A Modern Method of Filing Drawings
One of the problems always facing engineers is how to file large drawings in such a manner as to make certain they are kept in good condition and can be found quickly when needed. War-time conditions have introduced two further problems—how to protect them against fire, and how to ensure that highly confidential drawings cannot get into the hands of unauthorised persons.
A method of overcoming all these difficulties is to be found in the Art Metal Planfile. The planfile is a steel cabinet, the largest size of which is capable of holding 4,000 "Antiquarian" drawings (53in. X 31in.).
The drawings are filed in large red rope folders which slip into spring-compressed pockets. This patent-method of spring compression prevents the drawings from slipping down or becoming creased or “dog-eared " whilst in the cabinet. This makes the planfile as useful for flimsy tracings as for tougher blue-prints or heavy cloth drawings. In the lid of the planfile there is a visible index to all drawings in the cabinet.
As to fire protection, the planfile is of double wall construction. Two separate methods of insulation arc employed— asbestos and air—so that the internal temperature is kept down in the event of fire. At the same time the construction is such as to prevent the entry of water from fire hoses and sprinklers.
An important point is that a single lock enables all drawings to be locked away quickly in an emergency. For highly confidential drawings, however, a system of dual locking with "Brah-mah" locks is to be recommended. This locking system makes it essential for two people to be present whenever a drawing is removed from the cabinet, and the cabinet must be re-locked before the keys can be withdrawn.
Engineers and draughtsmen will also appreciate the fact that drawings arc filed or referred to from a standing position—there is no climbing or stooping as when ordinary plan drawers are used. Full details of the Planfile are given in catalogue DOE-40, obtainable from the manufacturers, the Art Metal Construction Company, 201, Buckingham Palace Road. London, S.W.I.
The Besco treadle-operated notching machines, marketed by F. J. Edwards and Co., Lid., of 359-361, Euston Road, London, N.W.L is equipped with a treadle rod and floor standard, and is capable of dealing with mild steel plate up to 16 gauge. It has a capacity of 2in. x 2Jin. right-angle cuts. With repeated blows, and by moving the work backward and to the right, larger notches can be made.
The machine is specially designed for such work as notching body blanks for tin boxes, and is also very suitable for cutting out the notches for hinge work on cabinets and similar articles. For the latter operation the machine is fitted with an adjustable stop to prevent the blade cutting too far. Although it is simple in design and operation, this little machine will frequently carry out jobs which would otherwise necessitate manufacturing tools and possibly the use of a fly press.
The sintered carbide or hard metal tools which are now being used to an increasing extent in workshops need special methods for producing sharp and durable tool edges and for reconditioning them after use. A new British machine produced by Messrs. W. G. Bowen and Co. (Engineers), Ltd., of 6, Broad Street Place, London, E.C.2, allows a very exact adjustment of compound tool angles and provides a sensitive hand-actuated lapping movement. Preferably diamond impregnated wheels are used, although good results are also to be obtained with fine-grade silicon-carbide wheels.
The main idea incorporated in this machine is to use two wheels in line, one for pre-grinding and the other for finish-grinding or lapping. A common saddle serves both wheels, so that the tool, in absolutely the same position, can be brought from one wheel face to the other.
The tool rest can be moved by a slide with a fine pitch screw to and from the wheel, or can be rotated about an axis' parallel to the wheel face, and adjusted for any compound angle in two directions, one perpendicular to the other. The graduated tool rest supports the tool near the grinding wheel, and sets the edge to be ground near the centre line of wheel; therefore on one side the tool can be ground downwards, on the other upwards without reversing the direction of wheel-rotation.
The lapping movement is carried out by a hand-lever arranged at the left-hand side of the machine; this movement extends over the full width of grinding ring. The cup grinding wheels of 5in. and 6in. diameter are protected by close-fitting hoods, having on their front part receptacles for the coolant fluid (usually soap-water or paraffin-oil). A special drip-feed supplies the coolant to a felt-pad, pressed against the wheel face.
One grinding-wheel, preferably the high-speed wheel, is directly driven from the motor by means of a flexible rubber coupling, whereas the other spindle is driven by means of an endless vee-belt, providing the necessary reduction in speed. The wheel spindles run in high precision plain bearings provided with a ball thrust bearing, and are fully protected against grinding dust.
Owing to the special design it is possible to readjust the bearings for wear without the necessity of dismantling the machine. The motor, usually of 3/4 h.p. capacity running at 3,000 r.p.m., is suspended in rubber blocks to avoid the transmission of vibration.
The present increasing demand for a hard metal-tipped tool grinding and lapping machine is unquestionable, and Messrs. Bowen are undoubtedly serving the national interests by placing a machine on the market which has hitherto been obtainable only from abroad.