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Overview

Perforated angle has 1/4" holes, centered and spaced 1" apart. This is the main building block of the Contraptor set. The angle is used as a structural component and as a linear rail for sliding elements. Quarter-inch holes, used in the set with smaller 10-24 screws, allow small adjustments at the time of assembly, which makes the design tolerant to errors.

The raw aluminum angle stock needs to be turned into perforated angle, however it's too time-consuming to do all at once. Only a few holes per piece are required for any given project, so it's recommended that the drilling be spread out over time as different contraptions are built from the set. To make drilling as-you-go easier, the hole locations are center-punched on the angle, which is significantly faster process than drilling.

If you have a drill press and don't mind spending the time to drill all of the perforated angle upfront, it can also be done, using a simple jig.

After all angle is center punched, it is sawn into pieces of required lengths. An angle piece is actually shorter than the whole number of inches by 1/16", i.e. 1" piece is 15/16", 2" is 1 15/16" etc. These are the lengths resulting from sawing longer piece of perforated angle into shorter ones, 1/16" being the kerf. It's convenient as it makes the ends of the angle a bit shorter so that they don't stick out beyond the angle footprint on 1" grid. In 3D models, on the contrary, angle lengths are whole numbers of inches - this is done so that different parts snap to each other easily during modeling. 

Materials

Aluminium angle, 1"x1", 1/8" thick

Tools

The following tools are needed:

Starrett 819 automatic center punch
Pegboard at least 2' long
Drill press - only if drilling all angle upfront
Countersink bit

Source Files

• This release: components/perforated-angle/
• Latest version: http://contraptor.svn.sourceforge.net/viewvc/contraptor/trunk/components...

Making

Depending on available materials, there are several ways to center punch a lot of angle:

Method A - with pegboard and automatic center punch

The pegboard must be at least 2' long and must be true in that direction (check distance between holes with measuring tape). In my experience, hardware store pegboard 2'x4' has a small error in one direction and bigger error in the other direction.

You can center punch all angle using this method if your pegboard is large, or use method B which requires a jig made from three 24" pieces of perforated angle:

Method B - with the jig and automatic center punch

The jig for center punching blank angle is basically three 24" pieces, aligned and bolted together to create the "X" shaped drilling/center punching template for the fourth blank piece. Two holes are drilled at the end of the blank piece, through which it is attached to the jig using 1/4" screws. It is then placed in the vise, and holes are quickly center punched through the jig with the automatic center punch. The jig is also used as a guide for sawing 2' long pieces. 

The same jig can be used to drill the angle on a drill press without center punching (see the next section). This can work if you have a drill press, don't want to drill the holes as you go and would rather take the time to do it upfront. 

Method C - with template labels

If you do not have (true) pegboard, you can use template labels to make 2' perforated angle pieces for the jig (method B). 

The template labels are located in the SVG file (there is also a copy in PDF if SVG can't be read or printed). The labels are 8" long and need to be attached to the angle one after another. Depending on your printer and accuracy of the cutouts, the actual printed labels may not be exactly 8" long, so before you attach the labels, measure and mark with a pencil exact 8" intervals on the angle, which should add up to the length of 8" x 3 = 24" for 2' piece. Attach the labels as described in the Howto section, steps 1-5. Basically, you want the hole marks to closely match the inch marks on the measuring tape across the entire angle span.

Once the labels are attached, center punch all holes using manual punch. Do NOT center punch with the angle secured in the vise - this will shift the labels. Drill the holes, remove the labels from the angle, and deburr the holes using the countersink bit. 

Drilling holes on demand

Drill 1/4" holes on as needed basis, using the marks from center punch. Deburr with countersink bit/sandpaper.