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Drilled Holes vs Tourched/Flame Cut Holes
10

Drilled Holes vs Tourched/Flame Cut Holes

Drilled Holes vs Tourched/Flame Cut Holes

(OP)
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?

RE: Drilled Holes vs Tourched/Flame Cut Holes

torch cut holes are normally a no no....but are OK sometimes

tell them to look into a magnetic drill with a rotary broach attachment.

drills much much faster than a standard drill bit, especially in larger sizes

RE: Drilled Holes vs Tourched/Flame Cut Holes

What will the heat do to the mechanical properties and does it matter for your application?  (Sorry still not familiar with most US grades of material)

How neatly/accurately can they make the holes with the flame?  Does it meat required tolerance?

KENAT, probably the least qualified checker you'll ever meet...

RE: Drilled Holes vs Tourched/Flame Cut Holes

Hand drilling could go OK.  I usually like to drill smaller pilot hole to locate, first.  Large drills have trouble removing that center portion.

RE: Drilled Holes vs Tourched/Flame Cut Holes

the rotary broach does away with the need of a pilot hole and has pin that centers up on just a center punch mark.

neat tool and fast and clean

RE: Drilled Holes vs Tourched/Flame Cut Holes

We are currently doing a job with a magnetic drill and one of these cutters..It's like an annular cutter, but has a spring loaded center. Cuts very nicely and clean. Most importantly, it's in the right spot.  I say no on the torch cutting it's it something even remotely precise.

RE: Drilled Holes vs Tourched/Flame Cut Holes

(OP)
We are going to attempt to use a Rotary Broach bit, one made by Milwakee called "Hawg Bit".  The holes are for anchor bolts so the precision is needed so the bolts sit snug in the hole.

What you guys have said is help full with the rotary info.  But i am looking for some theory behind why you should not tourch cut. I am an engineer and want to convey some theory on why tourch cutting is not recommended.

Talking throught the application, specifically the part about the holes need to be snug around the anchor bolts have given me some reasoning as why tourch cutting is not recommended but i would like more.

RE: Drilled Holes vs Tourched/Flame Cut Holes

OK. once more with feeling...

Quote:

What will the heat do to the mechanical properties and does it matter for your application?

This is the other big reason I know of that torch cutting can be a problem apart from the tolerance issue.

Like I said I'm not familiar with US grades but you're effectively applying some kind of uncontrolled heat treat to the surrounding material.  What will this do to the mechanical properties, or in some cases appearance?

KENAT, probably the least qualified checker you'll ever meet...

RE: Drilled Holes vs Tourched/Flame Cut Holes

Last page of this

http://www.hougen.com/downloads/punch_pro/Punch-Pro%20Catalog.pdf

for more options on rotary broach.

Depending on the location, you might be able to find a hydraulic punch with sufficient capacity.

This one comes close:

http://www.hellerson.com/hydraulic_punch.htm

You don't want to flame cut because:

You have no idea what the HAZ properties will be, or how large it will be.

The hole will have nasty edges that will be where the cracks start.

RE: Drilled Holes vs Tourched/Flame Cut Holes

Mint I thought of the rough edges after I posted, it's something else to consider especially if there's any kind of cyclical loading.

KENAT, probably the least qualified checker you'll ever meet...

RE: Drilled Holes vs Tourched/Flame Cut Holes

Torch cutting does not give circular holes.... and may leave all kinds of "junk" at the edges.  Also the accuracy of the size is doubtful.

The heat may also (will) change the properties of the steel.

If you are building "junk" then this is just fine - but if you are building something for real - don't allow it

RE: Drilled Holes vs Tourched/Flame Cut Holes

How about a portable plasma cutter?

Don
Kansas City

RE: Drilled Holes vs Tourched/Flame Cut Holes

If you want a good hole for snug fit you are going to have to ream after torch cutting otherwise you have point contact surface.

RE: Drilled Holes vs Tourched/Flame Cut Holes

(OP)
Kenat, i dont know what the heat will do.

We are in the process of locating an annular cutter, and we will begin cutting tomorrow.

RE: Drilled Holes vs Tourched/Flame Cut Holes

2
I wouldn't worry much about the heat effects on A36, it was probbly all flame cut to start with.

Regards,

Mike

RE: Drilled Holes vs Tourched/Flame Cut Holes

I like the rotary broach and mag-base drill method. Not knowing the arrangement, my concern about this is whether the material is directly in contact with a concrete floor and the slug would be difficult to remove and/or if the broach would come in contact with the concrete and dull quickly.

Is it possible to field weld some clips with the correct size hole? Under some circumstances this would provide quicker, better looking results.

The other option I see is to torch the holes and weld a heavy "square washer" with correct hole diameter on top of existing material.

RE: Drilled Holes vs Tourched/Flame Cut Holes

I'm surprised that no one mentioned fatigue. Depending on the loading, all of the irregular notches produced by the torch are crack initiation sites.

Obvious answer #2: fire hazard

Obvious answer #3: it will never be round or in the correct location.

Obvious answer #4: It is easier to make a mistake.

Obvious answer #5: Your customer will thing you done everything the cheap/easy way.

ISZ

RE: Drilled Holes vs Tourched/Flame Cut Holes

Uhm..

Quote (Me):

The hole will have nasty edges that will be where the cracks start.

RE: Drilled Holes vs Tourched/Flame Cut Holes

Whatever your project is it must not have too high of a degree of sophistication or you would be using plate with a higher pedigree than A-36 not that it is bad in any way.  I have had projects where we opted not to use A-36 because the engine block parts left in the plate from the mill tore up the drill bits.

rmw

RE: Drilled Holes vs Tourched/Flame Cut Holes

3
A36 steel work in the field, only 1/2" thick, and no indication what this is being used for?  I'm surprised the holes weren't torch cut before anybody had the chance to ask?!

RE: Drilled Holes vs Tourched/Flame Cut Holes

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.

RE: Drilled Holes vs Tourched/Flame Cut Holes

(OP)
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.

RE: Drilled Holes vs Tourched/Flame Cut Holes

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

RE: Drilled Holes vs Tourched/Flame Cut Holes

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.

RE: Drilled Holes vs Tourched/Flame Cut Holes

My apologies MintJulep - I missed that. ISZ

RE: Drilled Holes vs Tourched/Flame Cut Holes

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.
www.carbideprocessors.com

RE: Drilled Holes vs Tourched/Flame Cut Holes

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

RE: Drilled Holes vs Tourched/Flame Cut Holes

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

SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

RE: Drilled Holes vs Tourched/Flame Cut Holes

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.

RE: Drilled Holes vs Tourched/Flame Cut Holes

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?

RE: Drilled Holes vs Tourched/Flame Cut Holes

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.

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