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Member postings for Kiwi Bloke

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

Thread: Furrows on a milled edge
06/08/2019 10:06:58

Emco dropped the ball when they designed the milling attachment for the Unimat 3. It uses sleeve bearings, which can't be adjusted. The spindle end-float also can't be adjusted properly. The pulley is pressed onto the spindle - its position determines the end-float. It can be 'adjusted' by judicious use of press or more brutal techniques.

I have two milling attachments (don't ask...), both bought barely-used, but both have unacceptable play in the sleeve bearings, making the attachment effectively useless for milling. I would imagine that they have been like that since new and have not worn excessively. The result is as you have shown. I suggest you check your spindle for radial play.

Thread: Collet Chucks out of true
04/08/2019 11:12:01

'You get an item but it's not quite right so what do you do, use it or return it???' Good question, Tony. I suspect it depends to whom you try to return it. The people who understand that quality matters seem to be dying out - at least in the retail sector.

04/08/2019 11:05:07

There's been quite a bit of relevant discussion about these things in this forum already. If clocking the chuck taper suggests the chuck is 'out', it's a dud. The collet may also be 'out'. However, it has been pointed out that, even good-quality collets can't be relied upon to be perfectly aligned when the chuck is tightened. Applying a balanced torque (couple) to the nut may help. Collet 'pushers' are available. These are used to apply a temporary, radial force to what the collet's holding, as the nut is tightened. (Tighten a bit, clock it, tweak, tighten, rinse and repeat...)

As I understand it, these chucks were originally designed to hold cutters, not workpieces, so absolute alignment wasn't such a priority, given the short length of (most) cutters.

Thread: Dam Solution?
04/08/2019 10:52:41

However, on thinking about it a bit more, the laws of thermodynamics and energy conservation have to be satisfied, and I've conveniently ignored the energy accounting. I think I'll go to bed...

04/08/2019 10:50:03

Well, if no-one really understands how syphons really work, allow me my 50 cents' worth. I've skimmed the Wikipedia entry, so am now an instant expert and world authority...

The 'flying droplet' syphon is interesting. Elsewhere in the article, it's said that a syphon will work (assuming that it has been started, presumably) in a vacuum. But would the 'flying droplet' type work in vacuo? It seems to me that the discharge tube tries to empty, by gravity, just like water running out of a simk, thus reducing the pressure in the 'air chamber'. This 'sucks' up liquid in the feed tube. But this suction should only work if air pressure pushes the liquid up the feed tube, into the 'air chamber'. So, for this type of syphon, it seems to me that air pressure is needed to 'get over the hill', and gravity takes care of the flow down the discharge tube. Of course, the cohesive property of liquids helps the bulk flow in the discharge tube from breaking up and allowing air up the tube, to break the syphon. So, a combination of gravity and air pressure are required.

Does this mechanism seem a reasonable explanation for 'conventional' syphons too? ...Well, those not in vacuo, at least.

Thread: Steam powered RC aircraft
28/07/2019 09:40:45

S'pose it'll be illegal in Blighty - isn't there some law against 'carrying fire aloft'? Hot air balloons must be an exception. Perhaps I'm just making this up...

Thread: Guess the Chemical?
28/07/2019 09:36:07

If it's whisky - or indeed any other alcoholic beverage - I shall continue to use it in the manner to which I am accustomed, DIRE WARNINGS notwithstanding.

Thread: Setting wheel train on ML7
26/07/2019 01:44:50

Glad you're now all geared up. My apologies, my chart in fact suggested a 55T idler, not 50T as I said. I should have gone to bed instead of posting when tired...

Cutting the thread is easy enough - don't be scared. There's plenty of info out there. It's best to ensure that the cut is made primarily by only one side of the tool, either by making a small lateral movement for each in-feed, or by feeding down the flank of the screw, by setting the topslide round by half the included angle of the thread. Take a very shallow cut first, and check the pitch is what you intended, then gently does it...

Good luck.

Thread: Permission to Copy
25/07/2019 22:09:31

Brian Perkins' VW was published as a construction series in Strictly IC Magazine (USA), Robert Washburn's excellent mag. Sadly, I believe that both gentlemen are no longer with us.

Thread: Setting wheel train on ML7
25/07/2019 11:20:22

40T driver. This meshes with 38T, which is keyed to 20T, both on 'first' stud. The 20T wheel lies outboard of the 38T wheel. The 20T meshes with a 50T 'idler' on the 'second' stud, which in turn meshes with 50T on the leadscrew. My chart suggests a 50T idler. You have a 55T idler, which seems OK, if it fits - obviously, the number of teeth is unimportant. The first stud is on the higher slot on the banjo, the 'second' stud on the lower slot. So your setup looks nearly there, the driver seems to be where it should be, so it's just a matter of getting the 20T and 55T into mesh.

Meshing adjustment. Slacken the banjo clamp nuts, and swing the banjo downwards, to give you 'wriggle room'. Get the mesh of the idler 55T and leadscrew 50T wheels correct, then the mesh of the 20T wheel on the 'first' stud with the idler, then swing the banjo up to get the mesh of the 38T correct with the driver and clamp the banjo. To align with the idler, the leadscrew gear will have to be spaced outboard with a spacer or small dia. gearwheel acting as a spacer (you seem to have done this).

Don't mesh the gears 'tightly', but allow a little backlash. Some advocate a strip of thin paper between gears when setting up, to ensure some clearance. Lubricate the gears. Slideway oil is good - it doesn't get flung off as readily. Lubricate the studs too.

Hope this works - working from charts and memory, and haven't checked the maths (it's getting late). I have the luxury of a gearbox, so haven't done this very much since the gearbox arrived...

Edited By Kiwi Bloke on 25/07/2019 11:25:51

Edited By Kiwi Bloke on 25/07/2019 11:27:30

Edited By Kiwi Bloke on 25/07/2019 11:31:19 (I said it was getting late...)

Edited By Kiwi Bloke on 25/07/2019 11:38:37

Thread: CARBIDE BURRS
25/07/2019 10:58:23

Walk into Comwell Tools or Buck and Hickman. Branches throughout UK. Both have web sites. 'Burrs' finds the things within the sites.

Thread: How to cut metric threads on an imperial lathe and vice versa.
25/07/2019 10:01:27

After all that there has been written about threading calculations, confusion persists. The dissenters are correct. Perhaps gear trains and their calculation confuses people. Although Pete and Duncan have already explained, and not wishing to steal their thunder, let's look at it another, possibly simpler, way.

Say you have a lathe with an 8 TPI leadscrew. Each leadscrew revolution moves the carriage 1/8", or 25.4 X 1/8 mm. Multiplying top and bottom by 5, to get the calculation into whole numbers, gives 127/40 mm. So, in order to cut, say, a 1mm pitch, the leadscrew must revolve 1 / (127/40) = 40/127 revs. This must, of course, happen each spindle revolution. This is where the changewheels come in, but we don't need to bother with that complexity. The problem is closing the half-nuts at the right spindle and leadscrew relationship. The point is that 40/127 is inconvenient because the smallest whole number that can be used to multiply this fraction by, in order to get a whole-number result, is 127. Only then will the leadscrew and spindle be correctly synchronised. So, the suggested method would work if one had a 127 tooth pinion on the thread dial indicator...

Edited By Kiwi Bloke on 25/07/2019 10:02:20

Thread: Wiggler or edge finder?
22/07/2019 09:16:57

Clive. 'I suspect that your stiff "General" brand edge finder was intended to be used with the light line method rather than the kick off method.' Well, of course, it could be used this way, and perhaps it should be, as it's the most sensitive method. But my point was that the manufacturer's instructions are as I quoted, and they seem bizzarre. I'd be interested to know whether anyone has used General's method.

'Mentioning GHT reminds me that his analysis of how the things operate is wrong. Nothing to do with tilt. Just a matter of generating enough force between probe and ball for it to drive sideways along the surface. Once its moved a fraction off axis centrifugal force takes over and it flies.' I don't remember GHT's explanation. I'm not sure that I understand what you mean by 'enough force between probe and ball for it to drive sideways along the surface.' I may have misinterpreted what you meant, but, to avoid confusion, the probe's ball or cylinder does not drive itself along the surface it is contacting, as a result of friction at this interface. The sideways force is generated by asymmetric forces between the chuck and the ball end of the probe sitting in the chuck, once axial alignment is lost. Experiment confirms that the tip of the probe is driven sideways, from the chuck, but doesn't pull (or push) itself sideways. If centrifugal force deflects the probe, things may have got rather hairy. Better to arrange things so the probe doesn't whirl free, if possible.

Thread: Dangerous 2" Scale BB1 Boiler
21/07/2019 11:55:37

May I suggest that the above extract from the boiler regs is published regularly in ME? Whilst I would expect boiler inspectors to know this, how many builders would know to first pressurise their newly-built boiler this way? Not me, certainly - although I'm not into steam.

Thread: Wiggler or edge finder?
21/07/2019 01:49:33

Here's another twist. From an estate sale, I got a 'General' (General Hardware Mfg. Co., Inc., USA) 'Universal Wiggler and Center Finder'. It's of the spring chuck / collet / multiple probes type in appearance, but is intended to be used differently.

Its instructions state: 'Insert the large ball of attachment into spring chuck. With the spindle turning, make the ball run true by holding any blunt object against it. Apply a thin coating of layout blue on the ball and feed the work up to it until the blue is barely wiped.' Note, layout blue is specified. I suppose you're supposed to use a small brush, and ensure the probe is not deflected. No alternative method of use is given.

The chuck can be tightened, but, even at its slackest, it holds the probe fairly stiffly and 'roughly', and it's not suitable for use with the usual wiggler kick-off technique. How one is supposed to get the ball to 'run true' accurately, by the suggested method, is beyond me, but, since the thing is surplus to my requirements, I've never bothered to try seriously. I find it difficult to believe that this method is used, if for no other reason that one needs to be able to have a very good, close-up view of the probe in action. Anyone ever come across this method in use?

I have a flaky memory of GHT commenting on a 'stiff' wiggler that didn't kick-off consistently. He considered it useless, until someone pointed out to him that it was not supposed to kick-off. Memory thinks one was supposed to look for disappearing light between probe and work, so the probe had to be set running true, as above. Could be mistaken - memory nearly full, and stuff is being dumped to retain a little capacity...

The 'General' set also contains a cranked 'probe', intended to hold an indicator, which can be held stiffly enough by tightening the chuck. Perhaps those sets containing such a 'probe' are intended to be used as above, and not to 'kick-off'.

Thread: Surplus subjects learnt at school.
20/07/2019 10:46:21

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

Thread: Crucible for annealing cast iron piston rings
19/07/2019 23:01:30

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

Thread: Angle grinders - Dangerous or not
19/07/2019 06:05:48

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.

Thread: If it ain't broke don't fix it - or should I?
19/07/2019 05:54:02

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?

Thread: Crucible for annealing cast iron piston rings
19/07/2019 05:46:17

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... cheeky [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**

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