Sommaire pour April 2022 de Model Engineer & Workshop

Ukraine It’s impossible for me to write a normal editorial today. The invasion of Ukraine has been under way for a week. Cities are in flames; families are being ripped apart and millions of people are fleeing in the biggest movement of refugees this century. Individuals may provide humanitarian support for the victims of the war through the International Committee of the Red Cross or, in the UK, through the Disasters Emergency Committee. www.icrc.org www.dec.org.uk There are many other local and national appeals. My thoughts go to everyone affected by this senseless conflict. I hope a peaceful resolution can be achieved soon. Enjoy your Hobby At times of stress and worry, hobbies and pastimes can play a vital role in helping maintain our personal well-being; something so important through the…

I’ve been interested in the application of engraving dials, scales and small name plates for a while and more latterly seen the possibilities of milling small complex parts from 2D masters using a pantograph engraver and ‘copy text’, photo 1. My research into engraving devices, shows that there are multiple options from relatively inexpensive CNC based machines from China to second-hand professional desktop pantograph machines which used to be common in high street jewellers and various shops selling trophies and dog tags. Proxxon make a relatively simple pantograph engraver which can be used with their portable rotary tools or small mill/drills. Larger, ex-industry, floor standing machines such as the Alexander or Taylor Hobson can be reasonably priced, and I would have loved to acquire one but decided that it would…

The solution for the pulleys was to print each as two halves: the 50:50 split can be accomplished in Alibre or (as I did) by applying a Z-offset in Cura to lower each pulley below the build platform by half the thickness. The two halves were joined using 30-minute epoxy. Where smaller parts are to be joined then Plastic Weld adhesive is suitable, bearing in mind that the Methyl Chloride component evaporates so quickly that there is no time for repositioning. Designing the toothed Capstan Wraps was a fun exercise in Alibre, combining tools for taper and parallel extrudes, extrude cuts, (for the bosses and holes), a revolve pattern (for the teeth), filleting (for the edges) and finally a mirror to duplicate a single wrap to form a pair. Deciding…

TIP OF THE MONTH WINNER! This month’s winner is Jim Jennings with a handy tip for making flux removal easier when silver soldering. Silver soldering small items such as boiler fittings is usually easy enough, provided that the parts can be held in position. After cooling they can be dropped into a jar of acid (citric or sulphuric) to remove the flux. But then, it can be difficult to extricate them from the depths of the jar. I have found that an easy way of doing this, is to use a tea leaf infuser. These are usually made of stainless steel, which make them ideal for this purpose. After cooling the silver soldered components, they can be put into the infuser and then into the jar of acid for the…

I gave a golf trolley to my eldest son, as he’d taken up that game and I’d ricked my shoulder, so no golf for me. Within weeks, he’d accidently driven the golf trolley into a lake – he then gave it back to me asking if I could repair the trolley’s electronic board – needless to say, it went straight to the garage attic and there it stayed until my Covid-19 self-isolation caused me to spend my time in the garage doing those jobs one puts off until a later time. Turning the leadscrew of the mill drill’s table over and over hundreds of times, lead me to think there must be a better way to operate this machine. Then the penny dropped, the golf trolley in the attic above…

For aligning a milling spindle to an edge, I use the method of moving the rotating bit until it just touches the edge and then make allowance for half the bit diameter. This method is more than adequate most of the time. I find though that I need to align to holes more often than to edges. Devices I found to do this are one or more of expensive, needing alignment or big – requiring moving the milling head and loosing alignment. So, I decided to design and make my own as described below. I am not going to provide exact drawings and instructions but only guidelines to help the reader’s grey cells to come up with a final product to suit their circumstances. Requirements: • Accuracy better than can…

This machine was advertised on Gumtree. The advert was active for several weeks and during this time I pondered whether I should bid for it. Now at the age of 78 I have to be cautious about the wisdom of making such purchases. However, eventually I got the machine delivered as I concluded that it would complement my existing workshop equipment. The Centec 2A is a rare machine which seldom comes unto the market. Although Vertical Milling machines are now more popular, this well designed and constructed Universal Horizontal Machine merits a place in any small workshop. When I acquired this machine, photo 1, I naturally referred to my back copies of the Model Engineers’ Workshop magazine for any information. Fortunately, there was a report by Mike Haughton in the…

I can’t claim that I did this in a day, rather it has kept me occupied for several weeks. Nor is it main stream modelling but it is the sort of project we get landed with when you’ve got a shed. It all started many years ago when setting up home and second-hand furniture was to be found at reasonable prices in the local Auction room. SWMBO took a fancy to this folding rocking chair with inlaid star patterns and some “Arabic” hieroglyphics that we got for about £15, photo 1. Some years later, on holiday in the Isle of Wight and visiting Osborne House, we spotted a similar chair that was presented to Queen Victoria by an Indian Maharajah for one of her jubilee celebrations. So now the chair…

In this introductory article, I will look at two areas, computer aided design or ‘CAD’ and computer controlled machining known as ‘CNC’, which stands for ‘computer numerically controlled’ machining or manufacture. Computer Aided Design While there are still many people who prefer to draw out their designs on a sheet of paper, the back of an envelope or even a ‘fag packet’ the ready availability of computers and computer aided design (CAD) packages means that most hobbyists now reach for the mouse rather than a pencil. Gone are the days when hobby CAD meant using a program really meant for drawing, there are many affordable and even freeware programs readily available. While this brings many advantages some of the most useful are automatic dimensioning, which reduces errors, and the ability…

Basically, a drilling jig is intended to guide the drill to the required point on the work, without the need for marking off or centre-punching, and to maintain the drill in alignment while the hole is produced-thus saving time and promoting accuracy. There are cases, too. where a guide for a dull is essential, even for one hole, such as when there are variations in the texture of the material, or ‘the drill cannot be started squarely. These occur when drilling wood on the side of a knot, or starting a drill m metal on an uneven or sloping surface. Spacing jigs tor general use, jigs can he in mild-steel, thick enough to guide the drill by the diameter when the point engages the work. The hole(s), a close fit…

The following is the application of an economical Digital Calliper to the top-slide of a Harrison M250 that I installed several years ago, which has been very useful. The Harrison M250 has a “Newall” D.R.O. installed and the Digital Calliper is only used when the top-slide is parallel to the ‘X’ axis. It does not conflict with access to the Top-slide angular locking nut, is permanently fixed and only needed about four ‘M3’ tapped holes into the Top-slide, placed at an angle to ‘shed’ the swarf. The permanent fixings are two small 45° aluminium blocks (photo 1) and a guide pin from the underneath of the “shorn unit”. The calliper shank after alteration with a four-inch angle grinder with a 1mm cutting disc and drilling two 4mm dia. holes at…

A comparator, photo 1, does not measure directly but is set up using slip gauges or some other setting piece, such as a Master gauge. It compares the component being inspected, with the master, used to set it. In this way it is used to check if components passed beneath the stylus are within the limits set in the tolerance band. Why and How For many years a 4-inch diameter Baty dial indicator, with 0.0005 inch graduations has languished in a box on a shelf in the workshop. The graduations, being so far apart, would allow extrapolation, to give a measuring ability of less than 0.0005 inch, possibly slightly better than 0.00025 (0.006 mm). Photograph 2 shows the Indicator, with a steel rule to give scale. Fondly remembering the Sigma…

These were created to cope with my advancing age, a back suffering from sudden and unexpected departures from motorcycles in the distant past and acquisition more recently of heavy ‘model’ and ‘machinery’ components. I have one of those commercial ‘2 tonne hydraulic shop cranes’ on multiple castors, but it is difficult to manoeuvre in confined spaces. The first home built job is the ‘radial arm’ crane, primarily for lifting lathe chucks – as I now find an 8” three or four jaw chuck rather more than I want to struggle with – one approaches a half-hundredweight with one of these. This crane has also been used to lift a job from the floor to the installed chuck. Photographs 1 to 6 show this crane. The unit is a ‘commercial’ building…