The most helpful step for me, is to make a flat spot on a round surface, as
Joe mentioned.
A small, center-cutting endmill will do a good job, but a file an do just as
well at making a small flat spot.

Many vises don't hold a single small part well, beause the moving jaw often
has some play in it.
Making plates that can be temporarily fixed to the vise jaws (even
double-sided tape), with 2 sets of holes in the plates will allow 2 dowel
sections to be held at the same time (perpendicular to the jaw faces),
ensuring that any vise jaw movement will be canceled.

Drilling 2 sets of holes that are the diameter of the dowel sections, and at
the same horizontal height, should make easy work of creating the small
flats with a narrow file (or the edge of a wider file), since each workpiece
will act as a guide for the file.

The holes in the temporary jaw plates could be blind (thick plates) or thru
holes (thin plates), and it probably won't matter if the workpiees aren't
exactly the same length, as many vises will tolerate less than perfectly
parallel jaws.

The drilling steps could begin with a center drill, but a short, stiff
split-point drill, as DoN suggested (chucked as close to the drill point as
practical) should be adequate, eliminating the need for a center drill.

If for some reason the drill walks, using an automatic center punch or a
slight tap on a prick punch should allow the hole location to be
predictable.

For long workpieces, a set of soft jaws could possibly be machined along the
jaw joining line with a ball endmill (deeper than the workpiece radius), I
suppose (haven't tried it). The resulting trough would hold a round section
at any point for cross drilling at any point along the length.
This holding method would require a fairly well-made precision vise so the
moving jaw wouldn't creep up as the vise is tightened.

--
WB
..........
metalworking projects
www.kwagmire.com/metal_proj.html


"Michael Koblic" wrote in message
...
How do you drill cross holes in small cylinders (brass or steel). The
cylinders are 3/8 - 1/2" in diameter and often less than 1" in length. The
hole is 1/4"

I am having all sorts of problems with this: The clamping is limited as
the clamps often interfere with the drill, especially centre drill. I find
it impossible to clamp both ends of the cylinder for the same reason. I
tried drill press vise, v-blocks, side-ways chucks, you name it.

What usually happens is that the part tends to flex somewhat and even if
it does not there is horrible chatter.

Some sort of sacrificial v-block? But the part still has to be held in it
somehow.

--
Michael Koblic,
Campbell River, BC