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BCT Supercut - Bowl Turning |
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Let's make the point again: the Supercut is held in a horizontal position, parallel to the bed of the lathe; it will not cut as long as
it is presented to the workpiece along the axis of the lathe, as shown. |
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To start the tool cutting, the right hand is drawn back towards the operator, and as the angle of the shank across the lathe increases,
so the cut is "turned on" more. |
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By drawing both hands towards the operator equally, the tool will make a planing cut across the surface of the workpiece.By
increasing the cut more, a substantial cut can be made as shown in the right-hand illustration. |
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For heavier cuts, draw the right hand back towards the operator and press the tool tip onto the surface of the workpiece. The tool
nose will "burrow" into the face, creating a small depression.Reduce the angle attack a little and draw both hands towards the operator at a similar rate to make a substantial planing cut. |
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To form the hollow of the bowl, the tool shaft is progressively skewed across the lathe axis by drawing the left (inner) hand towards the
operator faster than the right (outer) hand. In this way the tool tip describes an arc which defines the bowl surface. |
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The hollow can be made progressively deeper in this manner, at will. The shape can be varied to suit the design in mind
and the tool can be drawn out parallel to the lathe's axis if a "squared" bowl internal profile is desired. To form an undercut rim, simply keep drawing the tool towards the operator - it will cut into
the "blind" recess and out again under the rim without drama! |
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Note that throughout the above sequence, the cutting head angle in relation to the shank has remained unchanged and the cutter has been set to the
same, approximately 45 degree, skew angle. |
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The bowl produced in this sequence is un-lovely, I will be the first to admit, but this was designed to be a technique demo! My excuse is that
trying to work around the tripod legs, at arms length and whilst keeping my big head out of the camera sightline gives me the excuse for any errors, however appalling!!I shall also confess that I was a little too
enthusiastic in my intital cuts and ran into the heads of the screws securing the workpiece onto the faceplate - hence the pronounced step towards the outside of the bowl's inner surface. Oops! |
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The sequence (left) illustrates, with the help of the above workpiece sawn in half, the method of cutting back under a rim - something
which is difficult to show on a complete workpiece.The first shot shows the tool position as it starts to transition from the base of the bowl into the undercut area. The tools shank remains
horizontal throughout. In the second, the tool is being drawn forward/outward (towards the tailstock) to create a curved wall to the undercut. Note that the tool handle has been pushed away from the
body by the right hand to angle it across the bed and allow the head to work under the rim without fouling. Finally, the tool is drawn inwards towards the centre of the bowl, keeping the cutting pressure
forward onto the underside of the rim to cut this surface. When creating the original bowl, this shape was created using two or three passes of increasing depth. |
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