I've had a general DIY plastic calliper as part of my toolkit for many years and it's proved quite useful, allowing me to transfer measurements from plans to model parts. In principle it should be especially handy when scratchbuilding or making corrections to a kit, but always lurking at the back of my mind has been the sneaking worry that it's just not THAT accurate… the jaws don't close precisely at "zero", the plastic is too flexible, and I don't even totally trust the ruler measurements.

Proof that my suspicions were correct arrived recently in the form of a professional digital metal calliper from Shesto Ltd. It was instantly obvious that this tool is in a totally different league, both in terms of construction and accuracy.

Going back to basics, the calliper is a 4-in-1 tool. The jaws are the obvious focus of attention, allowing both external and internal measurements to be taken, but an equally useful function is "hidden" inside the ruler part of the calliper; as you open the jaws, a depth measure extends from the opposite end. Finally, the reverse side of the jaws works as a step measure, and with a metal calliper, you can use it to cut plastic sheet or rod without fear of damaging the tool.

Shesto's digital calliper arrives in a solid foam-lined plastic case, complete with a spare battery (one is already fitted). The tool itself is very well made and finished - the metal jaws slide smoothly and precisely, with no play whatsoever, and a thumb-roller allows you to make minute adjustments that simply aren't possible with the plastic version. Finally, a turn-screw on the top allows you to lock the jaws tightly.

When I bought my original calliper, I don't think digital versions had even been invented, and I have to admit I was unprepared by just how much easier it would be to read the LCD than to squint at the ruler scale. Moving the slider switches the electronic display on (there is also a separate on/off button), which can be shown as either inches or millimetres. The imperial scale is accurate to 3 decimal places, the metric to 2 decimal places.

Such a precision display is all very well, so long as it's consistent – if the reading creeps, it's not much use. So I opened and closed the calliper to its fullest extent (152.88 mm) repeatedly and was delighted to find the measure returned to a solid 0.00mm every time. Should you actually want to mark a point as zero with the jaws open, you can do so at the press of a button. Should the battery run out, the digital measure is mounted on the slider in such a way that the left-hand edge of its case can be used as a "zero point" to judge a measurement by eye in the conventional way.

To get an idea of how the new digital calliper compared in action against my plastic one, I measured the spinner of one of the kits on my workbench. The digital measurement was bang on 14.60mm, while the old plastic calliper showed somewhat under 14.5! The real joke was when I used the digital calliper to check the scale on my old one… it was inaccurate, just as I'd always suspected. Thankfully, I've never used it for anything that really mattered…

The final plus point of the metal calliper is inherent to the material it's made of; the tips of the jaws are actually sharp enough to work as scribers on soft material such as styrene, so that measurement you've taken so carefully can be transferred directly to the model, should you wish.

Conclusion

Shetsto's digital calliper is precision made and without doubt the most accurate measuring tool I have. To be honest, it's rendered my old plastic calliper pretty much worthless at a stroke for serious work. It's the type of tool that you probably won't need every day in the course of normal kit building, but for scratchbuilders and anyone doing conversion work where accurate measuring is essential, it can hardly be bettered. Recommended.

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