Hand machined mechanical pencils

12mm shaft clamp coupler (24/08/14)

Here's a simple rigid shaft coupler for a 12mm shaft, made from aluminium. I first bored the inside to an accurate sliding fit over the shaft, then split it and drilled/tapped the holes. Slight problem - the internal stresses in the metal caused the bore to close up, so I had to force the clamp apart slightly to actually get it over the shaft. This was done using two sets of opposing screws, shown in the third photo below.

Shows how the clamp is spread apart using both M5 (upper) and M4 (lower) screws.