On Aug 27, 10:16 pm, "Michael Koblic" wrote:

This is where I run into a bit of a problem - drilling the centre hole.

The candlestick was made in India, I am not sure how.

Probably cast. They had sophisticated metalworking skills when my
ancestors were still pounding rocks together. AFAIK it was all done in
small family shops with simple equipment and never grew into an
industry. Holtzapffel book IV, "Hand or Simple Turning" has the best
description I've seen of the traditional lathes of the Middle East and
Asia and the details of Western lathe development to 1880. You might
find the book very useful because the earlier versions were easier to
make than a modern lathe. "Simple" is relative; the Holtzapffels were
masters of the geometric or rose-engine lathe.

The Indian lathe pictured is made of two short stakes driven in the
ground with nails through them for centers. The tool rest is a stick
tied between them with extra supports as needed. The turner rests his
foot on the stick with the tool between his toes for coarse
positioning, and guides the end with his hand. A kid pulls the ends of
a string wrapped around the work to turn it back and forth. The Arab
lathe is only slightly fancier, a box close around the work. He has a
bow in one hand to turn the work with the string.

The lathe doesn't drive the work, it only supports it between centers.
You could turn the work directly with the motor and belt from an old
sewing machine, or a rubber caster wheel chucked in a hand drill. Be
creative, think of things as what they could do rather than what they
were meant for.

Your candlesticks may well be copied from a 2000 year old design cast
from a wooden pattern made this way. The manual skills of artisans
2000 years ago were easily equal to those today. Perhaps now those
people are surgeons rather than craftsmen.

As Watt quickly discovered, those artistic skills didn't apply to
making precision machinery.

Either way not very
well so the whole thing is a bit asymmetrical. I tried to determine the
centre of the end to drill a concentric hole but found it almost impossible.
In the end when hooked up to the live centre (which is loose on the drill
press table) the live centre was running around in a small circle whatever I
did.

Fix that. A large pointed setscrew held by nuts and washers might
work. If you make the head slide down as I suggested you can drill
another small hole in the base plate near the large one. You can align
them with a piece of wire in the chuck, bicycle spokes work well. Turn
it slowly by hand and try to make the circle the point describes small
by bending the wire. Move the head until that small circle is centered
on your center point. You can check it with a ruler.

Now I understand (I hope!) that on a lathe the live centre on the taistock
is lined up with the centre of the chuck on the head stock and the hole will
be drilled in the centre by default. Not having a lathe the best way I found
to drill centres in a round stock is to make a paper tube around it and use
a tight fitting transfer punch to mark the centre. This works fine if the
stock is cylindrical, not on a candle stick stem which is not.

Make a pair of upright Vee supports out of thin material. Rest the
candlestick on them at places you consider circular. Turn it while
holding a supported pencil against the end. The pencil will mark a
small circle around the rotational axis.

How well did you learn Euclidean geometry? It has methods for finding
the center of a circle or any other shape. One simple way is to guess
at the center, put one point of a compass there and see how far off it
is when you rotate it. Find where the compass is out furthest and
correct half the error by moving the center point, then readjust the
other point to the circle and recheck. For me this centers within
about 0.010".


I found a thread on this group from 2004 which provided several options of
which the only one viable in my situation would have been to use a 3-jaw
chuck to center under the drill press spindle and then substitute the centre
drill. And I am indeed looking for a cheap 3-jaw chuck.

Are there any other suggestions ("Buy a lathe!" does not count)?

The other thing that puzzles me (and please note that the nearest I have
been to a lathe is in the movies and picutres in books) is how do you start
turning something that is irregular in shape? Or even how do you turn a
round piece out of a square stock? Does it not do horrible things to the
cutting tool when it contacts only at the corners? Or is there a trick to
get the shape roughly round first somehow? I want to change the shape of the
brass cup but the initial attempt was somewhat discouraging.

Brass is a little tricky but it has been turned into exquisite shapes
like watch gears with hand-held tools for centuries. Heron of
Alexandria's ancient Greek gadget book used (brass?) sheet metal and
turned shafts as if they were common hardware items back then. His
book described a steam engine and also a vessel with a secret
compartment that appears to turn water into wine.

If you keep the tool's support close to the stock you avoid those
horrible things, otherwise the lathe may practice knife-throwing. I've
only done a little free-hand turning of aluminum and can't give you
much detailed help. Trying to work metal without machine tools is like
going everywhere on foot.

When I turn something from oak firewood I draw circles on the ends and
rough the blank close to them with a hatchet. On a real metal lathe
HSS bits stand up pretty well to interrupted cuts like turning a
square steel plate round, just take light cuts. This is one of the
jobs that makes a screw-on chuck hard to remove.

You can use that drill press center point to drill a centered hole
straight through a long piece.

Jim Wilkins
who -should- be out scraping paint.