Press brake mods- Ok to do this?

[M. Moore]

I am working on adding a better back gauge to my small press brake. It is a Bantam 24" wide x 24 ton. The apron is 1.75" thick and I would like to drill a hole right in the center about 5" down to access the back gauge adjustment lead screw.

I can also do this by using gears and a chain to offset the crank so I don't have to drill through the apron. The apron has two holes in it now for the guide rods and you can see the bolt heads in the photo. I don't want to do something dumb that I will regret so I am asking first and my gut says that a 1/2" hole would probably be fine.

I just finished making a 3" bottom die so I can bend 3/8" flat bar and have a job that needs some accurate bends.

Thanks
Michael

 

[52 Ford]

The question is, "will a 1/2" diameter hole 5" down, in the middle of the apron compromise the structural integrity of the press?".

Right?

If so, I really doubt it.

Looks like plenty of "meat" there, especially if it's that thick. I reckon you could weld reinforcement around the hole if you're REALLY worried about it.

In any case, failure shouldn't be dangerous to the operator. I'd aught to be a ductile failure, not a brittle failure. In other words, exceeding the capability of the 'apron' should cause it to bend, not snap.

I'm no expert, though. So, don't take my word for it. Just thought I'd cast my vote and give a little bit of reasoning behind it.


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[john.k]

Just remove any sharp edges from the hole and thread that might be stress raisers......in general a hole of small size does not alter the tensile properties of the beam ...or whatever.

 

[M. Moore]

Thanks 52 and John for confirming what I thought was going to be acceptable. Small hole, large beam, not really a problem.

52, you are a night owl, John- enjoy your dinner or is it tea?

 

[Scottl]

Suggestion: Instead of a chain use a timing belt and pulleys. This will give you a more positive drive and a better "feel".

 

[M. Moore]

Scottl,
Thanks for the suggestion but I am going to drive the leadscrew directly through the hole I am going to drill in the front apron. I will have to figure out a way to make a removable crank. Most of the time it can stay in there but needs to be removable. I ordered a 24” digital scale so I can set the distance easily.

 

[Bondo]

I do accurate bends all the time with a manual back gauge setup. I machine a block that I can sit on the bottom die and set the back gauge from that. You can add shims or machine the block smaller to get it to move the back gauge 0.001 if needed. This only works for single bending though

 

[52 Ford]

52, you are a night owl

Indeed

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[M. Moore]

Bondo, I will be setting it manually for now and I can set it accurately enough but want a faster set up for the future. How does your machined block sit on the bottom die and give .001 accuracy? Got a pic?

 

[dkmc]

How about a second scale on the Z axis to control depth accurately as well?

 

[52 Ford]

How about a second scale on the Z axis to control depth accurately as well?

One of those Z axis DRO kits for a Bridgeport quill would be pretty cool.

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[dkmc]

I'm considering one of the 2 or 3 axis low cost China DRO's from Ebay for my 17-48 Diacro. Having a 3 axis unit on a horizontal mill and a 2 axis on 2 different Lathes, I'm very happy with their accuracy and log term durability.
So, for the press brake, one on the back gauge, one on each side of the ram, for obvious reasons. It could remove a lot of the guess work from setups. I'm referring to the actual DRO units with glass scales, not the iGauging type, although I know someone that did fit the super low cost iGauging DRO's to their press brake with great success as well. The total cost would be almost laughably low considering the added versatility without spending $6-8k for a cnc back gauge setup.

One of those Z axis DRO kits for a Bridgeport quill would be pretty cool.

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[52 Ford]

I'm considering one of the 2 or 3 axis low cost China DRO's from Ebay for my 17-48 Diacro. Having a 3 axis unit on a horizontal mill and a 2 axis on 2 different Lathes, I'm very happy with their accuracy and log term durability.
So, for the press brake, one on the back gauge, one on each side of the ram, for obvious reasons. It could remove a lot of the guess work from setups. I'm referring to the actual DRO units with glass scales, not the iGauging type, although I know someone that did fit the super low cost iGauging DRO's to their press brake with great success as well. The total cost would be almost laughably low considering the added versatility without spending $6-8k for a cnc back gauge setup.

Ah, I gotcha. That makes sense. Those little iGauging DROs are pretty neat, though. I've never used one personally, but have heard good things. ESPECIALLY for the price.

I mean, it's basically just a digital caliper.

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[dkmc]

I have one of the IGauging DRO's just on the table of my Hardinge horizontal mill. It's quite accurate for what it is. And for what it does, counting dials is for the birds.

Ah, I gotcha. That makes sense. Those little iGauging DROs are pretty neat, though. I've never used one personally, but have heard good things. ESPECIALLY for the price.

I mean, it's basically just a digital caliper.

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[Strostkovy]

You're fine.

I happen to know that Simpson Strong Tie regularly voids their press brake warranties by cutting huge slots or holes in their CNC press brakes.

 

[M. Moore]

I don't need a scale on the Z axis as I put a front mounted air shutoff switch with a bracket and threaded rod to set the stroke length via a microswitch. I got the idea from Dan Gelbarts video on press brake work for prototypes. He used an air shutoff switch but I did not have one of those in my stash of stuff but I did have an electric air shutoff solenoid switch so I wired that in and used the microswitch to turn the solenoid on and off. I just finished it on Friday and it works very well. This machine has stroke control at the back which is not very convenient so the front mounted control is perfect. The foot switch still functions as it should and the air switch just shuts off the air flow to the cylinders.
This machine only has two inches of stroke so if I need it I can just add a 2" stroke dial indicator to help with repeatability. (and a book to write down the settings)

 

[52 Ford]

You're fine.

I happen to know that Simpson Strong Tie regularly voids their press brake warranties by cutting huge slots or holes in their CNC press brakes.

LOL

I've installed a LOT of Simpson Strong Tie joint hangers.

They make a good product, anyway.

Edit; I can't get your name right in my head. I glance at it and I'm like, "Ah! Strosnovsky replied!"

Anyway, still trying to get it right, Stroganoffsky.

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