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Member postings for Alan Johnson 7

Here is a list of all the postings Alan Johnson 7 has made in our forums. Click on a thread name to jump to the thread.

Thread: Getting Myford oiled up
10/08/2021 10:22:21

MEW No.178, Page 46. An Oiler for the Myford Lathe, by Barry Forrest.

I made one, and it works very well - better than the original oiler, of which I have two.

Made from the scrap box and used an oil can I already had. The conversion of the oil can was non destructive.

Thread: Powder coating quality of finish
12/07/2021 13:44:52

My son-in-law has a patio fabrication business. All products are powder coated. I help him out as required - like today. I am the "trades assistant!" All that education, skill and knowledge gained through life is not required to be a "trades assistant!"

All powder coating powder is not created equal. Some are better than others, and the price varies dramatically.

Also, metal preparation is critical, and as he only deals with new steel and aluminium. I cannot comment about exotic metals, but I know from only working with new steel and aluminium that cleanliness is very important.

Outdoor products - like a steel verandah or staircase hand rail he has galvanised - after fabrication, and before powder coating. There is a "wait" of at least a week between the "hand rail" returning from the galvaniser before it is powder coated. It is also cleaned before coating.

Oven temperature is very important. Not hot enough is a disaster, as is too hot. Manufacturers of "powder" specify a minimum temperature and baking time. Equally, a maximum temperature and time.

The point of my post is that to make a living, the powder coater you choose will have to be attuned to the material that "he" is working with, so I can see that when an "exotic" job comes along - which he has limited experience with that it can all go bad.

Not much help really, but it does give some view on a "practical coal face" experience.

Thread: New use for a slide rule
23/05/2021 13:00:54

I have my Grandfather's wooden Faber slide rule. The slide is missing. He was born in 1875 and worked in Glascow as an mechanical engineer in a firm that manufactured roof trusses and the like before moving to Australia in 1920. They had planned to come in 1914, but were delayed a bit by some event or another in Europe!

A couple of years ago I was showing the slide rule to my son-in-law who is a mathematician and statistician. His response was "what is it?" After I explained how it worked, and that "the battery had never been changed" he grasped the simplicity of the device.

I decided not to mention ".... log tables" as I felt that would be a bit much for him!

How quickly is technology forgotten!

Thread: Soldering Electrical Connections to NASA standard
22/04/2021 11:13:20

In the 70's, when I was training, we were taught to solder to probably the same standard by our lecturer (a RADAR tecnician in WWII) who had trained in the USA when he was working at one of the satelite tracking stations here (pre Moon landing times). We were allowed 30 minutes for each joint!

He said that the Americans were "VERY DARK" when they missed a satelite coming over the horizon and failed to download the data it was sending. Apparently the memory on the satelites was very small, and a missed opertunity to receive it meant it was lost forever.

Yes, the solder had lead in it. I believe that even today aviation electronics must be lead solder as it is reliable.

Thread: Antikythera Mechanism : New-ish findings
28/02/2021 14:25:13

I am not sure if these two YouTube articles have been mentioned here before. If they have not, then they are worth watching.

Session 1:

Session 2:

One thing that struck me with the Antikythera Mechanism is that there appears to be no wear! This leads me to hypothesise that the device was a "new" one and it had been picked up from wherever for delivery to the new owner. It was not some old relic - like say, some of the bronze and marble statues on the ship.

The ship had accommodation for wealthy passengers. It was not just a "cargo ship," so it is not unreasonable that some wealthy learned person went to see the "manufacturer" and collected a new one and was taking it home, and was going to impress his learned friends with it!

19/01/2021 02:46:56

1st. Observation: the insulation resistance appears good, all be it at a very low test voltage from the multimeter.

2nd. Observation: as the ratio of resistance between windings is not the same, I suspect smaller diameter wire was used as the voltages get higher. This is a common practice in transformer manufacturing when costs count. As an example, the 240V winding has a resistance of 0.24R (a nice convenient number), so I would expect (if the wire was the same size) for the 400V winding to have a resistance of about 0.4R, but it does not.

Now to apply some voltage to it! You will need an incandescent lamp. Old fashioned 100W lamps are good, but a modern halogen lamp will work. This is connected in series with the supply to the transformer. The purpose of the lamp is to limit the current flow in the transformer. If it had shorted turns current flow would be large, so the lamp limits this.

Connect initially to terminals 0 and 4, and connect the supply earth wire to the frame of the transformer.

You are now dealing with MAINS VOLTAGE THAT CAN KILL YOU. Don’t proceed if you are not confident with what you are doing! Wear safety glasses and gloves.

Energise and wait for smoke, or a burning smell. No smoke or smell the transformer is probably OK. If there is an earth leakage, your household supply earth leakage circuit breaker will trip. If it doesn’t trip you can proceed. If it does, you are the owner of a piece of scrap metal!

Measure some voltages – same as you did with the resistance tests, and report back. Remember to use the AC voltage setting on the multimeter, and remember these are MAINS VOLTAGES, SO DON’T TOUCH!

Series Test Circuit.jpg

18/01/2021 08:25:12

If you test the transformer windings as per this test it would help.

transformer test sheet.jpg

18/01/2021 02:46:30

With your multimeter measure the winding resistances and draw a diagram with the connection points and the resistance between them, and the iron core, then publish it here.

If you have one, an insulation tester set at 400 volts between the 240/400 side and the iron core.

I would suspect the 240 / 400 etc. side terminals are connected to each other, and not the 1/2" stud side and DEFINITELY NOT THE iron core!

Thread: Henry Greenly Model Engineering
16/01/2021 10:02:21

Grand! I am glad it helped. I downloaded a copy for myself!

Thanks for telling everyone that the book exists. How else would we know?

If I could just access the National Library of Australia's collection in the same way - from anywhere in the world - for free it would be fantastic!

I can read old Australian newspapers to find out about Australian old machinery I am restoring at:

But I cannot read the list of passengers on the ship my great grandfather came to Australia in the 1860's unless I go to Brisbane - on the other side of the continent - 3,600Km just to read a microfilm!

15/01/2021 12:06:08

The 1915 edition is available on the US Archives site here:

I hope it is the same book.

As an aside, the owner's name is inside the front cover:

Charles H. Beach


14th. May, 1920.

A long way from New Zealand to the US Archives!

Thread: Odd Screw size???
03/01/2021 13:14:09

ISO Metric Threads

In Machinery's Handbook. I was reading a couple of days ago that the crest of the male thread is rounded to an amount of H/8. H being the pitch.

I was making M10x1.00 male threads (in brass). I calculated, using H=1.00, that the outside diameter should be 10.00mm - 1.00/8 - 1.00/8. or 10.00mm - 0.125mm-0.125mm. Answer is 9.75mm. It worked!

Not having the Handbook with me right now, I cannot check, but M4 x 0.75 should yield 4.00 - 0.75/8 - 0.75/8, or 4.00 - 0.09375 - 0.09375. Answer 3.8125mm outside diameter.

Happy to admit that my memory is not so good, but the new diameter is 91.325% of 4.00mm, which seems to agree with previous posts.

Thread: Taper turning
30/11/2020 01:37:34

I saw this taper turning attachment project for a mini lathe here:

I never built it - so many projects - so little time!

No doubt the design could be adapted to other lathes.

Thread: Jim Cox's books on Electric Motors
10/11/2020 12:26:37

Microwave oven capacitors used to have a high value resistor permanently soldered across the capacitor terminals. This was a good idea, as it reduces the number of microwave oven technician DEATHS, and subsequent funerals!

The presence of the resistor did not affect the operation of the capacitor in the microwave oven circuitry. From memory, which is really good on some, but not all days, the resistor had a value that was linked to five (or more -was it) time constants of the capacitor charge circuit.

Anyway, what I am alluding to is that: a permanently connected discharge resistor is a good idea! It works as expected until the discharge resistor fails, then the death trap is waiting!

A neon lamp and associated resistor (across the capacitor terminals) would be a better idea - in conjunction with the discharge resistor. I have a memory of this circuitry in valve radar transmitters, but again, the memory - after forty years is not so good.

The purpose of my post is to help reduce DEATHS!

Thread: Myford Oil Pump
28/10/2020 07:56:25

MEW No.178, Page 46. An Oiler for the Myford Lathe. I made one, and it works very well - better than the original oiler, of which I have two.

Made from the scrap box and used an oil can I already had. The conversion f the oil can was non destructive.

Thread: Using O Rings
21/10/2020 12:30:58

Thanks Les, you are on the mark! That was the article!

Thanks also to Clive and Windy as I didn't know about that source of information. I shall get a copy and learn.

Thanks again,


21/10/2020 11:21:36

I have read - some time ago - an article in MEW, or was it ME! Thearticle was about Using O rings, and designing for their use.

I have used the on-line search engines, and looked at the MEW published indexes, and I can't find it!

Would anyone know where it was published?

Thanks in advance.


Thread: J A Radford; Improvements and Accessories For Your Lathe
08/09/2020 12:40:12

Thanks ega and John. I have been to Christchurch several times, and visited Akaroa. I plan next to go through my old Model Engineer Magazines in the time of his death, to glean a little more, then it is into the newspaper archives if necessary. The Cemetery Board records are also very useful.

07/09/2020 13:05:27

J. A. Radford.

Would anyone know where his grave is?

I am planning a a trip to New Zealand next year, and apart from visiting the museum for Richard Pearse's aviation achievements in Timaru, I would be also like to visit Mr Radford's grave. He was such a clever man.

Thread: What does a tool look like?
06/09/2020 01:58:39

A Man and his Lathe by L. H. Sparey complements his other book, and Text Book of Turning by F. W. Hercus is also very good. This is available as a pdf down load from somewhere on the internet.

Thread: Easy method of 4 jaw centering
01/09/2020 12:34:31

By eye - use the tool or tool holder to give you an indication. Then, digital DTI. It is easy (if you have one). Set to zero at jaw 1, rotate to jaw 3. DTI will give you a + or - error. Halve it, and adjust jaws to correct. Likewise jaw 2 and 4.

Practice on a bit of round bar first. As others have said "prctice makes perfect."

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