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....
On Sun, 6 Jan 2013 15:53:54 -0700, Bob La Londe wrote:
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. :)
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 Sunday, January 6, 2013 2:52:50 PM UTC-8, Bob La Londe wrote:
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).
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