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Harold Hall

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Backlash

Consideration must be given to the backlash inherent in the dividing head assembly, if not, divisions will come out irregularly spaced. Because of this the workpiece, or the device holding it, must be restrained by hand and in the same direction each time to take up the backlash consistently. Alternatively, the method of a string and weight as was seen in photograph 11 could be considered.

 

Making your own division plates

It is probable that a dividing head owner will occasionally find a need for a division which the head cannot achieve. If this is because a division plate is not available making ones own may be the only practical solution. The following are three possible methods of achieving this.

 

CAD

If you have a CAD program on your PC then this is likely to be by far the easiest. First, decide the radius on which the holes are to be placed and mark the drawing with a centre point and one hole on the chosen radius. Make the marks using a very small circle, say 2mm diameter or less. Now, If say 54 divisions are required, then request the program to make 53 copies equally spaced on a PCD. My program calls this a “circular array”. This can then be printed out and used to centre punch marks onto the material from which division plate is to be made, See Sk. 3. Holes can then be drilled on the centre punch marks to complete the task.

 

My first use of the method used the firms pen plotter to produce the printout which I found to be virtually spot on. Subsequently, using my own laser printers I have found that the large circle is very slightly oval shaped, typically, with the height being 80mm as drawn but the width only 79mm. This has virtually no effect on the angular divisions but requires a detent with a little sideways flexibility, Photograph 16 showing my method.

 

This is using a piece of spring wire taken from an old umbrella frame though I do not think they are made that way these days. However,  if you do not have any suitable spring wire I think a piece of 2 to 3mm mild steel would have enough spring, if long enough, to make this adequate. Making the detent with a slightly tapered end ensures is will fit perfectly resulting in a backlash free situation.  The dividing plate seen in the photograph, and  made by this method, has 125 holes.

Metalworking

Workshop Processes

Dividing, using a CAD plotted dividing plate
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16

Important

This photograph is not one of an actual task, but was set up just to provide this photograph.

 

Unfortunately I overlooked that the detent had originally been used with a different setup and is too tall.

 

Ideally, the detent should locate a hole on, or close to, the height of the dividing heads spindle.