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Member postings for Nigel Graham 2

Here is a list of all the postings Nigel Graham 2 has made in our forums. Click on a thread name to jump to the thread.

Thread: Again - another whatsit
27/05/2022 22:55:52

New to me but I wonder if it measures sphericity, e.g on bearing balls, in some way: the object at the top might be calibration or comparator spheres. (Their flat "poles" being to fit them to the instrument.)

The handle is a bit odd, but looks as if in use it is folded back to be in line with the body of the device.

Lots of adjustments on it, but not apparently fine-control ones..

It may well have been made for a very specific purpose connected with a particular manufacturer, rather than being a generic tool for measuring (e.g. spheres) anywhere. Possibly even made in that company's own tool-room. If so it's feasible it was made to be clamped to, perhaps, a particular machine-tool or inspection-department metrology rig.

No name or label on the instrument (other than on the bought-in DTI) or case?

Thread: chips from cast iron abrasive ?
27/05/2022 22:26:51

What grade is used for car brake-discs?

I have cut up a ventilated disc for fire-bar material, but also have a couple of single-thickness discs reserved as cast-iron stock plate for more sophisticated use.

Thread: Impressive Animatronics
27/05/2022 10:04:29


I can see its merits, but one aspect of zoos that Kate Darling could have highlighted is that their conservation work often includes rescue services and the breeding of rare and endangered species.

I was never happy about "show-biz" aquaria whose primary attraction and purpose was merely setting animals up as entertainments, like pet dogs begging for a tit-bit; but I think that is waning in favour of displays that do not insult the creatures and patronise the spectators.

One problem perhaps shown by such performing marine-mammals, is all those people who profess to love animals, yet inadvently mis-treat them by projecting human traits onto them.

I saw this only yesterday, exemplified by yet another jogger with dog-lead clipped to her belt. Though the dog was a labrador capable of a canine lope at human jog speed, it is still enforced, unnatural behaviour. I suspect its owner would say" Fido loves it!" Errr, how do you know? How do you know a dolphin in a fairly small pool enjoys leaping about to entertain a crowd of gawping humans? Just as unnatural as the constant barking of some other local dog for hours on end - probably owned because it's the Thing To Do, but left alone for long periods by owners who cannot see the animal is probably terrified by the long, enforced isolation. Unlike our own species, most vocal animals normally call only when they need; in this dog's case, probably desperately trying to find its own "pack" .

So enter the Robot Dolphin....

Only would this bring another consequence, that of divorcing people still further from the natural world, and making it harder for them to appreciate the realities of that world?


On the purely human angle, we have heard for years people waffling about "robots" replacing our work, assuming that being our "new normal" work "we all" do at home, needing only a computer.

Such sweeping generalising, promoted by so-called "lifestyle journalists" in metrocentric glossy magazines, is obviously absurd, yet it seems to catch on; perhaps because so much paid work is just routine drudgery. Not just screwing cars together on assembly-lines (much of that now automated anyway), or sweeping floors, but very likely for most of those even in the ivory towers of Canary Wharf, too.


'Tis the Year 2060, the venue, the New Wembley Stadium Experience, in all its recyclable bio-concrete glory designed by AI and grown by robots controlled from its owners' office in the new Chinese capital, Harbin. The PA bursts into life:

" Ladies and Gentlemen! Will you all give a rousing greeting to the new music sensation of the century! Not holograms, not avatars, but all the way from Stockholm, a real live troupe of real live singers with real backing band... 'The New Abba' ! "

Thread: chips from cast iron abrasive ?
27/05/2022 08:35:26

Thank you for that, Michael.

I have wondered about this too, having seen warnings about cast-iron swarf particles on the lathe.

The cited document is fascinating - I had not realised cast-iron is so complicated! I have even book-marked it in my growing links folder labelled "Engineering".

Any intrinsic abrasive might be the silicon compounds and carbides, but the silicon is not accused of forming silica or silicates in the iron. I would think the greater hazard for the machine-tools is tiny grains of casting sand still trapped in cavities or corners even after fettling and cleaning.

Sand is mainly silica - silicon dioxide - occurring in nature as granules of quartz weathered from igneous rocks rich in that mineral, and from eroded flint / chert (silica agglomerations in sedimentary rocks); and nearly as hard as diamond. Glass is the same stuff, being basically fused sand.

Thread: What are the best quality needle files?
26/05/2022 23:24:04

Some species of wood are not only abrasive as Calum says. (I am not a biochemist but I assume the tree absorbs minerals that then precipitate as extremely fine crystals; and that might include silica, second in hardness only to diamond.)

They may also contain tannic acid - oak is particularly known for that - or other corrosive chemicals.

Thread: 1" Minnie cylinder block screws
26/05/2022 23:17:23

I doubt you'll find them ready-made. By all means try but I think you will need make them. Do so in the lathe to obtain threads properly concentric with the rod.

To make it proper tiddly there should be about one-and-a-half turns of stud thread showing above the nut when all is fitted, and the stud end is slightly rounded off.

To fit them, it is worth making a simple stud-box from an suitable piece of hexagon bar and a screw.

26/05/2022 17:55:02

It is not so important which thread standard you use, as keeping it consistent with the rest of the engine if at all possible. I believe you can now buy metric bolts with reduced-size heads for model fidelity.

(My own project has dragged on so long it's gained a right mixture of BS, BA and Metric, making future servicing problematical.)

What does the drawing specify for the bolt material - but are they not studs and nuts?

You can use phosphor-bronze, but do not use brass.

Anyone here built a "Minnie", who can advise more specifically?

26/05/2022 17:45:46

I think you'd be lucky to find an arbor support all on its own, looking for a good home. I owned one of the Centec 2s for a while, and had to make the drop-bracket. A bronze bush is fine, and probably as original. Race bearings really need slightly tight fits on both shaft and housing, not a sliding fit on the shaft.

I finish-bored my drop-bracket in-situ for concentricity in-situ, using a small boring-head with MT2 taper, and feeding the bracket in by clamping it to the over-arm, clamping to angle-plates on the table, and letting the over-arm act as a slide.

Gibs: Use bright mild-steel, not silver-steel (gauge-plate). Mild steel and cast-iron work well together, if kept lubricated.

Gearing: that 650rpm seems much too high, if anything, for a horizontal mill, though low for using small drills and end-mills. I assume the gears are original. Does Tony Griffith's literature tell you the speed range?

Arbour: similarly. You might be lucky but like the bracket, I think they'd be sold alongside poultry-dentures. Determine the length and see if someone like Home & Workshop Machinery or similar, who advertise in ME and MEW, have anything to suit. I obtained one by that means for my Denbigh horizontal, of about the same size as the Centec. Otherwise I think it's a matter of making one from precision-ground stock: the critical part being concentricity and parallelism of shaft and taper axes.

The stub-arbours sold by ARC etc are fine for their purpose - in a vertical mill - but may be a bit short even for these smaller horizontal mills. Even so it's worth seeing if they will suit this machine. You would need make a lathe-type centre for it, though, as it does not have a bearing spigot - and watch out for the thread direction. I had one that would unscrew itself under normal cutting load, on a vertical mill.

Thread: Is a 3" Cornish coal fire possible?
26/05/2022 17:18:22

Norm -

Christopher doesn't say where he is or if he's in a model-engineering society affiliated to one of the MELG Federations, but if he is, the boiler-testing problem should not too difficult. Depending on its boiler examiner... who can decline to test a boiler of personally-unfamiliar design, but should not do so out of hand.

The now-white-with-orange-lettering book explains the test requirement and process; a club may have some additional requirement such as the owner providing an adaptor to fit its test-pump hose.

The point would be to talk to the club's boiler-examiner first. He or she is likely to want to see the shell-strength calculation (a simple formula), and to inspect the work as it progresses, but there is nothing inherently novel about the Cornish Boiler design.

The sticking-point might be the flue strength at that diameter - heavily dependent on diameter, length, roundness and pressure, and very hard to calculate - and I would suggest no more than about 30-40psi WP and a wall thickness no less than 3mm as a start.

I though the idea is to run a Cornish-style engine from it. They used very modest steam pressures, and anyway a model version is not likely to be doing any significant work needing anything like even one kilowatt (well over 1HP!) of power.

Thread: Milling narrow slot on Myford lathe
26/05/2022 12:15:58

Another tip for safer break-through is to back the work-piece with a scrap of similar material so the cutter is effectively still in the middle of a solid block. The backing piece of course needs be at least the cutter diameter wide.

(It's analogous to using backing material when sawing or drilling materials like plywood or thin sheet metal.)

I must admit though I usually cut into thin air but just take that last bit very gently... without stopping and letting the tool rub. On the mill I nip the table lock up a little.

Thread: Best way to cut mild steel sheets
26/05/2022 12:07:23

I often resort to a hacksaw, so offer this tip:

Clamp the sheet flat on a suitable surface so you cut the steel at an angle, bringing more teeth to bear on the cut and reducing or preventing horrible vibration and noise.

Thread: How on Earth Do I Sort This Lot Out?!
26/05/2022 12:04:18

Perhaps the seller had acquired them among the effects of a deceased relative or friend, and genuinely had no idea of their identity or worth beyond perhaps something to do with model engines.

Some of the fittings in the penultimate of the first photos look as if they have been used, but others are still as new.

Anyway it's good that Mr. Local did think to ask you and not simply weigh them in for scrap or just chuck them in the local Council metals-skip. Clearly he didn't expect the very pleasant financial surprise! You never know, he might find more for you...

26/05/2022 11:54:58

Maplins RIP indeed.

It even sells what it calls "Weather Stations" .


It has been restored as "Maplin" - singular - but as only a supermarket retailing ready-made electronic IT equipment, cameras, gadgets, toys and such accessories as cables, batteries and power units.

It does have a range of "hobby" goods but that is little more than toy cars and some odd "kits" of little intrinsic use or worth, probably also aimed at children.

Though I did see the name "Raspberry Pie" and even a soldering-iron listed, so all is not lost for the serious hobby user.

Discrete components though? I searched for resistors and capacitors. "Never 'eard of 'em, Guv! "

Really no better for anyone with a genuine interest in electrical and mechanical engineering, than Currys or Argos, with a web-site to match.


Weather Stations though... Yes!

They took a bit of finding and only a few of about 10 products do anything I would describe as weather-station functions. The rest seem only to tell you little more than the temperature and relayed weather-forecasts, for which I've a thermometer and radio.

Unfortunately though for the OP, none of even the more useful ones include wind-speeds.

Thread: Key for a Cowells lathe chuck
25/05/2022 12:04:18

Daft question I know... but as their ads keep appearing next to this very thread, do Cowells not stock replacement keys?

Thread: Centre drill sizes
25/05/2022 12:00:06

Recommended in one of my reference books, is a minimum 1/32" (0.8mm) depth of the coned part of the drill; irrespective of drill diameter.

(I happened to find that while in this session, when replying to another question!)

I tend to go further than that. It does no harm, except perhaps to appearance if in a visible component on a scale model.

Thread: Between centres boring bar bit grinding
25/05/2022 11:54:45

Since our hobby is emulating industrial engineering practices at smaller scales, it's often worth looking back at both trade and model-engineering text-books.

Doing so I found that boring-bars generally hold the tool-bit at about 45º to the axis, close to the end so it extends a little beyond that; allowing use in blind or stepped bores. It also gives more support to the bit.

Sometimes the grub-screw gripping the bit enters from a corresponding chamfer on the bar end, so is correctly perpendicular to the tool shank. In others it enters concentrically from the end, particularly for screw-cutting bits more easily arranged at right angles to the axis.

Another form uses a tubular holder in which a long, close-fitting draw-bar cross-drilled to match the bar and bit, is tightened by a nut on its threaded end beyond the lathe's tool-holder.

The latter pattern can be used in between-centres mode if the draw-bar itself is suitably centre-drilled at both ends Its advantage is that the boring-bar is cross-drilled with only the bit-hole.

A boring-bar can be double-ended: angled bit at one end, right-angle at the other. I think I have a specimen of this pattern somewhere.


E.T. Westbury suggests in his Lathe Accessories - how to make and use them, that a hollow boring-bar bar be made from steel tube, which would have to be fully-drawn not ERW, with the tube and closely-fitting draw-bar as mutual stiffeners. (Drilling such a length, many times drill diameter, concentrically for full length, is feasible but not easy. I wouldn't risk it!)

Sometimes the work allowed the boring bar to have a smaller-diameter spigot as a pilot in a hole ahead of the main bore. Particularly suiting chuck and faceplate work, where it may be possible for the pilot to run through a bush in the lathe spindle, such a bar can of course be centre-drilled also for use between-centres.

The above comments also apply to internal recessing, grooving and screw-cutting tools in which the cutter itself is a small bit in a cross-drilled holder. Really, this is the HSS-bit version of the now-familiar carbide-tip tooling; and I can't think of any reason why pilot and between-centres type internal-cutting tools of larger diameters cannot be made for carbide tips. Fit a small, straight-shank indexing-tool through the boring-bar itself.

For setting the tool's height from the boring-bar, if you envisage a lot of such machining or a particularly critical operation, it could be worth making a suitable depth-micrometer or micrometer-thimble device based on a Vee-block.

For gauging the bore, make a ring-gauge that rides on the bar, perhaps parked on the tailstock nose or centre while the cut is in progress.

Between-centres boring-bars assume the use of a lathe with T-slotted saddle, or a horizontal mill. On the lathe, the principle can be extended to internal recessing and threading as second-operations without disturbing the work-piece setting.

I have seen a horizontal-borer, which is basically a development of the lathe, set to face, bore and internally thread a brake-ejector casting for a full-size locomotive. I don't know, but would think, the cones were separate parts fitted in parallel bores.

Thread: My Minnie
24/05/2022 23:44:48

I've not tried it for a cylinder saddle but others have, successfully.

Some use a between-centres boring-bar and set the work on the lathe cross-slide - assuming a slotted cross-slide.

Others use as I take it you mean, a boring-head in a milling-machine.

Either way of course needs a very rigid, accurate set-up; low speed and gentle feed, and to allow for the bar springing.

Unless you have some form of radius-measuring instrument, it would be worth making a radius-gauge from suitable, fairly thick plate (or if you have it, an offcut of the barrel material) to test the surface without disturbing anything.

24/05/2022 23:33:41

My suggestion would simply be to see if yours can be compared to a known one, perhaps in yacht-club, flying-club or similar.

I have read a description of the use of a vane-type anenometer used in an unusual experiment, that in turn led me to consider a particular aspect of wind behaviour. It exploited the point that such a vane will indicate direction as well as force, but only while the wind is moving perpendicularly to the vane.

You sometime hear art-critics waffling about the "resonance" of an auditorium or cathedral - the same people who muddle "acoustic" (adj.) with "acoustics" (noun) - when clearly they mean "reverberation". Yes, the air in the hall can resonate, just as the air in a bottle resonates when you blow across its top, but at fractional-Hz frequency. It can also happen in Nature...

The experiment, carried out in America, investigated the resonance in a cave observed to have a regularly reversing draught in a fairly narrow passage leading from the entrance to a large chamber. The vane, made from a sheet of plastic, was suspended from a spindle carrying a potentiometer as the transducer for a data-logger, so that it would read the wind's direction as a polarity oscillation, as well as its relative speed by displacement.

The acoustics did indeed match the nature predicted by theory, treating the cave as a flue-type organ-pipe with closed end, to reasonable certainty. I think they tried it in other caves but these were more complicated, giving less certain results.

I had noticed the same effect in a cave I helped discover in Norway, a single passage descending steeply to an air-tight choke of sand; and breathing" due to the wind blowing across its entrance. Indeed, we named it "Breathing Cave" , or "Pustehohle" if I recall its translation correctly.

So I tried to apply the American results to an exploration project in which I am involved on the Mendip Hills, but the same fairly simple maths predicted a volume too large to fit under the hill! Despite the apparent regularity of the draught reversals, we decided the cause was simply fluctuations in the wind blowing across the open top of the vertical entrance shaft; lined with concrete pipes for its first 30 feet depth from their rim a little above the field level.

This does though raise an intriguing question:

- Does the wind itself, blowing over a suitable edge, create a high-amplitude, sub-Hertz sound, different from the irregular gusts? In that location the edge is created by the steep SW face of the Mendip Hills, rising from a plain to a gently-undulating plateau surface. (The cave is not far to the East of Cheddar Gorge, so fairly close to the edge of the range; and the Gorge itself could also act as an acoustic lip.) So the cave's draught was influenced by the acoustic wave rather than the simple gusts marking turbulence in the air stream.

As our "dig" has progressed gradually downwards through an interminable mass of irregular boulders the "breathing" effect has largely disappeared; and the very chilly draught now, although weather-controlled, is generally fairly steady in direction and force.

Further to my thoughts are the shapes of some types of cloud cover, forming quite regular, parallel ridges of fluffy vapour separated by clear air. Though I have not often flown, I have seen from aeroplanes, strikingly regular swell effects on cloud cover lying below the flight path. Again, a very low frequency sound marked in clouds either by piling the vapour mass into waves analogous to sea-swells, or perhaps, by the sound-waves' compression and rarefaction controlling the vapour's condensation into concentrated regions.


That cave dig has an unlikely model-engineering link. We made for it a simple winch, revolving on plastic bushes on a cross-bar on a scaffolding tripod. The hexagonal side-frames about 3 feet across-corners, are welded from flat steel bar originally rails from a dismantled miniature railway!

Thread: Voyager 2 is back online
24/05/2022 22:19:41

As Danny says, a wonderful tribute to her designers, builders and operators!

Thread: Strange Miniature Bearing
24/05/2022 11:58:12

It is possible to buy just bearing balls, and that's likely what you'd need do.

You say your measurement is necessarily approximate, so that odd-looking 7.75mm might be an Imperial diameter, 5/16" (7.94mm) being the closest.

I don't know if the stainless-steel balls sold through "our" trade usually for clack-valves would be suitable, if appropriate bearing-balls prove as rare as fowl dentures.

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