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From: "Jim Wilkins" <muratlanne@gmail.com>
Newsgroups: rec.crafts.metalworking
Subject: Re: FWIW first welding job, 2 years on
Date: Sat, 7 Dec 2024 09:10:15 -0500
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"Richard Smith"  wrote in message news:m1a5d7bsh1.fsf@void.com...

I have contributed - this has started to happen.  I used "the bubble"
(spirit-level) on some fabrications, and found that what it cost in time
to set things off parallel at the first stage was more than made-up for
by the "ideal" time it took to fit-up and weld the rest.
Show the approach and the corrections, the owner and designer where on
the press-brake with dial-gauges, etc., and made adjustments.
ie. there is something positive going on. ...
-------------------------
Could you expand on that?

I found out the hard way how much welds can distort a precise alignment, 
especially a weld across an inside corner. I had to jack the sawmill ladder 
frame parallel (enough) and mill the shrunken gap in a bending brake hinge 
assembled from surface-ground plates. The surface welds along the sides of 
the plate stack didn't destroy the 0.005" fork/tongue clearance, but welding 
inside the fork did.

Do diagonal or fish mouth/tail ends (vs square) improve stress distribution 
and/or reduce distortion in butt joint splice plate welds? One end of the 
splice plate would be bolted, the other welded after aligning the beams.

When I was building custom machinery the press brake operator and welder 
compensated for distortion, the all-welded machine frames were square to 
1/32". They were mostly multiple 19" relay racks that we had to fit the 
equipment panels into, so we would see any error. I knew they marked the 
prints with allowances for bending and welding but they didn't share, and 
the front surface welds had been ground and filled as invisible as auto body 
repairs.
tia, jsw