So that the body can be easily rotated for each individual slot turn a disk a close
fit in the parallel bore in the rear of the body and fasten this to the milling machine
table, left of Photograph 5. Next, take a length of rectangular bar, say around 300mm
long and align one edge with two of the diagonally opposite markings, clamping this
to the body using a small workpiece clamp and one of the M6 tapped holes.
Place the body over the disk on the machine's table and line the bar up with the
table's axis. A high level of precision is not required so there is no need to use
a DTI, using a surface gauge with its locating pins against the front edge of the
table and checking both ends of the bar will be perfectly adequate. With that done
clamp the body to the table in that position, Photograph 6, do though fit a second
clamp as seen in later examples.
Set up an index position
Take one of your workpiece clamps or some other suitable item and clearly mark it
with a line and pack this up on the machine table to the height of the body. Position
this so that the line accurately lines up with one of the lines on the body, I would
suggest the 4.30 position, see Photograph 7.
Aligning the mill spindle.
Set up a needle point centre finder and align this with the body marking in the 9.00
position, Photograph 8, ensuring this is done with the table moving towards the rear
to take out the backlash in the correct direction. If you are not conversant with
the needle point centre finder it is held at the top in a friction held ball joint
and obviously when the mill is started up it is very unlikely that the point will
run true. With the mill running a block of metal is held on the machine table and
against the needle being advanced very gradually until the point appears stationary.
With this done the point is perfectly in line with the machines spindle irrespective
of the accuracy of the chuck holding the device. Of course, when the needle point
is used to locate the workpiece the machine is not running.
Setting the slots position
Having aligned the needle point with the 9.00 mark set the machines dial to zero
and move the table 16mm to the rear and lock the table firmly in this position so
that the setting is maintained until machining of all the T slots has been completed.