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Can I bend thicker than rated material on Apron Brake

Portable Welder

Cast Iron
Joined
Jan 9, 2015
Location
Milan, MI
I just a bought a used Apron brake that is rated to bend 10' of 3/16" material ( Hot Roll Steel ), I did a test piece at the Machinery re-seller and it did it effortlessly all 10',

With that being said can I bend 1/4" steel.

When using a standard press brake it takes 7.6 ton per ft to bend 3/16" plate with a 2" bottom die, to bend 1/4" plate with a 2" bottom die requires 15.4 ton per ft.

By my calculations I should be able to bend 5' of 1/4" plate provided the head will slide back far enough to leave room for the thickness of the material plus room for the radius as well.

I'm not looking to brake it but would certainly like to bend 1/4" if at all possible.
 
Thing to remember here is that if you say you can do this, then you half it again and again, you end up were can you bend a bit of 1" 4" wide yeah in theory you have a device that can apply the toruqe in your case to do the bend, problem is can the tooling handle that much force over such a narrow area (me thinks not!!). Hence you need to go carefull. A press break makes this easy, the tooling oftern has a max tonnage per meter - foot of tooling, go over that and bad things happen!
 
yes, of course you can- until the brake breaks.
And every individual brake is going to act differently in this respect.
How many percent was your particular design overbuilt?
Are there cast iron parts that have microscopic inclusions? Are there repetitive stresses on steel parts that have already been stressed X thousand times?
Are there places where somebody else has already weakened or bent the brake over stressing it?

And what is the tensile strength of the 1/4" you want to bend? A36, fer example, needs to be a minimum of 36,000lbs- but some of the cheaper stuff, particularly from offshore, can often be much harder, due to it being cheaper to just toss everything in the electric arc furnace, including stuff with more copper, molybdenum, or other elements, in the scrap than you would have in virgin taconite.

The list goes on- are there welds in your brake's construction?

Bottom line is, yep, you can do it, many people do. And, it could outlast you, doing this.
Or, it could break.

Just remember, the force required to bend metal goes up with the square of the increase in thickness, and thats assuming exact same tensile strength.
 
Thats my next question,When I tested it with 10' of 3/16" plate I used 6" wide flat bar and made a 3" x 3" angle x 10'. It is crowned in the center, Meaning. If I set it on my flat table with the outside of the bent area touching the table. So the question is will I be able to adjust that out of it or is it already sprung.

I already paid for it, just waiting for the check to clear so I wont know till I get it to my shop.
 
Thats my next question,When I tested it with 10' of 3/16" plate I used 6" wide flat bar and made a 3" x 3" angle x 10'. It is crowned in the center, Meaning. If I set it on my flat table with the outside of the bent area touching the table. So the question is will I be able to adjust that out of it or is it already sprung.

I already paid for it, just waiting for the check to clear so I wont know till I get it to my shop.

That's actually a pretty common occurrence with any manual brake when bending full length material at, or near, max tolerance...the reason being no matter how heavy the apron, it will never be as rigid or stiff in the middle of the leaf as it is at the hinge pins. There are adjustments on lighter ga brakes to work this out some...if you have a big nut in the bottom center of your leaf that is welded to struts going left and right...tightening or loosening that nut can raise or lower the leaf above or below the bed and help keep your bends it in straight

see page 11-12

http://www.mittlerbros.com/media/pdffile/2800_16Ga_22Ga_Straight_Brakes_Owners_Manual_04-25-2012.pdf
 
Thanks for the replies John M. and Ries, Yes this is a Dreis Krump, they are actually still showing it on Ebay, its all Gray and they have it listed for $ 10,500.00, I talked them down to $ 9,500.00 so I'm okay with that price, Its been tough have a full service welding, Fabricating and steel sales without a Brake, I have a 1/4" x 10 Accurshear and a 65 ton Scotchman Iron Worker so now I can be a lot more self sufficient.

It was nice to see how effortless it was to bend the 3/16" x 10' so I have to believe there is a reasonable amount of 1/4" that I can bend.
In fact, I diddnt even notice a difference when we ran the leaf with material and without. The speed and noise was the same.
I know there are guys somewhere that have used a brake like this, I'm just curious how much 1/4" they did.
 
If you look at press brake tonnage requirements over a given die size 1/4' requires about double the tonnage over 3/16" per foot. Not a direct comparison I guess but maybe useful?

Guy down the street broke his similar 3/16" power brake bending 1/4" for customers.

Don't know the details except heard he was not doing anymore 1/4" and had repaired it.
 
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It was nice to see how effortless it was to bend the 3/16" x 10' so I have to believe there is a reasonable amount of 1/4" that I can bend.
In fact, I diddnt even notice a difference when we ran the leaf with material and without. The speed and noise was the same.
.

The motor mechanism (gear system on the one Ries linked, I think I've seen some that were hydraulic as well) could probably take more load without a sweat, but that isn't the limiting factor. The fact that your test piece made a canoe shows that you are already pretty much at the maximum of that machine. Brakes like that don't like point loads, so even a narrow piece of flat bar could be detrimental.
 
I have an 8' 3/16" power box and pan brake made by Chicago/D&K. I have a factory letter stating it will safely bend 2' of 1/4" if the top leaf is set back 3X material thickness, rather than the normal 2X. It also states the bend should be made in at least three tries, releasing and reclamping the top leaf each time.

Your brake does have the stiffening angle attached to the apron, doesn't it? Capacity is derated 3-4 gages without the angle. The first brake in Ries' link shows the angle missing, but no note is made about the necessary derating.
 
Gbent, Thanks for your input, My brake is indeed a Dreis Krump and yes it has a stiffening angle but it is set approximately 1" down and based on the picture it has a 1" solid square bare sitting on it which is what comes in contact with the steel as it folds up.

I need to find out what size angle belongs on there, Can manuals still be gotten for these old dinosaurs.
 
A buddy of mine has a 3/8 x 6 apron bender. They use it to bend fifth wheel plates for trailers. I can see from the design that they are really built for what it can do. They aren't designed to more. Look at shear designations as well. Why can't a 1/4" shear cut 1/4" stainless? It's because it's too much for it.
 
The answer:

Can you - Yes

Should you - No

As an example, I can bend 1/2" material using a 2" die on our press brake. I can also show you on our 2" dies where it was done, and what happened. You've now got a machine with a reasonable amount of force. There's lots of things you CAN do with it. And there's lots of things that can go wrong.

We have a new brake quoted...and I've finally talked Matt in to keeping the old one around for bending stuff that's thicker than 1/4". In fact, if you want a perfect example, just look at our press brake...that's what happens when you don't take care of a machine, and consistently use it outside of it's capacity.

Give it about six months, we should have a new CNC press brake for your 1/4" stuff...but being able to bend all of your own work below that should save you a lot of money.
 
Snowman, Its not so much a money thing as its a convenience thing, the 20 minute ride each way, do you have time to fit me in, if you dont, what do I tell my customer.
Hopefully your new brake will be a 240 ton or better for bending 3/8" x 10'
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AS far as capacity, there has to be a reasonable amount of 1/4" that can be done where your not over stressing any pins, the brake that I bought but have not picked up yet doesn't have the proper size angle that mounts to the leaf, in fact, I think its like a 1" square bar so it will deflect under pressure so the first thing I will do is get a 3/8" or 1/2" thick angle x 3x3 or 4x4 to keep the leaf from deflecting.
 
A press brake is rated by ton, and you can put as many tons into it as it's rated for, as long as it's done in the center. That's because all of the force is kept in a vertical straight line.

Apron brakes torque the apron. If you stress it anywhere along the apron, you can stress it more in that place, and if it doesn't come back to shape you'll bend more of a canoe at that one place.
 
Thats why I want to put a big 4" x 4" a 1/2" angle on the apron to make that week point stronger, Keep in mind ( Using tonnage ratings ) The brake can bend 10' of 3/16" which if it were a press brake would require 112 tons of force, Lets say I want to bend 4' of 1/4" should put 61.6 tons of force.
So as far as the pins are concerned, I'm way under the maximum capacity provided I'm able to keep the top or head of the brake back 3 times the thickness of the material to make room for the radius.

With the heavier than normal angle mounted on the apron should disperse the load across the leaf to keep that from springing.

Then my next concern is can the tooling hold up to the heavier steel.
Base on a earlier post, one of the members said he had a letter from Dreis Krump that it will do 1/4" as long as the head is kept back 3 times the thickness and at 2' across.
 








 
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