On the Faceplate
Mount a disc onto the face plate and using a suitably divided paper strip round the
outer edge of the faceplate, (as described earlier using the chucks backplate) mark
out the disk for making a dividing plate. The positions can be marked using either
a simple guided centre punch, Sk.4 or using a motorised drill spindle if one is available.
Typically, using the method, a 150mm diameter faceplate marked with 127 divisions,
could be used for making a dividing plate for cutting an imperial to metric conversion
gear. For 127 divisions each space will be almost 4mm wide, so a fair degree of accuracy
should be achievable.
This process should make a dividing plate accurate enough for most applications.
If then it is used via a worm/wormwheel rather than direct, the improvement in accuracy,
as described earlier, would almost certainly make it adequate.
Photograph 17 show the same method employed using a guided centre punch, but for
a much simpler task. This to mark out the five positions required on a simple drilling
jig to be used for drilling a cylinder and its end cover.
Having worked out the coordinates for the holes required on the division plate, they
can then be marked out using the X and Y calibrations on the milling machine. For
more details on this approach see my pages elsewhere on the site.
“Dividing” Workshop Practice series number 37
These pages have given just a very brief insight into the subject of dividing in
the home workshop, but for much more detail the above book will be helpful. Of particular
interest for many will be the number of charts that give details of the divisions
possible with many ratios in addition to the common 40:1. This typically, both 60:1
and 90:1 which are common in the case of rotary tables. Unlike the charts supplied
with a dividing head, the charts in the book give more than one method of achieving
a given division, often useful if a quoted dividing plate is not available
Also included, are charts for my version of the semi universal dividing head, photograph
9, which, because it can use most of the changewheels meshed with the wormwheel,
can achieve many divisions that the commercial unit cannot. Similarly, charts are
also included for my basic dividing head which uses solely the lathe's changewheels.
This can also achieve divisions which are not easy with other methods, particularly
in its three gear set up. Of course, the charts will be equally applicable to any
dividing head that uses a similar ratio to those available with my dividing heads.