A full-size drawing must be made, and the requirements of a successful tambour are that it should have a truly square carcass with opposite ends or sides parallel, and accurately positioned grooves of constant depth to take the slats— which are always shouldered in the best work— sweetly round the curve. Attached guides or fillets (249:llA) to form the running groove can be used, with a tongue worked on the thick locking rail, which simplifies the installation, but it is better to work grooves in the solid (249:10A), and extra wide edging should be provided in laminboard carcasses or the core-work will show in the grooves, and the travel will not be so smooth. From 250 it will be seen that the grooves are radiused at the corners to carry the tambour round and out of sight, and slightly widened at the bends to prevent the slats jamming. This can be accurately detailed in the drawing by using a cardboard template cut to the shouldered section of the slat, and trial worked round the bend; while the cover fillet (250:2F) which hides the slats as they commence to open on the bend must be set to give sufficient clearance, for any rub-marks on the face of the tambour must be avoided. If the grooves are formed by attached guides the completed tambour shutter can be placed in position and the guides screwed on, but for grooves worked in the solid provision must be made for running the tambour in from the back (250:2, 3), and the groove is run out either as 250:1A or B. If the run out at 250: lA is adopted then it must be filled in with a shaped piece screwed on after the tambour has been installed. The locking rail, of which various forms are shown in 249:13A, B, C, prevents the tambour from passing behind the front cover guide (250:2F), but as it is of thicker section it cannot be entered from the back and must be sprung in from the front after the tambour has been finally run in, with the flexible backing glued on or taken into the rebate/rabbet and held with fine screws through an attached bead (249:13B. C). A false top or bottom for vertical tambours, or false sides (250:ID) and back (250: IE) for horizontal tambours, must be provided, not only to hide the movement but also to prevent the contents of the carcass from interfering with the travel. In all detailing it is wise to provide for withdrawal of the tambour at any future date without unduly interfering with the carcass-work, therefore the back should be fully detachable.
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