Boring and Milling Table - Home Model Engine Machinist

Boring and Milling Table
ADDS TO UTILITY OF YOUR LATHE
By C. W. WOODSON
HE SCOPE of work that a small lathe can
T handle may be greatly increased by the use of
the slide-rest attachment shown in Fig. 1, where
it is being employed in boring holes for the
crankshaft bearing caps in a model engine.
Here a boring bar is held between centers, the
work being moved against the cutter by the
automatic longitudinal feed of the lathe. Many
such boring jobs that would be hard or impossible
to chuck in the ordinary way can be done
with this attachment, as can also light milling
operations, keyway cutting, squaring the ends of
shafts, and similar work.
All the machining necessary in making this
useful attachment, with the exception of that
on the table itself, was done in the lathe for
which it was intended. The table is a simple
iron casting made from a wood pattern, but since
it measured 7¼" by 5½" and the supporting
column sleeve was at one side, it was too large
to be handled and therefore was sent out for
machining. This work consisted of surfacing
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the top and boring the hole for the sleeve.
If the table is made smaller than this, it can
probably be turned and bored on the faceplate
of the lathe itself, but the larger size
will be more useful.
After the machining had been done, the
holes for clamping work to the table were
drilled as in Fig. 2, and tapped ¼"-20. They
may be laid out to suit individual requirements,
or the table can be left blank and
holes drilled as necessary to suit the job in
hand.
Turning the clamping screw from solid
steel (Fig. 3) was a simple lathe job. The
screw was threaded 5/16"-18, and the hole
for it drilled in the table casting before the
clamping slot was cut with a hack saw.
One half of the hole was tapped to fit, the
other half drilled out to clear the threads.
This completed the work on the table, which
is shown with the clamping screw in place in
Fig. 4.
Cold-rolled steel was turned and bored to
the dimensions shown for the base of the
supporting column (Fig. 5). The bottom
of this piece was made to fit the lathe, so
that it can be clamped to the cross slide in
place of the compound rest. Reversed in the
lathe and supported by the steady rest, as in
Fig. 6, the column was left-hand threaded
for the adjusting screw, a specially ground
cutter bit being used. The keyway was
made with a Woodruff keyway cutter while
the work was held in a milling attachment.
A brass tube of a size to be a nice sliding
fit on the column was squared on both ends
while held in the three-jaw chuck and supported
by the steady rest, then drilled for
screws to hold the key fast. The end cap
was turned from steel to a snap fit in the
sleeve, then reversed in the chuck as in
Fig. 7 for threading the hole for the adjusting-screw
guide. Drilling and tapping the
holes for the two retaining screws, which
was done with the end cap snapped into
place in the sleeve, completed the supporting
column.
The adjusting screw was made from ½"
steel rod, centerdrilled at each end and
turned between centers (Fig. 8). The lefthand
Acme threads, 10 to the inch, were cut
to fit those in the steel column. The work
NOVEMBER, 189

Threading the end cap, turning the adjusting screw, the complete set of parts for the screw, and the screw
as it appears when assembled. Below, drawings of the table, the clamping screw, and the assembled column
190
7¼
.625 1½ 3"
18 TPI.
TAP 5/16 - 18
TAP ¼ - 2O
2½
2½
SAW SLOT
2½
CLAMPING SCREW
.187
2½
1½
DRILL .312
.125
.625
½
5½
2"
MACHINE
TOP ONLY
1" .625
.375
SLEEVE
KEY
KEYWAY
.250
1"
STEEL
PILLAR
. 094
MAKE TO
FIT LATHE
18 TPI
.625
2¼ ID
½ - 10
LEFT-HAND
ACME THREAD
1"
1.375
END
CAP
5 ½
4"
.563
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The drawings below give the dimensions to be used
in machining the adjusting screw and its parts
24 T.P.I.
8"
1¾"
.375
½"
WOODRUFF
KEY FOR
BALL CRANK
18 T.P.I.
.219
.500
.875
.812
.375
1" 1"
1"
1"
.375
.625
Left, the completed boring and milling table. Above, the base of
the column and the sleeve unit with the adjusting screw in place
TAP 3/8 - 24
.187
.687
.875
1½"
TAPER
DRIVE
FIT
.625
was then reversed, and 3/8"-24 threads were
cut on the other end, after which the keyway
for the ball-crank handle was cut in
exactly the same manner as that in the
column itself.
All the parts of the adjusting screw are
shown in Fig. 9. Although the ball-crank
handle can be made on the lathe according
to the dimensions given, one from a discarded
machine may be equally suitable.
Figure 10 shows these parts assembled on
the screw, and Fig. 11 the steel column and
the sleeve. The finished accessory is illustrated
in Fig. 12, ready for work.
NOVEMBER, 1941 191