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Member postings for Swarf, Mostly!

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

Thread: mercury or quicksilver........Barometer?
11/04/2012 10:10:29
Posted by thomas oliver 2 on 10/04/2012 22:50:23:

Try dipping the edge of a small piece of aluminium sheet about 16swg in the mercury. The mercury amalgamates with the alloy and hold it in suspension where it is attacked by the oxygen in the air. The alloy edge will begin to grow a layer of oxide which curls away and if you leave it, the entire piece of alloy will eventually eat away.

That's why mercury or mercury-containing items are not permitted on aircraft - it's not worth the risk of mercury escaping as a certain consequence will be its attacking the airframe!

As regards barometer manufacturers - there was an EU edict last year that outlawed mercurial barometers. There was a Downing Street on-line petition that collected a lot of signatures which were then (predictably) ignored!

I was recently told by someone in Academia that the current anti-mercury H&S attitude is what is causing so many ex-college & ex-Uni Fortins & Kew Pattern barometers to appear on eBay.

Best regards,

Swarf, Mostly.

Thread: Tornado
09/04/2012 15:31:06

Hi there, Rod,

Thank you very much for your explanation.

I remember the time when the four companies were nationalised at midnight - the bit I can't remember is whether that was before or after 1949.

Do you know if any steam locos were built (or completed) after nationalisation? If so, would numbering have continued to be controlled by the relevant loco works, e.g Derby, Didcot, Eastleigh et alia?

Thanks again and best regards,

Swarf, Mostly.

08/04/2012 13:20:14

Hmmm, Peterborough. I think it was there that I reached out of the window of a (stationary) South-bound train and actually TOUCHED the Mallard (also stationary).

Forgive me if this is too trivial a question but who chose the number for the Tornado and on what basis was the choice based?

Best regards,

Swarf, Mostly.

Thread: Linear division in early 20th century
31/03/2012 19:47:07

Hi there, all,

There's a device called a 'Merton Nut', basically a sleeve of cork or other naturally elastic material, that engages with several threads of the most precise screw you can make. The idea is that it averages out the pitch errors of the screw.

It isn't load-bearing so you can't use it as a leadscrew.

Best regards,

Swarf, Mostly.

Thread: Myford ML2 lathe
07/03/2012 15:24:40

Hi there, Barry,

You refer to 'missing change gears'. I can sympathise with your enthusiasm to complete the various aspects of your newly acquired lathe but I'm moved to offer a comment on the concept of 'complete set of change gears'.

I wouldn't know nowadays how to discover what change gears Myford supplied with the ML2 at its original sale but it wouldn't have been every number of teeth from 12 to 500! They most likely supplied gears that would cut the most common thread pitches, i.e. Whitworth & BSF. Furthermore, I'd venture to suggest that few owners ever used ALL the gears supplied.

I suggest that your approach should be first to acquire change gear tables for Whit, BSF, maybe BA, ANC, ANF & metric. You could compile those tables for the ML2 leadscrew pitch yourself or find them in the various model engineering handbooks.

Then decide what threads you're likely to want to screw-cut and shop first for those gears, say on eBay and/or at Model Engineering show flea markets. If a large number of ML2 gears shows up at an affordable price then go for it. But in the meantime, don't break your heart because you don't have the change wheels to cut a 3" Whit thread or other rare & exotic threads.

I hope this helps.

Best regards,

Swarf, Mostly.

Thread: Recycling aluminium
23/02/2012 15:25:27


You beat me to it!!!

Best regards,

Swarf, Mostly.

23/02/2012 15:22:44


If you have a spring balance and a bucket of water, you can determine the specific gravity of the casting. This is an up-to-date version of Archimedes 'eureka' method.

Weigh the casting hanging in air and then weigh it again immersed in water. It will lose the weight of its own volume of water. The specific gravity is equal to the dry weight divided by the difference between the dry & wet weights.

Suppose it weighs 10 kg in air and 8.5 kg immersed in water, then the specific gravity is equal to 10/(10-8.5) ie 10/(1.5) = 6.7 (This example doesn't apply to a real metal - I've just used easy numbers to show the method of calculation.)

Then look up the SG on the internet or in some Tables of Physical Properties. This method will distinguish easily between aluminium and the zinc-based die-casting alloy (aka 'Mazak'. I think pure zinc castings wouldn't often be encountered, Mazak would be more likely.

If you don't have a spring balance, you can use a rod or beam and a counterweight, with bits of string to suspend the beam itself and the casting and counterweight from the beam. You measure the distances from the beam pivot to the casting's string at the balance points dry and in water (keep the counterweight in the same position and move the casting to balance in each case. It's a bit more difficult to explain in a forum like this but by manipulating the two distances, you can calculate the SG.

I hope this helps.

Best regards,

Swarf, Mostly.

Thread: UK Supplier of Imperial Acme Threaded Bar?
18/02/2012 13:33:20

Hi there, Paul,

Just a cautionary thought - do you need your lead screw to be Left-hand or Right-hand thread?

And do you need a matching nut?

Best regards,

Swarf, Mostly.

Thread: 3 Phase Tripping
04/02/2012 16:53:16
Hi there, David,
Was it running from an RCD-protected circuit at the previous address?
Best regards,
Swarf, Mostly!

Thread: Basic geometry question
12/01/2012 18:37:10
Hi there, Otley,
If you're going to breathe the air from your compressor you shouldn't second guess the requirements for filtration!
Yes, you need to remove any water because it corrodes the interior of your diving cylinders. However, you also need to remove oil - it can cause lung disease.
You also need to take care what other vapours/gases are within the reach of the compressor intake - read Jacques Cousteau's account of their dives at the Fountain of Vaucleuse. (Apologies to any French readers if I haven't remembered or spelt the names correctly.)
If your compressor is specified as suitable for diving/breathing air and assuming that the makers/suppliers are a reputable outfit, I would personally recommend that you stick with their filtration system.
Best regards,
Swarf, Mostly,
(British Sub-Aqua Club, 1956-1977, sometime assistant equipment officer, London Branch)
Thread: Silver Soldering
07/01/2012 11:21:16
Hi there, all,
Regarding refractory bricks to localise the heat:
When our landlords condemned and stripped-out our gas fire, I hung on to the refractory 'radiants' with just this use in mind. However, I haven't had the opportunity to use them yet.
Best regards,
Swarf, mostly.
Thread: Cadmium, simple test for?
15/12/2011 21:51:14
Hi there, all,
I haven't personally encountered cadmium plated workshop tools (that's not a denial that they exist).
However, when I started in the electronics industry 'cadmium plate & passivate' was a standard treatment for the equipment chassis, panels and brackets made from mild steel as well as fastenings and spacing pillars. I remember it as being a light greenish-yellow colour rather than blue-grey. Maybe the final colour was dependent on the passivation dip?
I seem to remember also encountering it on the soft iron parts of relays and contactors.
When it corrodes in damp conditions, it can form a white powdery coating - contact with this would pose a risk of assimilation. (Now wash your hands, please!)
The plating shop used to use anodes comprising a metal basket into which they loaded spherical lumps of cadmium metal, about the size of a tennis ball. I have seen one of those lumps offered for sale on eBay.
Cadmium plating has been phased out and replaced by bright zinc plating (aka 'BZP'). However, as Neil has written, I guess many of us will have lots of Cd plated fastenings in our 'come in handy' boxes or racks of 2 oz. tobacco tins.
Best regards,
Swarf, mostly.
Thread: Drill chuck removal
20/11/2011 15:45:07
Hi there, Bob,
If you MUST remove the chuck from its arbor, I suggest that you first open the chuck jaws fully and look at the very back of the opening.
There used to be a fashion to drill and tap the end of the arbor and drill the back wall of the chuck to permit the fitting of a securing screw, say 4 BA. The hole in the back wall of the chuck was tapped with a larger thread to permit the use of a suitable screw to push the chuck off the J6 (or whatever) taper.
I seem to remember that this scheme was recommended in one of the Duplex books; Jacobs chucks didn't come from the factory so fitted.
Should your chuck & arbor happen to have been modified this way you'll obviously need to remove the securing screw and the push screw might then avoid the need for the wedges. I guess you might still need the penetrating oil.
I hope this helps,
Best regards,
Swarf, mostly.
Thread: Lathe alignment. What is good enough?
08/11/2011 12:31:21
Hi, all,
I hope the following isn't too far off-topic.
I was taught that a lathe should face ever so slightly concave (so that a faced surface will fit a flat surface without rocking). I know that there is such a thing as a cylindrical square.
Am I right in thinking that this is achieved by the setting of the saddle and cross-slide, rather than of the headstock?
Best regards,
Swarf, mostly!
Thread: Myford Turret Attachment, #1408.
29/10/2011 12:40:03
Hi there, Nobby,
Thank you for your messages.
My current project is to fit a quick-change gearbox to my ML7 - I suspect that your stop would compete for the same space.
Does the six-way stop auto-index or do you have to turn it to the next position by hand?
This really is the essence of my question about the cross-slide turret, #1408, if you have to loosen the top locking lever by hand, turn the turret to the next position by hand while operating the enormous detent lever by hand, then re-tightening the top locking lever by hand (and turning the six-way stop by hand) the whole thing seems more suitable for an octopus operator than a mere homo sapiens! I must be missing something!
Regarding your mention of 'sucking eggs', I'm still trying to master the 'grasp the egg gently but firmly with the thumb and first & second fingers' stage. When it comes to production turning, at any rate. Mind you, in engineering generally, I do know that to succeed with some jobs I have to 'hold my mouth right'!!
Best regards,
Swarf, mostly!

27/10/2011 13:08:13
Hi there, Nobby,
Thanks for your reply.
No, I don't have the stop. If I were to get really fired up on a high-quantity task I'd either look out for one or else try to make one.

But I'm not at that place at present - it's just that my curiosity has been aroused.
I do have the lever-operated collet chuck plus some imperial collets but my headstock doesn't have the cast-on mounting lug. I know there's an alternative mounting clamp but I haven't so far been motivated to acquire (or make) one.
'Under my bench', I have some parts of the cast iron frame from a neighbour's upright piano - it machines beautifully.
Best regards,
Swarf, mostly!

25/10/2011 17:24:39
Hi there, all,
I have had a Myford ML7 since 1970 and I've acquired a few (!!) accessories and attachments for it over the years. One of these is the Turret Attachment that bolts to the cross-slide, part number #1408.
My training (as an electronic engineer) included a spell in the company's trainee model-shop, where we filed square pieces of metal to fit into square holes, made sets of spanners and toolmakers clamps (mine must have been fairly good - someone nicked them!) and eventually progressed to one of the row of six ML7s to make scribers, centre punches and screws for the clamps.
Back in the 1960s I had a 5_1/2" Carl Hurth lathe and the ML7 hasn't been idle all these years.
So I got some instruction in basic turning but the only insight I got into 'production techniques' was the chapter in Lawrence Sparey's 'The Amateur's Lathe'.
The #1408 attachment has an operating lever that looks just the biz and I assumed that this would advance the turret round to the next station but (on my #1408 at least) all it seems to do is release the turret detent. Am I missing something or making some false assumptions? How is this gadget supposed to be operated. Taking the larger view, what book would you recommend I read to gain an introductory understanding of capstan or turret lathe operation? Or should I try YouTube?
Swarf, Mostly!
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