Object And Uses

In Fig. 6 there are drawn a number of objects suitable for elementary exercises in turning and allied operations. They comprise a Main or Master Chuck, for fitting to the nose-piece of a lathe headstock; an Auxiliary Chuck, for screwing on to the master chuck. There are usually a number of these small chucks, which are all fitted to the master chuck, ready to be fitted to any job that comesalong. The next drawing shows a Loose Centre, which is fitted into the sliding barrel of the tailstock, or in a carrier chuck; this should be made of steel, hardened and tempered. The next drawing is of a Drilling Plug which is also fitted to the tailstock. This is used for holding circular objects while they are being worked on or drilled, and it is an excellent model, introducing taper turning, taper fitting, sawing, and accurate filing. The next is a Hammer Head, which is a more difficult exercise, and involves turning by hand as well as with the aid of a slide rest, difficult drilling, filing, and hardening and tempering. The next is a Balanced Handle or Swape. This involves turning as above, drilling and tapping a stopped hole, screwing and fitting, and making a true square hole.

There are also the patterns to be made, and these should be of boxwood. This is more simple turning and patternmaking, but the easiest pattern to turn is the auxiliary chuck.

The Joints

The two projecting lugs on the wood pattern of the master chuck are simple dowelled joints; all the chucks are screwed joints, and the loose centre and the drilling plug are taper fitting or friction joints.

The Processes for the main or master chuck:-

1. Turn the pattern from a piece of hardwood; turn and fit the studs, and glue them in.

2. Cast the chucks in brass or gunmetal.

3. Pickle it to loosen the sand.

4. Turn it out to size for the female thread; face it, screw it, and cut away the first thread as shown by dotted line. Take care that it fits the nose-piece of lathe without any shake, and that it does not wobble when being screwed on.

5. Fit the chuck on to the headstock of lathe, turn the nose-piece, face it, and screw it with outside comb chaser-Ch. xvI, Fig. 18 (13)-to the size that is convenient for the auxiliary chucks.

The two studs are cast on, so that they can be tapped lightly with a hammer to tighten the chuck on to the spindle, and also to loosen it. If the stud farthest from the headstock is not wanted it could be sawn off.

Auxiliary Chuck

1. Turn pattern in wood.

2. Obtain casting.

3. Hold in a chuck, bore out, and screw to fit without any shake on to nose-piece of master chuck. A number of these should be fitted and then left so that they could be fitted to any work that comes along.

Fig. 6.-Top row-Pattern, casting, and finished casting of master chuck.

Second row-Aux. chuck-steel centre, vee block centre, hammer head.

Bottom row-Small handle and cross bar for a balanced handle, plan of hammer head.