"Jim Wilkins" wrote in message
...
On Aug 28, 11:51 pm, "Michael Koblic" wrote:
"Jim Wilkins" wrote in message
Some "thoughts" would make your hair stand on end...:-)
What little hair is left... :-( (that's a beard, I grow it wherever
I still can)
I've run the model shop in electronics companies and thus dealt with
the creative misadventures of clever engineers with no practical
experience.
Judging from your e-mail address you will understand how electronics were
done by amateurs before the advent of the black boxes. Except we did not
have black boxes: we had Wehrmacht surplus. And ingenuity. And fire
insurance...
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.
A large pointed setscrew held by nuts and washers might work.
Setscrew pointed upward for the center, nuts and washers to hold it
tight in the hole.
I see. I could actually clamp the "live center" in a drill press vise and
position it. 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...
...You can align them with a piece of wire in the chuck,...
I have re-read this about six times and I am not altogether sure that I
understood: I have no difficulty aligning the centre point of the live
centre with the centre of the spindle. However, when I chuck the gnomon
and
put the opposite end on the live centre (using the supposedly centre hole
I
drilled), the gnomon, being slightly out of alignment, moves the live
centre
around.
http://www.lindsaybks.com/bks/advmach/index.html
Don't be put off by its age. Production techniques may have improved
dramatically since then but manual lathe operations are still the
same.
For that I thank you. In fact I have been actively looking for older texts
which are more in keeping with what I am doing. I think I mentioned the old
blacksmith book with wooden bearings etc. He goes into lathes a bit but not
in enough detail (where, as far as I am concerned, is where the God is).
I am waiting for my first order from Smartflix so I can see these things
actually happening. They have some extensive courses on milling and lathing.
If it works out renting from them I should move forward more quickly. In any
case, I have ordered the book you recommended.
If the chuck doesn't hold the part straight you mount it between
centers and drive it with a dog.
I think a 4-sided pyramidal point held in the drill chuck is enough to
drive brass without a dog if you take light cuts. You don't need to
make the point run perfectly true as long as you mark it so you can
remove and replace the work.
Does the dog not object? Juvenile humour aside, now I have to study how to
use a dog! I thought a dog was a sort of bent thing which held parts to a
face plate if you did not have a chuck...
How well did you learn Euclidean geometry?
The euclid works if the cross-section is truly circular.
There are constructions for centering even a triangle.
A quick shortcut I often use is to center a thin 6" flex rule across
the work by equalizing the end readings.
For example one end is at 1-1/8", the other at 4-7/8".
Hold a scriber point against the work at the 3" mark, then turn the
rule 90 degrees and repeat.
I like the style of graduations called 3R for this.
3" yes. 0.3" no...
but the transfer punch/paper roll method beats it every time particularly
for small parts.
That's a good idea I hadn't seen before. Then again I have a collet
lathe which is the perfect machine for making small round parts. Mine
would be a little more perfect if it hadn't been abused in trade
school. A small lathe with a 3-jaw chuck is close.
http://www.mini-lathe.com/
Ha! You heard it here first! I have never seen it myself elsewhere, it just
came to me when I was trying to drill centre hole in the end of a 3/16"
copper rivet to stick on the end of my gnomon. I had to make another jig to
hold the rivet in the drill press vise but it works just fine.
Maybe with a centre drill you do not need to punch? Am I right in that?
See the center/spot/stub drill thread. With less rigid equipment like
your drill press and my 50-year-old milling machine you have to learn
what works and what doesn't. The punch mark is to align the drill bit
with your hand layout since it's very difficult to position the center
of the drill bit directly.
I have been following that thread - and I was not sure. I bought a centre
drill and promptly broke one end. The other end worked well, but I used a
punch. I believe you have to run them quite fast.
As an update: I bought a $17 Jacobs 1/2" chuck today and was able to chuck
one of the brass cups in it safely and tidied it up by the "reverse lathe"
method of holding it and rotating it by hand against a 220-grit belt sander.
I even found 3 1/2"-20 bolts of different lengths and am thinking of making
a jig to drill concentric holes along the lines recommended in the 2004
thread (there they used a wooden block on its side to drill a centre hole in
a long rod - rather ingenious I thought).
--
Michael Koblic,
Campbell River, BC
-ex OL1AGS
-ex G4GIU
-ex GW4GIU
-VE7EQG (QRT 7 years)