Drilling bolt holes in restored base metal

[StructuralNomad]

Are there are any guidelines on drilling bolt holes in restored base metal? In one of the modification project, the bolt holes are drilled in wrong location resulting in partial(in some cases complete) misalignment. The fabricator is suggesting to seal the bolt holes with plug weld and redrill over the weld for correct alignment.

AWS D1.1 recommends procedure for sealing the bolt holes but does not extend redrilling the sealed bolt holes.

Regards,

 

[connectegr]

This is done frequently. Use caution when drilling the holes. Drilling through weld metal can cause the drill to drift, resulting in a non-standard hole. If the intent is to burn new holes (not my recommendation), also use caution. I would suggested to burn a smaller hole and ream to the required diameter.

There may be other alternatives to repairing and redrilling holes. This can be very time consuming.

http://www.FerrellEngineering.com

 

[Tmoose]

what's the material and the "bolt" size ? Is the "bolt hole" tapped or a clearance hole?

 

[SectionIX]

Perform MPI in the target area, and UT of the area the greater of one inch or 2X the diameter of the re-drill area.

I agree with connectegr; burning the new holes will add to the thermal cycling of the base metal, which is never a good idea. Stacking heat affected zones on on top of another will weaken the area, and make drilling (and tapping operations as required) more difficult.

 

[connectegr]

Another thought...
use additional caution if these mis-aligned holes occur in a seismic connection detail. Restrictions apply on making repairs within the protected zones. Welding to repair the holes can create stress risers, which are not permitted.

http://www.FerrellEngineering.com

 

[StructuralNomad]

Thank you all.

Tmoose, bolts are 20mm in Diameter and the bolt hole are clearance holes.

Will cover the above mentioned precautions on my response to Fabricator's query.

Regards,