Drilled Holes vs Tourched/Flame Cut Holes 10

[TCPhoenix]

I am working on a project that requires holes 1-5/16" dia. 1/2" deep to be drilled in A36 steel. These holes being drilled are in the field, so we do not have the ability to use a drill press.

The contractor performing the work would like to tourch cut the holes instead of drill them.

Is there any reason the holes should not be tourched/flame cut?

 

[JamesBarlow]

I'm agree with Moltenmetal on this one.

It would take a good ironworker a few minutes to mark the hole and burn it out with a nice enough finish to structural work.

If your not sure of your guys then drilling may be the way to go but I would let my guys torch the plate with no concerns.

 

[TCPhoenix]

dvd,
we do not have the concrete under the steel when we are cutting the holes so we dont have the isssue of dulling the blade on the concrete. And we are limited with space so welding a clip on the side is not possible.

A flame cut hole and heavy square washer plate is something we might consider.

 

[swearingen]

The American Institute of Steel Construction specifically requires that bolt holes be reamed or drilled for many of the reasons stated above. If the anchor rods are to come in contact with your base plate, these holes should be drilled, not cut.



If you "heard" it on the internet, it's guilty until proven innocent. - DCS

 

[moltenmetal]

The AISC can say what they will, but you will see a torch in the hands of ironworkers all over a site when it comes time to make stuff fit. I doubt there's even a reamer on the site most of the time... Mind you, some of those guys could do brain surgery with a torch, they do such a neat job. You will also see heavy plate sections automatic flametable cut, complete with holes, with edges broken and interiors cleaned out with power tools as required. If this were in a structural steel fab shop, a hole that size in 1/2" plate would be punched by a hydraulic combination shear/punch/bending press, coincidentally also called an "ironworker".

The mag drills with shell cutters are fantastic little dealies- we've got quite a few of them in our shop. But the torch is king on a site. No cord to worry about etc., and far quicker in the right hands.

 

[IceStationZebra]

My apologies MintJulep - I missed that. ISZ

 

[tomwalz]

Theory?

Since you asked. Steel is iron with carbon in the lattice. Heat can make the carbon come out of the lattice and lead to graphitization on the surface. That can be very important when brazing to laser cut plate. In this case I think it would be marginally relevant at best.

Remember the haircut rule. You can lose weight by getting your haircut, but how important is it really.



Thomas J. Walz
Carbide Processors, Inc.

http://www.carbideprocessors.com

 

[Qshake]

From a structural engineering aspect it is always best to have holes that are punched and reamed. If there are issues in the field, mis-aligned bolt holes should be reamed to the next size and a larger diameter bolt installed.

There are two structural connections: bearing and friction. Bearing connections will resist load with the bolt actually bearing on the connected material. For the bolts to equally share load and keep connected material stresses to within the allowable it is necessary for the hole/bolt arrangements to have the same tolerances such that they all engage at the same time. I won't go into friction connections.

Burning the holes in will leave burring and uneven or irregular surfaces that will need to be reamed anyway for good work. Any work not reamed will leave potential micro-cracks in the irregular surface that can in cases propagate.

Usually a Hougan Drill is around somewhere just need the proper motivation for the contractor to bring it out....don't pay him until he does!

Having said all that, sure there are sites where no inspection is performed and ironworkers will unabashedly use the gas-wrench to fix things. However, when an engineer is on site and this is the area under consideration it must be dealt with. Bad practice is bad practice even if the ironworker says he's been doing it that way for 20 years.





Regards,
Qshake

Eng-Tips Forums:Real Solutions for Real Problems Really Quick.

 

[GregLocock]

In the automotive world all well designed bolted joints are friction joints, with clearance holes for the fastener, ie zero shear capacity.






Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[KiwiMace]

I asked a guy today and he promoted cutting all field holes with a torch but for one exception...

...when they are blind.

Gosh they are funny around here.

 

[tbuelna]

TCPhoenix:

A36 structural steel is generally referred to as "mild steel" or "low carbon steel" (ie. less than .25% carbon). Its low carbon and alloy content makes it easy to weld, makes it ductile, gives it low tensile strength, and makes it relatively unresponsive to quench hardening. So if you're going to cut a hole with a torch, A36 is the best steel to do it in.

Of course, having said that, why would you want to make holes using a torch in the first place? A36 is a very soft and machineable metal. Why not use a magnetic drill press? You'll end up with nice, clean, round, accurate holes, instead of jagged, inaccurate holes with lots of slag around the edges. And a warped plate to boot.

And besides, how do you control the depth of a hole (to 1/2"?) using a torch?

 

[11echo]

I've work in the oil fields and refinery for a number of years. When there is a problem with equipment and or piping components, it's usually the welders that are dealing with installation or assembly of said items that finds the problem. AND because the welders tools normally are arc welding machines and cutting torches it these "tools" that are used to "fix" the problem! I've seen a number of "fixes" done with a cutting torch! This is usually a quicker way of doing things and in this area acceptable as long as it gets the job done ...with out destroying the said equipment.