Drill Sharpening On The Quorn (2)

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There are lots of ways to solve problems. Sometimes you can apply enginuity and innovation. Other times throwing money at it will work. As discussed in the Drill Sharpening Jig page, the Quorn can do an excellent job of four and six facet drill sharpening. All that is required is a drill holding system that holds a twist drill accurately on center with the work head axis allowing the drill to be rotated 180° without the tip moving up, down, or sideways. This can be accomplished using parallel closing collets, and these, with careful work can be made in a modestly equipped shop. The big ones are easy enough, but for smaller drills, it becomes a bit tedious, so here's another way.

The "ER" series of collets were described in April 2007 issue of Model Engine News. As described there, they close at both ends, thus ensuring the axis of whatever they are closing on maintains the axis of the collet itself. For faceted sharpening, this is exactly what we need. The collets are available as Asian imports of quite fair quality and reasonable cost, so all that is required is to make a collet holder with a 1.000" shank to fit the Quorn work head bore. But wait! ER16 collet holders for use in CNC equipment have parallel shanks. Checking local suppliers found that a 25.0mm shank holder was as close as they come. Curse. Damn. The joy of living in a metricated country... So I bought one anyway and put it in the drawer while I pondered how to add 0.4mm (about 0.019") to the diameter.

The answer required the better part of 12 months thought (on and off, mostly off). When it finally came, it was, of course, blindingly obvious: get one from a country that has not yet gone metric! That narrows the choice to about one, I think, and a quick look on eBay found a brand new holder for $20 (plus another $40 shipping). Here's the result. The holder slides right in, takes the graduated index plate, and holds twist drills perfectly. This is a somewhat tricky job due to the relief ground into twist drills behind the spiral flute which greatly reduces the area over which a collet will make contact. But the proof is in the result as shown by the four-point sharpening of small drill bits with all facets meeting so close to the center, the eye can't pick any deviation.

The take-away from this is if you are considering building a Quorn and live in a metricated country, give serious thought to making the bore of the work head 25.0mm rather than 25.4mm (1.000"). This will give you the opportunity to use tool holders intended for CNC gear without putting the family cat in hock to pay the freight on the Imperial version.

See also:
  Drill Sharpening in the Quorn (1)
  A Rank Beginner Builds the Quorn

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  Email: Ron Chernich

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