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Harold Hall

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Other methods of dividing.

Whilst using a dividing head will, in most cases, be the ideal method, other equipment is often used. The reasons for this can be many and varied, but will most often be because either a dividing head is not available or that the project is simple and more easily set up using some other method. Typical of this would be when needing to make three divisions on an item in the three jaw chuck. In this case, placing a piece of packing between the bed of the lathe and each chuck jaw in turn would be accurate enough for most applications and certainly much quicker than setting up a dividing head.

 

An extension to this idea is to include a gearwheel into the setup and use this in a similar way to the previous example, Photograph 11. Using a weight on the end of a piece of string attached to the chuck key, would keep the packing in place whilst the operation of cutting the dial is carried out. The gear and dial are mounted onto a two step taper stub mandrel.

 

Another idea, but one having no limitation as to the number of divisions, other than a practical maximum, is to wrap around the chuck's back plate, a strip of paper suitably marked with the number of  divisions required. This may seem a simple idea but the space between each marking when in the flat is likely to be a complex value. Say with a 100mm diameter backplate the circumference would be 314.159mm. Dividing this into any number would result in a value that  would be impossible to work with, fortunately, there is a simple way out of the problem.

 

Wrap your strip of paper, a little on the long side, closely round the periphery of the chuck and carefully cut through both with sharp knife at the overlap, you will now have your 314.159mm strip of paper. Fix this down on a piece of paper and on this draw a line at an angle to the strip and starting from one end of it. For example, say you wanted 19 divisions mark the line at 285mm (19 x 15) and mark this off at 15mm increments. Using a straight edge and a draughtsman's square as illustrated in SK. 1, transfer the divisions to the strip of paper that  will now be accurately divided. Fix the strip to the chuck and use this to achieve the required result. Photograph 12 shows an example. The process in SK. 1 is a rare occurrence in the workshop for dividing length.

 

The methods above do though have one major problem, that is, there is no method of securely locking the spindle. With only a little care this should not present a problem for the tasks, such as calibrating a dial. For more arduous tasks though, such as machining a hexagon on a turned item, it would be a non starter. Because of this, even though the system can easily cope with any number, it would not be suitable for cutting that gear for which you do not have a suitable dividing plate.

Metalworking

Workshop Processes

Dividing, on the lathe
Dividing, on the lathe
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11

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12