Steve Smith wrote:

As I commented to the other Pete, I don't know a thing about
air/hydraulic. How come the instructions recommend squeezing the air
valve and pumping the handle at the same time? Hopefully you don't have
to rub your tummy too.

The instructions are a bit hinky. With the release valve at the front
closed, applying air (squeezing the air valve) will cause the press jack
to raise (press to lower if in a press). You release the air valve to
stop the jack.

In the case of a press you might want to use air to bring the press to
the contact point and then manually pump the press so you can operate
more slowly and have a better feel if you're pressing an expensive
bearing. If you're doing something less precise then operating on air
alone is fine.

Another trick if you add some sort of handle to the release valve (I
just hacked an old screwdriver handle to fit) is that you can leave the
air valve in the locked on position and control the press entirely from
the release valve. It uses a lot of air and is a bit noisy, but when the
release valve is open the pump will just circulate the oil and the
return springs will retract the press. Close the valve and it goes down,
open it and it goes up.


Noisy? Sounds like my press...

Probably comparable overall. A hydraulic power unit will be a constant
whirring, where the air/hyd jack is a rapid put-put-put when it's in
action.


So the air/hydraulic uses air to turn a hydraulic pump?

Not turn, cycle, it uses a piston pump (reciprocating) just like the
manually operated piston pump. In fact if you're impatient you can pump
the manual handle while the air is running and move the jack faster.
Overall speed is probably along the lines of 1/4" / second which is fine
for general pressing, but probably slow for the forging application.

Pete C.