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routine like this – tight to loose – can save a lot of time.
Most users aim for an end-to-end difference of not more
than ±0.00" over the width of the vise jaw.
VISE KEYS
Most precision vises come with key slots on the un-
derside machined exactly parallel to the fixed jaw. Key
slots, Figure 3-22, can be a great time saver. Properly
installed they allow the vise to be removed and replaced
routinely, accurately enough for general machining with-
out the need for indicating every time.
Figure 3-22 Vise keys installed on X-axis
On most vises the keys can also be installed on the long axis.
Most 4" vises have either 4 mm or 6 mm slots, calling
for shop-made T-shape adapter keys as Figure 3-23. It
is well worth the effort to make these precisely. Aim for
a snug fit in both vise and table, but not so tight that it
takes more than reasonable effort to lift the vise clear.
Case hardening is recommended, with final fitting using
a fine stone or diamond stone.
Figure 3-23 Shop-made vise key
Dimensions in millimeters
PM-940M 0-206 v.indd
TAPPING OPERATIONS
When threading a drilled hole it is essential to align the
threading tap properly in the bore. The mill is often used
for this purpose, ideally with a dedicated (non-slip) tap
holder or — for production work — an auto-reverse tap-
ping attachment. The drill chuck can be used instead for
sizes up to (say) M6 or /4", beyond which the chuck
may not grip tightly enough to avoid slippage. Tapping
can be done under power, or by hand-turning the chuck.
For either method, it is essential to use a tapping fluid.
Any cutting oil is better than none, but most users find
Castrol's Moly Dee the most reliable for threading steel.
If power-tapping bear in mind that reversing is not in-
stantaneous, so be careful tapping blind holes. Be sure
the quill locking lever is free, and start trial work with the
lowest spindle speed, L-.
Turning the spindle by hand is easier if you select
H-3. Revert to L-1 if backing out under power.
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