, measure and mark all your holes, then machine. Best practice is to use a pointed punch to make a 'home' for your drill bit. I've used a drywall screw for this in a pinch. Just put it over the hole center mark, and tap it a couple times with a hammer. Aluminum is soft. Then be sure the tip of your drill bit 'finds' the mark you made before drilling. This will minimize the drill bit's tendency to wander.

Of course, as Jeff mentioned, you can have the metal or machine shop do all of this for you, but it sounds like you wanted to have a go at it yourself.



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