Contributions from Drivers and Mechanics.
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TEN SHILLINGS WEEKLY for the nest Communication Received, and One Penny a Line of ten words for any
thing else published.
Drivers of commercial-motor vehic:es and tractors, and mechanics and foremen of garages or shops, are invited to send short contributions on any subject which is likely to prove of interest to our readers. Workshop tips and smart repairs ; long and successful runs; interesting photographs : all ore suitable subjects. Semi a post-card, or a letter, or a sketch to us—no matter how short, or how written, or how worded.
will "knock it into shape" and prepare sketches, where necessary, before publication. The absence of a sketch does not disqualify for a prize. When writing use one side of the paper only and mention your employer's name as a guarantee of bona fides. Neither your own nor your employer's same will be disclosed. Payment will be made immediately after publication. Address your letters to The Editor, THE COMMERCIAL MOTOR, 745, Rosebery Avenue, London, E.C.
The Gauging of Twist Drills.
[921] " H. M." (West Bromwich) writes :—" In letter Na, 904 [Our issue, 27th July.--En.] your correspondent W. S.' (Widnes) describes an ingenious rig for testing the accuracy of the grinding of twist drills, but I suggest that his method, although a simple and cheap one, is a little misleading to a beginner. It does not cover enough ground to make the instructions complete for the successful grinding of a twist drill. -Without being egotistical, I would suggest that your readers would do better to follow the instructions which were given in detail in my letter which was published in your issue for the 6th July last" [Letter. No. 895.—En.].
[Our Widnes correspondent did not suggest that his method was BO exhaustive a one as that of which we had already published a description: he merely offered a note with regard to his own method, which undoubtedly is remarkably simple and cheap, even if it is not quite exhaustive.—Em.] A Special Tool HO!der.
The sender of the following communication has been awarded the Ws. prize this week.
[922] " H.B." (Sandbach) writes :—" I herewith submit for your approval a sketch [We have had this redrawn.--ED.] and a description of a very useful device which I have called a radiusing tool. It is a very simple arrangement, and one which any ordinary mechanic might make for himself. It is occasionally necessary to turn parts with a concave surface to some desired radius, and this is generally done by the use of a special tool, ground to that radius. No*, it is obvious that a different tool is necessary for each radius, when a specially-shaped one is used. The arrangement that I have adopted enables any size of radius to be turned by a simple adjustment. I think the sketch which I enclose is
self-explanatory, but I may remark that the foot is clamped in the tool rest of a lathe, and the tool should be adjusted to the correct radius arid height. All that is then required is to put on the traversing cut by means of the handle at the top. It will be seen that the tool can be twisted round about the axis of this special fitting, and that the radius is settled by the amount by which the tool sticks out from the holder.
"There are no end of uses for this handy appliance, and I instance the turning of pulleys for wire cable, rope pulleys and eccentric sheaves which have a concave-shaped face.
" I think that it will be readily seen that, in order to turn a radius of, say, I in., it is only necessary accurately to set the point of the tool 4 in. from the centre of the upright spindle, and this is facilitated by turning the loose collar on the top of the tool to a standitrd size, and then case-hardening it. It is then quite easy to measure from this collar to the point of the tool, and thus to ascertain the total radius exactly."
250 New Accounts in a Few Months.
[923j " A•L." (Mile End) writes :—" You published a letter in a recent issue from' (Surrey) [Letter No. 907 in our issue for the 3rd August.—ED.], in which your correspondent recounted what he considered was a record mileage for the van which he had been driving. For three months his Commer Car' had been doing an average of 383 miles per week. I have been driving a 14-16 h.p. — van, and should like to tell your correspondent and your other readers how this machine has not only increased the trade of my employers, but has also given us a hold over a much bigger radius all round London, in spite of the fact that it has only been in service for a few months. We started work on the 6th March last, and our job was to deliver goods as the traveller sold them. Before my employers started using motors, they exclusively employed horsed vans for the delivery of goods. Our trade was therefore restricted to a radius of ten miles round our depot. Since we started the use of a motor vehicle, up to the week ended the 5th August, the machine has covered 9,000 miles. This gives an average of 1,800 miles per month. It is also interesting to note that the van has been the direct means of opening up no fewer than 250 new accounts round London. We have only. had one involuntary stop, and the repair which that necessitated was completed in under a, day. We never carry less than 15 cwt. but sometimes a great deal over 30 cwt. I think the rhachme of the type which I am driving takes a lot of beating for traveller's work. That motor vehicles can assure such increases in turnover is the chief lesson."
Cutting Out the H.P.
[92.1i (Glasgow) sends us a description of the manner in which he got home on an old Thornycroft steamier on which the piston had come away from the piston rod in the il.P. cylinder. The cylinder cover and the piston were broken, and the piston rod itself was bent. He adopted a method that was similar to several which have already been described in these columns. He plugged up the ports to the defective cylinder with wood, and so directed the live steam straight into the L.P. cylinder, and he got home quite satisfactorily, although the journey was a slow one.
For Loose Ball paces.
[925] " C.G." ((lower Street) writes:—" Referring to the driver's letter about a method of tightening up loose ball races [Letter No. 905.—En.], it may interest you to know that I have frequently used knurled surfaces in jobs of this kind, in order to get a better grip on a shaft whose diameter is no longer sufficient to guarantee a tight fit. I have as a rule, however, only used the knurling method when a hardened shaft has had to be pushed into a bush of softer metal. Many who have not used this method will be quite surprised at the strain that such a fitting will resist. If I were knurling a shaft in order to make it large, I should tin it as well ; the tinning would fill all the little channels which had been made by the knurling, and this would keep the oil from working into them, which otherwise would tend to loosen the fit. If, in such a case, it is possible to warm the two pieces up and so to allow the tinning to unite them, so much the better. It will be found that the joint thus made will never shift, and, moreover, it will be dead oil-tight. " Another excellent cure for a loose fit is to shrink
the outer collar, and it is surprising the amount, of skrinkage that can be procured in this way. I have frequently reduced a bore of 23 mm. by 3-10ths nun. and more. I always make all nuts which have become loose tight in this manner."
Our correspondent doe:; not, of course, suggest the shrinkage or inner ball races Into position.--ED.
For Worn Taps and Reamers.
[926] " S.B.H." (Huddersfield) writes:—' It sometimes happens that reamers and taps become dull or a trifle small owing to regrinding or for other reasons. In many shops tools are continuously used, even when this deterioration has taken place, and quite a lot of time is wasted in the repair, assembly and erecting departments owing to the necessity for retapping, rescrewing and filing on that account. I have noticed, sometimes, that when men have experienced this trouble, and have been unable to get to a lathe or to obtain a standard reamer, they will draw-file a shaft, or whatever the piece may be, in ortler to overcome the difficulty. Filing is very had practice to make the shafts, etc., fit. The difficulty of bringing any taps and reamers, which are out of order in the way we suggest, can be met by inserting a suitable strip of tin over the cutting edges. It is specially useful in the case of worn reamers, and a hole of the required size may easily be obtained by this method without any damage to the tool. In the ease of worn taps, where numerous sets of taps are not available, a piece of rag inserted with the tap will not only have the desired effect of cutting the thread full, but will also clean the tapped hole."
[fa our issue for the Mth September, 1909, we published a letter from a mechanic. correspondent, who suegested the wrapping of a piece of sheet brass round a tapered tap when it was desired to cut a thread slightly in
VKCOSA of tha standard size.—.En.]