Re: Thread milling!!

Jon,

Welcome to the world of thread milling...

Thread milling opens up all kinds of possibilities. You can easily
cut perfect "bottle" threads (like on plastic bottles)among other
types.

I impressed a customer by cutting a 4"-4tpi in a piece of 2" thick
steel plate. Took a few passes to get to depth, but I don't know any
other way to do it.

I like to use a lathe threading bar for thread milling. The insert
type work well. A 60 degree wheel cutter is good for external
threads, too. Your way with a tap is good since the price is right.

One time I ran across a chart giving the maximum cutter diameters for
given thread sizes. Wish I'd saved it. Have you seen anything like
that? For high quality threads that relationship is important.

Before I had a machine with helical interpolation I'd generate a
cutter path made up of short line segments using a spread sheet
program. I had it setup so I could specify a diameter, pitch and a
guess at the number of segments for a 360 rotation. The program
outputted the line segment deviation from a true circular path, so if
the deviation was too great it was simple to choose a higher value
until the deviation was acceptable. With a fairly large number of
line segments you'd be hard pressed to tell the difference between a
true helical path.

Doug

--- In CAD_CAM_EDM_DRO@y..., Jon Anderson <janders@n...> wrote:
> Have to make a couple parts for a design project I'm working on.
Last
> minute change resulted in needing a bottom tap in a size I don't
have
> and it's too late to order from MSC. I'm hoping to have the parts
done
> over the weekend. So, ground up a broken 1/2-13 tap to leave a
single
> tooth, dug out the manual, played with it a bit, and viola! A
perfect
> thread in nylon. Now to see if my cheesy cutter will work in 6061...
>
> Jon