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Thread: Widening HF 20t press for use as press brake?

  1. #1
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    Widening HF 20t press for use as press brake?

    I am looking at fabricating a wide press brake similar to the finger brakes that SWAG Offroad offers. I already have a 20 ton harbor freight press.

    What makes sense to me is to make a brake that fits on the press as-is for smaller, thicker parts (between mechanical work and the vast majority of fab projects the stock width would cover 98% of what I would ever need). That way I can multi-purpose the press as-is.

    However, I want a better way to more accurately bend sheet metal. The heaviest sheet I would bend, and have bent (I have the 30" HF brake) is around .90-.125" aluminum. I am not sure what grade, it was out of scrap sheets from a metal recycle place in town about 8 years ago. What I have in mind for projects I can't imagine being much heavier than that.

    What I'd like to do is widen the HF press frame (replace all the horizontal members) so I can get a full 72" of brake capacity inside. So that probably means the legs at 84" or so apart and the horizontal members closer to 90" overall.

    I am not too concerned with the hydraulic pressure off the bat (as in not having enough pressure at 20 tons). However, I am concerned about flexing under load. I do not think I can get away with the same dimensions (wall thickness, LxW for the C channels used) of horizontal members. Or, if I did use the same dimension C channel, I would have to use struts of some kind to get the rigidity up in the middle of the span - both flexing parallel to the pressure as well as twisting.

    The strut idea might complicate the assembly too much. I am not sure where to anchor the struts by the legs. So if I beef up the horizontal members it would simplify the set up. The question is how much should I beef up the horizontal members?

    Current C channel is 4.75"x2" with a wall thickness of about 3/16", maybe 7/64". I measured it with a tape, not calipers.

    I suppose another good thing about the brake idea is I do not need an open table. I can box it off as there will never be any parts that drop down through it. I'm not sure how that would affect making the parts rigid, but maybe it opens up some ideas - adding a plate on top maybe. Or, scrapping the parallel C channel idea and going with a a larger I beam then make "hands" that grasp the legs and set on the pins? An I beam might be a decent idea. I could borrow the design of higher tonnage presses where they use gusset plates on the upper flanges of the table to transfer the load from the horizontal flanges to the vertical webbing. If that was a whole length gusset plate it would effectively box the C channel, or I beam, which would certainly add rigidity to resist flexing and twisting.

    Thoughts?

  2. #2
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    Re: Widening HF 20t press for use as press brake?

    Hi,
    This is probably not what you want to hear, but...

    I think you would be putting lip stick on a pig, to try and upgrade what the HF press can handle.

    They are for guys that want to press out car bearings and such.

    To bend metal with a wider frame, I would just start from scratch and build a real shop press.

    You are on, a Welding Site so you must be able to fabricate, right!

  3. #3
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    Re: Widening HF 20t press for use as press brake?

    You are correct - this is a welding forum. There will be a good amount of welding on the parts no matter what way I go with it - both the "brake" portion and the parts for the "press".

    As for making use of the press being like putting lipstick on a pig - I had similar thoughts when I bought the press. I was going to fab one. However, when I looked at it and thought through the process I couldnt buy the steel to fab one for what I paid for the whole complete press. The only mechanical thing that can go south is the bottle jack. That can be replaced and retrofitted real easy. The rest of it is not very precise steel framing.

    So considering the steel framing is already fabricated for bolt together construction that minimizes the amount of work to do for everything else down the line.

    I dont see any reason to not use the original legs and feet - they are steel and have no moving parts. Why not use them?

    If the 20 ton bottle isnt enough it would be easy to retrofit the assemy to use, say, a pair of 12t or 20t (maybe even pneumatic over hudraulic) bottle jacks.

    Again, I wont need to bend any heavy gauge metal that is very wide. So I am not too concerned with having a lot of press pressure across the whole width (the 72" working width of the brake idea I have). What I am concerned with is balancing the pressure I do have so the assembly is rigid enough to get uniform bends across the 72" width. That doesnt take beefier legs and feet - it takes beefier horizontal members. Hence the questions posed in the original post and the overall subject of the thread.

    If I need more pressure or have a jack that goes south I can cross that bridge down the road. If I mushroom a leg at one of the pins from over-pressurizing the press I can make new legs.

    The working faces of the press (not the brake, the brake sits in the press) are the top of the table and the pocket on the underside of the top horizontal frame member for the jack to press against. Everything else is non-critical, so long as the strength in those members is such that it mantains the two working faces in their positions under load with minimal (the less the better) deflection.
    Last edited by FlyFishn; 03-17-2021 at 08:23 AM.

  4. #4
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    Re: Widening HF 20t press for use as press brake?

    You might consider looking at a tonnage chart for your press brake before investing any money. 20 tons is not going to go far. 45 tons is marginal for what I do regularly.

  5. #5
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    Re: Widening HF 20t press for use as press brake?

    Widening a HF press is a bad idea. All you'd be saving are a jack and some formed channel uprights.

    Here is a link to a 25 ton press brake 72" wide. It weighs over 3000 lbs and 25 tons is on the light side of bending force. Point being it will take a lot of mass to be able to accurately bend 72" of anything.

    https://hgrinc.com/productDetail/Fab...e/02211230003/

    Here is a link to my build thread where I modify a 20 ton HF press for press brake work and then move up to a HF 50 ton. I still have the 50 ton. (Apologies: The photos are old and on photobucket with the watermark but you can right click to see them. I can't access them through photobucket unfortunately.)


    https://www.pirate4x4.com/threads/la...a-new.1004514/

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    Re: Widening HF 20t press for use as press brake?

    Quote Originally Posted by walker View Post
    You might consider looking at a tonnage chart for your press brake before investing any money. 20 tons is not going to go far. 45 tons is marginal for what I do regularly.

    According to the calculator in the link below - 6061 aluminum at .090" thick, 72" wide, against a V die with an opening of 1.5" will take 10.26 tons. Same material and width at .125" will be 22.28 tons. That is at 72" of sheet in the brake, so shorter pieces will take less pressure. And as far as sheet metal work goes that is more than I can imagine doing at the moment. One project idea I have is to go 60" wide so my thought was to bump up the brake width by an extra 12" so I am building for expansion to something bigger or some extra room to move the parts around that I want to make.

    https://www.e-ci.com/press-brake-ton...oad-calculator

  7. #7
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    Re: Widening HF 20t press for use as press brake?

    Quote Originally Posted by walker View Post
    You might consider looking at a tonnage chart for your press brake before investing any money. 20 tons is not going to go far. 45 tons is marginal for what I do regularly.
    +1 to what walker said. 20 tons isn't enough. I had a 35 ton press and I was always maxed out. I'd consider 50 tons a minimum. I haven't been very impressed with the HF presses. My 35 ton press fit my 26" brake die set perfectly but my 50 ton is about 2 inches too narrow. If your primary use is as press brake you might look at building something with multiple cylinders to spread the load.

    I use this chart. They also have details on radius and tonnage factors based on material.
    https://www.americanmachinetools.com/pressure_table.htm

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  9. #8
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    Re: Widening HF 20t press for use as press brake?

    Relying on one bottle jack in the center won't work, I don't think. As others have said, you're stretching it's capability to the max and likely to get substandard results.

    In the end, you'd be replacing the horizontal elements and adding at least two more bottle jacks to stretch out the force applied to your steel. That being the case, you might as well start from scratch since you're already revamping 90% of the existing press.

  10. #9
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    Re: Widening HF 20t press for use as press brake?

    You may consider that beam deflection scales with length cubed. That means a 72 span deflects 13.8 times what a 30 span deflects (in the center) for the same load.

    The area moment of inertia generally scales by height of the beam cubed, so to make up the difference the 4.75 tall c-section would have to be 12 tall. Or wider and not quite as tall, but that should get you started estimating what size beams you will need.

  11. #10
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    Re: Widening HF 20t press for use as press brake?

    The problem is that once you bend that thin aluminum your imagination gets better.

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  13. #11
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    Re: Widening HF 20t press for use as press brake?

    I have build a custom press brake setup for my 50 ton air over hyd H press. I regularly bend 25 tons of pressure on it bending up to 1" solid rounds and wide plates.

    My between frame is 25.25" and I bent a piece of 1/8" on it 24" wide and the bend wasnt to great. The bend angles were way off from end to middle as I only have 1 center cylinder. I also have a 230 ton Cincinnati press brake, but this is my 1 time use/beater unit.

    Anything over 24" wide really needs to have 2 cylinders to keep it bending accurately. If your just bending 1/8" aluminum, I suggest you invest in a box and pan (apron) brake. These are much easier, adjustable, and customizable compared to a press brake setup. My 4 foot 14 ga tennsmith has bend 18" of 12ga stainless. It didnt like it, but it muscled through about 50 bends. Or at least I muscled it through.

    Sent from my SM-G960U using Tapatalk

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  15. #12
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    Re: Widening HF 20t press for use as press brake?

    Quote Originally Posted by Country Metals View Post
    Anything over 24" wide really needs to have 2 cylinders to keep it bending accurately. If your just bending 1/8" aluminum, I suggest you invest in a box and pan (apron) brake. These are much easier, adjustable, and customizable compared to a press brake setup. My 4 foot 14 ga tennsmith has bend 18" of 12ga stainless. It didnt like it, but it muscled through about 50 bends. Or at least I muscled it through.
    Thanks for the reply.

    I have a project in mind that could require 60" of bending a Z - a vertical sheet with a top horizontal flange and then a short rise. My thought on the 6ft/72" width is that is wider than I think I need for now = a bit extra capacity for something in the future. We'll see. I haven't been able to spend any time on this thought - I have a non-fab project that I am hung up on at the moment. Once I get through that I will hit the drawings again on the fab projects - this included - and check out some used listings on what is available in the area. I suppose if I got a deal on a box & pan brake of suitable size that might offset the fab work it would take to make what I want. Lots of thoughts.

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