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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: Whats the tolerance??
04/07/2020 00:57:53

Model-engineering drawings and any accompanying constructional articles very rarely if ever come with tolerances. They might become more common on items such as locomotive frame-plates bought laser-cut from a materials stockist whose system needs such tolerances. Otherwise there are no formal dimension controls in the hobby; just the principle of working to the best of our workshops and abilities.

If you are making something that does need a good-quality fit such as a piston and cylinder I can only suggest being guided by the industrial standard classes of fit summarised in publications like the Zeus books.

I don't quite follow the logic as you have phrased it though. I am guessing you are actually building a Weir-type pump. Your text seems to ask if the alignment is a function of the fit of piston within cylinder, but I am sure you do not mean that. A piston should be a smooth sliding fit for the full length of its stroke, and both it and its cylinder should be as closely cylindrical as possible.

If the machine has a rigid rod connecting two pistons in separate, in-line cylinders, the quality of alignment should be controlled by the surrounding metalwork and the concentricity of cylinders, pistons and rods; not by the fit of the pistons in the bores. As I am sure you realised, you cannot correct misalignment here by turning the piston down - that would not work at all.

The closeness of the bore to the drawing is of secondary importance to these, within reason measured in "thous", as long as the piston hugs the cylinder wall as it should.


There are no tolerances for two reasons.

Firstly, we are not normally making interchangeable parts in the way vital to industry. It would not greatly matter if someone else making the same engine as you, machined his cylinder bores 0.005 " larger than yours as long you both made the pistons to suit your own engines. Yet obviously if you swapped the pistons with each other, that mis-match would give an engine kit that cannot be assembled, and one that can be assembled but would not run.

Secondly, model-engineering has always worked on the principle that as most of us are not professionally-trained machinist/ fitters or designers using full industrial facilities, we have to follow the drawings as closely as we can with the abilities and facilities we have, so we tend to make mating parts fit each other by specific example.

You do see some notes like "A must be a close sliding fit in B", or on some older drawings, the strange term "bare" after the dimension. Tolerances though; no. You bore the cylinder as closely as you can to the design, and turn the piston to a slightly firm, smooth and even, sliding fit.

Thread: Lathe dogs
03/07/2020 23:59:41

We all have our preferences, don't we?

I have various of these dogs and have used them all at various times. I admit they can occasionally be a faff to set up on awkward work, and now and then none seem the right size, but I am glad I have them.

Yes, sometimes I have met the diameter problem but that's a not a reason to dismiss them out of hand. I simply found ways to improvise...

... As when I turned my wagon's crankshaft. I had to make a pair of steel blocks to clamp to the shaft ends, with the appropriate centres; and to drive those I bolted step-blocks borrowed from the milling-machine, to the faceplate.

Thread: What Did You Do Today 2020
03/07/2020 23:43:56

Completed the wheel-sets for my travelling hoist's crab.

Unlike a conventional railway axle - and the long-travel on this hoist - with a rigid wheel-axle fixing, I've adapted the four aluminium-alloy wheels I already had, to revolve on their existing bronze bushes, on a "dead" axle. They are retained by a shoulder, washers and circlips - no nasty split-pin ends to attack one's hands!

I recall rarely if ever seeing circlips and E-clips mentioned in model-engineering circles. Perhaps we are all conditioned by model practice, where visible fastenings do need replicate the full-size split-pins and taper-pins.

Had to "stretch" three stretchers on the beam assembly upwards so a 25mm-square tube laid across the axles will clear their undersides by about 1mm. Kitchen-fitting shims in the right places did the trick.

I painted the axles with ordinary spray paint. Based on an article a while back in ME about modifying a low-cost barbeque rotisserie to aid painting cylindrical items, I used the Harrison lathe, which will tick over at around 60rpm without upsetting the motor. A flattened carton behind the machine, a bin-liner on the bed and a lot of oil clinging to everything kept the overspray under control. I needed run the lathe for only a couple of minutes or so for each axle. Next thing- design and make the trolley itself.


Things are easing! My sisters graced me with their presence yesterday morning, to scrounge a coffee; using the side gate to avoid going through the house, and sitting in the sun in the garden the regulation 1-1/12 fathom apart. We live within walking distances of each other, but this was the first time we'd met since the week before the lock-down started.

As for my model-engineering society though... I'm afraid that's going to be tricky with a very small club-room and fear of using communal tea-making facilities, but in any case our hosts, a school, are still keeping the gates locked out of school hours. (That also bars access to public sports hall and outdoor pitches.)

Even where a club or society has its own access though, I wonder how many others, by no means confined to model-engineering, are in similar situations; not knowing when they will feel able to open even if allowed to open. My caving-club for example, has just announced members can use the grounds, with its lawn, couple of picnic-tables and kit-washing area, and can arrange to borrow club equipment, but not enter the building even for the toilets.

Also of course, how many older members of many clubs will feel unable to attend anyway.

Or to visit exhibitions. Fingers crossed for the Midlands one, with a decision I hear to be made in August. That does not give very much advance notice for the traders, though obviously they will all be aware of the situation, but it's hard to see what else anyone can do.

Meanwhile... carry on making swarf!

Thread: Poor mans mill feed speed control
03/07/2020 22:44:40

Not sure why that would have reminded me of the works first-aid courses in resuscitation, with either Nellie The Elephant or the BeeGees' Stayin' Alive the suggested timing-songs for that.

Especially since they might be a bit too fast for twiddling a hand-wheel but would soon wear you out when using a manual shaper...

Thread: Tungsten carbide for shapers
03/07/2020 01:30:01

A point no-one has mentioned but Cornish Jack approaches, is one made in the old reference books.

It is that the edge of the tool should be under the clapper-box fulcrum. The swan-necked tool Jack describes can help achieve that as well as adding that resilience he mentions.

A tool that is not so located may be one factor in it becoming dulled prematurely, but I don't know if anyone has investigated this.


My shaper is a manual Drummond, not a powered machine, but it's still possible to shock-load the tool and machine by too deep a cut. I always file a small chamfer on the entry edge to ease the tool in a little. I don't know if it actually makes much difference but it doesn't do any harm.

Regarding the impacts, think of a large face-mill with inserted tungsten-carbide shapes: that is often used at high speed but doesn't seem to mind. In fact I worry more about the hammering such operations can give the machine bearings, than the tips themselves.


it was me, by the way, who had asked about hard surfaces on hot-rolled steel. Oddly, some steel I was turning today seemed slightly inhomogenous, indicated by unusual changes in the swarf along the cut. The material was 18mm diameter mild-steel of probably BS Somewhere-Handy spec., as it had been a cable-drum tie-rod so not needing to be anything too particular.

Thread: Overview of fitting variable frequency drive (VFD) to a Myford ML7
03/07/2020 01:06:45

I think I am right in saying that Newton-Tesla do now sell totally-enclosed motors for the Myford lathes (or presumably any lathe).

It did surprise me though that whilst the first set I bought - for the ML7 - has a fully-enclosed inverter / controller (it has vents but at the back of the box and fitted with internal mesh) the sets I bought later for other machines all have separate inverters and controllers, and the former are not all that well enclosed. I think they are really designed to be fitted inside cabinets.

Thread: Old School Drawing Exercises and 2D CAD
03/07/2020 00:50:56

That SCAD code looks rather like something someone at work once gave me, called POV-Ray.

Now, POV-Ray makes no pretence to be a CAD programme. It is or was intended to be purely artistic, and you can make it produce the most wonderful renderings of very pretty but utterly unfeasible or useless objects!.

It too uses command-lines that are fairly simple to grasp and somewhat similar to that SCAD example; and although engineering-drawing is not its intended purpose I wonder if in fact it, or an up-to-date edition, could be used for making 3D-printer files.

Something POV-Ray , or at least the version I have, lacks, are a grid or ruler-set, but I suspect you could make it generate at least a grid for the individual project.

Thread: Neil Hemingway Kits
03/07/2020 00:37:37

I've made that boring-bars set, and am part-way through making their tool-grinder.

I've not yet graduated the boring-bar adjusters, but since the marks would be a long way from any fiducial line I may leave them plain and instead either directly measure the tool or use feeler-gauges. (The latter based on techniques I learnt years ago when working on a bench-drill in a sub-contract engineering company.)

A point that puzzles me a bit about the 'Worden' Tool-grinder is why, having gone to the trouble and customer's expense of (probably CNC-) engraving a big, clear degrees arc on the table, they did not have the numbers engraved too. Instead the instructions tells you how to make a simple jig for stamping them, but that risks slightly uneven marking and worse, distorting the plate.

Thread: Downwards-Counting Cross-slide Dial?
03/07/2020 00:27:19

I don't know why I have not spotted it previously but the cross-slide dial on my Harrison L5 lathe counts down, not up when advancing the tool towards the centre.

The top-slide counts up, when winding towards the chuck.

The dials on my Myford ML7, EW and yet-to-be set up "Micro Lathe" all count up towards the lathe axis and chuck.

So, anyone know why the L5 begs to differ?

Funny thing is, I have used that lathe for a good number of years before it became my own, and it was only today that I noticed its dial's nature! And then only because it nearly caught me out.

Thread: Old School Drawing Exercises and 2D CAD
02/07/2020 01:58:49

My wretched typing! I'd about finished this when yet again I hit an unknown key-combination and deleted it.

Orthographic! Yes of course! Thank you gentlemen for the correction! Same root though.

Of course I am aware that CAD calls the 3D images "models", but TurboCAD's view-changing tool offers two types of view and calls one isometric. I forget the other.

I am also well aware of the industrial practice now being taken up in some ways by model-engineers, of drawing-files translated straight to CNC-machine drivers.


Really, for us amateur engineers the choice of whether to use CAD, and to what extent, is by budget, time, preference, learning-ability and indeed interest.

First we are assuming designing our own projects, rather than sticking to published ones; and considering their complexity. This was my starting-point, as my main project's source is merely a few scrappy old trade photographs from 1908; and I bought a copy of TurboCAD 19 Pro.

Next, unless you have a particular gift for learning extremely difficult and unintuitive software, which I do not, it can take a formidable time to grasp sufficient CAD experience just for simple orthographic drawings adequate for your own purposes.

3D-model drawing adds greatly to the complexity; and when designing for yourself, you need ask why lumber yourself when you actually make the parts from 2D drawings. The one advantage I see, was that CAD enables 3D models to help determine complete assemblies. This too, helped sway my decision.

However, as engineers we should be able to visualise a 3D assembly from 3 orthographic views - depending on its nature.

So why 3D CAD for own drawings for own projects in own workshops...?

The only answers I can see are that either you have the desire, time and ability to learn it, or you've bought a CAD package that gives you no choice!

If we buy CAD because we want to design our projects, presumably we can already create engineering-drawings of appropriate standard. The trap is that of trying to learn the CAD package taking much longer than we would have spent drawing the project manually.

I bought TurboCAD but really, that it lets me draw a 3D image of, say, my engine's crankshaft does not mean I have to do so. I want to make a real crankshaft, not a pretty picture of one, and after untold hours of struggle better spent actually designing and making the engine, I was just about capable of a pretty picture of the shaft. By then I had made it, to a CAD drawing but orthographic, dimensioned and set out from the orthographic GA.

I did try other CAD packages.

I have a copy of AutoCAD 2000, which is 2D only I think, but no manual for it.

I found Fusion 360's brashness off-putting, and it assumes prior CAD-principles knowledge - to be fair, they all do.

I tried Alibre but I missed two episodes of the MEW serial. Why buy and learn a complete new package when I'd already bought TurboCAD? I thought the magazine series would make it easier to learn, than trying to teach myself what I already had. So I abandoned Alibre too - which took its publishers months to understand. Luckily, I already have a scribing-block.

Both Fusion and Alibre are based on 3D- model first - I do not use a 3D CAD/CAM system at home, so regard 3D as nice-to-have, but of limited use, extremely difficult and time-consuming to learn and frankly, not really necessary. It is for brochure artwork, not workshop drawings.

The only useful 3D images I have drawn were two geological diagrams for a caving-club magazine article.


Training materials?

TurboCAD's own on-line 'Help' manual is not much 'Help'; and I can't learn from videos. Far better than these is Paul Tracy's CD manual for TurboCAD, a step-by-step pdf primer.

D.A.G. Brown's general CAD primer has a very dated cover photograph, but does outline the principles of CAD engineering-drawing. Neill Hughes' more modern alternative, which I also own, is sketchier and more for the 3D-artwork people - and despite a British author and publisher, neighbours to France, it insists on calling "metres", "meters".


So to sum up, CAD can help us but it is not the be-all-&-end-all of model-engineering. Unless you also intend using CNC machine-tools as well, or buying a lot of profiled work-pieces, CAD is only worth buying if -

you design most of your own projects,

you need draw them accurately,

manually drawing them would take much longer than learning the CAD package sufficiently.

Thread: What Did You Do Today 2020
01/07/2020 23:50:32

Keith Wyles -

I did say the cm is used for some specific purposes, and the c.c. for small volumes of liquids was one of the purposes I had in mind; the other of course being engine cylinder capacities.

On which note, anyone know why car reviewers insist on giving a car's internal volume in litres, as if you're going to turn it into an aquarium, and sometimes engine power in some strange unit called the kP rather than either HP or W.

For some reason I thought that stands for kilo-poules (1000 hens?) but when I looked it up just now, I was given the kilo-pond - appropriate I suppose if you insist on measuring a vehicle's interior by how much water it can hold.

Andrew -

You are right that any self-respecting engineer can visualise 3D objects, but it's visualising 3D units of measure that can be harder. It was the inconsistency of units I had commented on.

Later Today...

Resumed work on the crab (the cross-travel trolley) for the workshop hoist. I had 4 aluminium-alloy, plain wheels with bronze bushes, running on mild-steel cores drilled 12mm through. I have no idea of their original purpose but thought they'd come in handy one day, and so they are proving; converted from plain rims to flanged, with a slight taper.

Thread: Old School Drawing Exercises and 2D CAD
01/07/2020 12:48:51

Draughtsmen (and most were men, though my Mum was a tracer in a drawing-office), were not only taught drawing thoroughly, but also how their creations would be made. They usually started as apprentices, and ones who back far enough were expected even to do things like making accurate cubes by chisel and file - despite the firm paying good money for the shaper and mill.

I have seen CAD examples that must have been real so-and-sos in the workshop, CNC- or conventional, thanks not to using CAD but to the draughting tool taking precedence over the engineering tool. And we all know just how difficult some cars can be to service, thanks to poor or no consideration of accessibility to what should be accessible, such as lamps.

Where does the fault lie? Poor training? Or good training but skewed too much to theory and design-tools? An assumption of the "Computer says X so X must be right" ?

Some of the old-style, professional, orthogonal GA drawings we see now via our hobby scale-replicating early machinery, or preserving the full-size, were fantastically detailed, needing considerable skill and experience over many days of patient work. These can still be produced in CAD - most of such a drawing is only standard lines, simple shapes and hatching, just lots and lots of them - and much more quickly.

The experience CAD user is no less skilled at draughting than his or her manual predecessor for the same level of drawing complexity - possibly more so. CAD can do awkward things like merging arcs and plotting pitch-circles and arrays, but it is not intuitive. Nor very efficient if it demands creating an isometric model then taking the orthogonal views from that; but even before the forbidding complexity of 3D, CAD adds a deep layer of skill of its own even just to stich a few basic shapes together.

(Some CAD makes, including TurboCAD, offer a straight orthogonal/isometric choice, even if the publishers appear not to know the word for a 2D drawing. Others, including Fusion 360 and Alibre, seem to insist 3D-first. Yet the workshop needs orthogonal elevations, not pretty pictures - though the fitter, operator and repairer need the isometric assembly-drawings.)

Yes, the skill at the keyboard, parallel-motion board or T-square on elm board is important, and may be very high-level, but is the intermediary.

What really count are the skills of designing, and the skills of making.

Thread: What Did You Do Today 2020
01/07/2020 12:02:29

Cornish Jack -

50mm / 50cm.

Easy mistake to make but you raise an interesting point.

I wonder how common such as mistake is becoming, thanks to schools teaching metres and centimetres even though the centimetre is not used for anything technical, except for a few specific purposes.

I find myself actually having mentally to convert sizes, usually those quoted in shops and catalogues, from cm to mm to be able to assess them. That I have often then to relate them to real measures - 150mm is close to 6 inches for example - is by-the-by.

It is the cm / mm point that sticks, and one a teacher tells me he encounters in trying to teach so-called "STEM" subjects rightly in millimetres, to pupils whose Maths lessons in the same school, use only centimetres.


As for the Groat and Bushel... It was a fine pub till the Far-East-owned chain that had bought it, renamed it thus within its ....and Bushel estate, so to run it into bankruptcy for cheap sale to a Mayfair speculator for conversion to second-homes for the Canary Wharf set!

Thread: Overview of fitting variable frequency drive (VFD) to a Myford ML7
30/06/2020 02:21:03

I fitted my ML7 with a Newton-Tesla set, which is electronics plus motor.

My version is just a straight swap plus finding a suitable location for the inverter/controller. If you tell them the machine they know which electronics to pair with which motor.

I say "my version" - I'll go by that to start with. You'll see why, shortly.

The lead from the motor has a special plug for the connector on the electronics.

The main lead is rather short, at least on mine, so I have to use a short distribution-board. That though is a matter of workshop geography so may not apply to yours.

I placed the inverter on the cabinet below the headstock, but that is in the way of oil and swarf so I made it a cheap-and-cheerful plywood shelter that sits in the chip-tray above it. It's there because although I am right-handed, the disposition of the controls is better for using left-handed on the inverter I have. In particular, reducing the risk of accidentally using the wrong Stop button.


I stressed that clause because the Newton-Tesla systems I subsequently bought for my other machines differ, by having two separate electronics units. Those do need more wiring - not difficult if you are reasonably happy with such work; but it is vital you put the right wire in the right place, of the mains lead and of the cable linking the inverter itself to the control "pendant". Which isn't really a pendant but a box with lugs for screwing it to a surface.

If the set you buy is of that pattern, put the inverter somewhere well out of the way of swarf and oil-spray, as it is not fully-enclosed.

That on my Harrison lathe is high on the wall above the tail end of the bed, with the controller just below it, still well clear of the muck. It also keeps me clear of rotating things - which can't be said for the rather dubiously-designed clutch lever a feature of the L5! Similarly with the set on a BCA JIg-borer - on the wall a bit above and in front of my shoulder when sitting at the machine. The set destined for the milling-machine will also be similarly elevated to a higher plane.


One thing to watch (having just given myself an expensive repair!).....

If the motor is the type with open ventilation holes in its ends, fit a shield to protect it from swarf, unless your lathe already has that luxury. Turning some bronze, most of the swarf "corkscrews" were falling harmlessly to the front, and I failed to see one sneak round the rather inadequate shield, and enter the motor. The resulting short to earth did not hurt the motor but damaged the inverter. I can say N-T's repair service is prompt, but obviously equipment like this is not cheap!

While the motor and inverter were away I fabricated a complete back-panel and motor shield - I've put a photo of it on the "What I Did Today" thread.



Advantages? There are three, really.

- Very much smoother and quieter running than with the single-phase motor, which tends to make the cabinet (standard Myford one) resonate.

- Better speed control, especially for operations like screw-cutting up to a shoulder. By still using the back-gear, you can have everything moving at a less nerve-wracking rate.

- Ability to adjust the speed during the cut, as sometimes useful such as when noise or chatter may indicate wrong speed for the other conditions. Also when paring-off large diameters.

NB: 1. These motors do not like being run too slowly, and the warning colours on the speed control are for low as well as excessive speed. (Used in conjunction with the headstock gears, I can run the Harrison at about 60rpm with the motor still happy at nearly 1000 rpm.)

NB 2: Don't use the Emergency stop-button as normal stop. The makers warn its frequent use can harm the electronics.


I've not found any.

So, I hope this answers your query!

Thread: Ultrasonics and citric acid
30/06/2020 00:41:14

I am surprised the sound waves actually pass through any intervening beaker or pan wall, rather than being reflected from it, making me wonder if the work-pieces are simply being pickled. Any vibrations that manage to negotiate the barrier would almost certainly be attenuated by it.

The ultrasonic cleaner I used at work - itself based on ultrasonics - had a stainless-steel work-basket nearly as large as the tank, and I would never put the work in a solid-walled secondary container unless advised in the operating-manual. Ours did not even mention it; and it is hard to see where it might be "standard practice" unless for some particular make and type of ultrasonic cleaner (jewellery or horology trade perhaps?).

These tools are otherwise meant to be used with the work-pieces immersed directly: suspended, in the basket supplied with the appliance, or just laid in the tank. I would use suspension for small items. All you need do is ensure the additives will not harm the tank.

Thread: Exploding Grinding Wheel
30/06/2020 00:08:36

I have often wondered about drill-grinding jigs too but they seem to exert very little and well-controlled pressure on the wheel, and work with a sweeping action that avoids eroding grooves in it.

Thread: What Did You Do Today 2020
28/06/2020 22:40:08

Finished and fitted the new motor-guard / splash-back for the ML7.

It's all fabricated from 3mm PVC sheet, glued with plumbing solvent-adhesive then the joints reinforced with hot-melt glue.

The panels are joined using "angle-plastic". All the bending was after softening the PVC with a heat-gun, then for the angles, pressing them manually between two lengths of angle-steel. The steel soon cooled the hot plastic, so my fingers on the opposite sides of the conductive metal informed me.

The former for the curve along the box, was the steam-wagon's rolled steel "stovepipe" chimney laid along the 'Workmate'. (Don't worry, it wasn't harmed!)

The rear of the box portion and its far end are fully-open for ventilation, and it is slightly shorter than the motor. The main panel has a big rectangle cut out from its end to match the exterior of the box.

The up-stand angle at the far end of the box is to impart a little extra rigidity and restrain any stray debris that gets up there. The "roof" is not temptingly accessible to use as a tool-tray!

Took a couple of photos of the assembly, then fitted it.

The box is held to the countershaft frame by 3 M6 screws through a shallow PVC channel bridging the frame's central hole, and tapped into an area with a doubler-strip glued behind it. The main panel is held to the Sterling-board workshop lining by 3 wood-screws, via simple wooden block spacers, along its top edge. All the holes are visible in the picture.

I made the circular raised portion that clears the motor mounting and stiffens the face also by hot-pressing, using a plywood disc " punch" and plywood "die" - actually borrowed parts of the lifting-cradle for my steam-wagon's boiler.

A different line of work from metal, and an interesting if sometimes awkward and frustrating process.

ml7 splash-back - june 2020 a.jpg

Thread: Inherited Lathes and Milling Machines
28/06/2020 21:51:01

Was your father in a model-engineering (or related-interest) society?

If so, from experience in my own society, I would also approach them for advice and they may even be able to find good homes for the machines and tools.

28/06/2020 21:47:10

Oh yes, I think we've all been there and done that at least with some of those things!

I used to know a rather eccentric character - long since transferred to a rather higher Link - for whom the tool-set for servicing and running a hefty 7-1/4 inch g. 0-4-2 tender loco was a 2lb hammer, a big pair of heavily-serrated pliers and for the more delicate tasks, a well-worn old adjustable spanner.

The pliers of course for gripping brass union-nuts that were nearly cylindrical thanks to someone habitually using a big pair of heavily-serrated pliers on them. Plus an oil-can with a powerful pump suitable for what the rest of us called the 'aim-and-squirt' technique, which least ensured the steaming-bays and oil-company dividends did not go rusty.

Despite (or because of?) this loving care and attention the locomotive actually ran well, though driving it from a seat on the tender on a raised track was, well, an experience.


Gremlins hiding things>

One tricky calculation in a model-engineering problem. Calculator... where are you calculator? Nowhere. Slide-rule...? Equally evasive. Large sigh, an earthy word or two and out with the logarithm tables. Next day I bought a new scientific calculator, surprised to find calculators following an inverse-dimension rule compared with other small electronics; i.e., growing larger as phones etc. grew smaller. Three weeks later I opened a drawer and there was the missing sums-box I knew I had not put there.

My conclusion? In keeping with the Age of Enlightenment I blamed not supernatural beings but Physics. Specifically, tiny Black Holes that are too small to sustain themselves for long, and eventually fade away (can something invisible because it prevents light escaping, fade away?), thereby dropping all the matter they have swallowed, in random locations.

Thread: Index backplate on which chuck?
27/06/2020 23:21:05

I take Ega's point - 12 holes will cover most indexing, but 24 has that useful extra integer of 8 - octagons and 8-hole pitch-circles are not very common but thinking a little laterally, this also allows setting-off at 45º. It's one of those rare things, an "extra" you might need only very rarely but are glad to have when you do, yet takes up no extra space!

I'd agree too with Old Mart if you elect to use only one indexed back-plate, use it for the 4-jaw.

No reason you can't have stopped holes for screws provided they engage fully. Holes that break out in a corner as you describe do look messy but worse, the breaking-through risks broken drills or taps. I take it the chuck is the pattern with long cap-screws running right though the chuck from its outer face.


A tip when indexing: clean the rim with a cloth moistened with meths, then mark the needed holes with a fibre-tipped pen or marking-out fluid. These marks can be cleaned off afterwards in the same way.

{I used similar for circumferentially and axially dividing the 120-off 3mm dia. holes in a strainer made from a bit of standard PVC sink waste-pipe. Having no formal method at the time, the dividing-engine was my EW 2.5" lathe simply standing on a table. The 60-tooth change-wheel on the spindle, with the relevant teeth marked by two differently-coloured felt-tips and aligned by eye with a convenient edge, gave the staggered bands of holes. A second, inked change-wheel acted as lead-screw "dial" for spacing the bands. I used a hand-held battery-drill, with a brass guide-block gripped by the tool-clamp. }

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