The Stephenson Trophy Competition 2020
If a year ago anyone had suggested that this year’s Stephenson Trophy would be just about the only national competition for hobby engineering, I would have thought it was a ridiculous suggestion. Alas, as well as causing loss and hardship for people across the UK and elsewhere, Covid-19 has upset so many other aspects of our everyday lives. For us not least among these are depriving us of the fellowship of club meetings and exhibitions, although online forums and the now ubiquitous online conferencing have gone some way to keeping us all connected with like-minded hobbyists.
This is the third year of the competition, the trophy being funded by readers and members of the www.model-engineer.co.uk forum in memory of John Stevenson. In accordance with John’s feelings about competitions and ‘glass case models’, all entries must 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. Criteria for inclusion on the shortlist was that the tooling must be practical and capable of being used for accurate work in a home workshop setting. It should demonstrate ingenuity, good design, economical use of materials and be appropriately finished for its function. The decision on which wins is up to you, all readers of MEW and forum members can vote (note you don’t need to be a forum member to vote).
The voting form is at the bottom of this page. Closing date is Halloween, 31 October.
The John Stevenson Trophy was 'crowdfunded' by forum users and MEW readers in memory of John Stevenson, one of the mainstays of the forum, who passed away in 2017. I'm sure John would have enjoyed seeing all the entries and discussing their merits!
Criteria for inclusion on the shortlist are that the tooling is practical and capable of being used for accurate work in a home workshop setting. It should demonstrate ingenuity, good design, economical use of materials and be appropriately finished for its function.
Please use the form at the bottom of this page to cast your vote.
The nominations for the trophy are:
Quick change tool system for my Sieg KX1 CNC mill
I have had my KX1 CNC mill for about four years now, and have made some very nice work on it, and overall I’m very impressed and pleased with its capabilities. This is my effort to solve what became a frustrating fight with the 2MT spindle.
Using my existing 2MT ER25 collet chuck, I designed tool holders to fit a standard 13mm diameter collet. Mainly because I had already previously made a little tool holder of that size.
These little tool holders really make a difference to using the KX1, giving me quick tool changes, consistent tool positioning, repeatability and ease of use.
Material was some 19mm medium carbon steel bar I just happen to have lying around. A batch of holders was made, all with the same 13mm diameter shank, and 19mm diameter body.
All were made to the same length. The shoulder which rests against the face of the collet, is the reference face for the CNC mill ‘Z’ tool heights. Holes were drilled and reamed for various common size milling cutters, including 1/8”, 3mm, 4mm and 6mm.
A quick check in the spindle revealed a slight run out in the milling cutters of about 0.002” to 0.003”, probably due to cumulative error with an over-size reamed holes and a slightly under size tool shank. But I think the run out isn’t too bad! I did take extra care with later tool holders and honed the bores to within a tenth of a thou, which resulted in much better fit, and less run out.
The tool stick out could be an issue, compared to standard end mill holders it is 35mm extra stick out, but I tend to take things slowly and haven’t encountered any issues with flex or tool creeping out of the holder.
A trial program to test the tool holders worked very well. Three different tools were used, 3mm end mill, 4mm end mill and a 4mm spot drill. Each tool had the tool heights entered into Mach 3 offsets, this took a couple of minutes for each tool.
The program produced a circular pocket, a square profile and six equally spaced spot drilled holes. This test was repeated a number of times to see if any extra material was machined at each step. I found that the tool position was satisfyingly accurate, a slight skim cut was noticed, but nothing more than maybe a tenth of a thou. Another test produced a 22mm diameter pocket to suit a 22mm diameter ball bearing, this produced a tap in fit on the first pass. Very good result.
So all I need now to change milling cutters is to use the ER25 chuck spanners and quickly replace the holder. No more fiddling around ejecting the 2MT taper from the spindle. ‘Z’ offsets are stored in Mach 3 tool library for the duration of the job, although I haven’t worked out how to fix the tool offsets for each tool holder for use in future programs.
I have for some time been thinking about ways to add accurate depth measurement to the tailstock quill on my Myford Super 7. As standard the only guide to depth are some rather crude lines on the quill itself. It is not often that great precision is needed when drilling in the lathe but there are occasions when something a little more precise is needed.
Some years ago I saw at an exhibition a tailstock mounted DRO which at first seemed the answer but suffered from a number of drawbacks: Firstly it required machining the tailstock casting to mount the brackets for the scale, secondly the collar fitted to the quill prevents short tapers being ejected as the quill cannot be retracted fully and thirdly it may get in the way during some operations. Another way was needed.
I could not think of a way to attach the required brackets to the tailstock. A little while back I took the plunge into 3D modelling and printing, which was a fascinating and welcome distraction during the present difficulties. In an attempt to solve the tailstock DRO mounting problem I drew the tailstock in Fusion 360 which enabled me to in turn model some fittings. The original plan was to make a mock up in plastic (PLA) and if it worked proceed to metal for a permanent solution.
I printed a few mounting brackets which was complicated by the compound curves that they were required to fit the tailstock casting The plan was to engineer some sort of clip system perhaps using the oil nipples as anchors.
While I was scratching my head trying to figure out how to attach the brackets, I was fiddling with a small then the thought hit me, why not use magnets to hold everything in place. I reprinted the brackets with holes in the base to accommodate some small neodymium magnets which I had left over from another project. The result was encouraging, but the magnets were not really powerful enough. I ordered some which were three times the power which worked well. I then reprinted all the plastic parts in PETG which is quite tough. All the parts are push fits apart from the rod that connects to the collar which is a threaded 5BA. To install the unit is placed on the tailstock, the collar placed over the quill and pushed on using the quill against the chuck. It only takes a few seconds. The collar is a gentle interference fit over the barrel. To remove simply retract the tailstock barrel and the collar slides off and the unit can be lifted off until it is needed again. accuracy is within 0.001” and it is a joy to use. If anything needs replacing it is a simple job to print a new part.
The photos show the final version as used now. The magnets can be clearly seen in the close up of one of the brackets.
Recently under lockdown and subsequent 2-month furlough I took the decision to go through all my Model Engineer magazines and reduce them to the articles that I was interested in or things I wanted to make.
I came across an article in the ME dated 16th September 1966 by “Duplex” (also known as Ian Bradley and Norman Hallows) called “For the Schools”. I don’t suppose schools would teach anything like this now.
The design looked good, but I never thought I needed a micrometer stand but I thought well let’s make it.
I followed the design reasonably closely apart from the base. Looking around the workshop I did not have anything suitable, however I have been stubbing my toes on an old cast iron backplate at least twice a week for 14 years that had been kept (in the best traditions), for that will come in useful one day.
This seemed an ideal use for the base and is was bored out and a scrap piece of mild steel machined and with some Loctite the base was done.
Now a micrometer stand to a design 54 years old does not sound that special, I mean you can buy one for about £15. But there is another side to this tale and that the micrometer that was recommended in the article, the bows should be ¼ inch thick, which was perfect for an old but very good condition metric Starrett micrometer that was given to me many years ago by an old toolmaker.
The whole thing cost me nothing and the small spring I robbed out of a ball point pen.
I have to say it has been a very useful addition to the workshop and I am glad I made it. I think re-utilising old but serviceable tools that have a useful purpose in a workshop is well worth considering.
Myford/ Drummond M Type lathe handwheel modification.
I have an M type lathe and it is the only one that I have seen that has a handwheel that appears to turn backwards to move the saddle along the bed. It has caught me out a few times and so I prefer to use the handwheel on the lead screw for most jobs. Anyway another member has done a modification to insert another gear in to the train and so makes the handwheel conventional in use and he has some castings for sale to do the job with.
Having purchased the casting which is only a flat plate with the basic outline of the original saddle front plate I decided to draw up the original casting and then add my own sizes on to the new casting, draw and make side plates to fit the casting and locate in the diameter holes so that the new bronze bushes that were to be made to match the proposed gear centres. I drilled and bored the casting to give a clearance on the gears but on the correct centres and the original holes were matching to the lathe. I then made the two gears to fit and cut a keyway to suit the new shafts leaving enough side clearance to have a location on the side plates and not trap the gears.
The side plates were turned from solid in a 4 jaw chuck and I had to leave a one inch by one inch boss on the back of the rear plate as well as boring through for the bronze bush and the location diameter on the other side. The front plate was simpler and less metal removal but both plates needed milling on the rotary table to mach the casting shape and with a bit of filing to tune them. The gear shafts were pieces of silver steel and I bought a new gear for the rack as I didn’t want to try and get the old gear of and I didn’t have a cutter to make a one off gear. I also bought a new handwheel as the old one had some damage.
The saddle went together quite well except that I had mis-measured the length of the new gear and it fouled the casting pad behind the rack. The assembly of the plate was a pain till I found that the screw for the lead screw nut assembly could be screwed from the front with a screwdriver slot in the end of the screw and then putting on the locknut. After a try out I was impressed and so painted it to match and I now use it all the time without worrying about crashing the tool into the job or chuck.
Grinding Wheel Dresser
After a period of use the grinding wheel loses its cutting efficiency. The grit grains become glazed and dulled, cut less efficiently and generate more heat. It is then advisable to dress the wheel to remove the blunt grains and generally reinstate the surface of the grinding wheel. This is especially required when a new wheel is fitted.
I used to dress the wheel of the tool grinder by moving an industrial diamond across the wheel face by hand. Just move the diamond over the face of the wheel in a smooth straight line, I found this easier said than done. To this end I evolved this more controlled method of sweeping the diamond across the wheel face in a guided manner. The wheel dressing device shows the grinder with the outer wheel cover removed. In my case it just clips on over the inner cover. The grinding rest has also been removed to allow for the dressing device to swing across the face of the grinding wheel. As to the geometry of the arm movement, it is virtually a straight line where it contacts the wheel face.
The pivot mounting block is slotted to fit over the edge of the inner cover lip and is secured with two M5 grub screws clamping it in position. The vertical arm has a long slot enabling it to position the lower mounted diamond at approximately the centre of the wheel. The diamond is mounted at an angle of 15 degrees to the wheel as is recommended by the diamond suppliers. The vertical arm assembly slides over and can freely rotate about the horizontal pivot.
An adjustment screw extends the full length of the horizontal pivot and protrudes to give fine adjustment to set the distance between the diamond and the wheel. The lower nut locks the pivot axis for the horizontal arm, which is set, by eye, to be parallel to the wheel. The upper nut clamps the horizontal arm, extended to set the diamond close to the wheel face.
With the diamond set to just scrape the wheel face the vertical arm assembly is then slid back to clear the wheel when the grinder is switched on. The arm is then moved forwards and rotated to clear the wheel. The arm is now swept, smoothly, across the wheel face making small dressing cuts to the wheel face by holding the ball handle. By gradually increasing the forward pressure on the ball handle further cuts can be made to completely cover the wheel face. It is not generally needed to make further adjustments to the fine feed as just slightly increasing the forward pressure enables subsequent cuts. The vertical arm can now be slid back and the wheel switched off. Just notice how much smoother the grinder is after dressing.
The horizontal arm can also be set at 90 degrees to the position shown to dress the sides of the wheel. In fact, it can be set at any desired angle. The final photos show the wheel finished and the dresser assembly.
This came about because I had just finished a Tailstock turret from a design in MEW.
I make my small parts on a Peatol Lathe which is a very capable machine. On occasion I have a call to make quite a few parts (30 to 50) which require several tailstock tools to be used to make the part so the germ of an idea to have a scaled down version for use on the Peatol.
The big difference was not just the size but the tail end, the Peatol does not have a taper socket in the tailstock but a parallel 1/2inch bore which has a slit at the rear to enable it to be locked with a screw. The parallel shaft was milled with a slot and a full length key screwed in place with 10 ba c/sunk screws, this made sure that the turret did not rotate while in use. As space is at a premium on a lathe of this size using things like drill chucks to hold centre drills, taps etc. was not an option as they are too unwieldy, so either dedicated holders are used or the er11 collet chucks are used. The collet chucks are made in my favourite material USACUT55 but the nuts are a bought in item. If they are made in the right order they will be accurate to less than a thou.
Here are some photos of my tailstock DRO, which uses a rotary encoder rather than the usual choice of fitting an old digital caliper. I had to make 2 bits of hardware and modify one the pulleys, as well as making the control box of course, but that's a load of bought in bits soldered together. The software is mine.
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