Special Drill Chuck.
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[1177] " A.H.H." (Cardiff) writes :—" In these days of specialization, even workmen must make themselves tools which are specially designed for doing some small job. Of course it does not pay to make up a tool to do one or two small bits of work, but if a man has a regular repeat job then it often pays hint to make up a special tool.
"This countersink holder is useful when countersinking crankshafts, brakes or brake liners, and other similar work. Care should be taken that the countersink used is a standard size, and has not been spoiled by grinding, for it is only when the heads of the screws bear all the way on the countersunk part that they secure a firm hold. "In making up the tool I first of all obtained a piece of steel and bored out one end to take the tapered part of the drill. I then turned and faced up the collar as shown in the sketch [We have had this re-drawn--ED.]. The thread I finished with the gas dies. Next I obtained an old steel union nut to fit the screw. At the top of the thread on the chuck
I drilled four 7-32 in. holes. Having done this I sawed four slots as shown in the sketch. Then, with a file, I just eased off the burrs. The final job was to harden the threaded end of the chuck and also the nut.
"When in use the drill is slipped up into its place, and the union nut is screwed on until it is tight enough to keep the drill from turning when at work."