Designing a Roller Gauge

I have a request from a fellow Proto:48 modeler for some roller gauges. These handy things are just the ticket for handlaying track and, as far as I can tell, not something you can get for Proto:48. (There are commercially available gauges for most of the regular track standards) While I am not prepared to make lots of gauges on my entirely manual Myford lathe (You would want a CNC machine to do this commercially) I am not averse to knocking out a couple. Once I finished my Milling About and rearranging the shop…

Milling trials having been concluded (more on that later) and shop having been rearranged including new task lighting and a shelf over the lathe, I am ready to actually make something which leads us to objective of this post.

The relevant dimension of the target rail is the width of the rail’s head since that is the part the gauge has to fit over. The measurement reported for ME code 125 is 0.056″. The rest of the numbers needed come from the NMRA trackwork standard for Proto and Fine Scales S3.1. From the Proto:48 line we get a gauge range of 1.177-1.203, a flangeway width of .036-.039, and a minimum flange depth of .026.

From those numbers, we work down to something I can aim for on the lathe. I say aim because I can miss a dimension by a couple of thou and still get working gauge. A couple of thou is a long way in machining(famous last words).

  • The desired target gauge is the middle of the standard so 1.190.
  • We want the gauge to fit through minimum flangeways so .036 wide and .026 deep.
  • We want the gauge to be accurate without being difficult to fit on the rail or roll along it. This suggests a loose running fit (had to look that term up) so I will add .003 to each slot to get .059. As a check, 1.196 is well within the standard’s maximum allowable gauge of 1.203.

Here is a very low tech sketch of the planned work:

Proto:48 roller gauge for ME code 125.

3 thoughts on “Designing a Roller Gauge”

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