I'm working on a bike and I'm having trouble telling whether the fork is slightly tweaked or not. You certainly can't tell by looking at it. There are no paint ripples. Using a straight edge, the head tube is in line with the fork blades.

The problem is I can't get a good adjustment on the headset. If I adjust it so there is no play, it binds a bit when turning the fork blade (it's basically adjusted right when the fork is facing forward and is too tight when you move it side to side.

I don't think this is the headset. I popped new ball bearings in the HS and the surfaces all looked good.

Is a slightly tweaked steerer column the most likely reason I'm getting some binding?

The most straightforward way to solve the problem is to buy a new fork, right?

You had the fork out already, right? Should have checked then. A straightedge along the steerer tube on four sides would probably tell the story. In my experience a bent steerer is pretty rare; usually the rest of the fork takes a beating instead, but it's not impossible. I can only recall one from my shop days in which that was the only fork damage.

New fork recommended unless the frame is of such quality that replacing the steerer is feasible (brazing, milling, matching paint).

To me, this suggests that the crown race seat and/or head tube faces need to be milled.

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^^^me too.^^^ Regardless, check the seating of the crown race and both steerer races.

This is a high end bike from the 90s. You'd think that this was done right at the factory and/or been corrected at some time in the last 20 plus years. The bike has seen some use.

But who the heck knows. I will check if the crown race and cups are seated right though.

What is the best way to tell if the fork is bent or not?

It didn't look bent I put a straight edge on it) when I took it out and it doesn't look bent now using a straight edge with the fork is installed on the bike. I'm thinking that this is a slight bent. Yes it's a high end bike but not worth replacing the steerer. I'd rather buy a new fork or just sell it to someone willing to deal with this.

I'll give it a shot. The frame would probably fit you,

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...FWIW, the custom frame guy here in the Big Tomato, Steve Rex, has milled a couple of for crown seats for me at a cash and carry price of fi'teen bucks. ONce you have the proper tool, it's not a big job. The tool is a little pricey unless you're doing this a lot.