I have an application where I need to make some small stainless steel core
pins for a mold. I have some .090 spring wire that would probably work
fairly well after I straighten it. Straightness does not have to be
perfect, so I'll probably just do that part by hand. Then I run into my
issue. I need to taper it from .090" down to about .070" over a reach of
about 1.25 inches.

The only thing I could think of is to to a shallow v block and clamp that it
the tool holder on the mini lathe. Then lay a file against one end of the V
block and slowly bring it back until its just scuffing the wire at the 1.25
inch mark. The grove is to hold the wire from bending against the cutting
force of the file. My concern is if I will be able to continue to cut the
wire with the file as it work hardens from the action of the file. My other
concerns are that I have my hands so close to the spinning lathe, and that
this seems to be a very hand skilled approach to the problem.

No the pre tapered pins for sale from McMaster absolutely WILL NOT work for
this application. Besides. I already have several hundred feet of .090"
316 spring wire left over from a past project.

I guess its time to go play with a file and see....

My apologies. Accidentally posted to the wrong group.

"Bob La Londe" wrote in message
...
I have an application where I need to make some small stainless steel core
pins for a mold. I have some .090 spring wire that would probably work
fairly well after I straighten it. Straightness does not have to be
perfect, so I'll probably just do that part by hand. Then I run into my
issue. I need to taper it from .090" down to about .070" over a reach of
about 1.25 inches.

The only thing I could think of is to to a shallow v block and clamp that
it the tool holder on the mini lathe. Then lay a file against one end of
the V block and slowly bring it back until its just scuffing the wire at
the 1.25 inch mark. The grove is to hold the wire from bending against
the cutting force of the file. My concern is if I will be able to
continue to cut the wire with the file as it work hardens from the action
of the file. My other concerns are that I have my hands so close to the
spinning lathe, and that this seems to be a very hand skilled approach to
the problem.

No the pre tapered pins for sale from McMaster absolutely WILL NOT work
for this application. Besides. I already have several hundred feet of
.090" 316 spring wire left over from a past project.

I guess its time to go play with a file and see....

Bob La Londe wrote:
I have an application where I need to make some small stainless steel
core pins for a mold. I have some .090 spring wire that would
probably work fairly well after I straighten it. Straightness does not
have to be perfect, so I'll probably just do that part by hand. Then
I run into my issue. I need to taper it from .090" down to about
.070" over a reach of about 1.25 inches.

Silicon carbide wet or dry? Seems like after experimenting, that would
come up with a reliable system that worked to the tolerances you
require, unless of course, you require conical-perfection.

Bill




The only thing I could think of is to to a shallow v block and clamp
that it the tool holder on the mini lathe. Then lay a file against
one end of the V block and slowly bring it back until its just
scuffing the wire at the 1.25 inch mark. The grove is to hold the
wire from bending against the cutting force of the file. My concern is
if I will be able to continue to cut the wire with the file as it work
hardens from the action of the file. My other concerns are that I
have my hands so close to the spinning lathe, and that this seems to
be a very hand skilled approach to the problem.

No the pre tapered pins for sale from McMaster absolutely WILL NOT
work for this application. Besides. I already have several hundred
feet of .090" 316 spring wire left over from a past project.

I guess its time to go play with a file and see....

On Sun, 6 Jan 2013 15:53:54 -0700, Bob La Londe wrote:

My apologies. Accidentally posted to the wrong group.


No problem, here is a formula to calculate the internal
volume of your tapered pin.

Volume = pi (r1^2 + r2^2) L/2

r1 = small end radius
r2 = large end radius
L is lenght

This formula is also used to calculate the internal
volume of wood power poles, which are manufactured
and sold by volume, "Cubes" in that business.

Making this somewhat on topic.

basilisk

"basilisk" wrote in message
.. .
On Sun, 6 Jan 2013 15:53:54 -0700, Bob La Londe wrote:

My apologies. Accidentally posted to the wrong group.


No problem, here is a formula to calculate the internal
volume of your tapered pin.

Volume = pi (r1^2 + r2^2) L/2

r1 = small end radius
r2 = large end radius
L is lenght

This formula is also used to calculate the internal
volume of wood power poles, which are manufactured
and sold by volume, "Cubes" in that business.

Making this somewhat on topic.

While the formulas are useful, I have gotten lazy in my old age. I draw a
3D representation in ViaCad and then ask it what the volume is.

"Bill" wrote in message
...
Bob La Londe wrote:
I have an application where I need to make some small stainless steel
core pins for a mold. I have some .090 spring wire that would probably
work fairly well after I straighten it. Straightness does not have to be
perfect, so I'll probably just do that part by hand. Then I run into my
issue. I need to taper it from .090" down to about .070" over a reach of
about 1.25 inches.

Silicon carbide wet or dry? Seems like after experimenting, that would
come up with a reliable system that worked to the tolerances you require,
unless of course, you require conical-perfection.

A polished conically perfect core actually seems to be harder to release
from the casting than one that is just a tiny bit rough I have found. The
initial moment of inertia requires greater force. I'll use a parting powder
(sprayed on dry graphite) so it should be a nonissue, but there is often a
small amount of discrepancy between theory and practice. LOL.

On 1/7/2013 12:30 PM, Bob La Londe wrote:
"Bill" wrote in message
...
Bob La Londe wrote:
I have an application where I need to make some small stainless steel
core pins for a mold. I have some .090 spring wire that would
probably work fairly well after I straighten it. Straightness does
not have to be perfect, so I'll probably just do that part by hand.
Then I run into my issue. I need to taper it from .090" down to
about .070" over a reach of about 1.25 inches.

Silicon carbide wet or dry? Seems like after experimenting, that
would come up with a reliable system that worked to the tolerances you
require, unless of course, you require conical-perfection.

A polished conically perfect core actually seems to be harder to release
from the casting than one that is just a tiny bit rough I have found.
The initial moment of inertia requires greater force. I'll use a
parting powder (sprayed on dry graphite) so it should be a nonissue, but
there is often a small amount of discrepancy between theory and
practice. LOL.





That makes sense to me, as that's how the Morse taper (or any other
taper, for that matter) works. That's why you have to make sure your
taper is clean before you mate the parts, otherwise you don't get the
tight fit.

On Sunday, January 6, 2013 2:52:50 PM UTC-8, Bob La Londe wrote:
I have an application where I need to make some small stainless steel core
pins for a mold. I have some .090 spring wire ...

... I need to taper it from .090" down to about .070" over a reach of
about 1.25 inches.

I'd think of etching the wire (reverse electroplating). A bit of dilute nitric
acid, a few milliamps of current, and the metal vanishes.
Maybe it'd help the surface finish to tune it up afterward with
a bit of 400 grit sandpaper.

Pull the wire slowly from the solution to make the taper (for quick
and dirty operation, a slow-drip drain from the plating solution tank
will accomplish this).