I need to use a press brake to get some work done. But there isn't one in my shop... or at least there hadn't been one in my shop. In this Instructable I will show you how I made my own press brake.
For those of you who don't know, a press brake is a tool for bending metal by pressing two dies together. They can be powered many different ways, but by far the most popular method is some sort of hydraulic cylinder to apply literal tons of force. Lucky for me my shop has a hydraulic press. So all I need to do is make up some press dies that fit into my press. And by another incredible coincidence I happen to have a lot of really heavy steel that could very easily (less so in hindsight) be made into those dies.
Step 1: The Plan
Anytime I build something I do it in a bit of a slap-dash fashion. No matter how detailed my plan I always find myself improving or changing things as I go. But the initial concept is usually pretty close to the final product.
Sometimes with projects like this I will take a look around on the internet and see if somebody else has better ideas than me. In this case there were a few ideas that I incorporated into my plan. The overall plan is to use the beefiest hunks of steel from the steel rack to make a base to hold the dies, and a heavy beam to distribute the force of the press cylinder over the width of the die. And for some reason I want interchangeable dies so I can do radius bending in the future.
What it's made of:
- 1" x 6" x 30" Steel bar
- 1" x 2" x 26" Steel bar
- 1/2" x 6" x 26" Steel bar
- 1-1/4" x 1-1/4" x 26" Steel bar x 2
- 3/8" x 3" x 28" steel bar x 2
- 3/8" x 4" x 30" steel bar
- 3/4" x 12" cold rolled round stock x 2
- 3/4" x 6" schedule 40 black pipe x 2
- 1/4" roll pins x 3
- And an old spring that didn't belong to anything important
Some things I used:
- Vertical milling machine
- MIG welder
- 7" angle grinder
- 4 1/2" angle grinder
- Horizontal band-saw
- And sundry other hand tools
Step 2: Cut and Prep
To start I cut the various pieces of stock to their prescribed lengths. Which in the beginning was the base, dies, guides, and beam. Later I would "decide" to add a few extra pieces.
Step 3: Machining Interchangable Parts
This is the most time consuming step. To make the dies I need to machine the stock to a shape suitable to be press dies. I did things a little out of order but it made sense at the time, or maybe not, I don't think well in layers. Because I want interchangeable dies I need a way for the die and press beam to attach to one another without being permanent. Which means my preferred method, welding, is out of the picture. Instead I settled for machining a slot the length of the die and cross drilling a few holes for roll pins. That way when I want to change dies I just drive the roll pins out and replace them with the new die.
The reason this takes so long is because I have to remove a half inch by one inch by the 26 inches of the die. Which is a quarter of the volume of the whole piece of stock. Most good machinists will tell you to remove material using the fastest possible method. Saw out the section of stock you need to remove then machine it to the desired dimensions. Rather than spending all the time machining all that material. Sadly there is no way to accomplish this quickly. None of my tooling other than the milling machine has the capacity to remove the necessary material.
Step 4: Machining Upper Die
After the slot has been milled I need to shape the die like a die. To do this I cut a bevel on both sides of the die. Because I removed so much material from the die to make the slot in it I had to slide a piece of 1/2 inch X 1 inch X 26 inch steel bar. This was so there would be something to resist the clamping pressure of my work clamps. Remember how I thought I might have done things out of order?
Also I am almost positive that there is a better way to setup this machining process. But with my limited tooling this is the best I could do. This is not high precision machining here folks.
So back to bevels. I set the head of the mill to 40 Degrees, because for some reason 45 Degrees seemed too aggressive to me. 40 Degrees also affords me the option of bending past 90 Degrees. Because 40 plus 40 is 80! I did not want a sharp knife like edge on the die either. Because I want to bend metal not cut it. So I decided on the arbitrary number of 1/8 of an inch to separate each bevel across the working end of the die. In effect creating a very tight radius die.
Step 5: Machining Lower Dies
The lower dies are machined in exactly the same manor as the upper die. I even left the head of the milling machine at the exact same angle. One reason for this is it gives lets me have almost perfectly mirrored angles to align with one another. But mostly it was because changing the angle of the milling head is a horrendous pain in the neck. I hate to make any adjustment to take something out of square, because it is so much work to make it square again.
So just like the upper die I cut a bevel in the two pieces of stock that would become the lower dies. The one oddity here is that the pieces of square stock I had laying around were not the same steel alloy. One die half was softer and was easy to machine. The other was harder and took twice as long to machine. In the future this could cause some issues, but paid for steel is paid for steel.
Step 6: Final Machining
Up to this point there is an upper die, two halves of a lower die, and other lumps of metal that need to become useful parts. The 1/2 inch X 6 inch X 26 inch piece of steel bar needs to have holes drilled in it to match the three holes in the upper die. And The 1 inch X 6 inch X 31 inch piece of steel bar and the 3/8 inch X 4 inch X 30 inch steel bar need holes drilled in them to accept the 3/4 inch round stock.
Step 7: Welding the Press Beam
Now to ruin all this pretty machined metal by welding it together. Honestly there was a path for me to make this a 100% machining project, but I don't have the patience or the time for that. I was raised by a welder, so welding is usually the easiest way to get stuff done.
The main press beam is comprised of four parts plus the upper die. The 3/4 inch pipe needs to be welded to the 1/2 inch X 6 inch X 26 inch piece of steel bar. But because of a lack of foresight it needs to be 28 inches long. Whoops! So in my slap-dash fashion two pieces of 3/8 inch X 3 inch X 28 inch steel bar will be added to the press beam. I have been telling myself this will add strength and rigidity to the part. But really it's just a hastily applied band-aid.
Step 8: Welding the Base
The guide rods (3/4 inch round stock) need to be welded to the the base plate (1 inch X 6 inch X 31 inch steel bar). These guide rods need to be square to the base plate to ensure proper and smooth operation. I didn't quite achieve this. The first rod went fine but the second one was a little sour.
When welding I always try to consider how the thermal expansion/contraction will affect your work. In this case I had a little too much heat in one spot for too long and the resultant "draw" pulled the rod to one side. Thankfully in this case it is manageable because of the short length of the parts. Otherwise I would have had to cut out the weld and tried again.
Step 9: Minor Adjustments
Part of managing the wonky guide rod is beveling the holes in the plate for the lower dies. The sharp shoulders of the holes won't move easily down the guide rods easily. The best way to deal with this would be to countersink the holes. But I don't have countersink bit large enough for a 3/4 inch hole. I do however know a way to add a bevel to a hole this large. Over the years I've found the easiest way to bevel holes is to grab a step drill and lightly drill the shoulder down.
Step 10: Welding the Lower Die
Now that the press beam and base are together the lower die can be welded. There needs to be some space between the die halves so I re-purposed some 3/8 inch key stock to act as spacers. When I get everything where I want it the welding can begin. After a few strategically placed tack welds I am able to remove the clamps and spacers and weld things in earnest.
Step 11: Clean-up and Finishing Touches
Once I have everything welded to my satisfaction it's time to make it as pretty as possible. Any sharp edge or corner is rounded over with a grinder. Splatter and weld smoke gets hit by a wire brush. And the unsightly uneven welds are smoothed with the grinder.
Step 12: Does It Work?
After making it pretty it's time to see if it will do the job it's made for. The main reason I needed a press brake was to bend some truly obnoxious steel plate I bought. This plate is a hardened abrasive resistant alloy. Every other attempt I made to bend it proved futile. But this homemade tool bends it just fine.
Step 13: Get Back to Work!
Like any boy all I want to do is play with my new toy.