Nees help - Non flame cut hole in 2.5" plate

[Mark @ Everlast]

Your living in the sticks and my living in the sticks are two different things LOL. My closest IKEA Is 500km away hahaha... Ikea is a measuring system now. I don't get to choose who does the cutting. I contract to the company that bids the work, orders steel and then give me steel and prints and says go. So I want to keep my costs down, and make my life easier. So far I am going to try a boring bar on a mag press and see how that works. That diamond core bit looks promising as well. Are they high speed? I am not familiar with them im assuming they are available in various arbors?

As far as plasma goes, its the same as a torch. Granted more accurate but still a flame, even a LASER is considered flame cut to an engineer.

No Ikea around here either. I do live in the sticks. Closest one is 200 miles...and most people here would have to Google it to find out what it was.

A hgih def plasma would be accurate and smooth...I'd go back to the engineer and have him define things better because there are accurate flame cut systms. Flame cut versus electric arc cut is different in my book.

 

[lostcause]

No Ikea around here either. I do live in the sticks. Closest one is 200 miles...and most people here would have to Google it to find out what it was.

A hgih def plasma would be accurate and smooth...I'd go back to the engineer and have him define things better because there are accurate flame cut systms. Flame cut versus electric arc cut is different in my book.

on this point i'm pretty sure you could talk to the engineer until you die of old age and you still won't get any satisfaction. in dealing with a 3" hole through 2 1/2" of steel you're going to have the chance of some taper in the hole and possible notches from the cutting, however small they might be. since this is a structure being built and then lifted into place, i'm betting the engineer wants these holes to be smooth and consistent to develop bearing across the entire length of the hole. in practice i'm sure that any hole would probably work, but you're asking someone to sign off on this, which is fairly unlikely. regardless of whether the tests show virtually no difference in flame cut and mechanically cut holes, they still aren't commonly allowed.

as another example, there are bolts commonly used in the industry that are held by a splined end when tightened. the splined end shears off when the bolt has been properly torqued. i worked a job literally 10 years after these bolts had been the norm, and the engineer would not allow them. he insisted on using a crushable washer under the nut to indicate proper torque, which was the old standard. no amount of talking would change his mind.

 

[Mark @ Everlast]

I don't know if you have ever seen a high definition plasma work or not...there's no notches and very little if any taper from what I've seen. There's as much or as little as a water jet.

 

[Shield Arc]

on this point i'm pretty sure you could talk to the engineer until you die of old age and you still won't get any satisfaction. no amount of talking would change his mind.

Boy isn't that the truth! If you don't have a PE after your name, you're wasting your breath. I've even seen it where two PEs would be arguing, sooner or later one of them will say, "well my number is lower than yours"! Standing back watching this reminds you of two kids on the play ground.:laughing:

 

[mjncad]

Doesn't have anything to do with accuracy but the changes at a molecular level that the flame/plasma/laser produces in steel.

I would think that any heat generated by any welding processes is going to cause molecular changes over a wider area than a laser ever will. Also a laser or waterjet will make a far smoother hole than a plasma or O/A torch will; thereby minimizing the chance of stress cracks developing at any ridges left in the hole from the cutting process.

However; the OP has mentioned these beams are fairly large, that he is out in the sticks and most likely a good distance from any laser or waterjet capable of cutting the required holes. If he can't convince the engineer that a plasma cut hole is acceptable; then it sounds like he's stuck with using a mag drill and whatever cutting tool he uses to get the job done.

I've worked with overly **** engineers and they can be like an old woman who can't make up her mind, and I've worked with lazy bum engineers that take the quick and easy way out. Fortunately most engineers I've worked with are well educated people with common sense, and in some cases if time permits will gladly explain their reasoning for an engineering decision.

When I was managing a CAD system, we had one project manager/engineer for some Gummint projects go on the war path over the quote marks in the AutoCAD SIMPLEX/ROMANS font looking the same as the foot and inch marks. Well DUH, they are since they use the same keys. He wanted little curlicue quote marks, and although I could have modified the fonts to accommodate him; I just told him that he would have to contact Autodesk directly. He went away. Besides I wasn't going to modify fonts that were used by every project in the company just to satisfy this clown's ego.

 

[Brad_Blazer]

Instead of asking the engineer of record for an exception, ask for a recommended reasonable method of cutting the holes. When I'm designing a part, I always consider how it can be made.

 

[mjncad]

Brad...you're showing common sense...be careful doing that. :thumbsup: I like your idea of throwing it back on the engineer to actually consider how something will be fabricated, not just dictate that it shall be done.

 

[lostcause]

Brad...you're showing common sense...be careful doing that. :thumbsup: I like your idea of throwing it back on the engineer to actually consider how something will be fabricated, not just dictate that it shall be done.

i don't think that a 3" hole in 2 1/2" of material is anything out of the ordinary to ask for, and i doubt the engineer would either. i've seen plenty of 2" and larger anchor bolts which will require a hole larger than 3" and the base plates are often well in excess of 2 1/2". these holes are always drilled. it just happens that this now needs to be done where there isn't a large fab shop available. quite often steel will travel thousands of miles to its final destination, so you don't consider that when it is designed - only the contractor with the winning bid needs to worry about that.

 

[mjncad]

it just happens that this now needs to be done where there isn't a large fab shop available. quite often steel will travel thousands of miles to its final destination, so you don't consider that when it is designed - only the contractor with the winning bid needs to worry about that.

That is very often the case; but it sounds like the engineer won't work with the tradesmen to come up with an acceptable alternate method of creating the holes given the job site location, tooling available, and schedule.

 

[Bikewanderer]

Just saw this thread. Not sure if this is still a need, but you have two really fast options. One is to find someone with a burntable and cut out the holes on it, the other is to use a mag drill and annular cutter. We've done up to 4" diameter with an annular cutter and something like 3" deep. Maybe 5 minutes per hole. Just make sure you're sitting down when you look up the price of the cutter!!