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Member postings for JA

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

Thread: Stepper motor control of X-Axis from MEW 199
23/01/2013 19:35:42

John

A few years ago I built this table drive system. Like yours it worked well except for the slow table speed, maximum about 20 mm/min, and the failure of the LED to work. Last year I replaced the R4 resistor with a 47k resistor and the potentiometer with a 1M one. I did not change the stepper motor wiring on the basis that it was working (and I am ignorant about stepper motors). The table speed range is now 5mm/min to 112mm/min. My attempt at getting the LED to light-up has been less successful.

JA

Thread: spiders
13/01/2013 16:48:01

Can I train them to catch mice?

JA

Thread: Black hole
04/01/2013 09:07:54
Posted by merlin on 03/01/2013 23:35:01:

Come back, trouser turn-ups!

No, not trouser turn-ups!

JA

03/01/2013 19:07:47

They particularly like small springs. They also increase the height of my motorcycle seats by half an inch each winter.

I have taken to assembling small items in an up-turned cardboard A3 document storage box lid to stop the escape of such bits.

JA

Thread: Turning Perspex rod
29/12/2012 18:36:13

Chloroform in air and sunlight oxidizes to Phosgene. Phosgene will kill you and was used as a poisonous gas in The First World War. This is why Chloroform is always kept in a dark coloured glass bottle and is never inhaled directly.

JA

Thread: First lathe
19/12/2012 15:28:19

I used EP90 for many years in the gearboxes of a number of bikes and never saw any corrosion to bronze bushes. Some boxes frequently ran with a EP/water mixture, the water entered the box down the clutch cable and the box was not hot enough to drive the water off. However I would not recommend EP oils for gearboxes or lathes.

Morris's sell their equivalent of Nuto32, Triad32, in 5 litre containers on the internet. However their Slideway oil comes in 25 litre containers and when questioned about this they suggested contacting Premier Fuels and Lubricants. They have sold me 5 litres of Slideway 68 oil over the internet. The cost of such oils is similar to good quality mineral, not synthetic, car oil.

When not in used I always leave the lathe's exposed metal surfaces covered, not smeared, in 68 oil. I only use neat cutting oil, generally Morris's Cora B, so that the metal surfaces do not become stained.

JA

Thread: Screw thread handbook
15/12/2012 12:48:04

I have just had a look at the above quoted German list, which is the DIN standard document, and the Maryland Metrics document. The latter appears to be a copy of the former. And I thought the common camera tripod mounting thread was 1/4 Whit! I am told it is 1/4 UNC.

No list of threads can be comprehensive. In the last ten years I have used the British Standard Microscope thread, a Whitworth thread, and I have no idea where I got the details from. In addition it was common practice in some companies in Britain at least to use their own threads. These were usually Whitworth form but with the wrong number of theads for their diameter. Three offenders come to mind, BSA (the bolts that held the sprocket onto the rear wheel on some of their motorcycles, AJS (pre1931) on engine parts and Bristol Engines on their big radial engines.

JA

Thread: workshop heating
14/12/2012 11:13:20
Posted by martin perman on 12/12/2012 21:04:50:

JA,

Sorry it took longer to respond, been working in London and didnt take Netbook with me, my brothers unit is a a Media/ Toshiba 3kw heat pump.

Martin P

Martin

Many thanks. I will continue following the discussion and look at heat pumps.

JA

09/12/2012 16:22:28
Posted by martin perman on 09/12/2012 09:52:56:

Gentemen,

My brother has recently fitted a small heat pump into his double garage/workshop, the idea is to see if it does the job and if all ok fit another. So far he is very impressed with it, it has taken the chill out of the building he reckons.

Martin P

Details of the heat pump please, Martin

I use an oil filled electric radiator in a relatively well insulated garage but if it is 5C outside it takes about four hours to raise the inside air temperature fron 6C to about 11C. Every so often I try to look for something better that won't overload the electrics without success. Also I find infrared heats not very satisfactory.

JA

Thread: Flattening tube ends.
09/12/2012 12:35:45

Many years ago, as a student, I had to flatten stainless hypodermic tube in a similar manner many times. When the tube was annealed there were no problems, You will need to experiment but heat to a good red heat and cool as slow as possible.

JA

Thread: Workshop tidyness
01/12/2012 12:20:06

I keep my milling machine covered with a barbecue cover bought from a garden centre. It has a plasticised inner surface that has started to break up and shed after about five years. Other than the little plastic flakes I heve never seen dirt or rust on the machine. Swarf is a different matter. Perhaps it is time for a new one. The Christmas list, possibly.

The lathe is protected by a Myford plastic cover but again this ages and starts to become stiff, or less flexible than a new one. I guess that it will eventually become brittle.

The workshop is a dry garage and I keep both the lathe and milling machine oiled, never dry. The adjacent garage, which is connected by a 6 foot wide opening, houses motorcycles. Every so often one is put back wet. I do not consider rust a problem, machine tools or bikes, but I don't ignore it.

JA

Thread: Is it model engineering ?
19/11/2012 12:27:09

I suppose the real question is "What is model engineering?"

A question that I would dare not answer.

Thread: Kiln - should I buy it?
03/11/2012 11:09:11

I would grab. Controlled heat treatment and silver soldering.

Obviously a controller would be needed.

JA

Thread: Replacing bronze bush in an aluminum alloy casting
25/10/2012 20:27:56

Is this casting on an engine that is going to go back into an aircraft and fly? Is so don't do anything before seeking professional advise since the casting contains part of the lubrication system.

If not, do what people who rebuild old motorcycle engines do. Clean the casting thoroughly (boiling in soap, not washing up liquid or biological stuff, and water removes an awful lot of oil from a casting) heat in an oven until spittle dropped onto the surface fizzes and boils and then gently drift the bushes out. You could crack test the casting afterwards but you might get a shock and find many cracks, hopefully small. Remember if you Loctite the new bushes in, to remove them the casting may have to be heated to a much higher temperature (Loctite is said to be good to 200C at least).

JA

Thread: Vulcan bomber XH558 to be grounded
13/10/2012 19:12:55

The Vulcan was also used as a flying test bed for the TSR2 engine (yet another version of the Olympus). During ground running at Filton the engine experienced severe vibration problems with one of its shafts and "let go". The debris punctured the Vulcan's fuel tanks and the plane was destroyed in the ensuing fire. Also destroyed was the airfield's new fire engine which had unwisely parked down hill of the aircraft.

About half a mile from where this took place stands unprotected from the weather a Concorde. It has been a tourist attraction but is now just rotting away. It is said to be destined for a museum of Bristol aviation but this is just a dream.

JA

Thread: If you had 2 hours in the Science Museum
07/10/2012 20:12:42

Michael's suggestion of machine tools is worthwhile but I believe the block making machinery has returned to Portsmouth. From distant memories the clock gallery was excellent.

What is worth visiting is the Science Museum store at Wroughton, near Swindon, but it is closed at present. Twenty five years or so ago they used to have open days but now they don't seem to welcome visitors at all which is a pity since some items, such as large aircraft, cannot be moved elsewhere without great difficulty.

JA

Thread: Lighting
23/09/2012 14:39:52

For a strobe effect with flourescent tubes the light flashes have to be at the same frequency, inverse of speed, as the chuck or a direct multiple. In theory this could happen but in practice it is unlikely. I light my workshop with low Wattage flourscent tubes for general lighting and low Voltage halogen lights over machinery and have never seen a strobe effect.

Just to worry you, I recall an article written by someone who had looked at the strobe effect of incandescent lights. Surprisingly some effect was present with most lights and it could be significant. I think it was in The Model Engineer about ten years ago.

Thread: Going to put companies out of business?
21/09/2012 09:25:32
Posted by SLOTDRILLER on 21/09/2012 08:31:30:

I wonder how long it will be before they work out how to make things using a powdered metal process?

Maybe a cold spray then bake operation ?

It may sound insane now but if you told the engineers at general motors in the 70s that the conrods of their engines would be made this way in the future you would have been my the guys in the white coats at the front door as you left !

I suppose only time will tell .

Before I retired at the end of 2007 we were using a powdered metal process. A bed of powdered metal was scanned by a high power laser which melted the powder. After each scan the unused powder was removed and replaced by a slightly deeper bed of powder. Items over 2 feet diameter and 10 inches high could be produced from any metal including high temperature alloys. OK, it was very expensive to produce a large item but the cost dropped rapidly if one was making a lot of small parts.

Thread: Drawing Projections
16/09/2012 12:07:54

During my working life I only ever met first angle projection once. I had to produce a sketch modifying a complex flange and did not realise the original drawing produced by a German firm was first angle projection. Fortunately when the flange was set-up on the jig borer nothing made sense and I was called for.

Never assume a drawing is third angle projection. If it is not you can produce an awful mess.

Thread: Magnetic swarf removers
20/08/2012 19:31:40

Hi

First forum posting

If the steel swarf is on an iron/steel plate, lathe, vice, etc you will only pick-up about half of the swarf each time you use the stick.

Also sooner or later you will use it to pick-up a dropped tool which will then become magnetised. Don't worry, small pocket demagnetisers are starting to come onto the market, selling for about £10.

JA

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