Civil Engineering Reference
In-Depth Information
Tighten the chuck
On the cheaper dividing heads usually found in the amateur's workshop, the
chuck will be threaded to fit on the spindle. This isnot ideal asthe chuck could
possibly come loose. So screw the chuck onto the dividing head, place the
chuck key into the chuck and give the key a slight tap with your hand to en-
sure the chuck is tight up on to the mandrel as far as it will go. There is no
need to use a hammer to tighten up the chuck.
Now that the chuck is tight on the spindle, as long as we mill from the front
of the table towards the back so the pressure on the chuck is in a clockwise
direction, the chuck will tighten up rather than undo if it moves at all. If in any
doubt that the chuck is sufficiently tight to resist movement, put a piece of
scrap material in the chuck and take a milling cut from the front to the back to
make sure the chuck will not rotate on the spindle.
SOME COMMON JOBS
Milling a hexagon head
One of the most common things you may be called on to do in the dividing
head is to mill a hexagon head on the end of a bolt.
If the bolt has a parallel shank you may be able to hold the bolt in the chuck,
but normally the bolt would be threaded and you will have to put the bolt into
a threaded mandrel in the chuck. If this is the case, tighten the bolt up using
a pair of pliers or mole grips on its head prior to milling the hexagon. It does
not matter how tight you do the bolt up as long as it will not come undone. It
will be easy to remove the bolt from the mandrel when you have milled the
hexagon; just use a spanner on the newly formed bolt head to undo it.
To mill the hexagon, take a small cut on one side, rotate the dividing head
180 degrees and take another cut at the same setting. Measure the width
across the two flats - this is the AF (across flats) dimension. Say we are
milling a 10mm bolt head and the AF dimension we have just measured is
19.5 AF; the AF for a 10mm bolt should be 17 mm so we have to remove
2.5mm, or 1.25 from each side of the bolt head. Raise the table 1.25mm and
mill all six flats, and we will have a 10mm hexagon bolt with an AF of 17mm.
Job done!
