Member postings for John Fielding

OK I found a similar keyway cutter, not the same company but the method is the same.

Have a look at the video to see how it works.

https://www.youtube.com/watch?v=XrFEN9veUfU

Edited By JasonB on 01/06/2016 09:32:02

Hi Clive,

After I posted the poliangolar (SP?) idea I went and looked again at the url I had stored and it was no longer active. The new Poliangolar system is completely different, more of an eccentric broaching system.

The one I saw, they even had a video of a guy sitting at a drill press cutting keyways in change gears!, it was a round spigot with a tiny side and face cutter poking out of the side. The drill chuck drove the cutter by a helical shaft, like a worm wheel, and it cut pretty quickly. No idea where the link is now but it was a very clever beast. Seems they had been around a long time and it was an American company. Another mystery!

Hi Ian SC,

The Rexon originally was a Taiwanese machine, but I believe they sold the rights to manufacture to a Korean company. In fact if you look on Google-Earth for their address you will find a lot of other companies in Taipei making almost identical machines. My mill-drill is the RF-25 which is the Rong-Fu machine company and they are less than 1km from Rexon! Seems that area of Taipei is the main source of most machines made in ROC, Republic of China, which is not to be confused with mainland China which is PRC!

Just after WW2 the Chinese government exiled themselves to the island of Formosa, today called Taiwan, and took all the governments funds with them. Following the war the Japanese were forced to relinquish Formosa to the chinese, but they wanted independence from mainland China as they didn't agree with the communist radicals then running the country. Mainland China want Taiwan back but the locals gave them the middle finger!

Naerok? Never heard of them!

But spell it backwards and you have the country of origin! The RDM 350 series is one of the first Korean machine tools on the market, not wonderful but OK. I believe they have been somewhat improved over the years.

Hi Mechman48,

I am in the same boat as you. Tried all the free software on offer and played with them all. I eventually selected QCAD which can be downloaded as a free package and it runs under Windoze! Got fairly good at using it and then found some of the extra features are "greyed out" so they don't work. Finally bit the bullet and signed up for the full version, it was quite reasonable in price and it works well. Perhaps not the best but it does what I need.

I wonder how many folks have come across the Polyangular key way cutter. It fits in a normal pillar drill and cuts key ways like magic.

It has a miniature milling cutter poking out of the side of the spigot and it is driven by the drill chuck. One pass to make a key way takes only a few seconds. There is a video on the net you can look at to see how the thing works.

How about the saying "a black art".

I know where it came from but how many others know its origin?

Incidentally a lot of the common sayings today are from Shakespeare's plays.

Having found my copy of Ivan Law's book I did some perusing last night. BTW it is published by Argus Books under their Workshop Practice Series and is a very good book to have to hand.

MOD = 25.4/DP and DP = 25.4/M

So a 25T gear with MOD1 has a pitch circle diameter of a fraction under 1-inch. That is a little finer than a 20DP gear which allows more teeth than a 20DP on the same size gear. Doubling the DP reduces the gear diameter to half for the same number of teeth. A 20DP gear with 25T would be MOD 1.27, a 20DP gear with 50T would be MOD 2.54 etc.

My guess is the modifier of the lathe worked for a company that only had MOD gear cutters and so it made sense to use them rather than the older DP cutters. Anyway, what you have looks perfectly OK and is probably better than the original Grayson/Myford setup.

You got me thinking about the Grayson gears and as I don't use this old lathe any more all the bits are stored away.

Out of curiosity I dug out the change gears and the quadrant etc to take a closer look. I was surprised when I cleaned off all the dirt that the big gear which normally fitted on the lead screw is a bit odd. I had measured it some years ago before storing everything away. It has what looks like a makers name cast into the side, seems to be PK and the other side has the number 112, presumably the number of teeth. But on looking more closely it actually has 90T and they are not 20DP. After faffing around a bit they seem to be either 16DP or 17DP depending where on the teeth you assume the pitch circle is. My assumption is it is a 16DP as odd number were considered an "oddity". I wonder if the previous owner used a 112T and machined the teeth off to cut new ones? There isn't a lot of metal left on the rim and that suggests that is what they did. The gear does have a key way but someone had fitted a sleeve to adapt to the 5/8-inch lead screw stub shaft.

The other smaller gears are definitely 20DP, same as the Super 7 ones and they are interchangeable. I have a fixed compound gear set that goes between the quadrant gears and the large 112/90T lead screw gear. Never noticed they were different! The age of the lathe predates Mod gears I think?

The tumbler reverse gears are also not 20DP, which I never noticed before. So it seems that Grayson may have used two different types and Myford simply copied the design when they bought Grayson all those years ago. The plot thickens!

It could be a type of sleeve valve engine. The sleeve is connected to the piston rod and moves to open and close the ports. As the exhaust seems to be directly opposite the inlet steam pipe that could work. But the piston must have been quite a small diameter compared to the cylinder outer diameter?

Hi Richard,

A very good book to tell you all you want to know is by Ivan Law, which Tee Publishing advertises. IIRC it is Gears and Gear Cutting, or something like that.

As others have mentioned the Myford/Grayson series of the smaller lathes used 20DP with a 14 1/2 degree pressure angle. The angle isn't important for now but the DP bit is. Basically the DP is the number of teeth for each inch on the periphery of the gear. So a 20DP gear of 20T is about 1-inch in diameter, a 40T gear is about 2-inch etc. The reason I say "about" is because the pitch circle diameter is measured part way up the tooth profile and not at the top. By measuring the number of teeth and the OD you get a pretty good idea what the DP number is, it is usually a whole number but there can be exceptions to that rule!

Any 20DP gear will mesh correctly with any other irrespective of diameter or number of teeth, you only need to adjust the center distance to have a good transmission via the gears.

The direction the lead screw rotates can be changed by the tumbler reverse gears and it depends on the number of idlers in the chain. With one idler the mandrel and lead screw will both turn in the same direction. With two idlers the lead screw is reversed, hence why the tumbler reverse gears are fitted.

On my Grayson 3 /13-inch lathe, the fore-runner of the ML7 it seems, the change gears have two types of studs and some have a spacer sleeve to change diameter as well. The nominal center hole is 5/8-inch and they have either one or two pin-holes for the driving pins. When Myford brought out the ML7 they added key ways and left out the pin-holes, but otherwise the gears are the same.

I think the engine is definitely a reciprocating type.

I assume the crank pin engages with the lump attached to the piston rod and it slides in the upper tail rod support. There is probably an oil well in the lozenge shaped bit which is bolted to the piston rod, you can see the cross bolt in the diagram. That would be enough to keep the crank pin and piston rod lubricated.

The governor is driven by the belt pulleys (belt not shown in diagram) and there must be a pair of bevel gears inside the casting. The governor operates the steam regulator. The mystery is - where is the valve gear? Possibly it is contained within the piston casting and as with most stationary engines it only rotates in one direction, so a simple piston or slide valve would do the necessary.

I have seen similar steam engines in old books but never one like this one.

There appears to be a sort of name or logo cast into the main support but it is too indistinct to decipher.

Hi Richard,

That ML2 looks awfully like my Grayson lathe! In fact Myford bought Grayson and copied it.

The idlers are exactly what they say they are, they simply allow you to span the two wanted gears to get from the mandrel to the leadscrew. So any two suitable gears will do that fit OK. Assume the mandrel has a 20T gear and the leadscrew has a 60T gear. If you could couple them directly then the reduction would be 1:3.

Now interpose any idler gear, let us say it is 40T. Then the idler gear will rotate 1 turn for every two turns of the mandrel gear. Now couple that 40T to the 60T leadscrew gear and it will rotate the leadscrew 40/60 per rev, that is a reduction of 1:1.5. Multiply 1.5 x 2 for the two ratios and you 3:1, which is what you would get without the idler gear in place.

So the idler does not effect the overall ratio and hence any suitable gear will work. Cascade as many idler gears as you like and the overall ratio is simply the first and last gear - as long as you have each idler on a separate spindle. However, if you couple two gears on a common spindle with the drive pins then it becomes a "compound gear" and the number of teeth do have an effect.

I hope that helps?

Hi Duncan and Neil,

Yes indeed the scrambling of special symbols when it is fed through the DTP software is a real headache. When I was having my various books edited the number of times the galley proofs contained errors was amazing. The worst seems to be Greek letter symbols and square root signs. In one portion of text I wrote about a "50-ohm" resistor using the omega symbol and when translated it came out as "50W", which at first sight didn't seem an obvious mistake. Fortunately it was spotted and corrected, but it made myself and the person doing the editing pay special attention in future.

Proof reading is bad enough at the best of times, especially when rushing to meet a deadline, so I sympathise with Neil and Diane!

Andrew you are 100% correct!

In the early days a prototype schematic was given to a draftsman and when it was done it often was a disaster, for all the reasons you have given. After a few failed attempts the RF engineers, like myself, did the layouts and the chief draftsman checked for compliance of track width, spacing etc before the job was signed off for manufacture. Over time the engineers did all the work themselves as they learnt the drawing standards.

Today with CAD schematics things tended to go backwards. Look you can do a very good schematic, which the engineer checks and corrects, then the PCB layout program loads all the components from the library and rats-nests the connections. But the placement of certain items is critical, so the engineer has to sit with the draftsman to get the layout the way it needs to be. This is unproductive as whilst I am spending many hours telling the layout chap where to move components I am not doing my real job. So an engineer has to learn to do both tasks and it is quicker and less liable to have cock-ups!

Often when designing a board layout you need to leap over an adjacent track with a zero ohm resistor, this doesn't appear on the original schematic so the cross check software throws up an error. You then have to "back annotate" the layout to the schematic to correct the error. This going backwards and forwards takes time and other errors can creep in. Today I have just a simple schematic with the vital building blocks and leave the final schematic until the layout is finalised. You might want to add extra components, like additional decoupling caps etc, as you go along. The original pad and tape method worked in a similar manner. As you put the tracks down you ran a highlighter pen through that part of the rough schematic until all the connections were completed.

At Marconi, in the early days, they had a rigid layout standard which decreed that via holes were bad news, so two had to used in case one went AWOL. If the connection from the board top to bottom used a component lead then only one via was mandatory, but with improved etching and plating methods this has fallen away.

Some of the published pcb layout plots I see in amateur publications make me cringe. They are obviously made by someone who has no experience in the art of laying out boards. Our chief layout draftsmen would chuck the films back at you if you made such a cock-up!

The old guy who ran the photographic department was old school, he had been a silk screen expert back in the days when domestic radios had the stations and wavelength printed on a glass sheet. Often if you took a layout down to him he would glance at it and hand it back and tell you to do it again. Slowly one learns the right and wrong way to do a good layout and with his advice I learned a lot.

Going from pad and tape layout to CAD was a transition but a better result with less effort. But you can't sit any monkey in front a computer and expect a good layout to appear! That takes years of experience.

Muzzer asked:

Who was it that used to make all the self-adhesive transfers, tape, pads etc? Letraset was it? Different set of tools - scalpels, translucent (matt) film, marker pens (to fill in islands), light boxes etc. Ah, manual PCB layouts - before CAD, like Cadstar, Pads, Mentor, Altium etc.

The pad and tapes I have in my bottom drawer are made by Bishop Graphics Inc, Westlake Village, CA. But there were many manufacturers, 3M seems to come to mind. Showed them to the electronic engineering students at the uni and they had never heard of such a thing!

Amberlith and Rubylith we used for double sided boards where a solid copper ground plane was required. Circular holes were cut with a pair of compasses with a carbide tip to cut through the top coloured film and then a scalpel blade was used to lift the doughnut leaving the clear mylar film underneath. A nasty part of Amberlith and Rubylith was it was very flammable. The off-cuts were normally tossed into the waste basket under the bench. One day a draftsman dropped his fag end into the basket and it burst into flames, filling the drawing office with acrid smoke and requiring an extinguisher to put it out!

The company had a LittleJohn plate camera which took up to an A0 drawing film for reduction to final size. Most pcb artworks were done at 2:1 or 4:1 and then photographed down to 1:1. For thick film hybrid circuits we worked at 10:1 of the final size. Layouts were done on a light-box with a transparent grid sheet to get the correct pin spacing. As most standard components used a 0.1" spacing these grids were made in house to suit the original layout ratio, 0.2" spacing for 2:1 and 0.4" for 4:1. Some silly bugger decided to use a metric grid of 2.5mm and then wondered why his pad holes ran out on a long IC!

The layout of a complex board could take several days and most of the time was working out how to orientate the devices to get the easiest tracking. For double sided boards rf boards, which was most of our work, two sheets of tracing paper were used and a red and blue wax pencil to draw the tracks roughly as to how they would run. On top of these another sheet of tracing paper had the components drawn in pencil, this was known as the "Puppet Sheet" and the outlines of the components was drawn using a stencil. The sheets were all punched and registered so you could move a sheet from top to bottom as work proceeded.

Once that was sorted then the pad sheet was placed on top and the pads stuck down using the grid lines to get the correct spacing. Then another sheet of clear mylar was added and the bottom tracks where routed using different width tapes. Finally the top sheet had the top tracks or Amberlith was used. The three sheets of mylar film were registered with a 3M Pin-Bar to keep the sheets correctly lined up. For the bottom copper the bottom tracks and pads sheet were then photographed to form a negative. Then the pads and top tracks were photographed to form the top negative. Targets were added to each sheet so the registration was always maintained when the copper clad board was screened and etched.

The good thing about manual tape and pads layout is it taught you to think ahead and to get the layout correct first time. If you "painted yourself into a corner" you had to start again. With CAD you can pick up and move a whole section and move it around to gain some space. The best pcb layout draftsmen were the older school who had used pad and tape, as they rarely got into trouble when converting to CAD based layout systems!

The various track layers and pads were always viewed as if you were looking from the top or component side of the board. So the bottom copper sheet had the writing reversed when looking through the stack of mylar sheets from the top. This was to ensure the board manufacturer got the film negatives the right way up.

On 4-layer and higher boards it could be a real nightmare and most draftsmen preferred to be locked in a room with no distractions and no telephones!

Hi Ketan,

I fitted a QCTP to my Super 7 last year. It wasn't the type you described, I bought it from Chronos and it was made by Shorba (India). The S7 had the 4-way tool post and had the detent pawl plate attached by three countersunk screws. This was removed and kept with the original tool post.

The Chronos QCTP wasn't supplied with a new bolt, just the body and the tool holders. It was a generic type not specifically intended for the Myford lathes, so I can't complain. I made a new center bolt to suit with a 12mm diameter as that was the hole in the body.

The one thing I discovered is how the original center bolt had caused the top of the top slide to become belled upwards. I had to take a tiny bit off the top face to correct this as the body would not sit down flat and it moved under a heavy cut until I corrected this problem. After that it was fine!

The amount I had to remove was minimal, probably less than 0.25mm, but without this modification it was always going to be a problem. The Chronos QCTP is bigger in footprint than the one you show so it may not be a problem with yours.

The thickness of the S7 top slide is a bit marginal and the counter bored hole also weakens the top of the casting a bit. As long as not too much stress is put on the casting it should be fine, but too much Sunny Jim could be a problem.

I would recommend that anyone changing to the QCTP check this problem, before fitting the new parts, by applying a straight edge to see if the mounting surface is truly flat.

Here is a tip for dressing grinding wheels a wood turning friend put me onto.

Buy a few cheap diamond coated blades for angle grinders. The sort used for cutting concrete. My local tool warehouse has packs of three for about R20, that's about One quid in the old money. Hold the disk gently against the grindstone and move it side to side. You will be amazed how it smooths the surface. When that bit of the diamond wheel gets worn simply rotate it a few degrees to expose more fresh diamonds. When it is completely depleted throw it away and use a new one. My last pack of disks has lasted two years!

I still have a full set of Rotring hand drawing pens and the new ink. Plus I have a good collection of Staedlter Sprint plotter pens which I use for the Roland A3 plotter when I want a draft plot when designing pcb laypouts. The plotter pens have a very hard tip so they don't get abraded away. The ink is a plastic (PVA?) solution which is waterproof and sets very quickly so it doesn't smear.

At the saltmine back in the days we had a whole collection of HP plotters from A4 up to A0 for the largest CAD drawings.

Nowadays the pcb file gets sent to the manufacturer by email and they make a Gerber plot straight off the data file. How times have changed with modern inventions! Does anybody remember Amberlith and Rubylith method of laying out pcb's with pad and tapes? I have a drawer full of pad and tapes which nobody uses these days.

Good quality chill-cast iron is an excellent bearing surface and it is a relatively inexpensive material. The reason I and Doug Hewson advocate its use is that good CI has a lot of graphite within it and this is in itself and excellent lubricant when the oil supply is marginal. As someone already mentioned, many lathes ran the spindles in the CI without fancy bronze or babbit linings and they just go on and on if you remember a drop of oil occasionally.

As far as sash weights go, forget them. They are made from pig-iron, the lowest form of cast iron and they are really horrible to machine and contain all sorts of other muck in them. If you just want mass then thay are fine but for anything else I would not consider them. Chill cast continuously poured CI round bar is cheap, you can also get spun cast hollow tubes but these are harder to find. When making things like piston rings about 95% of the CI solid bar ends up in the lathe swarf tray as scrap! So in these cases hollow tube is less wasteful, depends on the diameter mostly.

Modern continuous cast iron round bar has an excellent surface if the foundry workers get it right. Some 35mm diameter bar I bought last week is almost good enough without skimming the outer surface, but the surface finish can vary a lot between batches. The spun cast variety is also much harder and longer wearing than normal cast round bar, but it machines beautifully with a carbide tool, just like chalk but the dust isn't as nice!