Model Engineer & Workshop の July 2022 の目次

Changes to Customers Support and Subscriptions Customer support for subscribers is changing to Oak, Mortons own in-house subscriptions bureau. We are confident this will greatly help readers in managing and renewing their subscriptions in the future. By the time you get this magazine the contact details should be working, they are: Web – www.classicmagazines.co.uk Call – 01507 529 529 Email – subscriptions@mortons.co.uk If you are a subscriber who has a ‘continuous credit card’ subscription, the change in ownership means there will have to be a new renewal process. We will be writing to you individually to explain this and make it as easy for you as possible. Direct Debit subscribers should not see any change. Note that my own email has changed to meweditor@mortons.co.uk 25 Years of MEW and a…

For machining in the home and school workshop the advantages of using soluble oil are few compared to the disadvantages of mess, possible corrosion and smell. My wife was born and brought up in Staines on the other side of the river Thames to the Lagonda car factory (which at that time was Petters diesel engines) and whenever I had used ‘suds’ on a machine she would say “You smell of Petters”. Over the years I have used a small quantity of cutting oil applied with a brush, as the Editor mentioned in his final article in the series Lathework for Beginners, or in recent years sprayed with a garden-type spray. For heavy cuts I usually work dry, as small quantities of fluid boil away with the heat generated and…

Figure 1, or something like it, appears with minimal explanation in all virtually all the explanations referenced last month. This refers to Tredgold’s Approximation which takes a bevel of spherical geometry and maps the gear teeth onto a conical surface tangential to the sphere. The spherical description of the bevel gear emphasises that the relationships between the teeth are angular rather than linear. In an extension of this approach spur gears can be treated as bevel gears where the sphere is of infinite radius. The surfaces of Tredgold’s cones are developed into 2-D shapes as if they were made of thin sheet. The process is described as like rolling the cone on a plane surface. This is the basis of the arc BC in fig. 1. The gear teeth are…

The challenge with internal turning tools is different from external tip holders (see MEW issue 312). Due to the tool working position in the bore, the said “cutting angle” is now the front clearance, and the “inclination angle” the side clearance see fig. 1. This is because the tool is working in a bore, so: 1. The tip and tip holder must be smaller than and clear the bore diameter (no heel rubbing). 2. The shank must be as large as possible with a minimum protrusion to reach the bore bottom and avoid chatter but with some room around to lodge the chips. 3. The tool could be used also in a boring head and not just on a lathe. The first step is to determine the smallest bore diameter…

Fig. 11 Barrel lapping bar. The lapping bar is made from aluminium alloy bar and must be parallel over the full length and the diameter should good fit in the barrel bore of 32.5. Machine the 18mm diameter offset hole and chamfers as shown in fig. 11. Set the bar on a surface plate or a vee block on the surface clock and prevent it from rolling. Mark a line along the length of the bar on the centre line with a height gauge, raise the head of the height gauge 1.5 mm and scribe another line, and repeat another line 1.5mm below the centre line. Drill 6.8mm holes through the bar in the positions shown on fig. 11 in the centre line and tap 8mm through to the central…

I took up model engineering once again after more than forty years after I had tried to regain some semblance of the grandeur of a tall antique and much neglected skeleton clock. I had made a long case clock many years previously and still have an interest in these wonderful pieces. I had a small model engineering workshop many years ago, in the 1970’s in fact. My workshop consisted of an Atlas 10F lathe, approximately 30 years old by then, which had needed quite some work, a pillar drill, a reciprocating saw I had made, and the parts of a Dore Westbury mill I was in the process of machining on the lathe from castings. There was also a part built 5” gauge live steam engine. Together of course with…

Ever since owning a Milnes Type R with a drive clutch I have hankered after fitting a similar system to my Boxford AUD. The second hand VFD drive I fitted although it worked fine had none of the smoothness of the Milnes. The previous owner (and he had it from new) had fitted a clutch made from an old moped front brake hub bolted to plywood pulleys and when I collected it he implored me to lubricate the actuating lever every day to keep it working and prevent it wearing out. It’s a tribute to him that I totally ignored his advice and just used it for 15 years without greasing or adjusting it. The clutch gave me as much control of the stop and start and jog as my…

These articles by Geometer (Ian Bradley) were written about half a century ago. While they contain much good advice, they also contain references to things that are out of date or describe practices or materials that we would not use today either because much better ways are available of for safety reasons. These articles are offered for their historic interest and because they may inspire more modern approaches as well as reminding us how our hobby was practiced in the past.…

The pendulum There is nothing very radical about how I went about this; in order to ensure that the time between impulses is long, it is worth using a heavy pendulum bob, but beyond that, the design constraints are few and far between. I chose to use one of a pair of Invar rods I had obtained a couple of decades ago that were otherwise gathering dust, but there is little real need for a temperature compensated pendulum in a modern house where the temperature variation is in any case fairly small, and being realistic, if you want accuracy, building a mechanical timekeeper isn’t the right starting point these days anyway – the average £5 Quartz clock movement will deliver significantly better accuracy than you could ever hope to obtain…

In the early days of model engineering, a workshop with mains electricity was the exception. The fortunate powered their lathes with internal combustion engines or even small steam plants but the majority had to rely on treadle power. Today, mains power is almost universally used for machine tools In a short article like this, it isn’t possible to give a fully detailed description of how to install an electricity supply for a workshop. Any extensive work (such as putting in an entirely new supply) will need to be done by a qualified electrician, or at least checked by one, in order to comply with existing regulations. Simpler work, such as adding an extra socket or changing the type of socket is generally allowed to be carried out by the householder,…

THE SPRING is an indispensable mechanical device based on the property of materials to return to their original shape if not stressed beyond a certain limit. Long exploited, this property is still not always perfectly understood. Early man made use of it in steadying his descent from a tree top on a resilient branch, or when projecting an arrow from his bow. The pole lathe, the forerunner of machine tools, employed it in a springy sapling providing the reverse run of cord wrapped round the workpiece. Modem springs, in the restricted sense of the term, are mostly of special steels, hardened and tempered to bestow resilience. All, however, work on one of two principles, or in complicated cases, a combination of the two. These are by torsion, or by bending,…

Funded by many donations in his memory, the Stevenson Cup was first awarded in 2018. The cup is engraved “John Stevenson, 1948 – 2017, Remembered by his many friends” with “Awarded for Excellence in Practical and Useful Workshop Equipment” on the plinth. The John Stevenson Trophy is presented for just that, a well-made and usable piece of tooling, a modification to a machine or an accessory for a tool where the fact it works well is more important than making it look good. Unlike traditional judged trophies, we decided on a different approach to reflect John’s reticence about traditional competitions. After a call for nominations, a small panel of judges selected a shortlist, on which there was an online vote. Due to the disruption caused by Covid 19, the 2020…

People often wonder where the future lies for engineering related hobbies, especially in a world where technology has changed the face of professional engineering so much. One of the big changes has been the emergence of a younger ‘maker’ movement. While experimenting with 3D printers and electronic modules may seem a world away from lathes and milling machines, leafing through the pages of Model Engineer magazine from 1903 I found articles on making a ‘Zeotrope’ and ‘Vacuum Tubes’ (electronic valves). A quick search online shows that some modern makers are tackling exactly the same projects! Perhaps the only real difference is that today’s hobby engineers tend to look back rather more than our predecessors! Penarth Library Makerspace ‘STEM’ – science, technology, engineering and mathematics are very important in education these…