I'm looking for some tips on how to keep oversized holes centered where they're supposed to be when building welded assemblies.

I have run across several projects where I wanted holes to be slightly oversize to account for tolderances, so bolts go in freely. What I typically do is drill the hole the nominal size, use a jig to locate the parts, weld them together, then ream the holes oversize.

Do you guys have any tips for making this easier? A bolt with an oversized shank would be great, but I don't know where to get them. I could build a sleeve for the bolts, but I'd probably lose them.

Any other ideas?