Okay, so the consensus is both can be used on an Omega Nato, but the curved may offer additional space.

But here's where I'm not clear: are the curved bars curved but straighten at the tips, where they go into the lugs...or are they curved including the tip? Because if the latter, then it would seem that the lug holes themselves would need to be cut at the same angle, and I'm doubting that. Then the straight bars couldn't fit, could they? Any pics? Thanks.

 

Not sure but the OB used the curved on my spectre LE

 

The thick omega nato fits noticeably better with the curved bars. Before it was a tight fit.
The ends are angled but they fit nice and snug in the case. The pics are of the 20mm straight and 21 mm curved (for the grey side).

 

Excellent; many thanks.

 

Any pics of both bars on the grey side way we can see the difference? I'm mostly sticking to exotics but would like to see. They could be used with a custom exotic that the maker made the end curved though, correct? That would be handy for a bunch of watches that are designed mainly for bracelets if could use them that way.

 

Surprised that the ends are curved/angled.

 

Agreed. Seems like it wouldn't fit well if the lug hole were drilled straight. Must be generous tolerances.

 

Here is the Grey Side with both types
nato is a bit tight and doesn't travel well

Better fit on the curved. Much more room for sliding on the strap and the cordura actually fits now (cordura not shown in pic)

 

"nato is a bit tight and doesn't travel well"

What width on NATO is that? the one (031ZSZ002050) I got for my DSOM looks a far better fit, Omega recomended I used the standard bars that came with the watch and not to change them.

 

Standard oem nato
The regular one fits fine with straight or curved bars but the thicker leather and cordura natos are a tight squeeze

 

"Standard oem nato"

Thats why I asked because there isn't a standard width, they come in multiple widths so you can pick them to fit different watches. As I said the 21-22mm one I have looks a far better fit as you see nothing of the spring bars as in your pictures.

 

I'd agree with @Gsa in that it looks like @guelerct is using the 19-20mm Black Nylon Nato with grey border. The softer Nylon natos from Omega have two sizes (20 & 22) to fit four standard lug widths (19,20,21,22) with the expectation that the 19 and 21 mm wide lugs with be sized up for Nato width. Also, the curved springbars help in sizing down natos to smaller lugs.

The stiffer and thicker Coated Nylon and Barenia Leather natos come in four sizes to fit the standard widths exactly. Curved springbars help here with tighter fits as the lug hole to case distance varies.

As for lug hole tolerances, there HAS to be at least a little play in the hole size to accommodate installation, maybe 10% minimum. More than likely the hole has a 20% tolerance, so with normal spring bars of 1.8mm width the ends are 1mm, and with a 20% tolerance the lug hole size would be 1.2mm. Any curve in the springbars less than 8% should be able to fit with those tolerances, and the ones in @guelerct pictures looks to be well below that.

 

I see I can order a NATO strap from Omega online store. I see from previous post that people who ordered the Omega NATO strap got 4 spring bars. I don't see that written in the description. Does anybody know if that is a current practice?