August 2019 27
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Milling for Beginners
beginners who will already have ER collets
to fi t the chuck for their mill. In use it is best
to have the back of the nut against the
side of the vice jaw which acts as a length
stop. It is then simply a case of taking cut,
stopping the machine and repositioning
the ER block with the next face against the
fi xed jaw or bottom face of the vice, then
taking another cut and so on, photo 149.
Do take care to ensure that the block is
sitting fully down in the vice as there can
be a tendency for them to tilt if the piece of
work is protruding a long way out the back,
it should also go without saying that swarf
should be cleaned out of the chuck at each
resetting so that does not throw the work
out of position.
Collet blocks are also available to take
5C collets which are more oft en used for
work holding on the lathe. These are used
in much the same way as the ER blocks
except as they do not have a projecting nut
a vice stop needs to be used if you want a
set length of cut. Photograph 150 shows a
square being formed on work in a 5C block
and a stop screwed to the side of the vice
jaw. This is the best form of stop as it makes
it easier to slide the block out of the vice for
repositioning which does not need the tool
moved as far between cuts to get clearance
as it does to lift an ER block up and out of
the vice or if a rear stop was used on the 5C
block.
Indexing is not just limited to machining
external features, it can be used to ensure
such things as holes, slots, etc. are at
the correct angle relative to each other.
Photograph 151 shows the end of some
round stock that has fi rst been squared
up as described earlier, then the work has
been centred in the Y-axis and a hole drilled
which will ensure it is at right angles to
two opposite faces. In photo 152 the block
has been stood vertically with its next face
against the vice jaw and a slot has been
milled which will now be at right angles to
the hole. Provided the Y-axis was locked
between these two operations the slot will
also be central to the work so no need for
centre fi nding twice.
The same setup as shown in photo 152
with the block stood vertically can also be
used to drill four and six hole patterns on
a PCD if a suitable stop is used to locate
the block against so it remains in the same
X-axis position each time it is reset.Indexers
As well as giving a greater choice of
increments than 4 or 6 sided blocks an
indexer makes the job a lot faster as it
can quickly be spun around to the nextposition which saves a lot of time over the
stop-reset- start of blocks and if doing
something like a batch of hex bolts makes
the process a pleasant one.
Probably the most common one used for
hobby work is the “spin indexer” which is
designed to take 5C collets but a 5C to ER32
can be bought for them but the best option
is to get the “Stevenson” version from our
sponsors ARC Euro Trade as this comes
complete with a special sleeve and closing
nut that allow ER32 collets to be used as
well as the usual 5C with the added bonus
of reduced overhang.
They work by having a detent which
engages in a series of holes in an indexing
plate and the one supplied generally has
36 holes. To use the spindle lock is fi rst
loosened and the pin retracted then the
spindle and the division plate which is
fi xed to it is rotated to the desired position,
pin pushed into the hole and spindle lock
tightened. For simple indexing of numbers
that will divide into the plate holes such as
2, 3, 4, 6, 9, 12, and 18 the pin is kept in the
zero hole. If you need a number that will not
divide into 36 then the additional holes can
be used for any whole degree divisions such
as 36, 45 and 72 degrees should you want
10, 8 or 5 divisions. Photograph 153 shows
an octagon that was indexed with the pin in150 151
152 153
5C block in use showing positioning stop Drilling hole square to faces of square
Milling a slot central and at right angles to hole Octagon milled with spin indexer