SAVING LABOUR IN WORKSHOP AND GARAGE.
Page 67
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Some Useful Notes from Our Driver and Mechanic Readers.
Boring In the Lathe.
• lUrANY garage engineers experience • eatrlitlieulty when boring deep holes, • such as those for floating bushes, etc., in the ordinary lathe to be found in a garage. A. useful suggestion is made by L.M.C.," of Cardiff, who has found that it is possible to convert an ordinary lathe into a modified form of Gisholt, providing that the lathe be of the hollow-mandrel type.
The first step is to find a block of cast-iron, and face the under side, then fix it to the top slide of the lathe by means of the bolts that bold the tool. Care should be taken to drill steady-pin holes so that the Meek may be replaced in exactly the same position at any time. The next step is to drill a hole through the surfacing slide and reamer it for a taper pin, .so that the surfacing slide of the lathe shall be in a convenient place for the block to be bored to take the bar shown in the sketch. The object of this pin is to ensure the slide being brought to the same position whenever the boring bar is used.
Having determined what size of bar would be convenient for the lathe (1 in. is usually found best for general work), the next step is to hold a drill, slightly smaller than the bar to be used, in the chuck, and drill through the block. After this, hold a boring bar in the chuck, and take ieveral light cuts through the block so as to ensure its bole being central and in true alignment with the mandrel, then put a boring bit through the hole to bring it to the size of the bar to be used.
A bronze bush should then be fitted to the mandrel, and it is most important that a felt washer should be fitted to prevent chips getting in alongside the boring bar. A piece of bright shafting— not bright drawn rod, as this is never straight—will do for the boring bar, but a specially turned, hardened and ground bar is better.
A pair of setscrews will hold the bar in the block at any convenient position, and provided that brass pads are beneath the points of the screws there will be no harm done to the bar. A hole and setscrew to hold the cutter will complete the apparatus.
It will be seen that the hole for the cutter is not as usually made, at right tingles to the bar, so that no measurement is possible for the amount the cutter projects, but is slightly at an angle, so that a micrometer can be used to determine the diameter of the hole to be bored. The measurement 8hou1d he half the diameter of the hole to be bored, plus half the diameter of the bar.
This bar should be used in connection with the automatic sliding movement of the lathe, and if made and used with reasounble care works exeellently.
Securing Piston Alignment.
WHEY an engine is being reassembled it is necessary to test the pistons to ensure their being exactly at right angles to the axis of the crankshaft, as little inaccuracies may occur, due to the scraping of the big-ends or incorrect boring of the brasses after relining. The usual method is to hold a square on the upper surface of the crankcase, and try it against the wall of the piston, but owing to the limited space available for the stock of the squere to rest on, this is not often au easy job to perform with accuracy.
"D-D:I.," of CIeckheaton, suggests a very simple and accurate -method of dealing with the matter. Taking it that in a properly made engine the upper surface of the engine is in a parallel line with the axis of the crankshaft, he sets his engine by means of a spirit level, so that this face is level. When it is found to be correct, by reversing the level and noting that the bubble comes in the centre, no matter in which way the level be laid, he then applies the spirit level to the top of each piston. Should the pistons be flat-topped, this is an easy matter, but should they be of the domed-top variety he holds a small square against the side of the piston and applies the spirit level to the top of the square. The spirit level should lie in a line which is parallel to the axis of the crankshaft while the test is being made.
Making Woodruff Keys..
IT is often found, in reassembling a chassis after overhaul, that many of the keys are slack fits in their beds, and to replace such a key is not good practice. "D.D.I.," of Cleckheaton, has found that to take the next size Woodruff key and file it down is not only a tedious job, but that it is not easy to file it with accuracy, so he has found that by adopting the method he suggests a key of the kind can be made with exactitude to the required extra thickness or depth to make up for wear in less theo than the next size larger key can be reduced.
His method is to take a piece of steel of the required size and turn it to the diameter which will produce the right radius on the back of the key and with a parting tool cut off a section of the thickness required, having regard to the amount of wear on the old key. He then saws off a piece of the required depth and fits it in place.
In following this plan, it is well to see that none of the very soft mild steel is used, as some of that material is quite unsuited for the making of such keys. A piece of nickel or similar steel, such as an old axle, will give better results.
Lubricating a Rebored Engine.
THE experience of " C.A.S.," of Sheffield, may be of value to others, so we give his version of what he did in his own words:— " I recently overhauled an engine and fitted new pistons after having the cylinders rebored, and although these seemed to be afairly comfortable fit when assembled, the engine seized several times after being run for about half an hour. More and more oil was added to the already overfilled crankcase, but still the trouble continued. I was anxious to see the smoke issue from the exhaust pipe an that I could feel satisfied the oil was reaching to the tops of the cylinders, and as an extra air inlet was fitted oil was fed into the cylinders through this and had the desired effect of making the engine smoke profusely.
"This was all very well when standing in the garage, but could not be kept up while running on the road, so I hit upon the idea of putting a few Pints of oil into the petrol tank and went out to try the experiment, thinking that if the petroil system of lubrication was sufficient for several of the well-known twostroke motorcycle engines it would probably assist in lubricating my engine, which it did with the utmost satisfaction and kept up a continual smoke for two or three days until the engine was well run in."