Grussing_Custom_Knives
Well-Known Member
Hey I recently picked up this hydraulic cylinder 4 inch bore 18 inch reach and 1.5 inch rod coming out would it work for a forging press
Need help on hydraulic press
- Thread starter Grussing_Custom_Knives
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EdCaffreyMS
"The Montana Bladesmith"
In my opinion, no. Personally I would not build a forging press with anything less then a 6" diameter cylinder. Smaller cylinders have to run at pressures that I feel are too extreme in order to develop the tonnage necessary for forging (20-25 tons). And with the repetitions and the heat involved, safety become a big concern.
I've been in shops where guys were using 4 or 5" cylinders, and simply refused to stay there because they were running 3000+ psi on those presses, and you could see the press'es framework and lines bulge with each use. Its not a matter of IF someone is gona get hurt/killed, its a matter of WHEN.
What a person does is totally up to them, but as I said, I would not have a press in my shop with anything less then a 6" diameter cylinder. My current press "Orange Crush", runs a 10" diameter cylinder, never exceeds 2500 psi, and puts out 80 tons of force.
I've been in shops where guys were using 4 or 5" cylinders, and simply refused to stay there because they were running 3000+ psi on those presses, and you could see the press'es framework and lines bulge with each use. Its not a matter of IF someone is gona get hurt/killed, its a matter of WHEN.
What a person does is totally up to them, but as I said, I would not have a press in my shop with anything less then a 6" diameter cylinder. My current press "Orange Crush", runs a 10" diameter cylinder, never exceeds 2500 psi, and puts out 80 tons of force.
Grussing_Custom_Knives
Well-Known Member
Wow thats a ton of force lol how much do they cost to build
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EdCaffreyMS
"The Montana Bladesmith"
I purchased "Orange Crush" (the 80 ton press) pre-built.....from a close friend of mine in Canada. I got the press, a rolling mill, and a 4 cyl diesel power unit to run it all for $6K. I would guess to gather the parts and materials for the press alone, and build it, would likely run close to that much.
Grussing_Custom_Knives
Well-Known Member
Well I can't afford that rn... Have you made Damascus by hand before until i get a press
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EdCaffreyMS
"The Montana Bladesmith"
I spent the first 1/2 dozen years doing it by hand! I quickly realized that one day I'd wouldn't be able to swing a hammer like that.... Which is when I started rat holing money for power hammers and a press
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Grussing_Custom_Knives
Well-Known Member
Hhhh
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Bill Hubbell
KNIFE MAKER
Oh, to have found 'knife-making' when I was only 14! ..or 24...or 34...or........ never mind!:15: You sound like you are eager to make things happen. Don't give up, appreciate your Dad and his help, and keep asking questions!
Grussing_Custom_Knives
Well-Known Member
Thanks and cool ive been making knives for a half year or so
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John Wilson
Well-Known Member
Grussing, you never thought you'd need algebra and geometry to make knives, did you? Now you have a real life problem that you can solve- which makes those classes actually interesting.
Force is what you are after in a hydraulic press. Ed's can put out 80 tons. (That's a MONSTER hydraulic press!)
Your original question: How big a cylinder do you need? How much pressure do you want to use? How fast does the press have to operate?
Pressure is not what makes things move fast. Speed in hydraulics is a function of FLOW, meaning the amount of VOLUME (how much hydraulic fluid) you can pump to the cylinder. Pressure is the enemy when it gets too high, because just like Ed said, pressure makes heat as well as destroys things - and that's what will kill you.
Let's figure out what size cylinder we need.
Force = Pressure x Area
In the big scheme of things, what are we trying to do? Answer: push the cylinder's rod out. That's what does the squashing on the steel. The number one thing we care about is FORCE, because that's how strong your press is. So, let's start with Ed's number of 20 tons.
Force = Pressure x Area What's this? Math? Yes. It's easy. Let's just substitute, using what we know already. We know the minimum force we want: 20 tons. Substitute 20 tons for FORCE.
20 tons = Pressure x Area Ed also said you don't want to go over 2500 psi, or pounds per square inch. That's our Pressure. Let's plug that in:
20 tons = 2500 lbs/sq in x Area Let's move that pressure to the other side with some algebra. That will give us an equation where Area (what we want to know) is the answer.
20tons = Area
_____
2500 lbs/sq in
Hmmm... lets change tons to lbs so the units are easy to compare. We know that 1 ton = 2000 lbs, so 20 tons x 2000 lbs = 40,000 lbs. Stick that into the equation.
40,000 lbs = Area Awesome. simple division. The answer gives us the Area. Let's discuss Area and why we care.
_________
2500 lbs / sq in
16 sq in = Area. Great... What does that mean? Well, that's the area of the cylinder's piston that the hydraulic fluid is pushing down on. It means our Cylinder piston needs an area of 16 square inches to give us enough force (20 tons) at 2500 psi. But cylinders aren't sized in square inches, are they? Nope. They are sized by the diameter of the piston. Good, let's convert our area of piston surface to a diameter of a piston's cylinder bore. Don't get confused. The cylinder bore is the width of the tube that makes up the cylinder, that's all. We know the area of the piston, and all we're going to do is to convert that to a bore diameter.
Area (of a circle) = Pi x radius squared. Looks like gobbledygook. That's okay. We'll just substitute what we know like we did with our first Pressure equation. We know the area, we solved it to be 16 square inches.
16 square inches = Pi x radius squared. Good thing we already know Pi. It's always the same thing. Pi = 3.14 (later in school you'll carry this out a few more numbers, but for this 3.14 is fine)
16 square inches = 3.14 x radius squared Let's do some of that algebra again
16 square inches = radius squared
_____________
3.14
5.096 inches squared = radius squared
we take the square root of 5.096, and we come up with a radius of 2.257 inches. But we don't need radius, we need diameter.
radius x 2 = diameter
2.257 inch x 2 = 4.5 inches That's the bore size we need for our cylinder.
What does all of this mean?
It means just what Ed said.
It would take a 4.5 inch bore size cylinder just to get to the low end of force that we wanted, which was 20 tons. And at that low end of the force window we want, we'd also be at the high (dangerous) end of the pressure range, 2500 psi. Kind of the worst of both worlds.
It would be a fun exercise for you to work out what size cylinder you need to get a whole lot of force within a safe operating pressure. Once you know how much force you want, at what pressure, you know your cylinder size. The second half of the exercise is to figure out how big of a hydraulic pump you need to move that much fluid in a timely manner. It's not rocket science, but it takes more thought than just winging it. Winging it with high pressure and hot fluids gets people hurt.
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Grussing_Custom_Knives
Well-Known Member
Dang that made me want to quit knife making LOL. Well I want to be a engineer when i get older so yea lol. But 4 inch bore would be around 18 tons wouldnt that be enough ed?
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John Wilson
Well-Known Member
This is important: all cylinders are not the same. Cylinders are rated for a given pressure. The math on a 4in cylinder works out to about 15 tons (at 2500 psi), but will your cylinder handle 2500 psi? You also only need several inches of rod for a hydraulic press. (how far up and down the press needs to travel) You don't need a cylinder with a four foot rod, designed to swing the bucket on a gigantic track hoe. That one has 18 inches of travel, and you'd only use a small portion of that.
The cylinder you show in your picture is an Agricultural cylinder, not an Industrial cylinder. Get the specs on the equipment you use before you put that kind of pressure on it, just to be safe.
The cylinder you show in your picture is an Agricultural cylinder, not an Industrial cylinder. Get the specs on the equipment you use before you put that kind of pressure on it, just to be safe.
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Grussing_Custom_Knives
Well-Known Member
Ok thanks
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Grussing_Custom_Knives
Well-Known Member
Haha i love it... Well im 14 so I will be able to swing a hammer for a while lol. I know some people have strikers (thats what its called when u have someone else hammer while u move the billet around on the anvil kinda like a person power hammer lol) im sure my dad will lend a hand. Btw i have tried forge welding and It hasn't worked well I don't know if my forge gets hot enough. I haven't ever let it soak at the temp tho.
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Grussing_Custom_Knives
Well-Known Member
The reason i want a press is to get good forge welds not the time it takes
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Great post John! Nice to see it laid out so straight forward. As I'm pushing 60, I admit it was a bit tough for me to follow along, been quite some time since high school. Always glad for a refresher course!
John Wilson
Well-Known Member
thanks Jaxxas. Fingers crossed on my 2am math. By morning someone will probably come along and shoot holes in it!
I'm an electrical weenie, so that hurt my brain some, too.
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I'm an electrical weenie, so that hurt my brain some, too.
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EdCaffreyMS
"The Montana Bladesmith"
"Good" forge welds are not about the compression..... it's all about having the steel at the correct temp/plasticity state. I often tell folks that I can do anything by hand, that I do with the machines..... the only advantage to the machines is reduced labor, and time savings. Way back when I purchased my first forging press, I had to "rob" from our family savings account to do it....and at that time it was a LOT of money, and a considerable leap of faith. As it turned out, within 6 months I had produced/sold enough Damascus stock that I was able to replenish that chunk of money I'd taken, plus some.
The moral of the story being.... there's simply no way that the average person can go out and build or buy ALL of the things you'd like to have for knifemaking. Its a evolutionary thing..... make a knife, sell it, then turn that money around into materials or equipment and make some more knives, and so on. It takes time, planning, and financial discipline to build a knife shop...... of course unless you're independently wealthy..... but where's the fun in that.
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Grussing_Custom_Knives
Well-Known Member
"Good" forge welds are not about the compression..... it's all about having the steel at the correct temp/plasticity state. I often tell folks that I can do anything by hand, that I do with the machines..... the only advantage to the machines is reduced labor, and time savings. Way back when I purchased my first forging press, I had to "rob" from our family savings account to do it....and at that time it was a LOT of money, and a considerable leap of faith. As it turned out, within 6 months I had produced/sold enough Damascus stock that I was able to replenish that chunk of money I'd taken, plus some.
The moral of the story being.... there's simply no way that the average person can go out and build or buy ALL of the things you'd like to have for knifemaking. Its a evolutionary thing..... make a knife, sell it, then turn that money around into materials or equipment and make some more knives, and so on. It takes time, planning, and financial discipline to build a knife shop...... of course unless you're independently wealthy..... but where's the fun in that.
Cool... What about those hydraulic ait jack forging presses they only cost 100$ to make. Also do u have a Instagram i can tag u on a video on my forge
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Grussing_Custom_Knives
Well-Known Member
"Good" forge welds are not about the compression..... it's all about having the steel at the correct temp/plasticity state. I often tell folks that I can do anything by hand, that I do with the machines..... the only advantage to the machines is reduced labor, and time savings. Way back when I purchased my first forging press, I had to "rob" from our family savings account to do it....and at that time it was a LOT of money, and a considerable leap of faith. As it turned out, within 6 months I had produced/sold enough Damascus stock that I was able to replenish that chunk of money I'd taken, plus some.
The moral of the story being.... there's simply no way that the average person can go out and build or buy ALL of the things you'd like to have for knifemaking. Its a evolutionary thing..... make a knife, sell it, then turn that money around into materials or equipment and make some more knives, and so on. It takes time, planning, and financial discipline to build a knife shop...... of course unless you're independently wealthy..... but where's the fun in that.
Im also going to the usa knife maker show and there supposed to have Damascus deminstration and might let u try!
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