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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: What Did You Do Today 2021
10/07/2021 21:30:00

You know what they say...

He who never made a mistake, never made owt!

Thread: GigaFactory
10/07/2021 21:20:05

New cars of any type have never been and never will be affordable for hundreds of thousands of motorists .

Second-hand battery cars will never be affordable by the same motorists if the car is being sold because the battery is reaching the end of its life.

Re-charging at home will never be possible for hundreds of thousands of motorists - including me - as we do not have private off-street parking!

Street-side charging is just not practicable or affordable except perhaps in a few estates of very expensive homes being built with the facilities from new. Even some modern estates now built, are 'Nouveau Pastiche' style terraces enforcing on-street parking that can be some distance from one's home. Their aim was to deter car ownership on a notion that no-one needs or should go anywhere other than work-places near-by. The idea of chargers on lamp-posts came from one or two politicians, most of whom show no technical knowledge at all. In any case the system would require vast quantities of high-power cables and chargers installing in thousands of miles of residential streets with enough room for all those charger parking bays as well as the normal parking, to be at all realistic.

The half-hour coffee-break while your own car is re-charging to at least a reasonable level is only part of it. As a hint on waiting times, VW claims for its latest electric model, a theoretical 180-mile range from a high-power charge for 30 minutes. There will never be enough public chargers, or the space for them, on busy motorways and commuting-routes, to avoid queues that cannot possibly be forecast; especially on cold, dark Winter nights. So a long trip will require considerably more planning, timing and precautions than we would presently think normal.

The public chargers and car connectors must also be of one consistent standard and the units must offer the option to pay by credit and debit cards as on many petrol-pumps now. Easy for us on this forum to say that though. We are engineers. Politicians are not!

Thread: going carbide on a Myford
09/07/2021 22:10:30

No reason you can't use carbide tools on a Myford. What counts is the combination of tool and material, not the badge on the machine; and I find it necessary to choose tools on that basis.

Recently I turned a piece of right rough old steel, a portion of 18mm dia cable-drum tie-rod. Carbide tools would not work on it at all, fast or slow, without tearing. A freehand-ground but sharp HSS tool, reasonable speed and brushed-on cutrting-oil gave a fair finish despite the unpromising steel. Same lathe - an ML7.

Thread: Lathe gear calculation
09/07/2021 21:56:51

I must admit I find it easier to use tooth- and turns- counts than decimal ratios, for most inch threads, because the sums are direct and clear, and don't invoke error bands, but as long as it works. Using decimals comes into its own for calculating for metric threads on an Imperial lathe, and that was the approach my spreadsheet uses.

More importantly though...

To clarify your last paragraph there though, there should be a reverser, probably within the headstock on Bevel's lathe and as on my Harrison, (external on the Myford 7) to nullify the reversal introduced by a 4-shaft set-up. I think his photos do show this.

'

An artificial tooth-count of 1 (not 0 obviously!) for an idler cancels that middle calculation and any potential rounding-error completely. I never calculate the idler but select any wheel that fits sensibly. My Myford's own chart shows an idler by just a hyphen.

Thread: Cylinder drain cock thread?
09/07/2021 01:39:11

Mike -

With great respect I think you may have mis-gauged the thread, for as you say 25tpi doesn't match any standard.

I think it is most likely 1/2 " X 26tpi BS Brass, whose tapping-drill size is very close to the core diameter you quote.

You could try the dodges others suggest, but I would make a test-gauge by threading a short piece of brass (or use a 1/2 " BSB fitting if available) and carefully try that. The reduction in diameter suggests it was not cut right through for some reason, perhaps to create a taper-thread effect.

If it actually is 25tpi, it is an oddity indeed.

'

You also ask the holes' purpose.

I don't know the engine but if it's a vertical the holes may be for tallow-cup lubricators. If so, I would expect smaller holes in the cylinders, close to the ends, for drain-cocks. If a horizontal then they very likely are for drain-cocks. Those are the outer end covers: what equivalents exist in the crank-end covers

I consider it wise, indeed normal practice, to fit drains "even" with slide-valves, but as I say I don't know this particular engine's design.

Whilst it is possible the water might lift the valve off its seat sufficiently to relieve the pressure, there is no guarantee it will do so, and the engine still has the problem of disposing of the water.

Thread: Lathe gear calculation
09/07/2021 01:08:25

Just a gentle reminder gents...

Bevel's original query was an explanation of how the gear-train quoted is calculated to cut a 26TPI thread on a lathe with an 1/8" leadscrew.

Not metric.

Usually that is a simple arrangement but may need a compound train if the headstock pinion is large and the cut thread fine. This example looks very complicated in comparison, but we now know this is a function of the machine's design.

07/07/2021 17:10:58

Right.:

Starting from the top of the lathe, the leadscrew is driven from a pinion on the spindle (sometimes immediately following the tumber-reverse gear).

So that gear is a Driver.

It rotates another wheel, so that second is Driven.

That is common to any pair of gears: the one providing the motion drives the driven, but in the opposite direction.

Now, in a change-wheel set-up the spindle has to drive the leadscrew in the same direction. Therefore we interpose a third gear that does not rotate a shaft but passes the Driver's rotation to the Driven one; and in doing so it makes the Driven turn in the same direction as the Driver at the top.

That intermediate gear is called an Idler, or Stud, wheel, although the former term seems very hurtful because it is by no means "idle" ! It means simply that it is not rotating a shaft. Its teeth count does not matter as long as it fits between the other two wheels - in a simple train. It does matter in a compound train.

Now the calculations come down to matching the ratio between the thread to be cut and the thread of the leadscrew.

On an inch-dimensioned lathe with an 1/8" TPI leadscrew, if the thread you are cutting is an even number of turns per inch, the fractions are quite straightforward and you normally need use only one Driver (that up at the top on the spindle output) and one Driven (that on the leadscrew), linked by just one idler, on the stud somewhere in between them.

If we call the threads to be cut T and the leadscrew thread L, then L/T = Driver / Driven.

Make the two numbers small but even (as I did with 8/26 = 4/13) Then multiply both by 5: so 20/65 if the Driver pinion is of 20 teeth, making it a 65T wheel on the leadscrew.

'

I tried to understand that list you gave of 4 wheels but I'm afraid it flummoxed me and I wonder why it was so complicated. 70,65,30,60.

Sorry - if that is the correct order going down from the spindle, I could not make those figures fall out at all! I've tried various combinations of those but then I twigged 2 things:

- Have you quoted one extra: the 70T wheel?

- Does you lathe's driver pinion have 40 teeth?

For then, as you do not have a 130T wheel, you will need a compound train. It now falls into place:

The 40T pinion drives the 65T which is keyed with the 30T together on the stud. That 30T the drives the 60T on the lead-screw: Now use the (driver/driven) X (driver/driven) formula:

(40/65) X (30/60) = 0.3077. Which equals our original 8/26.

Eureka! If I have diagnosed the machine correctly, and that 70T wheel stays off the lathe.

Even-number threads with even-number leadscrews usually work out quite simply, and many need only a Driver-Idler-Driven trio. Fine threads do start to need compound trains and it looks as if this the case on your lathe.

So now: 8/26. Multiply by 5. (40/130) but to compensate for having no 130T wheel, we divide the work into 2 steps hence :

= (40/65) X (30/60)

A 46/65 duo with idler would cut a 13tpi thread, of course. That's not a standard inch thread but it is extremely close to 2mm pitch (45/65 inch = 1.954mm). Worth bearing in mind if you need cut a short M14 or M16 ISO coarse thread!

++++

One point regarding setting the wheels: do not push them into tight mesh but allow a very slight play between them. The favoured dodge is to put a strip of ordinary thin printer-paper between them, lock them into mesh then gently rotate the machine by hand to eject the paper.

Thread: dirty metric fudge
07/07/2021 11:14:02

I would not call it a fudge.

The important point is that you know its limits of accuracy (or precision - not a synonym but I can never remember which is which!).

Thread: Uncertainty of Measurement [Global Warming]
07/07/2021 11:11:00

The whole matter has been so poisoned by ignorance, politics and commerce it's hard to know actually what is happening, but poor reporting standards and possible bias make things worse.

I wonder how many "Londoners" really would be affected by even a 1m rise in sea-level: how high are the Embankment and Canary Wharf walls above the maximum tides they see now, including storm surges which the Thames Barrier protects against? How many homes are genuinely in danger? Food shortages would be the bigger problem by affecting everyone in this country, even up on the lofty heights of Muswell Hill.

I understand there was a recent "report" from a supposedly scientific-journalism organisation that highlighted the above but was found to have used no more than a few estimates from American sites!

Thread: Lathe gear calculation
07/07/2021 10:57:51

I can't help thinking there is a heck of lot of over-thinking going on here, of what has been and still is, a basic part of the art since the 19C!

The calculations for cutting a thread to the same units as the lathe (TPI on an inch lathe, mm pitch on a metric) are simple fractions; whether needing a single step or compound train, which is normally 2 but occasionally 3, fractions multiplied.

Cutting a thread of differing pitch-type (mm on inch and vice-versa) is a little trickier by usually needs a conversion 127 or 63T wheel, prime numbers; but not always. My Myford ML7's own chart gives several mm pitches with the "ordinary" wheels. Yet the arithmetic is the same.

Nor do you need know computer languages and programming for what is frequently a pencil, paper and calculator (or mental arithmetic) task.

The computer is valuable for creating tables made once and printable for workshop reference, but still only by ordinary "sums" in a spreadsheet. Mine, in MS 'Excel', gives metric and even BA threads, on an 8tpi-lead lathe with a simple 5-increment wheel range, to a fair degree of accuracy; by normal divisions and multiplications. It was a bit fiddly because I had to swap values around to narrow the errors, but a one-off that did not need compilers and languages, just the standard 'Excel' tools. It also shows the cumulative errors to assess maximum practical non-inch screw-cut lengths, usually longer than necessary anyway; and which may be impractical.

Engineering is performing physical, creative tasks in the best, simplest and most efficient ways, not adding work to make the most complicated ways!

06/07/2021 23:13:55

The underlying rule is that the Ratio of the change-wheel train = Ratio of the leadscrew TPI / cut TPI.

To take your example (and this is one I had to do myself recently). You don't tell us your lathe's headstock pinion tooth-count, and I am afraid I can't work out what that combination you show gives. If though the pinion is of 20Teeth the ratio works in a single step and uses what you have:

Leadscrew: 8

Cut thread: 26

8 / 26 : you can work from that but I prefer to halve both numerator and denominator first to bring it closer to the wheel counts, as this shows:

So 8 / 26 becomes 4 / 13.

Now with a 20T driver; multiply both numbers by 5 (because the wheels are in counts of 5)

(4 X 5 ) / (13 X 5) = 20 / 65.

The 20 Tooth wheel is the driver, up on the output of the reverse tumbler

The 65T wheel goes on the leadscrew.

Then put an intervening idler wheel on the banjo stud to connect them and make the work and leadscrew run in the same direction (assuming a right-hand thread).

'

In general form

LS / Cut thread = Driver (on headstock) / Driven (on leadscrew)

'

However, as you don't quote the headstock pinion (usually called the spindle):

If that driving pinion is not 20tpi, then you will need re-calculate to suit that; and this may mean a compound train as your question describes.

So if that wheel is of 40tpi you would need effectively a 130T wheel on the leadscrew to gain that 8:26 ratio. Not possible so we split the gearing into two sections; and the most likely is:

8/26 = 40/130 = 40/65 X 30/60 =

40T driver; meshed with a 65T wheel keyed to a 30T wheel on the banjo stud. The 30T then meshes with the 60T wheel on the leadscrew.

And so on for other driver-pinion counts: equate the overall gear ratio to the thread ratio.

'

In general form:

LS/ Cut threads = (Top Driver / 1st stud wheel) + (2nd stud wheel / leadscrew wheel)

++++

To answer your other question. 100 and 127T.

The 127T wheel allows cutting metric threads on a lathe with an inch-fraction leadscrew. So if we want a 1mm pitch thread; 1mm is equivalent to 25.4TPI

LS/Cut = Driver/Driven

8/25.4 = 40 / 127 (multiplying numerator and denominator by 5).

If we need a millimetric thread of different pitch we would therefore modify the upper part of the change-wheel train but the leadscrew wheel is still the 127T wheel. In practice, this is physically too large for some lathes and a 63T wheel can be used instead, with due consideration of the cumulative pitch error this will introduce.

I must admit I am puzzled by the " 100 / 127 Rule " you quote. I have not encountered that previously.

My Myford ML7's change-wheel guard conveniently holds a chart showing the wheel-trains for most common inch and some metric pitches, and fine feeds, with the standard wheel set. Do you have a manual for your lathe? That ought include a similar chart.

Thread: Universal thread cutting
06/07/2021 00:05:30

Millionths..... I'm lucky to find a thousandth!

For practical purposes I cut threads to near-depth then finish with a die, to form the profile as much as anything.

Thread: Screw cutting advice ml7
06/07/2021 00:00:37

I have somewhat similar problems on my ML7 with engaging the half-nuts, and if it doesn't engage neatly I kock it straight out of wherever it has stopped and try the next number or iteration.

It is just possible to clean and lubicate the mechanism fairly well without removing the apron, by taking the lever off and operating pins out. The lower half-nut can then be winkled out downwards. I washed the remaining innards with liberal squirts of WD-40 (which is not a lubricant), wiping what I could with a small brush and paper towels from under the apron; then lubricated the lot liberally with oil. It helped but I still have that trip effect so will examine the indicator alignment as suggested above - for which thank you.

I note suggestions to "re-align" the leadscrew. Any axial adjustment will simply take up end-float on the screw itself, and although that might help, it disguises the real mis-alignment.

Instead the half-nuts are adjusted by a small screw with lock-nut on the end faces of the apron.Not the lead-screw.

If you think about it the relative position along the machine of the saddle and screw is not important so adjusting the lead-screw will merely kick the saddle down the road, to paraphrase...

What matters is the mutual alignment of the two half-nuts, then the alignment of the indicator marks so they agree with the half-nuts and the screw.

On mine the stud holding the cam to the apron was working loose in the apron thread, and that won't help matters, by introducing a lot of slop.

Thread: What Did You Do Today 2021
05/07/2021 00:50:05

I suppose someone had to say it, Kiwi......

Thread: GigaFactory
05/07/2021 00:47:08

Vic -

I wish I could share your optimism but the whole concept just does not stack up as the green types and politicians imagine.

However many charging points they install there will always be queues at busy times; and what happens if the connector is incompatible with your car, or the chargers are out of action and you may be a long way from the nearest alternative assuming you know where it is? A parallel argument applies to availability of petrol or diesel of course, but their ranges are more reliably longer.

The ranges seem suspect, as if calculated or test-track conditions, not real driving in a hilly country in busy traffic in bad Winter weather.

The cost of the electricity in future is a huge unknown; even more so if /when subject to tax and/or the payments are via enforced "smart"-phones with their contracts and hidden middle-men fees. And variable signal coverage.

The new costs are not likely to fall to "affordable" levels; and if second-hand ones are cheap it's because their very costly batteries are dying.

'

Peter -

Well, I reckon motoring will go back to the 1910s when it was the preserve of those who could afford the proliferating battery-powered cars of the time.

If you can't join that exclusive car-owning club, how are you going to take your latest creation to the major model-enegineering show or rally? Assuming they exist of course thanks to it being no bad thing that most of us have to stay local apart from the annual trip Pwllheli or Fylde, so the attendances and exhibit lists at major events are uneconomically too small.

Indeed I foresee a time when huge swathes of the country's culture and leisure will die off , and what's left will be severely limited in choice and heavily constrained, as people become unable to go anywhere in large numbers, or to take anything anywhere, any significant distance from home. Replacing frenetic dashing to social and cultural events, clubs etc, with the more stressful isolation, sense of loss and monotony. Nothing man-made in this world comes for nowt, and electric cars come with a lot of owt.

Thread: Milling machine in the (wood floored) workshop
04/07/2021 23:35:10

I solved the same problem in my previous home by cutting four recta ngular holes in the floor, cementing small brick plinths to the underlying concrete a few inches below the shed floor, and putting a thick PVC pad as damp-proof / levelling layer between the milling-machine's angle-iron bench and the bricks.

Thread: Stone moving machine
04/07/2021 23:09:30

Two points:

Whether the Druids ever used Stonehenge, they did not build it.

More seriously, the stone actually used may have been hauled from no more than a few miles away. If I knew the reference I would give it but a geologist who has studied this recently pointed out that although the source was Wales, the rocks used in the building were "erratics"; moved far from home on an ice sheet that crept across Ireland and Wales to about as far as Wiltshire. More of the same rock is still there, where it was deposited by the melting ice.

(During the Last Glacial Maximum, Southern England was exposed Arctic Tundra, and ice-sheets rather than glaciers was the main ice cover extending down to about the Severn - Thames line.)

Would seem a classic example of three sets of experts - here professional archaelogists, geologists and engineers - not talking to each other then journalists reporting the first not knowing the rest exist!

'

What all the speculations on how ancient people moved umpteen-ton blocks fail to spot is the nature of the ground. The usual assumption in those "reconstruction" paintings, is tree-trunk rollers, which is probably correct; but that alone would be insufficient on almost all ground because the logs would partially sink. I suggest that they may have laid more tree-trunks longitudinally, as a sort of road-way.

As for raising them upright, one theory holds they would have levered and packed, levered and packed... I wonder if they used some form of rough derrick, or lashed an upright at least as long as the slab to its foot end, and applied the pull over that.

(I have used similar, with a scaffold-pole and rope, to recover a milling-machine that fell over into a bramble bush when we were trying to load it onto a trailer, and the ramp collapsed.)

Thread: Universal thread cutting
04/07/2021 22:41:36

Interesting point, Chris.

Perhaps it's too easy to think the more complicated the solution the more efficient the result; or that the solution even needs to be complicated; and I have seen others and been caught out myself by this tendency.

I suppose the main advantage of a gearbox is the ability to switch from screw-cutting to plain turning and back rapidly - I have a gearbox for my ML7 but am yet to fit it - but the chart in the change-wheel cover does give the wheels for several standard metric threads just from the ordinary change-wheel set. My Harrison L5 lathe manual gives similar combinations, but I think I have a 127T wheel for it anyway, and it has a narrow-range 3-speed shaft gearbox that extends the change-wheel sums.

It's probably worth looking at the intended work. Brian may wish to make long, very highly accurate threads so does need very close matching.

For most of us though I suspect most of our screw-cutting is over short lengths, less than 10 turns, and to ordinary accuracy standards; not long threads and still less, high-precision lead-screws. For those two, rare, instances it is usually simpler and not very expensive to copy industry and base the components on stock studding / lead-screw rod and nuts.

Consequently I spent a few lunch-breaks at work calculating by spread-sheet change-wheel combinations for odd-numbered and metric pitches on a simpler lathe than a Myford, with a 1/8" lead-screw and smaller change-wheel range; and was surprised how close many came within sensible tolerances. Having done that, all I then need is to print a copy for ready use! No need to search for prime-numbered wheels (though I did buy a 63T wheel), electronics,stepper-motors and the like.

By all means build an NC lathe as its own project but I am wary of going Long Way where the Short Way reaches the same point just as properly, with less overall cost and effort.

I have been there - making the thing far too complicated for its own good, then spotting how I could have done it and wondering why I threw so much extra time, steel and electricity at it. It's a matter of balance, but efficiency and quality count, not complexity!

Thread: What Did You Do Today 2021
02/07/2021 23:55:30

"Door opening training"... Ah, in this case the fatality was due to door closing.

Blow me, when I opened the workshop door this afternoon, there was a frog sitting on the floor immediately inside, staring up at me! They aren't easy to pick up without risking injuring them, so I chivvied it to hop gently outside and into a safe area. It had most likely crept in when I previously had the door open.

I did once have a genuine door-opening near-miss. It was at work, or at least on work duty, and I should probably have reported it. Driving somewhere on a work trip, I stopped at a service-area. It was a windy day, and as I opened the door to resume the journey a gust of wind caught it, jerked it out of my grip and rammed the very corner against my forehead. Half an inch lower and it would probably have had my eye out.

Thread: "footprint" of Dore Westbury
02/07/2021 23:41:37

I've mounted my machine at an angle to to the wall, and partially covered the corner at machine stand height. This gives a cubby-hole for things not needed in a hurry, and more usefully a compact tool shelf.

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