awesome project.

i

On 2010-07-11, DT wrote:
As part of a custom machine I have been fabricating (later) I needed to
broach 1/4" keyways in 1 1/8" holes in two steel flywheels and two
collars. I figured no problem, just call up a buddy where I used to work
and see if they can press them in the shop. To my surprise they no
longer have an arbor press with a high enough throat to press the 12"
long broach. Several friends have home hydraulic presses, but they have
short strokes and you need to do a lot of resetting to get a broach
through, at least two presses and maybe three for each pass of the
broach, two passes per hole. That's a lot of fussing around. Hmm.

So, I sez, let's build a press just for broaching. I have two possible
hydraulic sources. The first is one of those cheap, 4 ton manual
Porta-Power sets. But they are very high pressure (10,000 psi) and use
small diameter cylinders. I didn't think I could find a sub 1" cylinder
with a 12" stroke. Even then it would be a lot of pumping.

My other source is an old 12 volt hydraulic system that operated a
Corvair convertable top. I built it into a tire bead breaking machine
about 35 years ago and it works fine for that, but I no longer use it. I
put a gauge on it and it just hit 300 psi as it stalled out.

A quick email to DuMont and they said I needed 700 pounds of force for a
1/4" broach in 5/8" mild steel. A 2" piston would give me around 950
pounds.

I looked on the HGR Surplus web site and they have lots of pistons. I
drove over and immediately found a 2" diameter, 12" stroke cylinder,
brand new for $19.99. Cylinders are real cheap at HGR, most are $10 or
$20.

Since I already had a C frame for the tire machine, I just cut it down
to the correct height and bored a few holes and mounted the cylinder on
top. The hydraulic pump mounts on the upright and the existing steel
braided lines were just right. I'm good to go, only a few hours of work.

I cycled her back and forth for a while to bleed the air then give it a
shot. It does flex too much, I'll have to add a strongback to the 4"
channel frame. And I actually had to start the car I had it hooked to,
the extra couple of volts gave me just enough to push through, but it is
at the absolute limit with a 1/4" broach. Every keyway broached
perfectly, and those shaft collars were tough steel.

Here is a photo:

http://home.wideopenwest.com/~dthomp.../broaching.jpg

Dennis