Making Multiple Parts

To increase efficiency (and decrease boredom), some changes are needed when making lots of copies of the same part. In this example, the Strut Fixture (reference B4W5) requires thirty-four copies.

The normal procedure for one or two-off parts is to individually measure and mark each part, center-punch all holes, manually set the x/y coordinates on the drill press table once the part has been clamped in the vise and drill. Follow that by grinding, hole deburring, hand-filing and hand polishing with a ScotchBrite pad. However, that all gets a bit tedious after the first five, twenty or more parts.

My solution involved setting up a simple backstop guide on a wooden table that I clamped into my drill press vise. A chunk of walnut and oak that were laying around were clamped in place and a toggle clamp screwed down to hold the work in place.

With the 6061 aluminum being a relatively soft metal, the lack of a center-punched hole did not prove to be a problem. It doesn't hurt either that the designer allows for a generous 1/16" tolerance. Also, close examination of drilled holes shows a slightly triangular shape - evidence of a drill chuck taper/quill runout problem that I need to fix some day. Anyway, this method made pretty quick work of the drilling of the 104 holes (left)

The next step required making a 3/8" radius on the four corners. I started by clipping off a small amount of each corner with the band saw (one part in each hand, alternating and flipping), then grinding a smooth curve on the grinder.




















I forget to mention, I used a small flat file after the hole drilling operation to knock off any burrs, allowing the part to sit flat on the grinder table.

The next step was to hand-file the burr created by the radius grinding, knock off the burr around the radius and smooth the grind marks a bit.

The final smoothing and polishing was carried out on the drill press using a ScotchBrite aluminum oxide wheel at about 1,500 rpm.

There, 34 pieces. Almost time to go over the pre-flight checklist.