using free hand gas cutting

Date 08-20-2010 03:31

D1.1 doesn't address bolt holes much, i would look to AISC for that. Most project specs that I have seen specifically exclude freehand thermal cutting of bolt holes.

By Lawrence (*****)

Date 08-20-2010 04:31

Even one of these?

By MBSims

Date 08-20-2010 11:33

AISC Specification for Steel Buildings, Chapter M:

"Bolt holes shall comply with the provisions of the RCSC Specification for Structural
Joints Using ASTM A325 or A490 Bolts, Section 3.3 except that thermally cut
holes shall be permitted with a surface roughness profile not exceeding 1,000 micro in.
(25 micro m) as defined in ASME B46.1. Gouges shall not exceed a depth of 1/16 in.
(2 mm)."

If you can demonstrate that you are capable of meeting this on a mockup, and show him how you are going to verify it for every hole, the engineer may accept it. If he feels you may not meet the requirements, it is his responsibility to prohibit it.

By jwright650 (*****)

Date 08-20-2010 11:44

...to add to Marty's thought just a bit.....as a general fabricating practice, you also should get rid of the heat affected zone from the flame cutting operation, so the piercing of holes with a torch is OK, as long as you burn the hole undersized and then follow up with a reamer to achieve the correct/final hole size. This way you cut/ream away the HAZ.

By TimGary (****)

Date 08-20-2010 12:36

AISC doesn't allow flame cutting of bolt holes, and requires that bolt holes to be no more than 1/16" oversized.
It's been my experience, that whenever flame cut or oversized bolt holes have to be used, it is done with engineering approval and reinforced with welds that prevent the bolt plates from being able to slip after bolting.

Tim

By waccobird (****)

Date 08-20-2010 13:29

TimGary
Yes they do allow for flame cutting of bolt holes
Please feel free to submit a question/answer to solutions@aisc.org

http://www.modernsteel.com/steelinterchange_details.php?id=93

Steel Interchange

Thermal Cutting
Is it now permissible to use plasma or flame cutting methods to make bolt holes?

Question sent to AISC's Steel Solution Center

Answer
Although previous specifications limited the methods that can be used, the 2005 AISC specification, Section M2.5, allows the use of any hole-making method that results in a surface roughness not exceeding 1,000 microinches. Most methods can be used to achieve this, including punching, drilling, and thermal cutting with flame and plasma equipment.

Charlie Carter, S.E., P.E.
American Institute of Steel Construction

ANSI/AISC 360-05
An American National Standard
Specification
for Structural Steel Buildings
March 9, 2005
CHAPTER M
FABRICATION, ERECTION AND
QUALITY CONTROL
M2. FABRICATION
5. Bolted Construction
Parts of bolted members shall be pinned or bolted and rigidly held together during
assembly. Use of a drift pin in bolt holes during assembly shall not distort the
metal or enlarge the holes. Poor matching of holes shall be cause for rejection.
Bolt holes shall comply with the provisions of the RCSC Specification for Structural
Joints Using ASTM A325 or A490 Bolts, Section 3.3 except that thermally cut
holes shall be permitted with a surface roughness profile not exceeding 1,000 in.
(25 m) as defined in ASME B46.1. Gouges shall not exceed a depth of 1/16 in.
(2 mm).
Best Regards
Marshall

By jwright650 (*****)

Date 08-20-2010 13:49

We don't burn holes here at our plant, but we have pre-ordered 6" thick baseplates from a supplier before that have had the holes burned...when we asked the EOR, we have never had a problem with anyone accepting that practice.

I have seen many job specifications that prohibit enlarging or burning holes if they couldn't make up the connection in the field.

By waccobird (****)

Date 08-20-2010 13:59

John
I too have been on projects that the Beam even if wrong due to customers mistake had to leave site to be cut, holes worked or any discrepancies not allowing it's erection.
We have a piece of equipment that I fancied for a couple years waiting for AISC to do away with the line E.O.R. Approval for thermally cut holes.
Which they did.
Now we have automated some of our our procedures and cut days from projects.
http://www.youtube.com/watch?v=aVWzgmqtBKg
Best Regards
Marshall

By TimGary (****)

Date 08-20-2010 16:10

Thanks for the clarification.
I worded my post wrong.
I should have stated that free hand torch cutting of bolt holes within tolerances allowed by AISC is nearly impossible.
A good way to do it, as John mentioned, is to pierce the steel with a torch and then finish the hole with a mechanical reamer. This works well, as long as the hole is lined up properly, and can be done as a repair without engineering approval.
The intent of my post was to point out that hand torch cutting with imperfect results may be accepted if the appropriate steps are taken.

Tim

By nevadanick (**)

Date 08-20-2010 14:47

MAG DRILL AND A ROTOBROACH

By bert lee (**)

Date 08-23-2010 02:46

thanks for all your input.

it was resolved by revising the drawing that indicates "flame cut holes"

anyway, it is good to be reminded of the correct way by using "mechanical reamer" and the tolearnce on surface roughness if using flame cut.

bert

By tekla019 Date 05-17-2011 11:00

Question. Beyond roundness and roughness considerations, does plasma cutting bolt holes introduce stress in the area where the hole was made. That part of the beam gets locally heated (expanded) then cooled. Does the actual removal of material relive any stress or is there residual stress. A client of mine is looking into one of these machines: http://www.tekla-detailed-structural-fabrication.com
and wants to know if there is some factor they need to apply when analyzing stresses in bolted connections when the holes are thermal cut.