Charles E. Burroughs
The amateur boat builder, in working out a wooden hull, is frequently in a quandary as to the thickness of wood remaining at some particular place; he hesitates to make a cut fearing the gouge or chisel may go through, and yet desires to remove all the wood he can to get a light boat.
This is especially true of model steamers where the weight of the machine is generally so great as to necessitate the very light hull, to avoid too great a displacement. In pattern making similar difficulties are often encountered. In such cases a thickness caliper, like the one here described will be of great assistance.
as the thickness of wood or metal can be very closely ascertained without trouble. The shape of the legs can be varied to meet the needs of the work, the principal requirements being stiffness and a close fitting joint between the sliding leg and the bar.
The bar should be a piece of well seasoned, straight grained maple. A piece of "reglet," obtainable from about any printer is suitable, as it is finished in oil. For a small boat a piece 12 or 15 in. long will answer, together with four pieces 1 1/2 in. long.
If only approximate measurements are needed, the legs can be made of four pieces of a cigar box, which are cut out to the shape shown, and of a size to clear any projections on the work. Additional square pieces are needed for closing up the back. When cut out, the legs for one end are fastened together and to the bar with glue and small wood screws.
The sliding bar is put together in the same way, excepting that pieces of thin cardboard are put between the blocks and the piece at the back, which serve to give the necessary play so that this leg may slide freely, but not loosely. The two blocks above and below the bar should be spaced square with the bar and with only sufficient allowance to slide without binding.
After completing the two legs and mounting on the bar, the tips of the legs are brought together, and a mark made on one side or top of the bar with a knife. The sliding bar is then removed and a scale laid out, the divisions being made with the point of a knife and the marks filled in with India ink. If a very accurate reading caliper is desired, the legs should be made of brass; in fact, the whole tool may be made of that metal, in which case the joints are brazed. A combination tool can be made by slots in the two boxes on the bar and several sets of legs can be made, which are held in place by set screws. For general purposes, however, several different sizes made of wood will answer.