Phase 3: Punching, Drilling & Filing


Making excuses for the appearance of your completed homebrew rig such as "well it looks like crap but works like hell", are just that --EXCUSES! Home made projects can work very well and they can look good too! It is amazing what a bit of paint can do to dress up your project. It will not make it work better but it does demonstrate the pride of the builder in making the project complete.

I am now about to reveal some "tribal knowledge secrets" of how to make your project look just as good as it works.

1. Tools: I have no personal vendetta with Harbor Freight. In fact two of my major shop tools come from there including an 18 Inch metal brake and a 3 axis manual milling machine. The metal bender cost me about $30 and I think it is a bit more today like $38. That is a good buy if you have about $50 burning a hole in your pocket to cover tax and shipping. Builders may want to bend up their own chassis but is not needed for this project. But for hand tools like screwdrivers, pliers, nippers, files, hacksaws etc. get the Craftsman brand typically available at Sear's. One reason is the return policy --if it says Craftsman on the tool and it breaks --you get a new one free! The inexpensive tools often available at places like Harbor Freight are just that --usually good for a one time application. Get tools that will last! Hand drills are a must and a bench type drill press even better. I have a pedestal floor mounted drill press I bought from Sears about 20 years ago but often use the Mill as a small type bench drill press. Makita and DeWalt make some good hand drills. Measuring tools are another key piece. I have a metal square that is used for all of my panel layout measurements. A rusty screw driver with a chipped blade and a worn out (wobbly) hand drill is not a starting point for the Bitx40 project. While you are at it --get drill bits specific to building electronics and not the 100 piece unit that will dull in short order. Get pilot bits (1/16 inch) and bits that will drill undersize for threading 4-40 and 6-32 screw holes. I frequently tap holes in aluminum angle stock. This is especially useful when it is almost impossible to get my fat fingers into an area to start a nut. Thus 4-40 and 6-32 taps are a must for your shop. A metal center punch is as basic as a soldering iron! Last but not least is a rat tail file (3/8" in diameter).

Below is a sampling of some of the tools that I mentioned in this section:


2 Layout: It is really hard to replace metal once the hole is drilled or area cut out. Thus using a procedure to "mock up" a front panel before drilling or making any holes is well worth the time and effort. In the Phase 1 page, I suggested the use of "quad" type graph paper to trial run the panel layout. Paper is cheap whereas a metal chassis is not! Try several runs at your layout and think not only about the front of your panel but also what is behind the panel as clearances will be very critical once hardware is installed. I have made many cases and typically will use materials like sheet aluminum or even copper PC board. My method of attaching front panels to bottom plates typically involves the use of 1/2 inch aluminum angle stock. Translated this means no controls below 1/2 inch from the bottom and no circuit boards closer than 1/2 inch from the front or back panels. We covered this in the Phase 2 "Thinking Inside the Box" but worth a repeat here. Once you have a suitable layout and using the quad graph paper you now have a drilling template. The process now involves taping the graph paper onto the front panel material being careful to align everything so all lines are straight and true. NO! you do not take the 1/4 inch drill bit and have at it. Using your center punch make a mark at each location to be drilled. Remove the paper template (you may want to use it again) and store it in your project folder. In the next phase we will get on to the follow on serious metal bashing.
3 Metal Bashing. This is where after you have carefully marked hole locations with a center punch that you have at it. For all drilled holes start with 1/16 inch pilot drill and then gradually increase the size of the opening. Many of the small controls like the stereo headphones or mini-toggle switches use a 1/4 inch hole. Potentiometers can range from slightly greater than 1/4 inch all the way up to 3/8 inch. The stock 1/4 inch stereo jack usually take a 3/8 inch hole. For square or rectangular openings after drawing the size of the hole on the panel, drill a series of holes using a 1/8 inch drill that follow the pattern of the opening but at a safe distance from all four edges of the opening. Ultimately a piece of metal is completely drilled free from the panel. Next using a large flat file, smooth each side just up to the pencil outline. Then perform a fit check to see how much final metal must be removed. I usually employ masking tape around the periphery of the hole and this does two things. First it is clear what is to be removed and what stays. Secondly it protects the surface from wild/uncontrolled applications of the file.