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3 mm scale

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3mm finescale
Scale3mm to 1ft
Scale ratio1:101
Model gauge13.5mm, 14.2mm
Prototype gaugeStandard gauge
British TT gauge
Scale3mm to 1ft
Scale ratio1:148
Model gauge12mm
Prototype gaugeStandard gauge

3mm scale, also known as 3mm finescale, is a model railway scale of 3mm:1ft used for British prototypes. Introduced as British TT gauge, it sits approximately halfway between British N gauge and OO gauge, but is not as popular as either and there is no longer any mass manufacturer ready-to-run support. When TT gauge model railways were developed for British prototypes, in order to fit the small British prototypes, the scale was enlarged but without altering the 12mm gauge. The result, British TT gauge, is too narrow. This lead to the development of 14.2 mm (0.559 in) gauge 3mm finescale. Thus two finescale standards were developed. By far the more common of these is 14.2mm gauge track, which is accurate. Some modellers choose to use slightly narrower 13.5mm track due to the necessary oversize motion of outside-cylindered steam locomotives.

British TT, also known as TT3, was pioneered by Triang Railways as ready-to-run models.

Other gauges are also used to model other prototypes (Irish broad gauge, Brunel broad gauge, 84). For narrow gauges, N gauge 9 mm track represents 3 ft (914 mm) gauge; Z gauge 6.5 mm (0.256 in) track represents to 2 ft 2 in (660 mm) gauge

The 3mm Society caters for all modellers of 3mm scale.

See also