Tabla de contenidos para February 2023 en Model Engineer & Workshop

The Myth of the Overwound Mainspring I have come into possession of an automatic watch; supposedly a new one – not a Christmas present (I did get a nicer watch with a quartz movement though!) It arrived apparently fully wound but refused to run for more than a few seconds. Being somewhat naïve about the field of watch making the clearly tightly-wound mainspring made me think that it had been ‘overwound’. With nothing to lose from experimenting (it isn't a valuable timepiece) I tried various ways to see if I could get it to run. Moving the hands reliably started it but after a while the best it managed was nearly a minute. I soon found walking with it improved things a little, and after multiple starts it will now…

To BE pressure or liquid-tight, a valve of hard or rigid material demands an accurate seating. Of course, if a valve is of leather, rubber, or similar pliable material, or incorporates such in the form of a ring or disc, small inaccuracies in the seating can be accommodated-though the finish should be smooth and free from sharp edges. A valve, however, which is a flat disc, a ball, cone or poppet type, demands a geometrically accurate seating, since only by precise matching of valve and seating faces can leakage be prevented. In small and model sizes, suitable cutters can be easily produced from silver-steel or cast-steef rod and, after hardening and tempering, used in a drilling machine or by hand where the purpose is simply to finish or correct the…

While helping my son to build the Polly small steam plant designed by Tubal Cain, the drilling of the bronze ball for the safety valve raised an issue. The suggested method is to chuckthe ball and drill in the lathe, but it is only 3/16” (4.76mm) diameter and hard to position in a chuck which is agricultural in comparison to the size of the ball, so I decided to drill it on the vertical mill-drill, locating it instead in an ER40 collet mounted in a Stevenson collet block The only difficulty was then to stop the ball falling straight through, so the adjustable stop in photo 1 was quickly devised. The stop is made of three parts, a base and a sliding bar topped with screw and adjustable part support,…

A recent thread on the Model Engineer website entitled ‘Need Advice on Clearing Dad's Shed’ attracted many responses. These fell into a number of categories, all with the premise that the model engineer has died, leaving his/her family and/or executors to dispose of the workshop contents. The categories were: To sell it all on eBay, item by item, To sell it as a single lot. This category divides into two sub-categories: To advertise in the hope of finding a hitherto unknown person as buyer, To sell through the deceased model engineersclub The proponents of all these recommendations opposed calling in a workshop clearance dealer on the basis that ‘the dealer will offer peanuts!’. As I considered these replies, it seemed to me that the commenters were missing the point. I…

Many of our tools, models and other contraptions require sources of electrical power, in this article I will look at different options and ideas for powering those things designed to run on low voltage DC supplies, rather than from the mains suppy. Typically, smaller devices take single-use of rechargeable batteries. Larger equipment is usually designed to have an external power supply which may be plugged into the mains or can be substituted with a power pack allowing it to be portable. Often we want to use models or tools away from home, and sometimes at sites far away from any source of mains electricity, portable power sources can be important to us. Even when operating at home or in the workshop, the use of batteries can help minimise the ever-increasing…

Artemis completes its Lunar Mission NASA's Orion spacecraft splashed down in the Pacific Ocean, west of Baja California, at 9:40 a.m. PST on Sunday 11 December after a record-breaking mission, traveling more than 1.4 million miles on a path around the Moon and returning safely to Earth, completing the Artemis I flight test. Splashdown was the final milestone of the Artemis I mission that began with a successful liftoff of NASA's Space Launch System (SLS) rocket Nov. 16, from Launch Pad 39B at NASA's Kennedy Space Center in Florida. Overthe course of 25.5 days, NASA tested Orion in the harsh environment of deep space before flying astronauts on Artemis II. “The splashdown of the Orion spacecraft – which occurred 50 years to the day of the Apollo 17 Moon landing…

At last it's great to be able to share the results of the 2020 Stevenson Trophy Competition. After our covid-induced break this is the fourth time the trophy funded by readers and members of the www.model-engineer.co.uk forum in memory of John Stevenson has been awarded. In accordance with John's feelings about competitions and ‘glass case models’, all entries had to be a piece of practical workshop equipment i.e. a tool, jig, fixture or a modification to or accessory for an existing piece of equipment. The entries were all profiled in issue 321, November 2022, and online voting, open to all, ended on the 30 November. Once again, we had plenty of votes. Unlike earlier competitions this year's winner won by a length rather than a head, although the difference between…

The bracket The bracket was be made from a piece of angle 60 x 90 x 135mm that I found, photo 18. To make it fit the lathes tool post I cut the 135mm down to 100mm then, photo 19, the 60mm was then reduced to 25mm in depth, photo 20. The 90mm section was then cut at an angle to reduce the bulk on the up stand, photo 21. After cutting the angle, the lathe's QC (quick change) toolpost was set to the middle of its height adjustment then the angle was clamped in it, after this the tool holder with the cutter fitted was centred in line with the lathe chucks centre line, photo 22, and the tool holder was then clamped to the angle, photo 23. The…

I have long held an interest in the process of casting and over the years have tried several methods. Sometimes these were addressed at specific aims and at others it was just to play. This article covers a number of casting methods. It is not intended to be a “how to do it” article but more of an ideas article. I have subscribed to MEW for many years and find to me its prime strength is the wealth of knowledge from the authors which can be lifted and adapted for my specific needs. Different casting methods will be covered by way of examples although detail in some areas may be sparse due to the lack of illustrations. It is only in recent years and the advent of digital cameras that…

TIP OF THE MONTH WINNER! Rescuing a Tap Wrench This month's winner is Bob Lamb from London, with a handy idea for rescuing an otherwise serviceable tap wrench. I have a tip which I hope may be helpful to others to salvage damaged small tap wrenches: I quite like the small Eclipse T bar tap wrenches and got a couple more off ebay. Unfortunately the ends of the closing tubes of both of them, which were quite thin, had split, photo 1. I could not be bothered to send them back and thought a fairly simple repair might make them useable again. I made a small steel ring, slightly tapered on the inside, and silver soldered it in place. Nothing seemed to distort and the first one was operational again,…

Myford Gear Ratios Dear Neil, in MEW 323 Rod Jenkins describes the gearing used on his Myford gearbox lathe to cut 0.833 mm pitch Shaublin collet threads and make a suitable drawbar for his Pultra lathe. His article sparked my interest in gearing arrangements and without denigrating his work in any way, his spreadsheet analysis overlooked another suitable combination within the range he chose. A driver of 22 teeth coupled to a gearbox selection of 28 tpi will produce a pitch of 0.832 mm. It also provides the means of generating the pitch for Myford owners in North America having export gearboxes equipped for 23 tpi in place of 19 tpi gearing. I then thought about owners having change wheel machines and a set-up of 25/50 x 21/40 will generate…

The Tilting Jaws As I was making all these parts, I decided that a jaw facing would be needed which would allow the gripping of tapered items as when pattern making etc. I decided that a 5° taper would be quite satisfactory. Initially, I thought that I could hold the tilting jaw on to the vice with a strong rareearth magnet. However, I realised that this might present a problem if working on any steel objects as they could become magnetised, or filings and swarf would get attracted to it and impede the movement of the jaw. After a lot of thought about how the jaw should tilt, I came up with a satisfactory design where the jaw facing which tilts would be held firmly, to stop it falling off…

Parts made by professional modelmakers are often ground. Even a second-hand Jones & Shipman surface grinder would set you back around £6,000; I hate to think what they are new; certainly outside of my league. But a nice finish can be achieved in the amateur's workshop. Step 1 is to use sharp tools to get the best finish that your machines can deliver. Step 2 is to use a little coolant (soluble oil in water) when turning mild steel – just an occasional dab with a brush on tool and workpiece. (I also use coolant when turning cast iron, just to keep the dust down.) Lathe tooling has changed beyond recognition since I took up this hobby. We rarely have to grind tools from square HSS tool blanks and worry…