Civil Engineering Reference
In-Depth Information
We can use the same principles to mill any number of flats on any bit of bar
held in the chuck, from a single flat to multiple flats.
Milling dovetails
You can mill dovetails using the dividing head. Bolt a strip of flat metal onto
a bar held between the chuck and the tailstock. This bar can be square,
hexagon or round. If round, mill a flat on it sufficient to mount the flat bar on.
The flat bar must be parallel to the machine in the table's X axis. The Y axis
is not so important as long as there is sufficient material to clean up.
Rotate the dividing head so the edge of the flat bar is at the required dove-
tail angle and mill the dovetail. Rotate the dividing head so the flat bar is ro-
tated to the other side of the dovetail and mill it. You now have a very accur-
ate dovetail made with the minimum of effort and measurement. If you do not
want holes in the main face of the dovetail slide, either make the dovetailed
piece longer and cut to length after milling or use a clamp at each end of the
slide to avoid the holes.
Milling a gear wheel
You use the same method to mill a gearwheel as you do to say mill flats on a
bit of bar. The main difference is the shape and form of the cutter. The gear
cutter will have multiple teeth and the gear blank will need indexing by the
exact number of teeth in the gear. The gear cutter must be set at the exact
centre height of the dividing head. To do this, use a height gauge to measure
the difference from the top of the gear blank to the top of the gear cutter. This
dimension should be
1
⁄
2
the bar diameter less
1
⁄
2
the cutter diameter assuming
the cutter teeth are central in the cutter thickness. Set the height of the cutter
using the height gauge.
The gear cutter should be on the far side of the dividing head and the gear
cutter should be rotating in the same direction as a normal twist drill. The gear
cutter should be moving through the gear blank towards the chuck. If you
don't have agear tooth vernier, makethe gear blank diameter to nominal size,
touch on to the outer diameter of the blank and take a depth of cut according
to a tooth depth chart or a tooth depth calculation. Doing it this way should
ensure the gears mesh correctly.
