Civil Engineering Reference
In-Depth Information
Autolock holders
Another type of cutter holder is the Autolock holder made by Clarkson. This
holder is made for cutters that have a threaded end and parallel shank with
a centre in the end of the shank. The pitch of the thread is a slightly under-
size 20 TPI Whitworth form and is constant over the entire range including the
metric cutters; only the shank diameter varies.
These threaded cutters fit into a special collet which in turn is fitted to a spe-
cial holder. The holder has an internal back centre to locate in the centre of
the cutter shank. The front of the holder has a special nose angle that locates
the front of the collet in the milling chuck locking nut.
FITTING A CUTTER TO AN AUTOLOCK HOLDER
Screw the cutter into the collet, fit the collet inside the nose piece and screw the nose
piece onto the main body. Adjust the cutter and collet until the nosepiece closes up
completely. Undo the nosepiece about
1
⁄
3
of a turn and tighten the cutter by turning
until the tool shank is firmly in the centre fitted to the holder. Tighten the nose piece
the last third of a turn and the cutter will be locked.
I do not recommend using
1
⁄
4
in (6mm) diameter shanks in an Autolock hold-
er, as the small diameter shank is liable to break at the centred end especially
when the holder's centre is worn or damaged.
If you are offered an Autolock holder with a damaged centre, I would not
buy it. It is almost impossible to remove the centre for regrinding or replace-
ment. It can be done but it takes a very heavy duty press and a lot of brute
force. It took me a couple of hours to remove a centre and it finally came out
like a bullet. It is far better to buy an Autolock holder with the centre in a good
condition.
