Harold Hall

Workshop Projects

However, if you are using a large four jaw with a large centre hole it may not adequately support the part for machining the second end, in this case, make a taper stub mandrel to hold the cylinder and machine it whilst the mandrel is still in the chuck, do not remove and replace. If you are not conversant with taper stub mandrels see notes on later pages.


Mount fixture 2, together with the cylinder, onto the faceplate and machine the flat face as shown in Photograph 17 ensuring, as a result, that it is parallel with the bore. Do though pay attention to the positioning of the cylinder on the fixture as you do not want to machine more off one side of the flat than the other. If you do this you may find there is insufficient metal in which to make the 8BA tapped holes. Inspection of the casting should make this statement clear. The thick plate seen below the cylinder may appear to be supporting it but its sole purpose is to balance the assembly.


Milling cutter holders

It now becomes necessary to perform a simple milling operation but if you do not posses a milling cutter chuck then you will need some simple adaptors. The reason for this is that the helix angle of the cutter will result in it attempting to draw itself from the chuck, something it will inevitably do, as the grip with a three jaw, or drill chuck, is insufficient for their use in this way.


The economic way of overcoming this problem is to make an adaptor. All this needs to be is a length of say 3/4” diameter steel, skimmed on the outer diameter and then bored to fit the shank of the cutter to be held, this ensuring concentricity. Then add a tapped hole in the side to take a grub screw to secure the cutter. When tightening the grub screw the cutter should be pulled forward just before it is fully clamped so that the back edge of the flat on the cutter contacts the screw. This will prevent the cutter being drawn out when being used. Being made out of mild steel, and of a larger diameter, the grip will be more than sufficient.


If though you intend to do a lot of milling on the lathe an adaptor that fits in the lathe's taper would be better as concentricity of the cutter is likely to be less certain using an adaptor mounted in the three jaw chuck. However, just for this project, adaptors in the three jaw should be adequate.


With an adaptor made the next stage is to mount the fixture onto the top slide with the cylinder clamped in place and mill the 1/4” wide recess, followed by repeating the process on the other end, Photograph 18. Swing the top slide to a suitable angle and drill the hole between the recess just made and the cast-in steam port, doing this at both ends, Photograph 19 should make the method clear. If you aim the drill into the corner of the recess just made the drill will start without the need for a centre drill or it being centre punched.


The angle is not critical but aim to hit the base of the steam port recess so that it does not break into the flat surface which would distort the steam port aperture. To check the angle place a rule on the top of the casting and looking down on it align it with the drill being used. This should give a good enough indication as to where the drill will break through. Also, drill and tap the 1/4” x 32tpi hole that contacts the centre port.


Drilling and tapping the remaining holes will be carried out as the mating parts are completed.

Stuart 10V steam engine machining
Stuart 10V steam engine machining
Stuart 10V steam engine machining











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