On Fri, 8 May 2015 13:27:18 -0700 (PDT), whit3rd
wrote:

On Thursday, September 19, 2013 at 10:07:56 AM UTC-7, Ed Huntress wrote:
On Thu, 19 Sep 2013 08:49:21 -0700 (PDT), PCS
wrote:

I would think your push bar problem is less about compression and more about bowing.

It's so constrained by the bore that there would be no significant
bowing.

I'd think that it's important for the mating faces to match well and
to be most of the bore diameter.

So, does this mean your pushrod can be a stack of dowel pins, all ground flat on the
ends? The case-hardening of a dowel pin makes good burst (compressive) strength,
and a dozen two-inch pins doesn't break the piggy bank.

I've heard of using hydraulic force to push a button through a (threaded) barrel.
I wonder if some type of a grease gun would have enough pressure?

Hydraulics might work, but that just makes this BIG project. Easily available
hand pumps will do 10kpsi, fluids will go to 50-100 kpsi (with custom pumps).
If the pushrod is a piston, 0.3" diameter, it only gets 900 lbs force with
10kpsi.

PUSHING makes it a big project. Pulling makes it much easier.

There's no reason you can't pull a button, although the tools
generally are made for pushing. Cutting tools usually are made for
pulling.

If you can lap a barrel, button rifling doesn't hold any great
advantage. It's a production technique. It allows you to use a lower
grade of steel, because it work-hardens, and it leaves a cleaner bore
that needs less finishing.

But in the end, either one will work.

--
Ed Huntress