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Member postings for SillyOldDuffer

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

Thread: New Haven movement; Questions from a beginner
28/09/2020 10:33:56

Just for info, digging around the web, on the National Clock Repair website:

In England, Jerome & Co. Ltd. sold Jerome clocks for New Haven until 1904, when New Haven purchased the English firm outright.

The English firm Jerome & Co. Ltd. was a back reference to the Jerome Manufacturing Co, whose products they imported. In the US Jerome were a very successful maker of mass-production clocks, 444,000 in 1853, until a bad investment bankrupted the company in 1855. New Haven bought the wreck, and the new combine was great success, not finally biting the dust until 1960.

I'm intrigued by my granny's clock; in theory a British bought New Haven clock should have been branded 'Jerome', not New Haven. Did my great granny, who lived in a sea-port, buy a grey import? We'll never know...

Another curiosity; 'Jerome had made a historic contribution to his industry when he substituted brass works for wooden works, said to be "the greatest and most far-reaching contribution to the clock industry."' Strange because brass clock movements were made in England long before Jerome's time. I think it means Jerome was the first to use brass in cheap clock movements, replacing wood, resulting in much more reliable clocks. Back then British brass clocks were expensively made by traditional methods so they were an easy target for affordable mass-produced alternatives. It's a tough old world.

Dave

Thread: Restoring a wooden tool box, help needed
27/09/2020 21:28:33
Posted by Rod Renshaw on 27/09/2020 20:53:10:

Thanks Ian. I will try the meths and fire, it sounds like something a wizard might do!

Thanks John. If the meths does not work I will get some oxalic acid and try that.

Rod

Turps and Turps Substitute are both light oils, so although they dissolve out thicker oils the residue is also oily and bad for glue. I'd try scrubbing and rinsing the turps off with with a good dose of meths - a two stage clean.

I like the idea of setting fire to a surface splash of meths as a way of drawing out deeper oil, but it's an outdoors job with a bucket of water. Oil soaked wood and burning meths - what could possibly go wrong?

smiley

Dave

Thread: Copper Plaque Identification
27/09/2020 15:16:39

My guess is Chadwick's were a News Agency.

A news agency depends on journalists bringing it stories, and journalists would want to negotiate top prices from one of the senior men. It fits the 'we love you as much as you love us' tone of the sign.

There are about 30 small news agencies running in the UK today. They mostly collect local news, but some specialise in sport. Rather than the press sending their Ace Boy Reporter to Bodmin on the off chance the Magistrates Court will have an interesting story, facts and pictures are collected locally and sent up the line.

The firm isn't in Graces Guide because they focus on Engineering.

Dave

Thread: Cheap Milling Vice Question
27/09/2020 12:28:24

No-one knows unless they've tried a real one.

I've got the same generic type and it's fine. Mine is painted green and has a simpler handle, so it may not be from the same factory, which is part of the game. Almost any firm with light-engineering capability could make them.

Maybe this example is cheap because the maker over-produced a well-made vice and is trying to reduce his losses. Or it could be cheap because it's a reject or was made too cheaply. Too cheap means fragile, off-true surfaces, jaws that lift, and a nasty lead screw etc.

It's probably reasonable but there are no guarantees. Buying inexpensive tools is always a gamble. Less so today I think than in the past. Before WW2 there was a sharp divide between good tools and utter rubbish and very little in between. Much less clear-cut today because many tools are in the middle; not the best by any means, but far from being a waste of money.

If a tool has to be unambiguously fit for purpose, there's no alternative to paying full whack for the industrial version. Unfortunately prices rocket to meet the higher specification. How about a nice Kurt? It has to be a new Kurt, because second-hand may be damaged or worn.

I hate empty descriptors like 'quality' and 'decent' in connection with tools, preferring instead to think in terms of "fit for purpose" and "value for money". If this vice is a good'un it's certainly 'value for money', but there's a risk it won't be fit for purpose. It's particularly unlikely to be fit-for-purpose used for heavy accurate clamping in a busy professional workshop, but mine was OK.  Note a vice that's too big for the machine isn't 'fit-for-purpose', and this one is quite chunky.

We all have to make judgements about how reliable our tools need to be. In my case, the answer is 'not very'. Provided they do what I need, which is relatively genteel, I don't need to waste money on tools that last. It's not a perfect system because there's a fine line between inexpensive and cheap and nasty! I come unstuck occasionally, but don't moan about it because on average the balance is strongly in my favour.

Dave

 

 

 

 

 

 

Edited By SillyOldDuffer on 27/09/2020 12:30:31

Thread: Steam Raising Blower
27/09/2020 10:38:24

Just some theoretical observations about motor impellers that might avoid a really unlucky selection!

Most impellers help cool the motor without putting a significant load on it, ie most of the motor's output is still available on the shaft, not absorbed moving air. While it's reasonable to use impellers as a fan they won't shift air efficiently - too small, and generally crudely made. A table fan has whacking big aerofoil blades on the front while the motor inside cooled by a tiny impeller made of bent metal at the back.

Some electric motors, like the Universal type, can run away off-load and damage themselves. On these the impeller may be made deliberately inefficient so that it absorbs enough power at high speed to stop the motor running away. This type of impeller might disappoint in a blower.

Fans work more efficiently at high-speed rather than low, but the blade design becomes more critical. They're better at moving large volumes of low pressure air rather than creating a vacuum or compressing air. Efficiency goes to pot when either the input or output is constricted. So a top-notch design optimises the blade, motor power, rpm, volume, and pressure differential.

But for steam raising, I don't think fan efficiency matters much, and it might even be bad - too powerful a blower might cool the fire so much it goes out or lift loose fuel out of the firebox before it's delivered heat.

As electric blowers have generally been doing a good job on steam locos for donkey's years I don't think their design is critical, but the above might explain occasional failures and why some blowers outperform others.

Wild guess on my part, but I suggest:

  • An aerodynamic ran running with its tips close to the casing.
  • Fan speed close to it's design rpm, with the facility for the operator to adjust speed for best results.
  • Flared top on the outlet.
  • An inlet tube long enough to allow an adjustable air-intake near the smoke box and away from the fan. Purpose to allow the operator to bleed air into the system so the fan has enough to bite on. Rather than relying on the fan struggling against back-pressure to pull a vacuum, it would allow the operator to create an updraft, or not, for best results.

Probably all been tried already, a hundred years ago!

Dave

Thread: Vacuum Pump Advice Please!
26/09/2020 18:49:23

Pleased to report the pump is much better.

Took it apart again and went over it carefully. There are no valves.

I believe the improvement is down to putting oil in the right place. Not just a lubricant, I believe it's part of the sealing system. When the pump is running I think oil is pulled out of the padded reservoir and into the gap between the cylinder end and the rotor block where it fills the gaps and makes it difficult for air to leak past the rotor blades. I cleaned a thin layer of caramelised oil off the end-face that may have stopped oil flowing into the gap properly.

Anyway, the pump now pulls a markedly stronger vacuum on a rigid cylinder. Wish I could find the missing gauge to see how good or bad it is!

Dave

Thread: Macrome tools
26/09/2020 15:06:38

Grace's Guide as per Hopper's answer is a good place to start. I think more info is available if you subscribe, but from what's public the earliest mention of Macrome in 'Engineering' is 1929, and the latest is 1959. Mentions the firm moved to Wolverhampton in 1949, so the road must be named after them.

The 1929 entry is about their patent process for hardening tool steel, but the firm also made hand tools. Later they seem to have specialised in the tool toughening side of the business, offering to toughen any tool offered by customers. The purpose was to make tools last longer, and Macrome look to have got at least 20 years profit out of it.

Specialising in hardening tool steel may have been what did for them. In 1929 a process for improving tool-life would have sold like hot cakes. By 1959 tool-steels were standardised and industry was well into carbide.

What makes a tap and die set 'quality'? As all but the very worst examples cut accurate threads, 'quality' must refer to how long the tools stay serviceable. A cheap set might not be sharp to start with and is likely to blunt quickly. Also likely to be brittle rather than tough. A 'quality' set would fix theses issues in order to last longer doing exactly the same job. Reliability matters most in a busy workshop; taps and dies don't need to be wonderful in mine! I'm still using a cheap carbon steel BA set bought circa 1970. Maybe does 3 or 4 threads a year, sometimes none.

Work and neglect destroy quality. Not much difference between cheap and quality tools once they're knackered. Only the condition of Dell's set matters and it could be anything from as-new to worn out. How well are threads cut? Brass is a good test of sharpness; taps and dies that struggle to cut clean threads in brass, still work well on mild-steel. Good threads in brass are excellent news, if the set can't cope with mild-steel, it's done for.

Dave

Thread: Quality Problems With the Sieg sx2.7
26/09/2020 10:40:45

Posted by Nir Somthing on 26/09/2020 08:16:56:

...

Since everyone seem to not trust my measurements...

Nir

Welcome to the forum Nir.

Apologies of course if you know what you're doing, but the suspicion the measurement are untrustworthy is based on experience. As taking accurate measurements is a skill in itself, it's not unknown for newcomers to buy a mill, micrometer and DTI and immediately confuse themselves and the forum by measuring all the wrong things badly.

Another mistake is to strip the machine down, give it a good clean, and then do a poor job of reassembling it.

These machines are what they are - hobby machines, built down to a price. My experience is the design is sound, but assembly is done quickly and inspection is high-level only. All my machines have needed minor fettling, apart from my milling machine which was fine out of the box.

There's a hint big resellers and those who build relationships in China get better machines than those who buy them by the container full. I suspect factory and customer rejects are sometimes sold on by non-specialist internet traders, which is why I prefer to deal with an established UK business. The machines certainly aren't race tuned by master-craftsmen, but you can do that yourself.

Occasionally dud machines are sold in the UK by reputable suppliers, and the fix is to replace them or get money back.

You may have a dud, but may I suggest you start by using the machine to cut metal rather than assume it's no good based on measurements? In my experience, cutting metal reveals problems in a way measurement and inspection don't. If the machine cuts metal successfully, all measurements are irrelevant! And the forum is much better at explaining photos of bad cuts than it is at decoding showers of numbers, especially when some of them appear contradictory.

Measurements are vital after bad cutting is detected. They pin down problems and quantify what needs to be done. But one step at a time. For example, I'd rather test tram (head lean) in the first instance by flattening a test piece. Any error will become visible on the test plate, is easily measured, and it may not matter. If the tram is too wrong, measure and reset it with a DTI on a rotating boom.

Trained men assess machine tools by measurement but it's much harder to do correctly than it looks! I recommend beginners avoid precision measuring for this purpose at first. Until skills have been developed precision measuring done wrongly can be grossly misleading.

It's unfortunate these machines are expensive in Israel, presumably due to import costs. We can be sure the extra money paid by Nir didn't find it's way back to the factory, or get spent anywhere in the supply chain on improving the tool!

There's no hope of getting tool-room quality from an off-the-shelf Far Eastern Hobby Mill. For that expect to pay about six to ten times as much for a mill from the Industrial range.

If Nir was in the UK and really requires the best, I'd suggest exploring the second-hand market for a high-end machine in good condition. But finding one and exporting it to Israel sounds like a lot of expensive bother, especially if it too needs repairs. So, I'd see what the Seig does to metal. Provided it isn't a dud this class of mill is certainly capable of good results, but it may need fettling.

Fingers crossed this works out OK for Nir,

Dave

Thread: Help requested wiring VFD - Again!
25/09/2020 18:49:58

Have you tried Pn04=1 (Command from panel), and Pn03=1? Then press run, and twiddle the pot. Should prove the VFD is working.

I think you have the pot wired correctly (though what value is it?) but it's not clear where the external start input is. Just a guess, but it may be done by putting +5 on either FWD or REV. ie they are Run FWD and Run REV, rather than just direction options.

Dave

Thread: What sort of light source to use a strobe disc?
25/09/2020 17:18:35
Posted by Neil Wyatt on 25/09/2020 14:39:24:

Of course anyone who still has a filament bulb handy can do the test for themselves...

I just looked up 'blub smash slow mo' on you tube and in the first example you can clearly see the reflection of the filament (the filament itself is over exposed) pulsing at mains frequency. It doesn't go out but dims noticeably.

Neil

I sometimes notice 50Hz flicker on old bulbs out of the corner of my eye. The effect is more obvious on 40W bulbs than 100W bulbs.

I've read somewhere than machine lamps are run at low voltage partly for safety reasons and partly because thick high current filaments in low voltage lamps cool down more slowly than the thin filaments in high voltage bulbs of the same wattage.

Day full of appointments but whilst in my Sunday best waiting for the next one I programmed an Arduino to flash a yellow LED. (I believe these don't have any phosphor, just light off the junction.) I can just see a trace of flicker with 2mS pulses (500Hz). Distinct flicker at 150Hz and no doubt at all at 50Hz. Anything below 25Hz is sick making annoying until individual flashes appear at about 5Hz. If it has to flash, 1Hz is bearable!

Whoops, time to hit the road again!

Dave

Thread: Covid causing mental health issues.
25/09/2020 13:44:23
Posted by Hopper on 25/09/2020 12:25:00:
Posted by SillyOldDuffer on 24/09/2020 14:37:43:

Posted by Neil Wyatt on 24/09/2020 12:42:51:

... In fact IQ tells us very little that is useful ...

I've certainly found that whether someone is 'clever' or not is a definitely not a measure of their worth.

Neil

I'm not even sure it's worth measuring IQ because the whole concept is built on sand! There's a built-in bias because even with careful design IQ tests depend on education and culture, which aren't intelligence. They detect who is good at answering IQ test questions, which is only one of the many forms of intelligence....

And yet there is a definite correlation between IQ and income, confirmed by multiple studies. Those with higher IQ tend to have higher incomes over a lifetime, as a general trend. So IQ tests must measure something of practical use in life other than just the ability to take IQ tests.

Correlations can be misleading too. In the UK for over 30 years there was a strong correlation between violent crime and the sale of White Goods. Yet most people who buy washing machines and fridges aren't criminals. In the same time-frame, the equally strong correlation between violence and ever increasing sales of leaded petrol might seem a more likely cause, except that was unproven too as far as I know.

I suggest the link between income and IQ is as much to do with education and culture than intelligence. Coming from a wealthy well-educated family is more strongly linked to high income than having a disadvantaged background. Not just a matter of inheriting cash and property, it's because a successful background creates more opportunities and the contacts and confidence needed to do great things. Clever people can and do make it on their own merits, but it's much easier to become president of the USA if your dad was a billionaire.

Like a lot of things IQ Tests are useful up to a point, but it pays to understand they may not be valid. For example, IQ scores are rising across the world except in developed nations were it is falling. If IQ tests really measure intelligence, then most forum members reading this are in the group becoming more stupid! Lead in petrol again?

Don't panic, it may be the difference is down to culture. Maybe educated people in developed countries don't care about IQ much - we've moved on.

Just before retiring my workplace got emphatically into competences; ie acquiring skills and measuring performance using them against objectives. No idea if they still do it - as a way of getting people to increase output at reduced cost, I wasn't convinced! Created a lot of stress and inefficiency, but may have come good - I left before any benefits emerged.

Dave

Thread: A vacuum engine
25/09/2020 09:57:59
Posted by Ian Johnson 1 on 24/09/2020 21:57:51:

... That's a nice little engine, but only run for a few minutes! maybe that's why the plans were free? But I'll probably go with the plans I have and see how it goes.

IanJ

I admit to being a Jan Fan, but I doubt the trouble is with his plans. Jan's published many interesting engines, and some of them are difficult. For example, my first attempt at his Coffee-cup Stirling didn't work until I'd fixed all the tiny leaks and reduced friction at all points to the minimum. As built the engine didn't run, several hours later it did. Same design, same parts, but everything freed-up, flywheel balanced and the timing adjusted. Initially reluctant to start with run times in minutes, now it runs on an electric element for hours on end.

I noticed, in the failed state, that brass parts corroded, cause unknown, maybe heat, condensation and oil coupled with acid fumes from the sealant. The problem disappeared after the engine ran properly. Delicate engines may need repeated cleaning in the early stages: apart from debris due to machining and parts wearing in, if they're not working properly oil gums up, liquid collects etc etc.

Also a fan of Stewart Hart's Potty Mill engine. It's much less fussy and you can squirt high-pressure air into it. Provided the timing is right, and the parts turn freely, even a high-friction build will run. I found it a good balance of challenges. Made me think but none of it was too hard for this beginner.

Dave

Thread: Problem with tapered roller bearings fitted to mini Lathe
25/09/2020 08:56:20

Threads like this are jolly useful.

Changing the bearings on a mini-lathe isn't a matter of simply slipping the old ones out and popping in a couple of replacements! It would be straightforward except the bearings are a very tight fit. When I stripped the internal gear on my mini-lathe I got the spindle bearings in and out with brute force and ignorance. I was seriously concerned the bearings would be damaged, and I'd have to buy new and try again.

Got away with it, but reading this thread first would have saved a lot of bother. It was before I discovered this forum and how good everyone is at answering questions.

Thanks for sharing Patrick, and well done for fixing it.

Dave

Thread: Vacuum Pump Advice Please!
24/09/2020 18:27:07

Oh dear, not to expect too much of it - the worst answer!

The vanes slide in and out freely - no springs. The construction doesn't seem to provide much of a seal at the ends which implies low compression. Could be it's a dental spit sucker, designed to run continually without enough power to disembowel anyone!

Got a vacuum gauge and a pressure either of which would show how good or bad it is - both are Absent With Out Leave.

crying

Dave

Thread: Chatter
24/09/2020 17:21:04
Posted by Peter Cook 6 on 24/09/2020 14:28:52:

A quick look suggests that CCGT tips are supposedly for Aluminium or non-ferrous metals while CCMT are for steel and ferrous metals.

What advantage would there be in cutting steel or cast iron with a CCGT Tip?

Jason's answer is spot on, but may I add that most of the advice on the web and in catalogues about carbide inserts is aimed at industrial users, not us?

Industry go for fast deep cuts because time is money. They have powerful, fast heavy machines designed to drive carbide to the max, and their operating conditions and best choice inserts aren't the same as ours. A production mill might run 5 times faster than your Seig, have several horses turning the spindle and it will be built like a tank. And cost as much!

So Industrial guidelines aren't completely relevant to 'our' lighter and slower machines. It's been discovered - for example - that the sharp inserts designed to allow the professionals to cut non-ferrous metals at high-speed are rather good for hobby machines cutting mild-steel.

Don't be afraid to experiment.

Dave

Thread: Vacuum Pump Advice Please!
24/09/2020 16:55:32

Another fine mess I've got myself into. I'm building a clock (which doesn't work yet) intending to run the pendulum in a vacuum. Years ago I bought an Edwards 3B vacuum/compressor from a nice man at a car boot sale who assured me it was a high-vacuum pump. Was he a naughty fibber?

dsc06317.jpg

dsc06311.jpg

Got it home, fired it up for a quick test, seemed to work but not good today. The motor runs but the compression and vacuum fail to impress. No manual or info on the web.

Suspected it needed oil and have the right sort. Sprayed myself & workshop, I think by filling the pump through the wrong hole at the top. Fortunately the big output filter was off and the oil came out without fuss. On second thoughts this type of pump may be medical, and not meant to be oily.

Opening it up revealed a rotor with four fibre vanes running in an offset circle - a vane pump.

dsc06313.jpg

The black nozzle top right photo above is for the vacuum hose. Below near the base is a plastic screw screw cap covering a felt pad with access to a chamber filled with coarse fibre: could be a filter, or an oil pad. Anyone know if this is the oiling point? The pump would have to be tipped sideways to use it.

Just underneath and to the right of the black vacuum connector is a big spring loaded slotted steel screw ending in a rod fitting into a hole. It probably communicates with the vacuum side - see below. I think it's a valve of some sort. Anyone know what it is?

dsc06315.jpg

dsc06316.jpg

The vanes don't seem worn and there's no physical damage inside to speak of.

As the pump is covered in cooling fins and has a 500W continuous motor I was expecting a more powerful vacuum and better compression. Have I bought the wrong pump and am I expecting too much?

All help and suggestions gratefully received!

Ta,

Dave

 

Edited By SillyOldDuffer on 24/09/2020 16:55:53

Thread: Covid causing mental health issues.
24/09/2020 14:37:43

Posted by Neil Wyatt on 24/09/2020 12:42:51:

... In fact IQ tells us very little that is useful ...

I've certainly found that whether someone is 'clever' or not is a definitely not a measure of their worth.

Neil

I'm not even sure it's worth measuring IQ because the whole concept is built on sand! There's a built-in bias because even with careful design IQ tests depend on education and culture, which aren't intelligence. They detect who is good at answering IQ test questions, which is only one of the many forms of intelligence. Exams when I was a lad were faulty too - they tested memory as much as anything else.

Cleverness also depends on context. Shakespeare's plays show he had no aptitude for maths, while William Shockley (Nobel Prize winning co-inventor of the transistor) was an appalling man-manager who moved on to controversial views, including the idea that anyone with an IQ under 100 should be sterilised. See Neil's graph for why that's ultimately stupid! James Watt was a bad businessman. A colleague fluent in French and German couldn't stay awake during meetings. How about engine designers expert in thermodynamics who can't service their own car. I can write computer programs but don't ask me about music. Most of us shouldn't play poker for money! The list is endless.

Society is a team game, and I reckon the species has evolved the range of brain qualities needed to support all the necessary specialists. Blokes who are good at making things are needed as much as intellectuals and vice versa.

Never believe being clever at one thing guarantees being smart at everything else. Off our patch we are all stupid. There's always a time when the intelligent approach is to send for an expert.

Like IQ, valuing people by what they earn is another horribly misleading measure. Can't be right footballers earn more than nurses because we can manage without soccer! Following through on footballers vs nurses, logic insists anyone who enjoys sport must be a bit thick because they believe men who kick balls should be rewarded more highly than life saving professionals.

devil

Sports fans needn't take the criticism too hard, I don't believe it myself. I'm suggesting the example of dodgy logic and IQ tests are only valid up to a point. Don't take either too seriously! You are all wonderful.

Dave

24/09/2020 12:35:59
Posted by RMA on 24/09/2020 09:24:49:
Posted by Sam Longley 1 on 22/09/2020 21:42:21:..
...

The thread/conversation has as always, diverted 'off track' and I don't understand what IQ has to do with mental health. Where did that come from? S...

My take is the thread isn't about Covid or Mental Health either. I think it's about a perception elderly men have had since time immemorial. We believe young folk today are feckless, weak and useless compared with their superb forefathers!

Chaps who feel this way are in good company: Aristotle and the Romans thought the same. However, the theme repeats itself from generation to generation and across cultures. If it were true, civilisation couldn't exist, and it does. The belief is wrong.

One give away is it doesn't matter how old you are, in the opinion of your elders and betters you too were rotten to the core in your youth:

  • 1938 “Parents themselves were often the cause of many difficulties. They frequently failed in their obvious duty to teach self-control and discipline to their own children.”
  • 1945 “…in youth clubs were young people who would not take part in boxing, wrestling or similar exercises which did not appeal to them. The ‘tough guy’ of the films made some appeal but when it came to something that led to physical strain or risk they would not take it.”
  • 1951 “Many [young people] were so pampered nowadays that they had forgotten that there was such a thing as walking, and they made automatically for the buses… unless they did something, the future for walking was very poor indeed.”
  • 1984 “A few [35-year-old friends] just now are leaving their parents’ nest. Many friends are getting married or having a baby for the first time. They aren’t switching occupations, because they have finally landed a ‘meaningful’ career – perhaps after a decade of hopscotching jobs in search of an identity. They’re doing the kinds of things our society used to expect from 25-year-olds.”
  • 1993 “What really distinguishes this generation from those before it is that it’s the first generation in American history to live so well and complain so bitterly about it.”
  • 2001 “They have trouble making decisions. They would rather hike in the Himalayas than climb a corporate ladder. They have few heroes, no anthems, no style to call their own. They crave entertainment, but their attention span is as short as one zap of a TV dial.”
  • 2020 "Where is the stiff upper lip? How would these people go on if they had been alive 200 years ago? Ever heard of cutting your coat according to your cloth? Sorry, I have no sympathy with these snowflakes."

Examples all pinched from 'History Hustle' apart from the last, which is Model Engineering Forum.

I suspect old-chaps belittle the young for psychological reasons. I'm finding being an ex-Alpha-male difficult to accept now I'm retired. Once a mighty power in the land now I'm told to take care by ignorant boys in their fifties. And I'm not trusted to go shopping for a loaf of bread without a list.

Out in the world things are constantly changing without my approval, and I don't get half of what's going on. Surely it's enough to know who the Rolling Stones are!

A very natural reaction is to reject change because old dogs can't learn new tricks. Therefore all new things are bad.

To counterbalance this sense of decay, I now believe I'm a wise old sage. I may not understand smart phones, but I am fully qualified to make to choose how the country should be managed. As my time is short, quick results are needed from measures that won't effect me: bring back hanging, national service and the birch. It's about power: I must assert my authority, otherwise I am a zero.

In truth, human nature hasn't changed at all. Society is much the same as it ever was, and grandad doesn't like it, often with good reason. But trailing behind is our problem, not the youngsters. They have to deal with the future, not us. The job includes clear up our considerable mess as well as facing new challenges. The past is a foreign country, they do things differently there. Accept it and let the youngsters get on.

Final thought: if young people really are snowflakes, it's entirely their parents and grandparents fault. No different from making stuff on the lathe - if the result is bad, you know exactly who cocked-up!

I've every sympathy for anyone finding Covid difficult. It must be the worst crisis this country has faced since 1941. Poly-trauma to businesses, families and individuals. Covid may be no more than a mild inconvenience to retired persons with no debts who can isolate but be aware millions are taking a good kicking. Too easy to say other folk should be brave when you haven't tasted the whip yourself.

Dave

Thread: Chatter
24/09/2020 10:27:26
Posted by Peter Cook 6 on 23/09/2020 23:19:19:

... I needed to bore the bearing holders to 16mm. First experience of machining cast iron! I got (as I expected) some chatter but was fascinated by the regularity of the patterns produced.

The bearing block was held in the 4 jaw chuck (image 1) not balanced, so there as some vibration. However the pattern produced was very regular (image2), suggesting some sort of harmonic vibration at a higher frequency than the out of balance rotation.

 

This is related to one of my many stalled projects, an attempt to identify faults by analysing vibration.

Causes and mitigations have been well covered already, but the pattern is related to some mix of vibrations produced by the set up. The unbalanced bearing block will vibrate the whole machine at a frequency related to spindle speed, while the boring bar vibrates at a higher frequency related to the insert being energised by bouncing and resonating at a frequency determined mostly by the bar, but also by tool-holder, saddle and lathe. Bit like holding a rule flat on the edge of a table and twanging the free end - boing.

grc radio companion is a useful tool for experimenting with waves and mixing. I knocked this up in a few minutes:

grcmixer.jpg

It makes two streams of complex numbers from Signal Sources representing a 600Hz sine wave and a 6000Hz sine wave and adds then together. The result is converted to floating point and sent to an Audio Sink top right: this is my computer's loud-speaker so I can hear the noise - it's horrible, nothing like either of the pure tones it's generated from. Bottom right, the GUI Time Sink graphs the two waves mixing together:

mix.jpg

Now, although the output's a spiky mess, it still has a regular structure based on the two clean inputs. Although the Taig mixes vibrations in the same way, it's not working with two clean sine waves of equal strength. So the pattern produced on the work by chatter is probably dominated by the two main components - off balance and boring bar vibration - but modified by the rest of the machine vibrating. Vibration being related to rigidity means it's much easier to avoid chatter on big heavy machines bolted down on a concrete floor than small ones on a bench. (Testing stepper motors on my dining table proves it makes a good sounding board!)

Dave

Edited By SillyOldDuffer on 24/09/2020 10:29:40

Thread: Black 5 missing parts
23/09/2020 16:53:18

Welcome Darran. Sorry I can't help with the missing bits but I'm sure someone will know!

Dave

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