Circuit board preparation

Bare board waiting for holes

Here's the bare board laying on the scaled drawing. The sizes match up quite well.

This weekend’s fun was all about getting the circuit board ready for population with components. Secondly I had to make sure it fit in the chassis correctly as that was the only thing holding me back from painting the chassis.

Drilling holes using the fence

Drilling holes using the fence made for fast and accurate work.

My first step was to make sure the drill plan for the board was correct. I ended up using the main layout drawing as my template as it was closer to the size I wanted. I ended up getting it copied and scaled by 114% at Kinkos so that it was approximately 12 inches by 3 inches. I cut out the template with a craft knife and used masking tape to stick it to the board. You can see from the template that there are 4 distinct rows of holes (not including a few random holes for wires or the ones to secure it to the chassis). This meant I was able to use the fence that came with my drill press to keep these lines straight. Drilling with a brand new 3/32nd” bit was quick and easy with this material. I made sure the drill speed was nice and high (about 3000 rpm) and used slow pressure. It only took about 10 minutes to drill all the holes. Where I new the holes were for mounting to the chassis, I used a 7/16th” bit.

The middle hole

The middle hole drilled with the board snugly attached to the chassis (temporarily)

Once drilling was complete I needed to make sure it fit in the chassis’s existing holes. I knew there might be an issue as I had used a scaled drawing, and sure enough when one pair of holes were lined up the other two were off by about 1/8th of an inch. I used a spherical grind tool with my Dremel to enlarge the holes in the circuit board. It took less than 30 seconds to make everything fit neatly. With the board attached to the chassis with 4 screws and the standoffs, I used the existing ‘middle’ hole in the chassis to drill all the way through into the board.

Staking tool

The staking tool setup in the drill chuck. The vice bolted neatly onto the bed of the drill press for added stability.

Now the time had come for “staking the turrets” (such a medieval term). All this required was for me to install the staking tool according to the instructions, place a turret in the tool, place the board over the turret using a free hole and then pull firmly down on the drill press. This action squeezes the conical tool into the bottom of the turret causing it to flare out. This causes it to grip the board firmly. I had initially tried to do this by loading up 10 or so turrets into free holes and then flaring them, but they’d always fall out so any time savings I made were lost by searching the bench for dropped turrets. Once I got quick at loading turrets into the bottom part of the tool, and then placing the board over the turret I became quite adept. Total time for all turrets was about 10 minutes.

More staking of turrets

More staking of turrets

All board material, turrets and the staking tool were purchased at Hoffman Amplifiers.

Next steps: paint the chassis (now I have all the holes finished and soldering components onto the board. (must remember to order said components).

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