DoN. Nichols wrote:
According to :

[ ... ]

It would seem to be more reliable(though not easier or cheaper) than
using Delrin rods.

It may well be cheaper than using Delrin rods. After all, these
are mass produced to standard diameters and lengths. Delrin tends to be
rather expensive (though something like 1/8" diameter rods would not be
that expensive, and you would simply have to turn them to the desired
final diameter and cut them to length.

I do have a lot of Delrin that I could probably make as many pins as
I'd need.(Though turning it down to 1/8" of an inch may be asking a lot
of the lathe). :-)

Hmm ... how big is the Delrin to start? Anyway, if you are
turning a length down to 1/8", and the length is something like 9/16" or
so, it *will* bend as you try to turn it. The way to accomplish the
task is:

I have Delrin of Different shapes, but I'd use the scraps which are
basically about 1-1/2" x 2.00" X 12". I'd take it to a band saw first
to make it manageable for the lathe to turn down.

1) Start with a very sharp HSS tool -- ground to the angles
which are right for turning Delrin. (Note that carbide inserts
are usually a bit too dull to do this job well, though the tiny
uncoated inserts for my Compact-5/CNC tend to be quite sharp
enough. They are hard to find, and are usually quite expensive.

2) Turn only the end-most 1/8" down to 1/8" diameter.

3) Then turn the next 1/8",

4) Repeat until you have enough length to part it off to your final
length.

And -- don't have any more of the Delrin sticking out of the
chuck than you plan to turn for that one part.

Thanks. from what I've read, I should treat Delrin like Stainless steel
as far as the sharp tool and cutting speeds.

I also have several 4" diameter Delrin cylinders that are about a foot
long, I'll be slicing them into 3/16" or 1/4" thick disks that I'll
need to do six plunging operations involving making different sized
holes/slots in each of six equal "pie" slices.

The roll pin expands to fit the hole, within reason. But
without special fixturing (other than the V on the top of a bench
block), I would suggest that you drill through both the sleeve and the
rod at the same time. The hole may wind up a bit off center, but it
will be the same for both parts, so the roll pin should fit through it
easily enough.

What if I used a sharp punch of some sort to start, followed by a
center drill in the lathe, and then drill after that? since the 1/8"
hole is only 1/8" from the bottom I'd probably have to balance things
by using a tube with a 7/16" I.D. to fit over the rod/sleeve,
effectively lengthen it so it would slip out of the chuck.

Hmm ... how do you plan to use the lathe for this? I thought
that the hole was from one side to the other, not into the center of the
end.

I think my wording int hat last paragraph was bad, because a chuck
couldn't be used.

First I wanted to be clear that the purpose of the S.S. sleeve situated
around the turned down portion of the S.S. rod would be to keep three
1/16" plates(Delrin/stainless/Delrin) from sliding off.

Now. yes, the 11/16" long(7/16" diameter) sleeve will have the turned
down end of the rod already inserted into it so I can drill the 1/8"
diameter hole all the way through *both* at the same time. That 1/8"
diameter hole will be located only 1/8" from the end, so gripping it so
it could be drilled would pose a problem.

My idea is to make a "holder" out of a 5-1/2" long, (perhaps 1"
diameter) steel rod. I'd mill a 7/16" wide slot(1/2" deep)down about
half of it's length, so I can place the work(S.S. rod/sleeve)inside it.
The un-slotted end of this "holder" would be bolted to a face plate,
and the threaded end of the work(opposite the sleeve) would be screwed
into a 1" square block which would also be bolted to the face plate.
This would keep the work(S.S.rod/sleeve) from turning in the "holder".

After it is secure to the faceplate, drilling all the way through it
would entail a tool steel punch, followed by a center drill, followed
by a drill bit to get the 1/8" diameter hole(all the way through).

Now of course I'd have to slot and drill through the "holder" first.
:-)

If the holes must *all* be the same distance from the end, you
will want a V-block clamped to the drill press table, with a stop to
keep you from sliding the workpiece in too far.

Ok. If a $50 drill press would be easier then I will get one.(Hopefully
better than my last one).

P.S: I'd like to point out that I discovered that the 5/8" thru-hole in
my lathe was not a reference to the spindle bore. The spindle bore is
..787".

This is the part that I misinterpreted: "3-jaw self-centering chuck
(bolts to spindle: 2-3/4 inch capacity, approx. 5/8 inch dia.
thru-hole)."

Thanks a lot.

Darren Harris
Staten Island, New York.