Press question...or how to prove how little I know about forging!!!

R

RobertHankins

Joined
Jun 10, 2001
Messages
1,385
I have been looking at making a press for some time now. The question keeps poping up in the back of my Brain.
Why couldn't you use a 20ton Harbor freight manual hydraulic press and frame, ditch the manual hydraulic cylinder and replace it with a short stroke, two way, air cylinder maybe 40 ton and the reinforce the hell out of the frame.

I was told you would need a huge compressor to get enough pressure to run the Ram. Doesn't make sense...I see small compressors that run out at 125psi all the time. The big ones just have a larger tank capacity and less pressure usually top out at 90psi. That is for continius heavy use of air tools that bleed off all the time. I don't think an Air cylinder does that, closed loop!?. With squishing Damascus (Drawing it out) it is done for a short spurt and then the blade goes back into the forge. IE:Time for the compressor to catch back up if it needs too.
I just can't afford to be wrong at this point in time, Know what I mean!

Any body who knows more about this than I do (Probably most of you) Please chime in and tell me why an 40 ton air cylinder will
or will not work.
 
Robert,

My experience is very limited also but it is my opinion that for about the same money you could get a twenty ton log splitter that is very easy to convert to a knife press. The only problem being the gas motor that runs the pump. On the other hand an air cylinder usually is set up to make a single blow instead of a squeeze. So What you do is use a double acting air cylinder rigged up so that when the air is turned on the cylinder raises up. Then when you step on the pedal the ram and the attached hammer delivers the blow. Let off the pedal and the ram retracts...
I belive that you can get plans from ABANA that shows you how to plumb and set up a recipricating valve so that when you step on the pedal the air cylinder starts to cycle giving the same action as a mechanical hammer. just my two cents and definately not worth more than that.

Bill
 
I'm sure someone with more expertise will jump in here, but from what I know, air should probably be reserved for an air hammer, not a press. I've seen an air hammer in action, and it requires a big compressor to keep things pumping. Unless you already have one, i'm thinking it would be cheaper to build the press than buy the required compressor for an air version. I built a press last year, and I'm NOT mechanically inclined, so I would think you would have no problem!

Wayne Goodard touched on presses and the air power question in the last installment of BLADE magazine, and it may be worth a read. Good luck, hope you get the info. your looking for.
 
Robert, your logic is 100% correct. However lets look at the practicality...

For example, 40T=80,000lbs. Now lets figure what size bore the air cylinder needs to generate 80,000lbs of force.

Here is the formula: Force=Pressure X Area, F=PA

...do a little algabra to put it in terms of the area and we get


A=F/P


given that the force is 80,000lbs and the pressure is say 100psi

then the air cylinder area is 80,000lbs/100psi= 800sq inches.



Now we determine what Diameter air cylinder has 800sq inches of area.


The formula is A= pie X r^2


more algabra to get the equation in terms of the radius:

r^2= Area/Pie = 800/3.14=254 then take the square root to get r=16"

That's it, the radius of the cylinder needs to be 16" ....or 32" diameter!

Also consider that the volume for a 4" stroke comes up to about 22 cubic feet of air....That's like filling your car tire everytime the ram goes up and again when the ram goes down!

OK, the real killer is that air is compressable. Pnuematics are designed around pressure, where hydraulics are essential designed around displacement. You will have more control with hydraulics. With air, you get a snappy hammer blow, and with hydraulics you'll get a controlled squeeze.


So to summerize my 2 cents...

Hydraulics are much smaller and compact, offer better control and I simply have never seen a 3 foot air cylinder :eek:


Take care,
Rob
 
Whoa Rob
you and my boy would get along great
I can see the numbers flying now:D
Robert
If you could roll it IMHO it would be better but
the press would be better than the Hammer for control
like said here. (everything has its place.)
for a hammer I think I'd go with a flywheel type.
just 2 more cents, :)

The steel factories roll it hence cold rolled / hot rolled
 
If you are gonna go to alll that trouble to rebuild might as well build new one. Presses and air hammers do different things. An air hammer properly constucted has a lot of control it needs a heavy "anvil" to work properly. Plans are on the ABANA site and improved circuitry on the Alabama forge council page.

See some presses and buy Batsons plans on www.dfoggknives.com site.

Presses excel at making welds hammers excel at drawing out quickly.

Rolling mill?:D
 
Originally posted by mikeS


Rolling mill?:D
Click to expand...
for those that don't know.:confused:
The steel factories roll it hence
the terms cold rolled / hot rolled:( ;)
You can buy a gold rolling mill to use in the shop
of course the two would be different but the principles
are the same.
 
I don't know anything about forging besides, get it hot and whack the hell out of it. :D

But I've got a little experience building things with hydraulics. Its really as simple as your standard plumbing for water, you just have to buy different components. If you've got a good farm supply store nearby, like a Tractor Supply Company, Farm and Fleet, or something like that they probably have everything you need on the hydraulic end. The lines come in different lengths, sizes and grades, fittings and everything are all threaded, you just have to put some teflon tape or TFE paste on and put it together(might need a torque wrench, to make sure your getting the fittings in tight enough). Cylinders come in different bores and strokes and are surpisingly cheap. You might have to special order one to get up to 40 tons, or you could rebuild a log splitter. Thats a good way of going at it since you get a good hydraulic pump(thats the real secret to getting the pressure your looking for)most of the lines you'd need, and the resevoir for the fluid is already there too.
Most of them are built on a big I beam, which is a good platform to build off of too.

The gas engine is probably not as convenient as electric, but its cheaper than trying to find equivalent power in electric. Our splitter is probably a 25-30ton ( its so old I don't know for sure) and it has an 8HP Kohler engine. It can cut across the grain of a hard log,doesn't seem like anything can stop it. That motor does have to work though. I would just tear the muffler off of it (it doesn't do a hell of alot anyhow), and pipe the exhaust outside the shop through a chimney or something. Should make it pretty quiet in the shop and eliminates the problem of fumes.
 
The home shop rolling mill was invented by Hugh McDonald Click on one of the tutorials given by Hugh and you can get a link to the rolling millrolling mill
 
Robert That's cool
should be very easy to make the most expense would be the gear reduction box.
it's on my list to make now.:) Thanks for the link.
 
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