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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: Now What Have I Done? (Odd Display Effect)
31/05/2022 22:18:43

Mark -

Thank you for explaining it!

Old Mart -

It is not on by default. I found it only by pure accident; inadvertently pressing some key combination a web-site creator would know but as you say, is not part of normal use.

Thread: Bearings or bushed
31/05/2022 22:14:43

Oh, this doesn't need anything too fancy especially if the shaft's bearing surface is just the raw pipe surface, but remember to lubricate the bearings well with grease before storing the rotisserie, as well as prior to use. Especially with aluminium bushes.

Thread: Which stand for Myford ml7
31/05/2022 22:10:30

Bazyle -

I was faced with that problem in my previous home, so made a concrete base for the shed, then cut holes in the wooden floor to build brick plinths on the concrete for the machines.

David -

That sounds reasonable though I would fit steel angle or channel cross-pieces to the bench, below the boards, so they rather than the boards take the weight.

.

Regarding riser-blocks, I don't see why structural steel channel could not be used, with levelling screws as its own surface or the bench on which they stand may not be very flat or free of twist. It may be possible to obtain short off-cuts from a steel-buildings company or a steel-stockholder that cuts to order for its trade customers. Fit it with the web upwards, like a little tunnel.

Thread: What is "Mathematics"
31/05/2022 11:46:13

Isn't that last technique - for areas - something of a forerunner of the Mid-Ordinate method of Integration (which I recall vaguely as summing rectangles of [Area = Width X Centre-line Height] ) ?

Thread: More beginner questions
31/05/2022 11:39:55

Looking at your selection, the tools all seem still serviceable, perhaps with some judicious re-grinding.

The shiny ones are of High-Speed Steel (HSS).

It's not entirely clear to me if some are lying on their sides; so the clearance angle, if that is what it is, on the fourth down is a bit large but that should not matter. For steel and phosphor-bronze, the top of the tool should slope 2-3º or slightly more, diagonally down away from the very cutting-corner. Aluminium - the slightly more. Brass - flat (0º ), giving more scraping than shearing. In all, the flank and front face below the cutting-edge is angled back below itself for clearance.

The top one was perhaps of special purpose, and being round bar, unless there is a flat along its underside it needs to be held in a shallow V-groove pad or a clamp-block, in the tool-post . It might cut neat chamfers.

 

The dark ones: high-carbon steel (like cold-chisels etc.). Fine, but they will not withstand much heat without losing the temper, spoiling them. That with the long slender "neck" will work into the corner of a wide groove. Next down; a general, and very much used, knife tool for straightforwards turning including facing. No.3's semicircular end may have been for profiling grooves for, e.g., sealing- or oil-retaining rings. Don't try to use it as a parting-tool: it will jam in the cut.

The tool in the middle may be another "special". Hard to see its geometry properly but it might turn the right-hand face of wide grooves, cutting towards the tailstock.

.

Height:

I usually set my lathe tools by pointing them at a centre or scribing-block, then fine-adjust if an initial facing leaves any centre-pip on the metal.

A properly-set tool leaves no pip, but by shaving it down, not shearing the last bit by force (tool too high). If the tool obstinately refuses to remove the pip, it is too low.

A tool-post without height adjustment of its own, such as your 4-way one, needs a good assortment of shims for packing the tools to height. Save expensive "shim stock" for its intended use, aligning machine parts. Instead, off-cuts from ordinary strip or sheet metal, including from food tins, etc.

Even semi-rigid plastic. Some of my shims are from expired plastic bank or club membership cards - a fairly tough, precisely-finished material, so ideal shim where it won't become hot.

Many model-engineers make a simple height-gauge for tool-setting.

.

High-speed steel tools are fine, and have advantages over carbide inserts, not only by being much cheaper. (I use both.). They are relatively easy to sharpen many times to a standard that will give you decent results; and are less fussy than inserts which are really made for quite specific materials and cutting conditions. Some aver insert-tooling can only work at very high speeds, but that is not quite so. They work like that in industry for rapid production at very high repeatability. The HSS tools sometimes give a better finish, especially on steel not of free-cutting grade.

[If the work-piece is to be welded, especially for anything critical, it must not be of a free-cutting steel anyway. Their additives, usually lead, embrittle the weld.]

.

Grinding:

As Calum says, a simple bench-grinder is fine for HSS tools. In fact it is necessary!. It takes some practice but you can grind a tool free-hand to give good results, even on the crude rest usually fitted to these grinders.

A final honing by oil-stone or lapping-plate will help give even better finish, but the finish is mainly dependent on tool geometry, speed, feed and material. The very tip should have at least a tiny radius in plan, even for turning into a shoulder as on your sample.

Hence another caution. If the part is to be heavily-loaded (e.g., a crankshaft, a locomotive driving-axle), internal corners need a little root radius for stress-distribution.

It's worth examining industrially-made parts to see how such principles are applied.

.

I would recommend Harold Hall's Tool & Cutter Sharpening - lathe-tools, drills and in a limited way, milling-cutters; No. 38 in the Workshop Practice Series by Special Interest Model Books. (www.specialinterestmodelbooks.co.uk). Buy from them, or as as I did, from TEE Publishing. Mr. Hall's book gives designs for attachments to turn a simple bench-grinder into a moderately comprehensive tool-&-cutter grinder - useful exercises as a bonus. Just a simple plate adjustable for angle in both directions, on brackets screwed to the bench in front of a grinder itself screwed down, will greatly facilitate sharpening lathe-tools.

It goes without saying the grinder should be well away from any machine tools!

Also note that with perhaps some specific, controlled exceptions (see the book's cover photograph!) the side of a grinding wheel should not be used. The concave radius from the wheel's rim does not normally matter.

.

Cutting Fluid:

A cutting fluid is a coolant and lubricates the cutting action, for steel, phosphor-bronze and aluminium; and can help maintain a decent quality of finish (with all other criteria met). Cut brass and cast-iron dry - note as another thread here discusses, cast-iron chips are abrasive.

Steel and bronze: one of the water-soluble oils, pumped or gravity-fed to the tool tip; or applied with an old paint-brush. For Aluminum: paraffin, white spirit or WD-40 (which is mainly white spirit); but note that these will wash out lubricating oil from the lathe. (WD-40 is not a lu

Edited By Nigel Graham 2 on 31/05/2

Thread: Riser blocks
31/05/2022 09:15:30

That does depend a lot on the design of lathe. They allow two things:

- With blocks fitted with the appropriate screws, ready "levelling" of the lathe (i.e. accurate mounting so the bed is not strained).

- Clearance around the machine for removing swarf and if you use flood-coolant, facilitating draining.

Some lathes are or were designed to bolt directly to the chip-tray and stand, but these have machined pads for the lathe's feet, and an accurately-made stand.

What does your lathe's handbook say about it?

Thread: Now What Have I Done? (Odd Display Effect)
31/05/2022 08:59:55

Ady -

Is it W10, yes.

Martin-

Possibly. Sometimes I accidentally hit something that opens a window full of computer-ese such as formatting commands. This was different. It was a too-bar that looked more like a user's menu, as it included a list of "smart"-'phone makes and models, a control for turning the display round and a touch-screen emulator..

F12 though - no. I was nowhere near that key, even with my cack-handed typing. but I don't know if some function keys have combination-key equivalents using CTRL or Caps or something.

From which, perhaps it was a set of tools for viewing Internet material on a 'phone. I'm not sure how you'd make a complicated CAD model or examine a big spreadsheet on such a small screen though.

Oddly, whatever it was has gone! Turning the computer off overnight has reset the previous display.

Thread: Which stand for Myford ml7
31/05/2022 00:03:22

I don't know its trade-name name, but the bench surface under my EW lathe is a material made for laboratory and light-assembly benches, and my piece was indeed one of such, obtained from the scrap skip at work!

It is a very dark synthetic resin-bonded paper board 15mm thick, with thin, light-grey outer laminae for appearance. It is hard and abrasive to cut and you don't want to breathe in the saw-dust, but it is very stable. The exposed edge can be polished to a tidy sheen.

Even so, and I think this particularly important for any machine-tool bench, the lathe's weight is transferred through it to cross-members on a welded angle-steel frame (itself on castors).

I have also used same to cover my inherited timber work-bench which though well made, has what look like scaffold boards for its top. This carries both a Meddings bench drill and a Drummond hand-shaper without problems, both held by bolts in though-holes tapped in the laminate itself.

Thread: Questions on an MLA inspired toolpost
30/05/2022 23:30:08

A slot-drill rather than end-mill, surely, to cut those big slots?

(Use the end-mill for the block's exterior.)

It's a neat design but I think I'd prefer a rectangular block to support the tool-holders' full length. I'd also worry about unwanted rotation when slacking the device to change holders; and whether the taper would release as intended.

Still, try it and see how it all works out.

Regarding putting the height adjuster at the back (towards your side of the tool-post) rather than the front, I think that is the right approach. Mechanically there is no difference, but the less clutter near the tool itself the better.

You might in the end find a separate spanner more of a faff than a handle, so if 'twere I designing this, I'd do so to keep my options open - allowing simply swapping nut with handle or vice-versa. It may prove possible to adjust the handle's operating arc by washers to keep it in the optimum position for your use.

Thread: Now What Have I Done? (Odd Display Effect)
30/05/2022 23:09:55

Typing a contribution to another thread, my big fat fingers hit some unknown-key combination that shrank the message screen in such a way only part of it was visible.

I managed to pull it back to near original size but it's revealed a curious system tool-bar above the forum pane itself.

Its tabs are -

- "Responsive", which opens a long index of instruments by make and model (Galaxy, Samsung, etc.)

- Size by pixels (1666 X 800) at the moment.

- A symbol for what I found is a Viewport rotator.

- DPR: number. 1 to 3. It's presently on 1.

- No Throttling, This seems to be a menu of portable phomne networkl settings such as "Good 2G", "regular 3G" and so on.

- Finally a blue finger on a button, presumably for Smurfs (it's actually a Touch Simulator on/off control).

Never seen any of these previously, but Gates Towers had another trick up its sleeve, new to me, in that locating the cursor by a click changes it from a little "I" to a sizeable blue tear-drop shape. That turns off as soon as you press a key.

I have no idea what I had pressed by mistake. Sometimes I feel like putting a rigid steel cover over those hazardous keys on the left - I'm forever inadvertently turning CapS LOCK On, often not noticing it for several words. (I have never mastered touch-typing.)

I ought add that there are two keys in that corner, of purpose unknown to me: one with a blue "Fn" label, another with the Windows trade-mark. I might have pressed on of those, perhaps?

So what the heck have I been and gone and done now?

Thread: What is "Mathematics"
30/05/2022 22:46:32

A former superior of mine told me a slightly similar tale of his university course - and one oddly relevant to this forum.

The test question was to imagine a conical mountain of H height, A angle, etc. A railway spirals down from the summit to the plain, rather like a helter-skelter. A truck weighing M runs freely down it. .... Calculate its speed at the foot.

My manager said there were 20 marks allocated to it, but he made a simple arithmetical error right at the end.... and was given 0 out of 20.

Protesting, he was told gravely, something like "Mr. E---, in the real world the answer has to be correct!"

.

On Argand diagrams and imaginary numbers, though they are above anything I ever learnt (well, was taught...) might these be exemplified by a graph produced by a standard test of electro-acoustic transducers?

These resonate at a given frequency and the test applies a broad frequency run of pure sinusoidal electrical signals with the resonance expected somewhere in the middle.

The resulting graph is of impedance v. conductance, or vice-versa, I forget exactly. For a well-behaved transducer element the trace is a loop; a circle with a near-vertical approach and exit asymptotic to the y-axis. All values are positive but the resonant frequency typically lies half-way round the loop, on [x=something, y=0). It's a bit like the steam-engine indicator-diagram in that it conveys a lot of diagnostic information on the subject.

I was paid just to test the things. The scientists did the analysing, but I did ask one what the curve is. "The real part and the imaginary part" , I was told, as if that answered everything.

Art one point I chanced across a paper on investigating the so-called "wolf note" that can be produced on a cello. Not intentionally, I don't think! The paper briefly described the mechanical bowing arrangement set up on a cello in an anechoic chamber, then set off into the realms of Very Hard Sums Indeed. Among them though, I recall seeing a very similar loop graph, though of mechanical equivalents to the electrical characteristics.

So I take it this is widespread in such fields as vibration and harmonic analysis.

When though was the Argand diagram - if these impedance and cello-note loops are indeed such a graph - invented? Did it pre-date such physics but happened to find itself in such areas?

Edited By Nigel Graham 2 on 30/05/2022 22:49:00

Thread: Old lathe identification
30/05/2022 00:00:16

The base does not look as if originally made for the lathe even if on this lathe from new. It might have come from a small milling-machine. That raising block - is it a casting? It looks like a piece of angle or Z-section found for the purpose.

What do the isolated nuts and bolts in the base hold?

Oh, probably commercially-made parts but the headstock doesn't seem quite to match in style to the saddle and tailstock. I wonder if it came from a different source; or perhaps the same manufacturer but a different model.

Intriguing and rather pretty little machine anyway, and it would be good to see it all bright and serviceable again, even if just for small items of wood-turning or brass-work by hand.

It was probably driven by treadle originally, possibly the type advertised as a "foot-motor" when sold as a stock item for driving any small machine.

Thread: Ml7 just bought, need help to set up
29/05/2022 23:33:28

Welcome Chris!

That machine looks in pretty good fettle. I'd not worry too much about the paintwork but I think you can obtain the proper colour. I don't know if you can also obtain a new transfer.

No rogue grooves or holes in the chuck and faceplate - that and the generally tidy appearance is a good sign the lathe's been used and looked after well. The darker grey patches on the faceplate might be shallow corrosion stains, perhaps from damp storage at some point, but not enough to worry about.

It it is well worth while, indeed adviseable, buying a copy of the operating and servicing manual if one didn't come with this lathe.

Those, spares, accessories etc: try www.myford.co.uk. Other more generic accessories, also from ARC, RDG, etc.

There are also good reference books about on turning. Some go off into making great arrays of fittings and tools that you may find useful.

'

The thing with the "dimple" is a catch-plate used when turning between centres. The plate is screwed onto the spindle in place of the chuck. The work, located by a centre in the spindle and tailstock, is gripped by a "dog", a steel forging with a tear-drop shaped hole and a set-screw, and the dog's tail is either straight and engaged by the pin (the "dimple" ) or is bent at 90º to locate in the catch-plate slot. At least one of those types of dog should have come with the lathe, hopefully; along with the centres.

Tool-post screws: probably BSF but you'd need measure their diameters and pitches to find out; or use a known screw or nut as a comparator. I'd ask of the various suppliers who advertise on here and in the magazines, in the first instance. If you use standard screws I would recommend turning a little chamfer or spigot on their lower ends so their thread starts don't become crushed. It's also a good idea to put a strip of brass or aluminium betwixt screw and tool shank to take the wear, especially if you use tools with soft shanks / holders. I have found...

'

Did it come with its set of change-wheels?

I had to buy all mine - the few that came with it second-hand might not be original so might not mesh correctly with proper ones: correct pitch etc. but the unknowns may be of different pressure-angle.That is a very subtle difference determined only by special measuring, but is enough to harm mis-matched wheels.

There should be a chart inside the cover, giving their selections for all the threads you or I are likely to need; including common metric pitches, and fine feeds.

.

THE one thing not to do when you fit to a bench, if you don't have its proper cabinet / stand and "levelling screws" , is simply bolt it straight down to whatever angle-iron or worse, timber, table you happen to have. That is a recipe for distorting the bed, maybe only ever so slightly but enough to ruin its accuracy and over time, induce uneven wear. Note that "levelling" in machine-tool parlance refers to ensuring straightness and parallelism of the machine, rather than level to the building. That is good, but less critical, within reason.

My ML7 had suffered like that in its previous owner's workshop, but luckily seems to have recovered. It had been bolted hard down to a wooden bench via a strange cast-iron tray that did not even have planed or milled faces for the machine's feet!

Thread: What is "Mathematics"
29/05/2022 22:38:56

Sometimes I think rather waspishly that a "pure mathematician" is one for whom the best mathematics has no physical, let alone practical, application at all; but are there in fact any branches of maths like that?

Does mathematics at very advanced level diverge from physical things that work to numerically-consistent ways, to areas that work in themselves if you plug simple numbers like 2 and 3 into them, but which describe nothing real at all? Becoming really just very hard number-puzzles that never find problems to solve other than themselves?

I don't include rather pointless stunts like calculating pi to the umptee-umpteenth decimal place (I think that's an infinite trigonometry series, but well above my pension grade), but rather arcanities like the theories of numbers themselves.

For it reminds me of an incident at work...

One of my superiors asked if he could use my computer, in a small room off the laboratory, to find a reference to a paper concerned with the particular engineering-physics experiment he was carrying out. It saved him having to traipse back a very long way to his office.

When I returned to it I discovered he'd become side-tracked (he told me when I asked), and had opened a paper in English, by two Russian mathematicians. I say "English". There were not many words, but they did reveal the Muscovites were offering an alternative way to solve some equation bearing what looked like a French name as its ... inventor? discoverer?

I have no idea what it was about, in fact I had never even seen many of the symbols in about three screen-fulls of pure algebra. It might find some very arcane application, perhaps in quantum physics or the like; but the paper was pure and unsullied by any such references to trade.

'
I rescued from a works clear-out a coffee-mug apparently from a museum gift-shop. Its artwork commemorates the 18C English mathematician George Green, and bears the following quote from his work. It makes sense if you read all four question-marks as Integral signs. I had copied it in 'Word' using the correct symbols, but it has been through image and forum text editors that do not know Calculus.

greens formula.jpg

I do not know what it tells us, nor if it has any purpose - but that is not as facile as it seems. For it's possible Green derived it within some abstract study, but later workers have found real-world uses for it as science and engineering developed since his time.

It's certainly a candidate for being followed by that mathematicians' equivalent of the Haynes "Re-assembly is the reverse of the dismantling procedure" , the time-honoured, "... from which we can see that..." .

.

So perhaps while mathematics is not determined by physical applications, the applications are certainly determined by mathematics; but in many areas of practical uses of maths, which came first? Was the maths already known as an end in itself, or non-existent until the application revealed it by its own nature?

Thread: Drain cleaning brushes
29/05/2022 17:47:22

... That sort of ..."coal fires and Flue Brush..."

Oo-er! To what size of lathe have we progressed from one that fits round a plughole-gunge brush?

Still, I like Derek's suggestion, though do wonder how you are meant to wash a plughole brush used as such without simply rinsing the gunge whence it came.

If it's too short for your particular lathe it would seem simple enough to cut the original handle off and fit the brush stem into a hole drilled into a length of dowel.

Regarding using a gun-brush, a boiler-tube brush may be a good alternative.

I usually just push a ball of kitchen-roll paper through the spindle, using a suitable rod or dowel.

...

For cleaning out the chip-tray I find a child's polythene toy beach-spade, with a blade about 2 inches wide and a short handle, makes an effective "dust-pan", used in conjunction with an old paint-brush. It fits neatly in the trays around the machine feet in both of the lathes, and the mill.

Edited By Nigel Graham 2 on 29/05/2022 17:51:16

Thread: What is "Mathematics"
29/05/2022 13:25:28

Perhaps how we define Mathematics depends much on our own experiences.

Maths was my worst subject at school, and I disliked it intensely.

I am not good at abstract concepts, and sometimes need how things work to understand how to use them; while externally the subject tended to be taught as abstractions with little mutual reference, let alone with real things. Why did know where the cyclist from A to B will pass the walker from B to A?

Most school text-books do not explain anything clearly: a definition or two, a couple of worked examples and a set of exercises. They were written to support a teacher who could actually teach - as some of mine could not. Oh yes, they knew mathematics, but not teaching!

So that was my early dreams of being a scientist of engineer scuppered. (Dad was a Chartered Electrical Engineer working as an MoD Scientist; my uncle worked in British Railways' Technical Centre in Derby, though I don't know in what capacity.)

It was really my hobbies and later work that made me see Maths as a set of useful tools for real things.

Model-engineering uses much mensuration and some trigonometry; as well as arithmetic of course.

Geology made me see what Differentiation is. In a geology-club lecture on analysing river gradients to reveal rock boundaries hidden by valley sediments and vegetation, something made me write a simple formula in differential notation. Suddenly I twigged what differentiation does: show how much you go up (or down if you are a stream), for a give distance along.

Logarithms and the slide-rule were still in use at school, with calculators only just appearing in my last Year. I could use logs for times and power sums but had no idea how they did it. Until some decades later, as a lab assistant in a sonar lab, I became used to such glories as " -211.5dB re 1V/µPa " . db? Decibels? They be logarithmic, they be; mercifully all to base-10.

I found my way to understand them, by remembering first doing sums by writing "H T U" at the heads of the columns, to understand that any ordinary number is really a string of counts of integer powers of 10.

.

I have found elsewhere and typified above by Pat's accounts, an apparent much bigger difference in education across the Atlantic than simply maths / math.

The British school system has always given a selection of different topics within a maths syllabus itself part of the school curriculum. Hence the overall nature of the exams at the end of the entire course, even if over two or three papers to cover the syllabus. So you leave school with a qualification in Mathematics as far as the syllabus has taken it.

The American schools - and I invite PatJ to correct me if I am wrong - seem to treat each "math" topic as a completely separate curriculum subject. So presumably you might leave school with a qualification in geometry, and a qualification in Algebra, etc.

.

Many who struggled with Hard Sums consider Algebra as one of the sticking-points; perhaps because like me they found the abstraction hard. It has none of the obvious belay-points I later found in eccentrics' angles of advance, Dorset's rivers and measuring sound. (That strange value I quoted is the receiving-sensitivity I still recall, of a particular, commercial, laboratory reference-hydrophone.)

So I gave the matter some thought and realised that by starting as seeing it as shorthand for how to work out real-life things like areas, thence a shorthand way of writing the rules of arithmetic itself, it starts to make much more sense.

Going on from those, I became curious about the bats whose underground roosts I visit sometimes, as a caver. (We are very, very careful not to disturb these wonderful little animals.) In particular, what they might image acoustically when flying by sonar in total darkness: do their brains create something akin to the sea-bed images from side-scan sonar? I realised I needed understand not only deciBels (rather than just measuring them at work) but also how hearing works; using the human ear as a reference as finding the information for human biology is easier than for other animals. It also gives a neat comparison.

It led to one of the most staggering facts in biology I have met. The 0dB level for airborne acoustics is set by the minimum Sound Pressure Level in air for the fully-healthy human air; and it equals 20µPa. (Marine acoustics uses 1µPa . We can't use 0 as the minimum because that puts a divide-by-0 impossibility in the conversions.)

Let's explore it:

We need typically 6 Bar to propel a miniature steam locomotive.

Perhaps 3 to 4 Bar in our car tyres.

1 Bar is Standard Atmospheric Pressure - as we breathe at sea level.

1 Bar is also 100 000 Pascals.

So a Pascal is not much use in ordinary life... nor in sound. It's far too big for that! So we divide it by a million.

So 1µPa = 1 / 100 000 000 000 Bar.

I.e. Our 20µPa faintest sound pressure level at full otical health, is just a five-thousand-millionth of atmospheric pressure.....

Puts the whispered sweet nothings barely audible in the darkness of the boudoir, in a rather different light!

Thread: Again - another whatsit
29/05/2022 12:00:54

Dave -

You could be onto something with that drawing, but surely it would need a plunger not lever type indicator?

(The jig shown by Hopper would also need a plunger indicator, and its drawing seems to give that.)

My thought though was perhaps for measuring the actual diameter to fine limits readily than by using a rather unwieldy caliper, using chord geometry to measure the radius.

The only fly-in-the suds though is that there appears in the photo to be no method for accurately measuring the ball-to-DTI centres. Unless that was done in some way on a surface-table or against a reference gauge, and then the method becomes one of change from that set datum.

So I looked back at your drawing....

... and played Whatif.

IF the handle stays in the position shown in Hans' photo, as you have drawn it, and the plate between it and the rest of the device has a ground outer face hidden in the picture....

Also, note there are two "shiny things" on the device, one each side, not just one.

Place the instrument as you have drawn, on the surface-plate with the appropriate ball pair for the size-range.

Use parallels and slips to set the ball axis at the lathe's centre-height, but from where the device will stand on the bed or saddle; not necessarily the lathe's nominal centre-height.

We already know the height to the indicator plunger, as that is constant.

Now set the balls and DTI to touch an angle-plate with the indicator reading 0.

Transfer the instrument to its predetermined place on the lathe, where with the balls just touching the work, the radius is a function of the half-chord length given by the ball to indicator centres, and the DTI deflection.

Having two spheres symmetrical about the axis automatically aligns it correctly perpendicular to the work axis.

Geometrically, the deflection is the chord's distance from its diameter intersection to the circumference.

.

Thinking on again, if this is all so, it use need not just be on the lathe but also on some other machine-tool types or a surface table, as long as the centre-distance from the datum plane is known. In some situations, e.g. a plano-mill, it might need clamping to an angle-plate or some other vertical, true surface.

It might also measure a large-radius sphere, since the two reference-balls will always place the instrument's axis on a diametral plane.

Given that it has a lever indicator it might have been intended as a comparator against a reference radius rather than direct measuring tool.

.

I don't know if this the right answer, nor if what I suggest would work: the lever DTI shown may not be the right type, and it does rely on full concentricity so is not for initial setting-up.

Worth a thought though....

.... and I'm still intrigued by that round thingamyjig with its strange numbers we saw back in, err, 2019?! (A calibrated Tuit?)

vice

Thread: Chris Deith
27/05/2022 22:58:26

Sad news, and our thoughts are with his family.

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.

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