"DoN. Nichols" wrote in message
...
If you add a V block to the vise to keep things from shifting.
upright round objects are difficult to clamp reliably in a vise, but add
a V-block and you can do a better job with a cylindrical item. However
a live center typicaly has a Morse taper shank, so you'll need some
extra tricks to make up for the taper itself.

My vise has a sort of vertical v-block incorporated. My "live centre" really
only remotely resembles a proper lathe live centre.


I was just thinking what kind of rotation will happen to the
piece if its so bent that it moves the centre around when *not* clamped.
I
guess it will find a way...

It is used with a face plate, to impart rotation to a workpiece
suspended between centers. The one in the headstock spindle rotates,
but it does not have enough contact area to really drive the workpiece,
so the dog is clamped onto a part of the workpiece which you are not
(currently) changing, and its tail is driven by a slot in the faceplate
(if a bent-tail dog), or by a bolt through the faceplate (if a
straight tail dog). These do not wag. :-)

For that you need a wiggler?

If you are trying to drive something with a drill chuck which
has a poor enough finish on the end so you can't clamp it and prevent it
from wobbling, then you clamp the drill chuck onto some steel rod, take
a file to it while it is rotating to form it to a point (60 degree
angle), and use this to hold the upper end of your workpiece. You will
then need to clamp a bent-tail dog onto the upper end of the workpiece,
and a collar of some sort around the drill chuck to drive the dog's
tail.

OK, now I found some nice pictures and I understand it. Sort of.


Another thing to worry about is that most drill presses don't go
slow enough, and if the workpiece, collar, and dog are not fairly well
balanced, the drill press will try to walk around the floor (or the
workbench, if it is a benchtop drill press).

At this point using the canine arrangement on my drill press fills me with a
sense of dread. Also, the parts I am turning are very small, so a really
small dog would be required. A chihuahua...

How large a diameter of center drill? The proper speed for one
is a function of its maximum diameter -- and the metal into which you
are drilling.

1/8"


To avoid snapping off the point, you need a way to prevent the
workpiece from tilting in the drill press. Also, a proper
coolant/cutting fluid would help them to survive. But center drills
(like all drills) are "consumables" so keep spares on hand.

I swear the first one snapped just by me looking at it...

I just took apart a very old Sears cordless drill and liberated a 12V motor
as well as a 3/8" chuck and a whole bunch of cool little gears. Also I found
an old 12V motor with some strange reduction gear which, many years ago was
going to be a pottery wheel for kids. Some of this stuff has got to be
useful even though 12V is not exactly ideal.

If it was straightforward it would not be fun...

--
Michael Koblic,
Campbell River, BC