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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: Motor size
28/04/2022 12:15:53

I had thought that Myford recommended nothing more than 0.75HP (0.56kW).

Thread: Phosphoric Acid experiment
18/04/2022 12:50:40

I left a piece of mild steel in phosphoric acid (Chemtech Rust Off Remover - from local hardware store) overnight - because I forgot! Nothing to do with my age! Same effect. No "grey" finish, more a rusted orange colour. I will attempt to find it tomorrow and photograph it.

Thread: Thread-cutting oil
27/03/2022 12:09:32

Angel's Breath.

MEW Issue 72 (March/April 2001), Page 58, by J. R. Lait, Lincoln.

He said Angel's Breath is ideal for drill and tapping 25BA holes in extremely tough armour plate type alloy.

DMB (above) described it as Guy Lautrard's formula.

It works very well, but you must use genuine turpentine - sometimes called Artist's Turpentine. Smell is pleasant too, and doesn't become rancid.

Thread: A sticky Mercer Gauge
19/03/2022 10:26:39
Posted by old mart on 18/03/2022 21:37:48:

I had never thought of using IPA for cleaning things other than my tonsils.devil

IPA = Indian Pale Ale......

Now I am confused!!!!

Thread: At my wits end trying to remove pulley
11/03/2022 09:39:30

A set of Litchfield Pullers would do the trick, or a hydraulic press and a a couple of bits of thick flat bar to support the pulley as you press the shaft out........ unless I am mis-understanding your problem. A photograph would be worth a thousand words!

Thread: Hello from Wyoming (USA)
23/02/2022 03:08:10
Posted by Ady1 on 22/02/2022 18:29:39:

Welcome to the nuthouse shane

The sole difference between me and a madman is that I am not mad." Salvador Dali.

Thread: HarrisonM300
23/02/2022 03:00:56

The Harrison M250 circuit diagram does not show a fuse in the light circuit. This does not really help, but I would be surprised if the Company changed "philosophies" between models.... but then again, it may have been modified by a previous owner!

You will need to track the wiring back. Conductors break in places where the cable is being flexed alot - like where the cable goes into the light fitting, or back into the machine. A good wiggle at these points may "shed light" upon the problem - if the light switch is "on," and the switch is not physically broken. The M250 diagram does not show a switch, but it could be an integral part of the light fitting on the M300. The light fitting itself may have failed, but I am sure you have already checked that.

Thread: I need help to identify shaper
22/02/2022 09:30:16

The essential dimension of a shaper is the maximum length of the stroke. This dimension is missing!

Thread: Voyager 2 is back online
18/02/2022 09:19:51

Here is a better site about Voyager 1 and 2. There is no advertising, and is not on Y-tube. Also, I think that the information presented is coming from "the horse's mouth!"

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.

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