This month David Parker looks at calipers which are very handy tools when it comes to taking some of those more awkward measurements.
Whether it is installing a pricey deck fitting or just making something yourself you want to be sure you get the measurements exactly right before the saws or drills come out. On a boat we all know that it’s much easier to get something right first time rather than try and put it right afterwards. The tools which can really help with this are often overlooked because they are not the most regularly used measuring tools but they are very handy if you want a really accurate reading when taking inside, profile or curved measurements. These tools are calipers. They are also extremely useful when it comes to checking part sizes (particularly if ordering stuff online.) Basic models are reasonably priced and you’ll be surprised when you have them how much you use them.
The first type to consider are caliper gauges which are also sometimes known as vernier gauges. Sophisticated varieties are made in boxwood and brass or even solid brass but the engineer’s steel types are a good deal cheaper and do a good job. A caliper gauge can be used for taking inside and outside measurements of many shapes and has a finely graduated scale on which you can read off measurements taken. They can be used to read off diameters, bores, hole depth, screw sizes, help position fittings or give you an accurate footprint of a cleat etc.
The caliper gauge has one fixed and one movable jaw with a locking screw. The lower part with deeper jaws is typically used to measure external dimensions and the upper jaws for internal ones. The sliding jaw moves across a scale marked in millimeters or inches. The vernier scale is an additional scale to measure things even more accurately – like on a sextant. Modern designs of caliper gauges also come with digital displays which have various functions including metric and imperial conversion. Caliper gauges can also be useful for reading the depth of a rebate and if you are planing timber you can go along the length of the stock of wood to check it’s all the same width. Checking the width of joints when fitting a tenon into a mortise is another function. They are also good for setting up machine tools, for example if you want to make fine adjustments to the rip-fence scale on a bench saw or shave the width of a board you’ve just cut.
To read the rest of this guide see the February 2013 issue of Sailing Today – available here.