This article was originally published in Practical Engineering 1940 Vol No1. Information within this article is therefore correct as of 1940. The publication of this material aims to provide historical insight on the subject and its place in industry.
Heating engineers, electricians, plumbers, gas-fitters and mechanics will be interested in the "Enox" tube cutters manufactured by Fry's (London), Ltd., of 56, Southwark Street, London, S.E.I. These handy and efficient little machine tools are made in two sizes — the No. 1, which will deal with tubes from 0.1in. up to 1in., and the No. 2 for pipes fin. to l-3/8in. diameter.
The "Enox" tube cutters are designed to make a clean and rapid cut through brass, copper, lead and light-gauge steel tubing, such as conduit. The design of the cutter is clearly shown in the accompanying illustration. The die-cast body is guaranteed against breakage, and the cutting wheel is of high-speed steel. All screws and rollers are case-hardened to give long life.
Both of these cutters are fitted with a special reamer, and when not in use the blades fold up into the body. The reamer is used for removing the slight burr thrown up inside the tubing when the cutting wheel is allowed to go right through the metal. To ensure a clean cut without burr, the best method is to cease cutting when the wheel is nearly through and then snap off the tube. A leaflet giving full particulars and prices of these cutters can be had from Messrs. Fry's (London), Ltd., on application to the address given above.
Delco-Remy and Hyatt, Ltd., of 111, Grosvenor Road, London, S.W.I, have recently made several improvements in their 1/3 h.p. and ¼ h.p. electric bench grinders, details of which are appended.
The 1/3 h.p. size is now of even heavier construction than previously, while its appearance is more streamlined, allowing greater clearance and working space around the wheels. At the back of each wheel guard an opening is provided for the ejection of grinding dust. Provision is also made for the fitting of eyeshields, and the tool rests are universally adjustable. The motors are designed with a large overload capacity, and are fitted with permanently lubricated and sealed ball bearings. The 1/4 h.p. model is of split phase construction, while the 1/3 h.p. model is of the permanent condenser type.
Each unit is supplied with two vitrified wheels, one fine and one coarse grit. The smaller model has 6in. diameter wheels and the larger model 7in. diameter, both sizes having a width of 3/4in. The tool rests are adjustable by means of wing nuts to allow for wear in the wheels, while those on the 1/3 h.p. model are also adjustable in height of working plane.
On both models the wheel guards are of rigid construction, with provision for attaching-eyeshields. The 1/3 h.p. model includes an end-cover and is also designed to allow the dust from grinding operations to be ejected through an opening at the back of the guard.
The grinder is controlled by means of an "on" and "off " switch mounted in the base, and a length of heavy duty three-core C.T.S. cable is provided for connection to the mains. Both models are available for use on single-phase A.C. only, at 200-250 volts 50 cycles. The price of the 1/4 h.p. model is £6.17s. 6d., and the 1/3 h.p. model costs £9.17s. 6d.
Where a supply of compressed air is available, a small machine tool for which a multiplicity of uses will be found is the Aerograph DeVilbiss air duster illustrated herewith. It is a product of the Aerograph Co., Ltd., of Lower Sydenham, London, S.E.26.
Two main types are available, and the one shown here is the Type DGA-521, the other being a larger and slightly heavier model. As will be seen, it is of neat and compact design, while the shape of the body is such that it can be held easily and comfortably in the hand. It is light in weight, and the air valve is quickly and easily operated regardless of the position in which the duster is held, while the straight-line design enables it to be used at close quarters without kinking or bending the air hose. In spite of its small size and compact design, it has the same air capacity as the larger standard models. All types are fitted with 3/64 in. internal diameter nozzle as standard, but a larger nozzle of 7/64 in. internal diameter can be fitted if desired. With the 3/4in. nozzle the approximate air consumption is 1.5 cubic feet per minute at 401b. per square inch, and with the larger nozzle the consumption is 8 cubic feet per minute.
These air dusters are particularly useful for removing loose dust and dirt from surfaces to be painted, drying out joints and seams after wet rubbing down, blowing out dust from motors and intricate machinery, removing chips and shavings from machine tools, and for numerous other similar purposes.
Where the work is of such a nature that a dual air pressure is necessary, the larger model already mentioned can be obtained with a special air-control valve. This is arranged so that upon slight depression of the valve air is delivered at low pressure, but on further depression of the valve the air blast is increased to the full pressure of the available supply.
A well known London firm of electrical tool specialists — S. Wolf and Co., Ltd., of Pioneer Works, Hanger Lane, Ealing, W.5 — have recently placed on the market two neat little electric hand drills known as the "Wolf" Torky featherweight ball-bearing drilling machines. The model shown in the accompanying illustration is the type TP2, a hand model with thumb-operated slider switch. The other model is the type TH2, this being of the pistol type with trigger switch.
The outstanding features of these drilling machines are their compactness — the overall length being only 6-1/8in.— and their light weight. The hand model, type TP2, weighs 21bs. 4oz., and the pistol model, type TH2, is only 2oz. heavier. The machines are, therefore, of special interest to those engaged in the production of aircraft, and in assembly work generally.
The design of these drills is neat and workmanlike, and in spite of their small size, they are robustly constructed. The armature and drilling spindle are mounted on ball bearings, while the gears are of the spiral type, of nickel chrome steel, specially heat treated. The drill spindle speed running light is 2,500 r.p.m. and on full load 1,675 r.p.m. These speeds have been found the most suitable for drilling holes up to 1in. diameter in duralumin and other metals, on which the machines will be mainly used. On full load, the current consumption is approximately 166 watts.
Extensive tests have been carried out, including a full-load test for 1,000 hours, with entirely satisfactory results, and the makers state that the machines can be used with confidence on production work where it is of a continuous nature. Each drill is supplied complete with 15ft. of 3-core C.T.S. cable, 1/4in. three-jaw keyed chuck and a spare pair of carbon brushes. The price of each model is £6.15s.
An extremely interesting machine tool accessory of comparatively recent origin is the Eclipse non-electric magnetic chuck developed by James Neill and Co. (Sheffield), Ltd., of the Composite Steel Works, Napier Street,. Sheffield, 11. This new type is an improvement on previous models in that it employs permanent magnets, and is, therefore, not dependent upon any electrical supply. Moreover, the danger of work being spoiled through the failure of a current supply while machining is in progress is completely eliminated.
There are two separate and distinct models of this chuck. One is of the rectangular, or table type, while the other is a circular model for lathe work, and is in effect a magnetic faceplate. Both chucks employ the same basic principle, however, which is that of a series of powerful nickel aluminium magnets, which are said to maintain about five times more energy than would be possible with similar tungsten magnets, and their retentive properties are nearly fifteen times greater than that associated with old types of the horseshoe form.
The inner poles on the chuck face are of similar polarity and the top plate forms the outer pole of opposite polarity. The pull of the magnets is thereby concentrated on any work piece that bridges an inner and an outer pole. The magnetic flux is controlled by means of a lever which displaces the permanent magnet unit relative to the pole pieces with a simple eccentric movement, and thereby renders the work-holding surface energised or de-energised.
The applications of the chuck cover a wide range of work. Magnetic chucks are primarily associated with grinding machines, but the Eclipse chucks, being free from electrical connections, can readily be transferred to certain applications on millers, shapers, etc., while they are particularly useful on the bench for scraping, marking out, and rapid assembly work.
In the tool-room, the chuck can be used for holding punches and dies during regrinding operations, when it frequently effects a great saving in time in setting up. It is ideal for holding thin flat sections, and as it is non-electric, there is no internal heating, thereby reducing warping to a minimum. Workpieces can be easily removed after grinding as there is practically no residual magnetism in the chuck when turned off, so that highly finished parts are seldom damaged during this operation.
The "Greenbat" hand-operated portable tensile testing machine shown in the accompanying illustration is for testing specimens up to 20 tons tensile. As can be seen, the machine consists of a body, in cast steel, which contains a fixed straining head and moving straining head, the latter being directly connected to the piston of the hydraulic straining gear.
The fixed straining head is provided with a spherical seating to allow for any slight inaccuracies in alignment due to the specimen. The whole of the straining gear, including a hand-operated pump, is carried in the end of the body casting, the straining cylinder being machined directly in the body casting.
Easy operation of the hand pump up to maximum load is claimed. Oil is carried in the straining cylinder, and when testing, is pumped under pressure to the straining side of the piston. The load gauge, seen in the illustration below, is in the form of a large hand-calibrated pressure gauge. Pressure can be released by opening a valve on the pump body, and the straining head is adjusted by hand through a lever and link motion.
Hardened grips are provided to take: rounds up to 5/8in flats from 1/8 to 5/16in. thick x l-1/2in. deep and flats from 5/16in. to 1/2in. thick x l-1/2in. deep.