John, I'm a blacksmith and I have a powered, hydraulic forging press
that I've used to make Damascus with. I haven't seen Steve Dunn demo,
don't know his techniques, but I don't think you're going at this in a
way that will work.
In my experience, the main issue in forging or forge welding with a
press is being able to drive the press tooling into the work faster than
the work cools. About the worst case is welding a Damascus billet--big
flat dies that soak up the heat rapidly. If your pieces are clean and
lightly fluxed, just squishing them a little bit (maybe 1/8" over a 2"
billet) should make a good weld. This doesn't take a lot of pressure; I
haven't measured it when welding (paying attention to the weld, not the
press), but I bet my 30 ton press wasn't even up to 15 tons. I think
that for both general purpose forging and for making Damascus, a 20 ton
press will do the job. More tons are always better
, but I've never
had much need to go over 30. For typical size work, if your press is
actually pushing with 20-30 tons, it tells me that the work is getting
too cool to forge nicely.
So why won't the HF press do the job?--speed of travel during forging.
It does have a means to move the press tooling up and down rapidly when
under no load (via air). The problem is that air can't give you a lot of
pressure in the dies. The manual on your press says air at 100 psi; my
press is at an internal pressure of about 2000psi when the dies are at
30 tons pressure. Quite a difference. How the HF press works is you use
air to move the dies into contact with the work, then switch to the hand
pump, like with most shop hydraulic presses. This is *very* slow, way
too slow for forging.
Here's an example. My press has a hydraulic cylinder with a 6" diameter
piston. The area of the piston times the pump pressure gives you the
amount of tonnage the cylinder will put on the dies. In this case, a 6"
diameter piston has 28 square inches of area. Multiply this by 2000psi
and you get 56,000 pounds pressure, 28 tons (I guess my press is
'almost' 30 tons). The issue is how fast you can move at this pressure.
My press moves 1/4" per second at 30 (alright, 28) tons pressure. This
takes a pump driven by a 3HP motor, not something you can contemplate
doing with a hand pump. Maybe you could motorize the pump, but it isn't
designed to work at this kind of speed and I'd expect it would fall
apart quickly.
This also means that modifying a 20 ton shop press (hand pump) won't get
you where you want to go. You could imagine adding a motorized pump to
such a press, but the cylinder has no provision for the high pressure
plumbing. You could replace cyinder and pump, but you might as well
build the whole thing at that point.
Being a welder, I recommend you build a press. There are some really
excellent plans available by Jim Batson. You can get these plans from
Norm Larson ). Norm has most every blacksmithing
book available for sale, and he's a great guy. I'm sure you could also
get the plans from Jim, but I don't have contact info for him. Jim not
only gives you detailed press plans, he also gives you a good
understanding of how hydraulics work and how to estimate mechanical
stresses in your press (if you want to use different material sizes, or
change the press tonnage). I think Jim has two booklets out now, one on
an open sided press (C style) and another on H style presses. He also
discusses converting a motorized log splitter into a forging press.
Rather than using a combination of air and hydraulic, Jim's design uses
a log splitter pump to achieve fast motion when not loaded. Log splitter
pumps will pump at a high volume rate as long as the pressure is low,
switching over to a lower volume rate at high pressures. This keeps your
motor HP down. My press has a pump that runs the 6" cylinder at 1" per
second up to around 600 psi, above that, the dies slow to 1/4" per second.
Some specific comments:
1. Don't bend over with your eyes right next to a billet being welded in
the press. 1800 degree F flux can unexpectedly squirt out from between
the layers. You don't want your face anywhere near this, even with
safety glasses.
2. I find 1" per second travel (unloaded) plenty fast. I do a lot of
different kind of work on my press. I originally set it up for 2" per
second. This is *way* too exciting if you're doing any bending, almost
out of control.
3. The log splitter pumps claim that they work up to 3600 rpm. This was
how mine was originally set up to get 2" per second. The pump just
screams at this speed; not only don't you need 2" per second, but I
don't see how a pump making that much noise can possibly last long. I
now run mine at 1750 rpm, much quieter.
Here's a picture of mine:
http://www.metalworking.com/DropBox/...iles/Press.jpg
http://www.metalworking.com/DropBox/...iles/Press.txt
It probably cost me about $700, given some careful scrounging. Note that
the email address in the text is no longer valid.
Steve
John P. wrote:
Gents,
After recently completing a week long course on Damascus at the ABS
school (Taught by MS Steve Dunn, incidentally) I am considering the
procurement of a forging press. However, I am a complete novice when
it comes to hydraulics, which limits my ability to make any sort of
decision.
At the ABS school, there is a press made by Uncle Al of Riverside
Machine (http://www.riversidemachine.net/item16342.ctlg). The two
features that seemed important were 1) it would accept interchangeable
dies and 2) the foot pedal would lower the press at a constant speed,
it would hold at a certain level, or if you took your foot off it
would raise up.
I was with MS Chris Marks (http://www.marksforge.com/) when he used
this press to create a demo billet of damascus and remember him saying
it wasn't strong enough. I believe his press was closer to 50 tons.
Anyway, this brings me to my question. Does anyone have any
experience with or opinions on the Harbor Freight 50 Ton press found
he
http://www.harborfreight.com/cpi/cta...emnumber=46768
My thoughts, questions and observations:
- What powers this press? Can you just hook up a compressor? I have
a 5hp / 60 gal / 13.3 cfm @90 psi unit. Would that work?
- How would one convert the unit to be foot pedal operated?
- It looks like one would have to raise the bottom table up quite
high to use this press on a billet of steel that was only 2-4" tall.
- The manual says that you basically use the air supply to lower the
ram to the material and then pump it by hand. Can't you just keep
using the air pressure to ram into the material? Or does it lack
sufficient force in that manner?
- It looks like it would be difficult to fit dies onto this unit.
I'm only aware of two commercially available presses. Uncle Al's, and
the one from Carolina Knives.
(http://www.carolinaknives.com/press/press.html) If anyone knows of
others I would appreciate a reference.
Finally, would I be able to build my own press using the $70 HF 20 ton
bottle jack discussed in the other recent thread? I am a good welder
and a reasonable metal worker and handy sort of guy in general. I
just don't know anything about hydraulics...
Thanks in advance,
John P.