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Locating Holes in Welded Structures

Question asked by John Wayman on Aug 21, 2019
Latest reply on Aug 21, 2019 by David Matula

Not altogether Solidworks-related, this one.

We are a one-off, special-purpose machinery type of organisation, mostly robot-based equipment. 

Much of our kit is based on a welded, box section, steel frame, to which all the remainder of the equipment (top plates, covers, HMI brackets, etc.) is bolted. The welded frame is made by a sub-contractor.

We have constant problems with mounting holes in the welded structure (sometimes tapped into the box section web, but more often through clearance holes) not lining up with the holes in the items we bolt to the frame.

We have tried specifying, on the drawing, that holes should be drilled after welding. That doesn't seem to happen, however.

We are always up against short timescales, so there isn't time to send it back and get them to re-make it.

We invariably end up drilling holes out oversize, or slotting them with a file.

I am wondering two things:

1. How do other companies address the problem of holes in welded structures not lining up?

2. Is there a good way to fit some kind of floating nut to the wall of a box section?


Thanks for reading,