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I recently bought some parts to repair my columbia AT, including a nice cast bedplate restored by Gregg Cline to replace the pot metal one that had disintegrated, but now I'm met with a problem, these old machines would have had some variance over the production run, and seemingly the earlier cast iron and later pot metal bedplates must have had slightly varying dimensions, nothing noticable, but it just means that only 1 of the screw holes on the bed plate are lining up, as photos show.

I'm lucky enough to have good tools to do the work, but the best way I can think of repairing this is to plug the three original holes that dont line up, done by screwing and cementing short lengths of threaded rod into them then drilling and tapping three new holes to match this bedplate with new screws, does this sound like a plan?

The alternative I could think of would be altering holes in the bedplate which would be visible and most likely risky as the holes have a good chance of reaching beyond the bedplate

First, let's settle on the correct terminology. The part you had restored by Gregg is the upper works, I am assuming. The bedplate is the nickel plated flat steel piece underneath it. If we are on the same page, then your idea of drilling the bedplate to match the holes in the upper works is a good one. Your idea of tapping the old holes and filling them with threaded rod, then re-drilling the filled holes and re-tapping them should work just fine... Make sure that the one hole you leave as original allows the upper works to align correctly and then fasten it before marking your new holes...

Good luck...

Curt A wrote:First, let's settle on the correct terminology. The part you had restored by Gregg is the upper works, I am assuming. The bedplate is the nickel plated flat steel piece underneath it. If we are on the same page, then your idea of drilling the bedplate to match the holes in the upper works is a good one. Your idea of tapping the old holes and filling them with threaded rod, then re-drilling the filled holes and re-tapping them should work just fine... Make sure that the one hole you leave as original allows the upper works to align correctly and then fasten it before marking your new holes...

Good luck...

Can I blame autocorrect?

I'll give it a go

Kirtley--nice machine. Very "Steampunk" in design--kind of nifty, it looks super modern and Victorian at the same time!

Kirtley,

If you're only off by approximatly ½ a hole, you may find it troublesome to plug a hole, as you suggest, then re-drill on the new location. The problem may be, that your plug will fall out once you've essentially drilled half of it away. Is it possible to simply elongate the "bad" holes till the bolts will pass through, then put a nut on the backside? I realize this is not as "proper" and invisible a fix as you propose, but maybe a second choice, if need be.

Jerry is probably right about the half hole problem, but my thought was to enlarge the new hole to encompass the half hole, then a larger piece of threaded rod could be inserted and tapped. I actually used this method on a reproducer that didn't match the holes on the tonearm I was using and it worked fine...

It didn't prove to be a problem, I plugged the original holes using screws from the destroyed pot metal trunnion, the newly drilled holes didn't cross over to the original holes, came close, but didn't touch, so I tapped the holes and put my new lathe to work on it's first proper project making new brass screws for it

Made your own screws, wow. Proud of you!

Great... glad it worked...