Below is the key for the Metric Hole Test Pattern object, which is available at Shapeways.com. It is a flat, 3 millimeter thick piece with standard metric drill bit size holes, and can be used just as a decoration, or to measure detail, accuracy, and distortion (holes and flatness) in printed materials. It’s also useful for judging the printed sizes of clearance or tap holes, or choosing a hole size to match a part you already have.
Holes range in size from 1mm to 3mm in 0.1mm steps, and from 3mm to 10mm in both 0.1mm steps and 0.25mm steps.
The holes organized in “rows” and placed as efficiently as possible in order to limit material use. This results in a unique and beautiful shape. There are also small bumps on the edges to indicate the odd (x.25 and x.75) measurements. It is 3mm thick so that it can be printed with a variety of materials, including stainless steel.
It was a bit of a challenge figuring out the ideal hole placements…