Member postings for Kiwi Bloke

In retrospect, none of the subjects were 'surplus', although it didn't seem like it at the time. Some of the teaching was, however, dire: how is one expected to learn a language from grammar text-books and vocabulary lists? What is the point of being expected to be able to recite 'the dates' of the kings and queens of England? However, I wish I'd paid more attention to the non-science subjects that didn't come easily - they seem so much more interesting now. I was told to 'try harder', but what did that mean? No-one ever explained...

Edited By Kiwi Bloke on 20/07/2019 10:47:18

Oops! Too late to edit a slip-up in my post. Correction: Chaddock's method described in 1967, not '57.

Nasty, dangerous and scary machines, but I'll continue to use mine and hope to get away with it. The alternative doesn't bear thinking about.

In Oz & NZ, Jaycar sell a soft starter kit for power tools. I've just bought a second one. I think they are running low on stock. The design was published in Silicon Chip magazine, July 2012. It reduces the start-up kick quite well. The design is, I think, unnecessarily complex. In essence, a NTC thermistor, with a cold resistance of about 20 Ohm, is in series with the load, until it's shorted out after about 0.5 second. Not only is the kick reduced, for the benefit of the operator, but the inrush current is severely limited, which may be helpful in some electrical installations.

Probably would have been better with lubricant, assuming tool geometry and all other variables were OK. It's often helpful to bore with the tool 'upside down', working on the 'back' of the bore - the surface furthest from you (perhaps you did...). That reduces the risk of chips getting dragged between tool and work and spoiling the finish. Also, the feed is applied by conventional and familiar use of the dials, rather than having to subtract. But if it works OK, why bother?

Trimble wrote up 'his' method for piston ring manufacture in Model Engineer V153, No 3735, 17 Aug 1984 and later in Strictly IC V2, No 7, 8, 9, 1989. The method is very similar to that written up by Prof D H Chaddock (of Quorn fame) in Model Engineer V133, No 3319, 21 April 1957. I don't remember Trimble's ME article, but I'm pretty sure that he did not acknowledge Chaddock in his SIC articles, although it seems rather unlikely that he was unaware of Chaddock's method. Another example of Americans thinking they invented everything first (computers, powered flight, "Moore-pattern" scraping, etc., etc.)? I wouldn't be surprised if they claim to have been first to set foot on the moon... [with a nod to a recent thread, I should explain that this unnecessary, silly image is included for those who can't appreciate innocent tongue-in-cheek comments and sarcasm without help.]

A useful overview, which hopefully gives the information you seek, can be found at **LINK**

Don't despair, Dave. Wisdom comes with age. We can cast our pearls and smile at the antics of the young. They don't know any better, poor, semi-literate dears, although the arrogance of youth blinds them to this. I note that these ridiculous pictures-instead-of-difficult-words have been inflicted on the world by Apple. Well, you don't have to live on Planet Apple...

MG. Good question; where indeed is the evidence? IQ scores are often glibly stated (= assumed) to follow a Gaussian distribution, but it's very hard to track down raw data or to discover the characteristics of the study population. It's a mess and is probably too PC-sensitive anyway. I'd put good money on the distribution having a fatter tail of low scores - the result of developmental defects, injury, illness, etc. Quite a lot of brains get damaged by unfortunate events, but few of such events increase IQ. It's unfortunate that many (most?) medical data is assumed to follow a Gaussian distribution when it doesn't. This is assumption is really for the convenience of stats calculations, and, of course, is 'good enough' because it covers the majority of the population.

Good question. I suppose the answer is 'It all depends...' Major determinants will be the configuration and size of the job and the relative accuracy and suitability of the machines to hand.

One consideration. If you want to make something like a machine spindle housing, or quill, with a bearing housing at each end, a between-centres boring bar in the lathe can bore the central hole, be adjusted to bearing housing dia, then bore each housing, by swapping the bar end-for-end, with guaranteed concentricity of bores, all without having to change the set-up of the workpiece. I can't think of another way to do this so simply (and am happy to be corrected...).

Edited By Kiwi Bloke on 14/07/2019 11:18:53

Michael, we seem to crossing swords today - not my intention at all. I admire the nm-resolution (and, presumably, accuracy) of the gizmo, but was suggesting that, unless the rest of the apparatus was remarkably stable, such resolution was wasted, and the achievable performance would be determined by things other than the gizmo. A bit like putting a micrometer head on a micrometer frame made from rubber? Incidentally, could the system be used to check gauge blocks - simpler than optical interferometry, I'd imagine?

Michael: earlier, you asked why I found it difficult to believe that the 'camming out' was designed in. I was answering, not arguing with you. My original scepticism was in response to MK_Chris' post.

Wikipedia suggests that the 'camming out' was not a designed-in feature, and cites references. I think this is another instance of the harder you look, the confuseder you get...

Dave (SOD). Wikipedia says 'The Pozidriv was patented by GKN Screws and Fasteners in 1962'. (So you see that I'm just recycling dubious info. found on the web...). I skimmed the patent to which you linked (how does anyone read this stuff?), but wasn't clear that it was put into production.

Michael G. To design a screw/driver combination to 'cam out' at a desired torque seems pretty heroic, given that the applied axial force, let alone the alignment of the driver to the fastener can't be controlled in the field. And then the driver wears and it all goes to hell. The taper of the driving flanks (ignore the point angle) is, to the Mk 1 eyeball, far shallower than a Morse taper, so one might hope that the screw jams onto the driver, rather than it being a self-releasing taper. I just don't believe that the tiny flank 'slope' will produce a big axial force from reasonable torques.

Anyway, for whatever reason, Phillips and Posidriv drivers can 'cam out', although leaning on an unworn driver with sufficient determination seems to be able to frustrate the (Phillips) designer's supposed intention. If the designer really didn't care about the need for subsequent screw removal, then I still would call him an idiot. There's a lot of them about - especially in the auto industry, where dismantling for service and repair is commonly frustrated by lack of thought - or Machiavellianism.

Grinding a bit of the point off drivers is often worthwhile, allowing better driving flank engagement.

I stand by what I said: "That non-temperature-controlled apparatus thinks it can resolve 1nm repeatably enough to justify the scale's resolution? Delusional, surely. It reminds me of a friend tickled pink by his small bench-top oriental CNC mill. He discovered that his CAD software could work to microns, and sincerely told me that he could now machine things 'accurate to a few microns'."

I can accept that the piezo gizmo can, in effect, change its length by 1nm, repeatably and accurately, but I'm talking about the apparatus as a whole. I'm not clear whether the piezo gizmo is a positioner or a displacement sensor, and if a positioner, whether it's working 'open loop' or 'closed loop'. In any case, the gizmo seems to be attached to a complex mechanical assembly, with a complex, cantilevered shape, which presumably has built-in clearances, etc., and the whole lot is subject to temperature effects. Is the apparatus to which the gizmo is attached dimensionally stable to within 1nm? The chain can only be as strong/accurate as its weakest link. Hence my comment about the CNC mill.

Edited By Kiwi Bloke on 08/07/2019 06:43:20

If a cask ("What's a keg?" asked the ex-CAMRA member) contained anything other than ale (and "air" , I wouldn't touch it!

(Multiple edits to try to exterminate invasive emojis. Grrr!)

Edited By Kiwi Bloke 1 on 07/07/2019 10:03:11

Edited By Kiwi Bloke 1 on 07/07/2019 10:03:47

Edited By Kiwi Bloke 1 on 07/07/2019 10:04:27

Edited By Kiwi Bloke 1 on 07/07/2019 10:05:46

One often sees deep crescent 'oil pockets' applied to the upper face of horizontal sliding ways. If these surfaces can be exposed in use, the pockets can accumulate fine, abrasive crud, not just oil. My belief is that the pockets should be a feature of the upper surface only, the lower being smooth, so the way wipers can keep the muck out. The problem is that visible crescents = $$$ of added showroom appeal. This isn't to say that the lower surface shouldn't be scraped, just that one should aim for a relatively smooth surface.

That non-temperature-controlled apparatus thinks it can resolve 1nm repeatably enough to justify the scale's resolution? Delusional, surely. It reminds me of a friend tickled pink by his small bench-top oriental CNC mill. He discovered that his CAD software could work to microns, and sincerely told me that he could now machine things 'accurate to a few microns'. Hmm. But then he also thinks that scraping has been made obsolete by modern CNC machinery. Hmm again.

I find it hard to believe that the Phillips drive was designed to 'cam out'. The axial component must be very small, given the very small wedge angle of the drive flanks. Whether the driver 'cams out' or not will depend on the axial force applied by the operator (in my case, often a large proportion of my somewhat excessive weight) and the friction between driver and recess. And if it was an intended feature, the idiot designer didn't think about subsequent removal...

Good old-fashioned screwdrivers for slotted screws (remember them?) are, of course, tapered too. Is this a designed-in torque-limiting feature too? Parallel-tipped drivers are much more secure than tapered tips. Interesting that gun-makers of old often used screws with very narrow and deep slots, designed to be driven by the finely-tapered tips of 'turnscrews'. These fancy-named screwdrivers wedged securely in the slot, making slip-out unlikely. Useful when fixing very expensively-engraved actions into stocks, etc.

I thought that GKN patented Posidriv in the mid-'60s, so it was a late-comer, in competition with long-established Phillips, and the yanks adopted a 'not invented here' attitude. I think the popularity of the different patterns has more to do with commerce than engineering.

The Robertson drive is very common here in NZ. Note that its driver is also tapered, so might be expected to 'cam out', if the Phillips theory is correct. I have driven about 100 in the last few days, without any problem.

Posting after I should have gone to bed after a bibulous evening was a mistake. Thanks Barrie for reminding me about Emcoshop re spares availability: I should have checked before posting. A bit of detective work, cross-checking numbers and availability between ProMachine Tools (www.emcomachinetools.co.uk) and Emcoshop reveals the following:

A5A 020 011 Saddle (A5A 050 020 appears to be the cross-slide)

A5A 021 010 Cross slide feedscrew bearing / mounting plate

A5A 000 091 Longitudinal leadscrew nut (adjustable)

Above available from Emcoshop

A5A 020 060 Cross-slide nut (adjustable)

Above apparently not available from Emcoshop, but is available from ProMachine Tools, who can also provide A5A 000 091

Also needed would be A5A 020 050, the adjuster / retaining nut for the cross-slide nut, not listed by either supplier, but could be made easily enough. As expected, the prices are depressing. Hope this helps.

My experience is that months of immersion in molasses doesn't cause the base metal to be etched - but the rust goes.

It does rather seem that 'chelation' is a term that gets used without being strictly defined. Oxalic and citric acids get called chelators. Both remove rust. Both are acids and, as far as I know, form iron citrate and iron oxalate. Is this chelation? Are these relatively simple metal salts of organic acids chelates? I'm not getting much further in this particular quest for knowledge...

Same problem here. My early-model, second-hand Compact 5 arrived with an excessively free-running cross-slide feedscrew. The cross-slide feedscrew bearing in the alloy plate is also worn. The lathe shows no other evidence of significant wear or abuse. The nett result is that the un-balanced handwheel will rotate because of machine vibration, and the cross-slide will withdraw, unless the gib is adjusted more tightly than I like. The screw-nut backlash is not excessive. I have not used the machine for milling, but would expect to have to lock the slide after each feed adjustment. The worn feedscrew bearing makes it impossible to get a smooth rotation without allowing additional backlash at this bearing.

The idea of making a machine with no provision for replacement or adjustment of the feedscrew nut is ridiculous, and leads me to suspect that Emco never really expected the machine to be taken as seriously as it has been. The later modification - to provide for adjustable and replaceable cross-slide feedscrew nuts - is an admission that the original design is defective. But that's no help to owners of earlier machines. As far as I know, new saddles, and all the other bits which would be needed to revamp old-spec machines (except the nuts) are unobtainable new. Pity, although, knowing Emco prices, they would make an upgrade very expensive. One day, I might get around to re-engineering the thing. Until then, it remains in storage - a reminder that it's not only the Orient that can produce disappointing machines.

Machines are still rebuilt by scraping, presumably because of a combination of the accuracy achievable and the ease with which long dovetails, etc. can be attacked. No need to hoist heavy machines into awkward set-ups for machining or grinding. Slideway grinders are thin on the ground, and you'd still want to scrape. It's quite possible to scrape several thou off slideways, to remove the effects of wear, and then bring the surface to a few tenths all over, and to a similar level of accuracy of alignment to another surface. And all with hand tools...

It's hard and tedious work, although fascinating. I scraped all the sliding surfaces of a late model Senior Universal. It took ages, and much metal was shifted. It was hardly worn, but alignment was all over the place. Perhaps it was a Friday job, but it made a bit of a joke of the frequent advice to buy British if you want quality. For the next rebuild, I'll buy a Biax power scraper - to hell with the cost, I'm not getting any younger, damnit!

There are videos around showing Swiss commercial rebuilders of Schaublin (etc.) lathes, scraping away. At the other end of the scale, there are videos showing how bad slideways may be, when roughly hewn out of chineesium, and how readily they may be corrected by hand-scraping. There's actually a lot of it about...