Bridgeport and Big Blu

G

grizzled gizzard

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Aug 31, 2010
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Would there be any problem with having a 110lb air hammer on the same slab as a Bridgeport milling machine?

I can't run them both at the same time, of course. The hammer is bolted down in one corner. I just got the Bridgeport.

The pad is about 12'x30'x6" thick, with a 12"x12" thick perimeter, poured well, about 50 years old. It's solid.

The hammer doesn't seem to jostle stuff on the pad much, but when I'm working large stock down, you can feel it in the ground 100' away.

The Bridgeport has digital readout, which is one reason I'm somewhat concerned. I need the Bridgeport perfectly leveled and solid, so I don't know if a guy can use some sort of vibration dampening material under it.

Thanks for any help!
 
It would make me somewhat nervous, but to be honest whatever vibration is transmitted can't be worse than taking a really heavy cut with the Bridgeport. You might consider putting the mill on some rubber blocks, even pieces of tire would work ok. It would keep anything sharp from making it through to the DRO scales, which is the only part to really worry about if at all.

They do make rubber vibration mounts that would work, just look at McMaster-Carr or similar. I can probably dig up a part number for you if you're not sure what to get.
 
if you set a glass of water on the Bridgeport table, then use the hammer, do you get much movement in the water? I know this sounds stupid, but it will give you an idea of transmitted shock.
 
I had this same set up with the Bridgeport J head and a 100 lb Big Blue air hammer. My floor is 6 inch concrete with 4" of packed fill under it. The base of the Big Blue had a slight bow across the base plate, caused by welding heat. I placed rubber coal belt under the base plate then bolted it to the concrete floor. This made the hammer response very stiff but without any bounce. Mounting any hammer directly to a concrete floor is not advisable. The Bridge Port, which set 12 feet away from the hammer was set directly on the concrete floor and shimmed to level. I ran this set up for 3 years, the mill was accurate with no deviation and the air hammer moved big billets with ease.
The coal conveyor belt is very dense, it is laced with nylon fiber and incased with rubber. The belt I have is 1/4 inch thick.

Fred
 
Thanks a bunch for the replies, Gentlemen!

I used 4 layers of the type of rubber pad that folks use to keep a rug in place, or line tool drawers with, under my hammer before bolting it down. I know it gets squished to nearly nothing, but I didn't want there to be much shock absorption, just a little something to take out any unevenness in the floor, and maybe a little sound barrier. The hammer works great.

I ordered "vibration damping sandwich mounts" part # 9376K53 from McMaster Carr. They were the biggest ones I saw, with 720lb cap. each. Max deflection, 0.4", so they sound pretty soft.

They have a 1/2" bolt on top and bottom. I figure I'll put threaded or lead sleeves in the concrete, and go ahead and bolt them to the Bridgeport.

I understand the significance of the Bridgeport staying perfectly level, so if I use the dampeners, I'll have to keep an eye on that, especially if I have something very heavy on the bed.

Now that I've gotten more input, I'll take everyone's advice into consideration. I'll check how much shock is transmitted with the water dish before I add the dampeners. I just don't have any experience with this sort of thing, but it sure seems like the hammer puts out some serious vibrations. If I can feel it in the ground a hundred feet away, I don't imagine that's doing the Bridgeport any good.

On the other hand, I'd guess having the Bridgeport bolted solidly is pretty important to maintaining it's level position.

I guess that brings up another question. The Bridgeport should all line up square, whether it's perfectly level or not. Is it more important to be level or have reduced shock?

Fred, did your Bridgeport have digital readout?

Vintagefan, are the DRO scales you speak of part of the digital readout?

Sorry to be asking such simplistic questions. I'm just switching from making everything out of wood, to making everything out of metal. It's a big difference in equipment!
 
I wouldnt think the vibration would hurt a Bridgeport. It may be tough to get a great finish if you were in the middle of a pass on the mill and someone was cranking on the hammer at the same time. But running one and not the other as you mentioned would solve that.

The Bridgeport has probably had a few long truck rides in its time and Im sure the vibration during that was much worse. Glass scales (they provide the feedback for the digital readout) are pretty sensitive to severe shock but they should handle regular vibration just fine. The "glass" part is usually mounted with a silicone adhesive that provides a little flex. Not all scales are glass though so.....

FWIW my Bridgeport is not bolted down but I do try to keep it level, just for the fact that I have a couple jobs I run that I use a bubble level/protractor to set an angle
 
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