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Member postings for Martin Kyte

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

Thread: 5BA Threads
27/09/2020 17:03:15
Posted by Clive Brown 1 on 27/09/2020 16:48:47:

Reeves sell some even BA cap screw sizes at rather less cost.

Not countersunk hex socket screws they don't

regards Martin

27/09/2020 15:38:32
Posted by Keith Long on 24/09/2020 22:31:46:
Posted by Martin Kyte on 24/09/2020 22:20:03:

Someone is now going to astonish me with a supplier no doubt.

Yes, Cromwell Tools have them in their catalogue, you might be a bit shocked at how much they cost though.

Wow, at £2.75 each for the 6BA hex socket countersunk I'm sitting on a fortune not to mention all the other sizes and varieties.

:O)

Martin

Thread: Recycling Fire extinguisher pressure gauges
27/09/2020 15:31:36

Are gauges not just indicators and have nothing to do with boiler safety at least on models. No idea what the boiler test procedure is but I would have thought it would involve setting the safety valves to some external full size calibrated guage.

regards Martin

Thread: Myford set up.Time to get it right.
26/09/2020 17:29:29
Posted by paul coombs on 26/09/2020 17:16:11:

Not sure what MT socket is? However, that wouldnt explain the movement though would it?

The spindle taper is 2 Morse same as your test bar.

Take the chuck off, clean the spindle taper well and insert the test bar. Now do your test again. Do ensure you are just pulling the test bar and you do not have your other hand on the cross slide. Ideally put your other hand in your pocket.

regards Martin

Thread: Restoring a wooden tool box, help needed
24/09/2020 22:46:56

Once you have stripped back to bare wood damp the side down over a period of time (put it in a bin bag with some damp newspaper for example and then clamp up to some strong straight battons and allow to dry out again.

regards Martin

Thread: What sort of light source to use a strobe disc?
24/09/2020 22:36:39
Posted by Neil Wyatt on 24/09/2020 21:27:36:

Despite all the scepticism, back in the '70s my Dad had printed card discs that were used to check the speed of record turntables.

They worked under a filament lamp but were best with some fluorescents - depending on the persistence of the phosphor I guess.

It's nothing to do with superhuman vision. Persistence of vision actually helps the effect.

Neil

I'll go with that. You aren't trying to see the flicker of the bulb but the contrast created on the disk. Eyes are logarithmic so lower intensity will help. Human retinas will respond to approx 4 photons minimum and frogs can do single photons so I am told. It's not enough to generate a neural response at that level but the molecular machinary is active down to that sort of photon count. As Niel says the pigments take a little while to switch off again so there is some integration of coherent images (static black lines on your disc) which would increase the contrast. Interesting thoughts.

regards Martin

Thread: 5BA Threads
24/09/2020 22:20:03

As I was completing the assemply of a small brass bracket yesterday using a couple of 6BA countersunk hex socket screws it struck me that these must be as rare as hens teeth these days.

I inherited the Lab's old stock of BA fasteners about 20 years ago so they are possibly as much as 50 years old by now, maybe more. I did have the passing thought that maybe I should not be quite so profligate with them but then realised how little the stock had gone down over the last 20 years maybe not.

Someone is now going to astonish me with a supplier no doubt.

regards Martin

Thread: Chatter
24/09/2020 09:43:53

Don't just think about the buissness end of the boring bar. The back end is long enough to act as a tuning fork. Either swap to a very much shorter bar, cut the end off, clamp a mass to it. and abosutely ensure that all the clamp bolts are screwed down tight. If that packing piece goes the whole length of the boring bar add some toolmakers clamps.regards Martin

Thread: Home workshop accuracy & tolerance?
23/09/2020 20:27:23
Posted by Neil Wyatt on 23/09/2020 17:16:57:
Posted by Martin Kyte on 23/09/2020 11:26:40:

Interesting to note that when I made my telescope mirror I was able to achieve a variation of less than 50nm over a 10 inch glass paraboloid disc surface using purely hand work and simple optical measurements . It still astonishes me.

regards Martin

A classic example of where relative accuracy is what matters. Things like Ronchi tests make it relatively straightforward (if a long drawn out process, requiring skill) to achieve a parabolic mirror to within an extreme level of accuracy.

But a hand-ground a mirror is not made to exactly a particular focal length - something within a few inches of nominal is fine.

To compare with what we do, we might finish a shaft to within 0.0002" diameter but the accuracy of the actual circular profile may be accurate to within 10 or 100 times that.

Neil

Actually ou can get to better than 1/4 to 1/2 an inch without too much trouble especially as you can measure the radius of curvature when still on the grinding process rather than the polishing although most people make the mirror and then design the rest of the scope round it.

I does however illustrate my point about repeatability. To produce two identical mirrors with the same focal length takes much more effort.

Industry cheats there too. The chinese optics manufacturers effectively beat the rest of the world by high volume output and then measuring and grading what came off the line according to quality with the best lenses and mirrors commanding the highest prices. I am told similar things used to happen in race engine building when using production engines. Buy a slew of engines, strip and measure everything and build a few out of the most accurate parts. Tecnically it's a production engine but the chances of all those 'good fit' parts finding their way into the same unit commercially is remote.

As the man said "There is no substitute for cheating" or when someone is admiring that perfect model "yes but no one see's all the bits you threw under the bench"

regards Martin

Thread: PP Thornton (successors)
23/09/2020 20:00:53
Posted by Michael Gilligan on 23/09/2020 18:32:18:
Posted by John Haine on 23/09/2020 17:53:09:

Well, that was an interesting read Michael! Not entirely clear, but it seems that they produce the cutters using in effect the "button" method to impart the required profile to the teeth, the "buttons" (or their equivalent) being made from carbide, ground to shape using diamond wheels. The "soft" 12-tooth HSS blank is turned on a form-relieving lathe after gashing, then vacuum heat treated to harden. Doesn't sound easy to reproduce at home!

.

Not forgetting the pantograph reduction, and the inspection work

.... suddenly, it makes the price look very reasonable

MichaelG.

Especially as they do a sharpening service at half the price of the cutter.

regards Martin

Thread: Home workshop accuracy & tolerance?
23/09/2020 12:35:11

Mind you it was easier to get quality rules.

Martin

Thread: Covid causing mental health issues.
23/09/2020 12:18:35
Posted by pgk pgk on 23/09/2020 00:58:29:
Posted by Martin Kyte on 22/09/2020 22:33:27:

So if the population is 3 and they have IQ's of 50 100 and 120 the average is 270/3 = 90 which means in this case only 30% of the population is below average IQ. Maybe it's not so glaringly obvious after all.

regards Martin

IQ was always the average of the population= 100 but with any statistic and particularly when it is determine by low population numbers you have to eliminate the wild cards. Statistically invalid but for your example the new IQ would be 110 (on the old scale) so 1 each above and below and a wild card.

pgk

Is that not the median rather than the average?

regards Martin

Thread: Home workshop accuracy & tolerance?
23/09/2020 12:14:11

. . . and then there is that age old process called easing the fit, used where you have generated your exactly mating parts and have to open everything up to make it run. I have done my fair share of that in the past.

regards Martin

23/09/2020 11:26:40

Interesting to note that when I made my telescope mirror I was able to achieve a variation of less than 50nm over a 10 inch glass paraboloid disc surface using purely hand work and simple optical measurements . It still astonishes me.

regards Martin

23/09/2020 08:50:24

I would say that we were able to work to very close limits when required. What we probably cannot achieve is repeatability by which I mean we cannot expect just to rechuck/recollet blanks and dial up the same settings and expect exactly the same sized part. Working with dead centres, lapping, scraping etc are all techniques we would use rather than precision grinding for example. We tend also to have the luxury of swapping the order in which we make stuff. For example turning a shaft to fit a reamed bore rather than having to produce a bore to fit the shaft. Probably the biggest limitation is surface finish with less rigid machines, slower speeds and less sophisticated cutting tools.

Lastly we get to make more parts until we get one that fits which you can't really do commercially.

regards Martin

Thread: Covid causing mental health issues.
22/09/2020 22:33:27
Posted by David Noble on 22/09/2020 21:52:23:
Posted by pgk pgk on 22/09/2020 19:15:21:

Posted by martin perman on 22/09/2020 18:52:13


...50% of the population have below average IQ...

pgk

I know this is glaringly obvious but it hadn't dawned on me before. It explains a lot!

David

So if the population is 3 and they have IQ's of 50 100 and 120 the average is 270/3 = 90 which means in this case only 30% of the population is below average IQ. Maybe it's not so glaringly obvious after all.

regards Martin

22/09/2020 20:51:15

The short answer is stress pushes people who are close to the edge over it. The Covid pandemic not only increases stress for many people but the neccessary social distancing can remove the very things that alleviate that stress.

Those in robust mental health will get through pretty much intact, those whose mental health is more fragile may not.

What your workshop is to you the swimming pool may be to someone else.

regards Martin

Edited By Martin Kyte on 22/09/2020 20:51:36

Thread: Balance Weights King Loco
22/09/2020 08:36:44

bump

Thread: which older mill to complement a ML7?
21/09/2020 20:20:01

I don't think it was by chance that Myford commisioned the VMB/VMC mills but as a compliment to the ML7 and the Super 7 so whilst I am not suggesting those mills and only those mills they will be a good yardstick for anything else you come across. I have a VMC and have been very pleased with it. Especially as I picked it up for £500 when the Lab decomissioned it. I had my eye on a Centec but someone beat me to it.

regards Martin

Thread: Balance Weights King Loco
21/09/2020 11:45:13

Leading wheel

weights2.jpg

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