S? Wait a second there turnout standards.

I like tables and I like data. It’s just the way I am. So with that brief preamble I wandered into the NMRA’s Standards and Recommended Practices on their website (nmra.org) and, in particular, their one for track standards (S3.6). Since I have a pretty decent of inventory of rail and ties, in a variety of scales (your guess is as good as mine as to how that happened…) I figured I might indulge in building a turnout, maybe in Sn3 or S scale, standard gauge. Before embarking on that, I figured it would be handy to invest in some gauges or at least familiarize myself with what the standards might be for S.

What surprised me was that, in what the NMRA refer to as “Standard Scales” the standards defining turnout dimensions are identical between HO and S so, in theory, I could use the NMRA HO track gauge I already have on hand during the construction of an S scale, standard gauge, turnout. Here are some example dimensions from S3.6 as examples (units are millimeters):

Scale Scale Ratio Gauge Points Point Clearance Flangeway
S 1/64 22.48 20.88 1.6 1.22
Sn3 1/64 14.35 12.75 1.6 1.22
HO 1/87 16.54 14.94 1.6 1.22

Obviously, the track gauge is different between the scales but the dimensions around the flangeways are the same. I thought I’d check these using their S3.6 for 4.2 wheel standards. The tread that they recommend is the same code 110 tread. The HO scale flange depth is recommended to be 0.028″ where in S they call for 0.030″. In theory, if could apply this to the idea of simply re-gauging HO scale and gauge wheels to S if you really wanted to get carried away.

While here anyway, I whipped out my calculator only to find that those bricks I was making in 1/35 wouldn’t be unreasonably small in S either. Just something to think about right now and maybe later on too.





  1. Not only that, but if you went with the popular code 88 profile wheels, which loads of people easily get to work in HO, you’re very close to Proto:64. Why didn’t I think of that?

    I considered S scale back when I was starting to think about modelling the Canada Atlantic. S is a really nice scale to work in, and it would be much easier to get the engines to work if they were 25% bigger than my HO scale ones. And it’s not like I would have to scratchbuild more stuff! Perhaps I made a mistake.

    Oh, so many options, so little time!

      1. I didn’t do this research when I started Port Rowan, but then I learned about it from my friends in the S Scale Workshop. It’s another S scale secret – the flanges that look too big in HO are just fine in 1:64.

        As you know, I’ve used Code 70 Rail on my layout to replicate the light rail of my prototype. Two rails in Code 70 look really, really small when laid 22.48mm apart – much smaller than they do at HO’s 16.54mm. And yet, they’re also big enough for easy handlaying and they provide a solid electrical path from track to locomotive – especially when combined with the larger mass of S scale equipment.

        I remember laying a similar light branch in HO in Code 55, and the rail would kink if you looked at it too aggressively.


        – Trevor (Port Rowan in 1:64)

      2. I like code 70 too. It works out nicely in S, to represent the very light 70lbs rail used on some sections of the PEI railway until the very end.

        I’ve used code 55 and 40 in HO to represent similarly small rail. I’m used to working with it from various N scale projects that I’ve fooled around with. A couple of years ago I built a HO scale micro layout using code 55 (photographed in this post: https://princestreet.wordpress.com/2013/10/15/the-great-small-layout-giveaway/)

        I think the big attraction to code 70 in S is the larger area around the throwbar in the turnout in terms of attaching the point blades to that throwbar.


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