Tc 9-524 fundamentals of machine tools

8-13

---

TC 9-524
mounting the various holding devices and attachments. These
T-slots extend the length of the table and are parallel to its line
of travel. Most milling machine attachments, such as vises and
index fixtures, have keys or tongues on the underside of their
bases so that they may be located correctly in relation to the
T-slots.
METHODS OF MOUNTING WORKPIECES
Clamping Workpieces to the Table
When clamping a workpiece to the worktable of the milling
machine, the table and the workpiece should be free from dirt
and burrs. Workpieces having smooth machined surfaces may
be camped directly to the table, provided the cutter does not
come in contact with the table surface during milling. When
clamping workplaces with unfinished surfaces in this way, the
table face should be protected from damage by using a shim
under the workpiece. Paper, plywood, and sheet metal are
shim materials. Clamps should be located on both sides of the
workpiece if possible to give a full bearing surface. These
clamps are held by T-slot bolts inserted in the T-slots of the
table. Clamp supports must be the same height as the
workpiece. Never use clamp supports that are lower than the
workpiece. Adjustable step blocks are extremely useful to
raise the clamps, as the height of the clamp bar may be
adjusted to ensure maximum clamping pressure. Clamping
bolts should be placed as near to the workpiece as possible so
that the full advantage of the fulcrum principle may be
obtained. When it is necessary to place a clamp on an
overhanging part, a support should be provided between the
overhang and the table to prevent springing or possible
breakage. A stop should be placed at the end of the workpiece
where it will receive the thrust of the cutter when heavy cuts
are being taken.