If the 0.070" is at the end of the wire set up for electropolishing and
repeatedly dip the wire into the solution and remove it. I've made needle
points 1/8 to 3/8" long that way, you should be able to do 1.25" of taper.
I was never successful just slowly removing the piece from the solution
once, it was too irregular. Repeated dipping averages all of that out.
With the tiny surface area you won't need much of a power supply, maybe 5-10
V and 1 amp.

-----
Regards,
Carl Ijames
"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....