Never thought of it that way but you're probably right. Columbus tubes were most likely true metric ~0.6mm while Reynolds tubes were BWG (Birmingham Wire Gage)and the metric equivalents were approximate...
24 BWG = 0.022" = 0.56mm
22 BWG the other common size Reynolds seat tubes were 0.025" = 0.71mm
Chas. Colerich Oakland, CA USA
Phil Brown wrote:
>
> On Nov 16, 2009, at 10:27 AM, verktyg wrote:
>
>> Theoretically a 1 1/8" diameter seat tube with 0.6mm wall thickness
>> would take a 27.2mm seat post that would have 0.09mm per side for fit.
>>
>> A 0.7mm (Columbus SP)seat tube would take a 27mm seatpost.
>>
>
>
> It seems that a 531 .6 seat tube is thinner than a columbus .6 seat
> tube. A 531 .6 seat tube is usually happier with a 27.4 seat post while
> a Columbus .6 seat tube is happy with a 27.2 seat post. Waterford is one
> of the few builders to recognize this. I think this is the reason why
> English frames frequently have crushed seat lugs and Italian frames-for
> the most part-don't.
> Phil Brown
> My 2 cents in Oakland, Calif.