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
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
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 here:
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.
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...
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 ( firstname.lastname@example.org). 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:
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.
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.
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:
probably cost me about $700, given some careful scrounging. Note that the email address in the text is no longer valid.
I totally agree with your comments regarding the speed and heat of the welding process, and you confirmed for me that the air simply lacks the power once the die comes in contact with the work material.
Interestingly, on another thread Pete Stanaitis briefly describes how he is employing one of those hand pumps to make Damascus. I'm waiting on his response to learn more about how he's doing this. But I take your point that if the jack isn't designed for this it could fail rather quickly.
Yes, Don Fogg talks about that a lot on his site, but I'm just scared of starting a project I can't complete. I really know absolutely zero about hydraulics. Still, everyone says that Dr. Jim's book does a good job of teaching. I guess I need to get a copy and see what I can learn.
I agree that the press speed is probably way too slow for the work in question, but I think you misunderstand how the air/hydraulic presses work. The 100 psi air does not directly act on the press piston, it operates a reciprocating air motor that operates a small pump cylinder for the oil, same as the manual pump cylinder works. Given proper air line pressure, the air operated pump will build pressure up to the hydraulic relief valve setting just as the manual pump will.
You have a direct acting powered hydraulic press, more or less the same as a log splitter, this is quite different from the basic hydraulic jack powered H press.
I disagree, the commercially available 20T H presses are quite inexpensive and will save a lot of time and effort tracking down the steel, welding and trying to keep things square. My recommendation would be to use a commercial 20T press frame as a starting point. The 20T jack can readily be used separately as a normal jack.
You should be able to find a suitable hydraulic cylinder, valves and pump unit from a place like
and have a fast powered unit operating in short order.
Hello, Steve. I am not a knife maker, but I have used the HF 20 air over hydraullic jack in a 20 ton press to weld damascus billets. I don't understand why you say to use the hand pump. I never do. The air pressure does the same thing that the hand pump does and to the same degree, as far as I can tell. We use two of these presses on a pretty regular basis, one for general work (and the occasional billet); the other for pressing bearings where we approach the 20 ton limit often. I agree that you don't need a lot of tonnage to weld. A friend of mine, Mike Blue, from Cannon Falls MN got me started with this HF air/hydraulic press idea when he said that he turns his 50 ton press down to about 12 ton for welding damascus billets. As far as speed goes: certainly, if I had the money and the time, I'd go with a "regular", noisy 50 ton all hydraulic press. The ones I have seen, particularly those with the 2 speed pump, move a lot faster, and as you said, speed is important. My press is set up with two foot valves. One for down (the stock air cylinder) and one for up (a 1 inch cylinder I added to the release valve). I move down to the point where I am close to the thicknes of the billet before I take it out of the fire. Then press, release a little, press a little, etc. With the two valves, the ram only goes up as far as I tell it to, not a full or large retraction. I get about 4 "squeezes" per heat.
I just put a few pix up on my website.
Not trying to be argumentative, just reporting, Pete Stanaitis
OK, I don't have a clue (except the one you just gave me) about air/hydraulic. I didn't actually see anything like that in the manual (which recommended switching to the hand pump), but it was a quick skim. This does still leave the question of if the press moves fast enough; the instruction manual is (typically) pretty thin on info like that. I'll change my comment to "I don't know".
I should have added that if you live in a rural area, see if you can find a tractor junkyard (or just a well stocked junkyard). I bought several cylinders off of the one I used to live near.
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.
Noisy? Sounds like my press...
So the air/hydraulic uses air to turn a hydraulic pump?
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.
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.
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.
Thanks for jumping in Pete. Let me see if I understand correctly:
If I were to purchase, from Harbor Freight, the 20T Air / Hydraulic Bottle Jack (Item 41487) along with the 20T Shop Press (Item 32879), I could replace the stock manual bottle jack with the Air / Hydraulic bottle jack to more or less duplicate your machine?
And all I would need to do is hook it to a sufficient air source for power? Would a 13.3 CFM @90 PSI compressor do the job?
Also, being a complete newbie at anything air or hydraulic related I am not following along very well with how you created the foot pedal or the use of the Bimba. Could you attempt to explain exactly what is going on with the control unit?
Assuming the press will work for Damascus, even if it isn't ideal, I will purchase the components and fabricate it. I'll even document the process for everyone's benefit. But I'll definitely need a little more information / guidance on the foot pedal stuff.
It was a different Pete that posted about the foot pedal and air cylinder operated release valve. I believe he posted a link to some pics. As for the basic press, the 20T air/hyd jack will just swap in place of the 20T manual/hyd jack that comes with the press.
90 PSI probably won't make the full 20T, but it should produce close to it. I think you need close to the 120psi max in order to reach the relief valve limit. Easy enough to test, just stack a couple solid press plates and press on them. If the air pump stops cycling then you haven't reached full pressure, increase air pressure until the pump keeps cycling and you've reached the hydraulic relief valve setting.
If you need a faster full hydraulic powered press you can still take the basic 20T H press as a starting point. Remove (or don't install) the 20T jack. The top frame will be two "C" channels with a gap between and a heavy plate welded on the bottom.
Find a front mount ~10" stroke hydraulic cylinder that will fit the gap between the "C" channels. Drill the appropriate holes in the heavy plate to mount the hydraulic cylinder from the top with the ram pointing down. Where the ram touches the upper press plate where the original jack would sit, weld a piece of steel pipe to act as a receiver for the ram so it can't slip to the side.
After the cylinder is mounted it's simply a matter of connecting a hydraulic power pack and valve to complete the press. The GPM flow rate of the hydraulic power unit will determine the press speed. A power unit with a two-stage pump will provide a faster closing speed followed by a slower pressing speed. Valving can be anything from a basic lever actuated valve, to a rocker foot pedal, to a solenoid valve and hand button pendant.
The ultimate pressing force will be determined by the hydraulic cylinder bore and the max PSI of the power unit. 2,200 PSI or so would be typical for a setup like this. If the cylinder that will fit between the channels does not have a large enough bore, you could use a larger one with a longer stroke that can mount above the channels and use longer grade 8 bolts to fasten it to the bottom plate.
Either way, starting with the commercial 20T press for the $200-$300 will save you a lot of work.