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This is a very useful little device and well worth making. It is adapted from a picture I saw in an old ME magazine, there were no dimensions of course but those I've given on the drawings work just fine on the prototype I made. I believe it's available commercially (or at least was..) but I have never seen one advertised. The attachment consists of a hollow Morse Taper shank with a through-bore of 3/8" holding a ram with a small capacity chuck on the end. The chuck is ideally a Jacobs number 0, 1/8" capacity, a chuck I've found very accurate and ideal for small diameter drills. If I can figure a way of getting one of my No.0 chucks of their 1 MT shanks I'll use it - they are stuck solid and there's no provision for a jack screw. (Later... the only successful method was to drill through the back of the chuck - which does it no harm - and punch the shank out with a substantial pin punch). Anyway, if you want to use something different, perhaps a No.1 1/4" capacity or even a small pin chuck, simply adapt the ram nose to suit. There's little point in using a chuck larger than 1/4".
A lever handle operates the ram through a linkage giving just over 1" travel and offers lots of 'feel' with miniature drills - something that is absent using the standard tailstock barrel. This attachment should reduce the occurance of drill breakages (especially those delicate 1/8" center drills which I used to break regularly) as you can better monitor the drilling progress, and it's also a lot easier and quicker to remove the drill to clear swarf. The design accommodates the attachment being rotated in the tailstock barrel to provide either vertical or horizontal alignment of the handle - whatever suits you best.
This simple to make attachment really doesn't warrant extensive construction notes, as this should be quite obvious from the drawings. The design assumes a 2MT tailstock bore but this can be altered to suit if necessary. The linkage yoke is Loctite'd onto the MT shank using 601 retaining compound. Take extra care to maintain concentricity of chuck/ram/MT shank and bore during construction otherwise the finished device will be less than useful - the drill really must be held dead on centre. I've had to make a small adjustment to the drawings since it was first posted, the 3/8" slot in the yoke needs more clearance than I first thought otherwise the linkage jams with the ram fully retracted.
(c) Chris Heapy 1996.
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