Hand machined mechanical pencils

Sherline spindle drawbar remover (01/10/12)

I recently broke two small carbide milling cutters (0.5mm diameter, 3mm flute length) by whacking on the end of the collet drawbar to release the collet. The shock transferred through to the tool, propelling the tip right off. So, here's my take on a "gentle" drawbar removal tool. This is based partly on designs at http://www.sherline.com/tip33.htm and http://www.proto-jem.com/mill_tools.htm.

A hunk of aluminium is bored out to fit snugly over the top end of the spindle, and is then split so that a 25mm shaft collar (http://www.technobotsonline.com/zinc-collar-25x40x14mm.html) placed on the outside can clamp the aluminium piece to the end of the spindle. The other end of the aluminium piece is tapped for an M8x1.25mm bolt; this will press down on the head of the drawbar bolt to remove it. Finally, a short handle is attached which can either rest against the motor housing or can be gripped with one hand while unscrewing.

It removes the collet drawbar easily, and has the advantage of not needing a collar permanently clamped to the spindle shaft. Something to watch out for - the extractor screw must have a coarser pitch than the drawbar bolt, otherwise there will be not force applied downwards when the extractor screw is tightened. For example, the M8x1.25mm bolt I used here doesn't push out the drawbar used on the drill chuck, since it's a coarser thread. I just whack it ;-)