• Punching with a Hydraulic Press

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    david hyde
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    Punching with a Hydraulic Press

    A while back I made some gates that involved a lot of punching, something like 30 off 80x12mm slots through 40x60mm bar... the hardway up. Given that I'm at that age where my body starts to creak (literally in the case of my knees) I always like to get horsepower to do as much work as possible for me. Hydraulic presses are great for this.

    This article gives a few notes/ observations about using one to punch with. If your curious you can see the finished gates on this page of my site:     Forged Steel Sliding Gate

    I didn't take many photos when doing the slots so I'll use some recent pictures of 30mm holes.



    The press is a home brewed H frame relatively quickly lashed together. I can't remember the cylinder or pump sizes but did did once calculate the force as 15Tonnes. Most important of all is the motor size; I use 8hp. When discussing the idea with a more experienced smith I was told I'd need about 30T. Having used the punch I'd say that speed is just as important as pressure, using a well lubed fast moving slot drift seems to let you get away with less pressure. I can effortlessly punch 30mm holes through 40mm bar in one heat ..... and still have more than enough heat to straighten the bar

    Note the "alignment arm" that stops things moving round



    Hopefully the photo below explains the business end of things. I do it by part punching though one side, turning the work over, punching from the other side, sliding a bolster with a suitable hole under the work then drifting from both sides .... pretty much as you'd do it by hand ..... but a damned site easier Some people do it all in one go with pegs that use the forming bulge to move a "split" bolster as the punch goes through the work. Doing it from both sides means you get a more even bulge and going off centre is slightly less a problem as doing it all from one side.


    Note the swingable stripper plate. Its important that you start punching bang on centre, especially when working thin bar hard way up. Moving the stripper out of the way means you get a better view. I usually give the punch a quick "peck" to mark the steel when it's got to dull red. You can see if it's on centre then and don't need the stripper to pull the punch out of the small hole. If it's off centre (sometimes the bar "rocks" slightly as the punch hits the work) turn the work over and use the other side ...the first mark will be more or less flattened out as the hole is punched. Sometimes I get real unlucky and both trial marks are off centre ..... fill with weld and grind.

    Punchs are H13 ... good tough stuff that takes a lot of punishment. Use plenty of graphite grease as a lube, cool with cups of water. Low tech but works. Sometimes the tip will "ball up". Alan Evans (a true punching Guru) says this is no bad thing because it keeps the sides of the punch away from the heat, cuts down on the heat transfer paths.

    Note the kiss block when the solid part of the bolster is used



    One of the hard bits is locating the punch when the bar is turned over. You usually can't see any dark "witness mark" where the steel has cooled because there is that much heat in the bar and it quickly reheats. I use "scale disturbance" to find the sweet spot. Centre pop marks dont work cos they're flattened out and almost impossible to see with the heat. Chisel notches on the corner of the bar are good but they do spread out a lot with the swelling and can be "too noticable" on the finished work.



    It's worth keeping a big hammer nearby.



    Being a one man band moving long hot heavy bars from the forge to press can be awkward. Having a stand helps but I've found sometimes rocking the bar back and forth to get "position" can rock a stand over ..... not good. I've welded a big lunp of steel to the base of one of my stands. and then have three little "feet" for contact points. Can be moved around but is VERY stable



    Photo below shows some of the punches I use. Note some are two piece. This means I can forge and spread out the ends for wide slots and still fix then to the threaded end of the cylinder. Grubby hand is for you to use as a scale rule.



    You can get some pretty clean and even slots/ holes going through deepiish material if you're carefull aligning the punch at the start. Thickest material to date is a 30mm hole through 60mm thick steel. Hammers are a piece of **** to do nowdays, hardest part is swapping the tooling over. I'm beginning to wish I'd designed it "quick change" but I've invested too much time in my existing punch collection to re do things.





    Note the set up used to straighten the bar. Alan Evans told me about this, works a treat. Fly press is a number 6 Norton deepthroat. Nowadays I use a 30Tonne C frame press to straighten (still use the 15T to do the holes) Not so much for the 30Tonnes but as much because I can use the foot treadle and have both hand free.



    Hope this is useful to someone. The week or so rigging it up has probably extended the working life of my joints by many time over.
    Comments 22 Comments
    1. Grant's Avatar
      I'm amazed that you can get so many holes near perfect "by eye". My first temptation would be to make guides fore and aft of where the punching is happening, clear of the swelling. Sure seems to work for you. Pretty cool "slide forth and back" bolster plate.

      I've preached for years that 15 ton is enough and get all the speed you can. Redemption! You sure make a convincing case!

      Those ball-end hex wrenches are sure a life-saver, aren't they?
      Reply
    1. Larry L's Avatar
      Great stuff YD. I guess I better get to work on my press!
      Reply
    1. david hyde's Avatar
      Quote Originally Posted by Grant View Post
      I'm amazed that you can get so many holes near perfect "by eye". My first temptation would be to make guides fore and aft of where the punching is happening, clear of the swelling. Sure seems to work for you. Pretty cool "slide forth and back" bolster plate.

      I've preached for years that 15 ton is enough and get all the speed you can. Redemption! You sure make a convincing case!

      Those ball-end hex wrenches are sure a life-saver, aren't they?
      Early days I used to use guides, they're great working on flat or square but with the tall thin stuff there's often a tendancy for the bar to rock if the sides are not perfectly flat. You think you're going for the middle, punch touches bar, bar rocks ... This is why I've got into the habit of doing a trial "peck" to see what happens. I guess guides would be good where productivity is an issue.

      It's a while since i wired/plumbed the press and I can't remember the control details but I used some Fancy Dan electrical valves that I switch in. These reduce the pressure so I can "peck" without having to have lightening fast reactions on the control switch (cos the punch goes into far/fast before you pull it out). If the bar's going to rock it'll do so when it's pecked. When I'm happy the punch tip is centred I switch to "normal" operation and the punch will fly through.

      Yeah 15T is more than enough, almost goes through it like a knife through butter. I suspect I could probably do 40mm through 50mm in one heat (with a slot drift) but as yet haven't had the need.

      Induction heaters sure would be great for punching (though maybe some of the excess heat from the gas forge acts as a usefull heat resovoir in the bar)
      Reply
    1. david hyde's Avatar
      Quote Originally Posted by Larry L View Post
      Great stuff YD. I guess I better get to work on my press!
      which one, you've got dozens of the buggers
      Reply
    1. Grant's Avatar
      Well Mr. Hyde, does Dr. Jekyll ever make an appearance? So, you gotta know we all wanna see videos now.
      Reply
    1. david hyde's Avatar
      Quote Originally Posted by Grant View Post
      Well Mr. Hyde, does Dr. Jekyll ever make an appearance? So, you gotta know we all wanna see videos now.
      Videos mean a second person or a tripod ..... hardly room for either in my tardis/shoebox/place of sanctuary............there is room for an induction heater though
      Reply
    1. JNewman's Avatar
      Just weld a bolt to the top of one of your stock stands. Just make sure you wait till the bolt has cooled completely before threading on the camera. Don't ask how I know that.
      Reply
    1. Grant's Avatar
      LOL! Yep, you're either making money or learning! Heck David, you can take video with your Iphone!
      Reply
    1. JNewman's Avatar
      Quote Originally Posted by Grant View Post
      LOL! Yep, you're either making money or learning!
      That's a good way of putting it, the couple of jobs I just finished this weekend made up for lots of learning this year.
      Reply
    1. Grant's Avatar
      If you're gonna be it business, you gotta be philosophical about it. "Making money of learning", heck, that's my two favorite things!
      Reply
    1. pete/BLF's Avatar
      hey there great "article"" do you think 15 tons set up the way you have yours would be enough to punch 2 1/4 inch toolsteel(1080)
      Reply
    1. Grant's Avatar
      Hey Pete! David probably will have some input, but I'll make a couple observations. Notice his tooling enters with a very small cross-section and gradually opens the hole. You're talking about a smaller hole and 1080 at forging temperature works pretty easy compared to high-alloy steels. I don't think you'd have any problem at all.
      Reply
    1. Grant's Avatar
      Great article David! Your next assignment (should you choose to accept it) is to create a photo album and show us more of the stuff you're doing. Thanks for the contribution!
      Reply
    1. Larry L's Avatar
      I'll second that... great info and walk through of the proses
      Reply
    1. david hyde's Avatar
      Quote Originally Posted by Grant View Post
      Great article David! Your next assignment (should you choose to accept it) is to create a photo album and show us more of the stuff you're doing. Thanks for the contribution!
      mission accepted. Isn't your message supposed to self destruct after ....
      Reply
    1. david hyde's Avatar
      Quote Originally Posted by david hyde View Post

      It's a while since i wired/plumbed the press and I can't remember the control details but I used some Fancy Dan electrical valves that I switch in. These reduce the pressure so I can "peck" without having to have lightening fast reactions on the control switch (cos the punch goes into far/fast before you pull it out).
      Here's a picture of the valve I used. I researched a bit about hydraulic control to build the press but have since forgot most of what I learn't. I got a bunch of them (whatever they are) from an old fashioned stand around, freeze your nuts off, auction a few years back.

      Flow in can be normal or electrically switched in to rduce flow/pressurre. Flow out is normally. It seems to rduce both flow and pressure. Ie ram moves slowly with little force. It's adjustable. VERY useful when inching the press.
      Attachment 657
      Reply
    1. Danger's Avatar
      Nice work David, 15 Tonnes is plenty alright, did you size the drifts in proportion to a 8" stroke? How long are they?

      Grant would a impact press would have to use a shallower angle on the slitter and drift to avoid getting it stuck?
      Reply
    1. Grant's Avatar
      If you are using "sticky" tooling you can adjust the thrust bearing for a little extra slop so the flywheel can get a little momentum before it starts stripping. Or, I suppose, you could mount your stripper with a little extra clearance to do the same thing.

      The angle of the tooling has a big affect on what the finished part looks like. Notice how little "drag down" David has on his holes.
      Reply
    1. david hyde's Avatar
      Quote Originally Posted by Danger View Post
      Nice work David, 15 Tonnes is plenty alright, did you size the drifts in proportion to a 8" stroke? How long are they?

      Grant would a impact press would have to use a shallower angle on the slitter and drift to avoid getting it stuck?
      Danger, I think the cylinder has a total stroke of about 500mm but I generally have the table set so as little of the ram is projecting as possible; keeps things more rigid.

      In the early days I was just punching small (20mm holes) and the punch lenght was dictated by the the size of the H13 bars I aquired. I tapered them to what I thought "looks right". As I started punching bigger holes I more or less kept the taper the same but made the punches long. As a bench mark the one in the photos doing the 30mm holes has about 6" sticking out past the collar that screws onto the ram. The tapered section is about 3"
      Reply
    1. Daryl's Avatar
      David and All:
      I have a 50ton press which sees a major amount of work and I was thinking of speeding it up from a single stage 1.6 GPM ? to a 5 hp two stage 2.9 GPM and 10.6 GPM low pressure. I'd go larger but I'm pushing my electrical service, in my backyard shop. My original thinking was that I would ad a smaller 4 inch dia. ram to my H frame press, to get some real speed.

      Today I talked with an Hydraulic guy and after a bit he suggested keeping my 50ton as is and building a separate press for the four inch ram. I kind of like the idea, the material cost isn't that bad as I can get some good drops at 15 cents a pound, so major cost is the time, but I would mind making some changes to the design of my press anyway. I have been thinking that a C frame might be handy after this last job forging an 8' length of 2" x 2 1/2" it would be nice to just slip over to the C frame. I have never used a C frame so don't know the disadvantages, I do like the 50 ton H frame, the only disadvantage with it is the speed and moving in and out long lengths. your thoughts are appreciated.
      Daryl
      Reply
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