The material is now moved from the chuck sufficient for the length to be turned and
the cutter set just short of the end of the material. In this position the arms will
already be supporting the material. The lathe can then be started and the saddle
traversed to reduce the diameter to that set, Photograph 9. It is essential that
once the cut has commenced it continues to the end without stopping, more about that
If the diameter is being reduce to that required in one go this is definitely the
preferred method. However, if a piece of 20mm diameter steel had to be reduced to
6mm over a long length then a depth of cut of 7mm would be required to meet that
aim, obviously this is too much for the smaller lathe . For this the material would
have to be reduced in stages. This presents two problems. 1. After the first stage
the workpiece will be projecting too far to use the setup method above, and 2. With
the arms leading the cutter the next stage would have to stop short of the initial
reduction in diameter.
The following will overcome problem 1. Having made the first reduction by the method
above, move the the saddle back a little from the previous finishing position and
reset the arms on the reduced diameter just made. Then, move the cutter to just clear
of the end of the workpiece and using the cross slide set on an additional depth
of cut and repeat the machining process. If now we have taken two cuts of 3mm deep
the diameter will 8mm which still needs to be reduced to 6mm. If the final diameter
is relatively unimportant the existing diameter can be measured and from this the
cross slide can be set and the process repeated. If the final diameter is crucial
then it may be required to make a cut to get even closer and then repeat the process
making just a light cut. However, travelling steadies require a reasonable depth
of cut to keep the workpiece against the steady's arms so this is not ideal.
Having now used the method there will be steps at the end where the arms prevented
the cutter producing the full length each time. This though is easy to overcome
as these being near to the chuck the offending metal can be removed conventionally
unaided by the arms of the travelling steady.
Method 2. When dealing with round material method 1 is definitely the method to use.
However, if one were attempting to make a long screw with an hexagonal head then
it is quit impossible for the steady to lead the cutter and therefore the cutter
must lead the steady, Sk. 3.B. Set up is therefore different to that above for round