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Drilled Holes vs Tourched/Flame Cut Holes 10

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TCPhoenix

TCPhoenix

Mechanical
Jan 23, 2007
24
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?
 
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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
 
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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...
 
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Hand drilling could go OK. I usually like to drill smaller pilot hole to locate, first. Large drills have trouble removing that center portion.
 
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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
 
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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.

Drill1.jpg
 
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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.
 
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OK. once more with feeling...

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

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...
 
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Last page of this


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:


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

Regards,

Mike
 
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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.
 
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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
 
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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
 
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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?!

 
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