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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: What Did You Do Today 2021
03/10/2021 10:52:03

Whoo Hoo! I've got back into my workshop after a long break. Daughter bought a new build flat but her move was repeatedly delayed due to Covid, shortages of building materials, and lost paperwork etc etc etc. My workshop was filled with boxes expecting her to move in a few weeks, actually it took nearly 5 months.

Unlike the tools, which are fine, I've gone rusty. Previously I could align a machine vice on my mill in a few minutes: took me quarter of an hour last night, and it's still not right. Similarly, I had to think about shimming lathe tools to height, where before I did it on auto pilot. And because the workshop was tidied to make room for boxes, now I can't find anything! Gawd knows what will happen when I attempt to make something complicated: I feel like a beginner again!



Thread: Unwanted Taper
03/10/2021 10:16:07

To be explicit, an ordinary bubble level won't cut the mustard. They're good for putting up shelves and most other purposes but aren't sensitive enough to detect a twisted lathe bed.

You need an Engineers aka Machine Level. They are made to detect tiny deviations from level, as required to set a lathe accurate to a thou or two over several inches. Typically, in a new installation the lathe stand is set up with an ordinary level first, and then the lathe is tested. If not cutting straight a Machine level is used to check for bed twist, which can be corrected by shimming a foot: some machines have screw-adjustable feet.

This example is made by Dasqua and sold by RDG.

In theory new lathes are confirmed to cut straight on a true level surface in the factory, so plonking them down on any decently stiff flat surface should be good enough. In practice, don't expect too much of inexpensive hobby or elderly lathes. Note flat rather than level. It's not necessary for lathes to be level provided the bed is straight: they work perfectly well in storm tossed ships. Levelling is just one way of eliminating twist, and a bent stand is one way of accidentally twisting a machine.

In my book Machine Levels aren't good value for money. Pricey and much too sensitive for ordinary work. Fussy and the bubble takes an age to settle. Good for anyone installing lots of machines, dubious for putting one into a shed! After being used once to set-up the owners lathe, I suspect most Machine Levels end up in a cupboard. As an alternative, Rollie's Dad's Method takes longer and is more complicated to do than detwisting with a good level, but it requires no special equipment.

A word of warning: high-precision measuring is so difficult it's quite easy to lead oneself up the garden path into a deep maze of confusion. A wobbly DTI moving on a slide will cause trouble. When measuring into the 0.02mm / 0.001" region don't rush to adjust anything based on amateur measurements: they're likely to be flawed because taking them properly is a skill you don't have!!! Therefore, keep measuring simple and use the right tools: detect taper with a micrometer, not a DTI. Check everything - it may take several hours practice to get a micrometer to repeatedly read the diameter of a precision rod consistently. Positioning the micrometer correctly is important, and so it applying the same pressure to the screw every time. The ratchet helps, but trained craftsmen rarely use it; they develop a 'feel'. Some are better than others, so find out how good you are by practising. In the meantime, don't jump to conclusions!


Thread: cutting spur gears on a mill
02/10/2021 12:34:08

Posted by brian jones 11 on 02/10/2021 10:29:40:


I expect them to function as workable gears for light duty by a DIY method available to those with limited workshops who would otherwise never considered knocking up a gear train.


Unfortunately there's a nasty gap here between expectations and reality. Brian's DIY method is only useful when friction, distance between centres, low operating life, backlash, exact ratios, and low power transfer capability don't matter. All good if these can be ignored, otherwise free-hobbing is overly simple.

What does the customer want? Probably not a quick easy way of producing gear-like thingies with lots of shortcomings.

Much easier to design gear trains around proper gears. Anything else is an awful time-waster because fitting unpredictably dimensioned gears together is such hard work. Brian has yet to explore applying free-hobbed gears in anger: he'd find tackling John's 2:1 challenge educational. I suggest making the challenge a priority Brian - I'm sure you can make it work, but you need to experience the grief. And if by chance the first attempt goes well, try making 4 or 5 of them!

If WaM stands for 'Wet and Messy', I agree!


Thread: Grinding tool bits
02/10/2021 09:30:05

Posted by Steve355 on 01/10/2021 10:19:58:


2) when grinding a plane blade, of course the grinding wheel leaves a small amount of curvature. But I just hone this off on the sharpening stone, through several levels of grit and then strop it for a “scary sharp” finish. But on the lathe bit, the area I’d need to hone is much bigger, and I don’t have a nice sharpening jig to keep it perfectly flat against the stone.


Steve mentions honing, which I've never done to an HSS cutter intended for use on metal. My logic, which could be wrong, is that metal cutters don't need to be super-sharp because they wedge rather than cut. Note in the picture below, the tool tip isn't in contact with the metal.

The wedging action is taken to the extreme with most carbide inserts which are on the blunt side. A sharp edge is only needed to start a cut or to remove tiny amounts of metal. As a very sharp edge is easily damaged and metal is hard, sharp edges are easily damaged.

It's still important that metal cutters have an edge, because being too blunt is a disaster. Never let cutting tools rub!

In my mind, metal cutting is rather different to slicing through soft fibrous materials like wood where being razor-sharp is a major advantage. I don't see any value in honing lathe tools. Am I right?


Thread: cutting spur gears on a mill
02/10/2021 08:53:31
Posted by JasonB on 01/10/2021 18:37:37:

I have chinese hobby benchtop machines as do many amatures, I've not even got an engineering background like a lot of the members here just a bit of metalwork at school.

I have much the same kit as Jason, except my WM-280 lathe is a later, improved, model.

For some strange reason Jason's workshop is far more productive than mine and his work is better finished. How unfair! Then I remembered it's not the size of your tool that matters, it's what you do with it...



01/10/2021 13:36:28

Posted by brian jones 11 on 01/10/2021 12:42:59:


OBTW there are those blinded by Mistic spray who think this thread is a waste of space, well it has had over 17,000 views and 339 replies (mostly temperate) so here's cheers to the silent majority (50:1) supporting the freedom to think out of the boxlaugh


I doubt anyone reads this thread in support of freedom to think out of the box! It's value lies elsewhere, mainly:

  • Posts explaining why free-hobbing isn't used much. It's because the method is both unreliable and unpredictable. Practical rather than armchair reasons that can't be ignored for most gear applications. Choosing to ignore them solves nothing. John set a simple 2:1 challenge, and Brian needs to repeatedly solve it.
  • Posts explaining various ways gears can be cut reliably.
  • Posts referencing software, tables, and respectable gear literature.
  • Entertainment - what new Snake Oil is on offer today! Will Brave Brian finally defeat his imaginary foes? (There are no Dragons in Armchairs!)

Brian believes he's invented a new method. Not so! Free-hobbing is as old as the hills. It works up to a point, but no-one has ever got it to work reliably. I don't see anything in the thread to change that.

Free-hobbing is caught in a pincer. It doesn't satisfy the need for gears that fit between design centres and mesh efficiently at a fixed ratio. And if a bit of slip doesn't matter, free-hobbed gears aren't as easy to make or as effective as pulleys, where the centres problem is fixed by the belt.


Thread: Grinding tool bits
01/10/2021 11:29:25

At a couple of pounds each cutting HSS blanks is more trouble than it's worth. If you must, grind. I've done it with a Dremel. Also possible to machine HSS with Carbide.

The world of Model Engineers divides into those who find it easy to grind HSS and those who don't! Them as can find it incomprehensible that anyone else struggles. Actually, I suspect not everyone has the necessary eye-hand coordination. Practice helps, but my own efforts, though serviceable, are multi-faceted in a bad way!

Many prefer Carbide Inserts to HSS, but they're not a straight substitute. Carbide 'prefers' fast deep cutting, for which a stiff powerful lathe is needed. I use carbide inserts for about 80% of what I do, and switch to HSS if I can't get a good finish, need to take very fine cuts, or require a specially shaped cutter. Hint: a useful amateur trick is to use the sharp carbide inserts designed for non-ferrous metals on steel. Sharp inserts are better suited to lathes designed for HSS.

Otherwise the answer with HSS is practice, practice, practice. You might take to it like a fish to water, or it might take time. Persist!

Practice is important, especially if self-taught. Quite a lot of machining, especially with hobby or worn machines, requires the operator to compensate for shortcomings. A bit like learning to ride a bike. Several things I once found difficult, like parting off, suddenly became much easier after several attempts. Experiment and ask - although it's not rocket science, there's a reason turners once served long apprenticeships.


Thread: Old rule divisions twelfs etc
01/10/2021 11:01:53
Posted by Michael Gilligan on 01/10/2021 08:07:52:

[ once more … with feeling ]





Still with you Michael! My response is a rule graduated in 0.2mm increments isn't much practical use either - not without a microscope.

This table shows what I don't like about fraction rules. It spans one inch assuming the user has rules graduated in eighths, tenths, twelfths, twentieths, and sixty-fourths.


The table can be eyeballed to see 3/8" is smaller than 25/64" which is smaller than 2/5, which is smaller than 13/32". They all approximate 10mm and 25/64" is the closest. But, as a general way of measuring, it's fairly obvious from the decimal fractions that the usual common fractions don't step evenly: they jump.

The graph has a sawtooth rather than a straight line:


In practice, this means it's best to work with a limited range of common fractions when using rules. Although you could have several rules, making anything dimensionally complicated is clumsy compared with working throughout in decimal fraction such as thou. Thou and millimetres are smooth, for example it's easy to go to tenths or nanometres when more accuracy is needed. But not measured with a rule!

Michael: I suspect some of our exchanges are being misunderstood: we're perhaps being a tad pedantic or arcane for most tastes. For the avoidance of doubt, Michael and I aren't having an argument! And I don't think I'm doing a good job explaining myself, so apologies for not being clear. Maths isn't my best subject.



Thread: Under & over reamers?
01/10/2021 09:56:20

Fits are an example of the sharp divide between amateur and professional machining. The relatively simple methods of our forefathers are well-suited to small workshops and prototype work, hence we can and should work with old-school fits. For this Tubal Cain's Model Engineer's Handbook is excellent. He gives generalised fit information for Shrink, Force, Drive, Wheel Keying, Push and Slide fits, plus dimensions for six other running fits. Shaft/Hole fits are on page 5.18 of my 3rd Edition.

The different fits aren't a fixed reduction or increment; rather the difference between hole and shaft depends on diameter, so a Shrink fit is undersized by 1.5 thou per inch of diameter, while a slide fit is oversized by 0.45 thou per inch diameter.

In my rough workshop I use Tubal Cain as a Guide rather than 'the law', and I suppose most of my efforts are either 'Wheel Keying' (requiring more-or-less light tapping) or something vaguely between a Push and Slide fit I guess many other Model Engineers would put more effort into fitting parts! Normal practice is to cut the hole accurately to size and then to adjust the shaft to fit: there's no need for special reamers.

The professionals are much more scientific due to the needs of interchangeable manufacturing. Their system covers adjusting holes to fit shafts as well as shafts to holes, and is much more complicated. Tubal Cain deals with fits in half a page; this PDF on ISO Dimensions and Tolerances is 39 pages long.

ISO is no problem to a production engineer: if he needs a few thousand unusual reamers, he rings up the supplier and calls them off in bulk. And in bulk, they aren't particularly expensive. No such luck when an amateur wants just one! Small quantities bought new retail are liable to give grandad a heart attack when the bill is presented. So my advice is to buy a copy of Tubal Cain and stick to that!


Thread: cutting spur gears on a mill
30/09/2021 21:23:29
Posted by JasonB on 30/09/2021 20:28:24:

... even a printed out (ink on paper) division plate would be reasonably accurate ...

Wrapping a saw blade around a mandrel and counting the serrations works too.


Thread: (old) Proxxon BFW 36/E vs. (new) Proxxon BFW 40/E
30/09/2021 15:31:44
Posted by Michael Gilligan on 30/09/2021 12:58:51:
Posted by JasonB on 29/09/2021 11:50:09:
Posted by John Smith 47 on 29/09/2021 11:37:18:

Robert Butler:

I still can't find a single photo of the Unimat 3 motor driving the mill.

How hard did you try looking, put "unimat3 mill" into google […]


John only did as instructed, Jason

Tricky stuff, Grammar


Michael might mean syntax or semantics rather than grammar, but it may help internet search engine users to know there's a big difference between searching for

unimat3 mill


"unimat3 mill"

The first form helpfully opens the search up by looking for anything with unimat, unimat3, unimat 3, and/or mill in it. As this openness finds a lot of matches, the search engine uses other algorithms to put what the user is most likely to want on the front page. For example, pages that contain unimat3 and mill and have been read by many different users will be near the top, while unpopular pages that only mention mill once will be at the bottom.

Fuzzy searching mostly does a good job, but the method isn't perfect! Quite often users only want to see exact exact matches only. One way of specifying this is to put the search term inside quotes marks: the quotes tell the search engine to only return pages containing that exact phrase. In tight-mode the search engine may warn of typical user typos, which is why Google asked in this case 'Did you mean "unimat 3 mill"? (Yes!)

MEW or ME did an article recently about advanced search techniques: sorry I can't remember which. Worth reading when searching the internet for specific targets, which is a common requirement in technical subjects. There's a degree of art in it as well. Apart from knowing how to drive advanced search engine options, the way a query is assembled can make a big difference too. In the complicated world we live in getting the best out of search engines is yet another skill most of us don't have - common sense fails again!



Edited By SillyOldDuffer on 30/09/2021 15:33:11

Thread: Old rule divisions twelfs etc
30/09/2021 10:41:05
Posted by Michael Gilligan on 29/09/2021 11:50:38:
Posted by SillyOldDuffer on 29/09/2021 11:45:07:
Official size is 18.0mm; what's that as an inch fraction?





PostScript: __ You are guilty of conflating resolution, accuracy and precision, Dave

… There are important distinctions between them

And this is what the inch fraction ¹⁄₁₂₇ scale looks like, magnified!


If the pictured scale looks uneven on your screen, its because ¹⁄₁₂₇" pushes display technology - jpeg photos and the your computer screen both struggle,

I'm pointing out the shortcomings of fractional rules rather than fractions, but Michael's 18mm conversion highlights a few problems:

  • There is no standard ¹⁄₁₂₇" rule: it would have to be specially made
  • ¹⁄₁₂₇" is too small for the human eye to read reliably
  • ¹⁄₁₂₇" (about 8 thou) is about the width of a finely printed graduation, which introduces significant error
  • There are no natural halves or other sub-graduations to help the user find which graduation represents ⁹⁰⁄₁₂₇" - mistakes are too easy
  • In practice, with a standard inch rule gradated in say sixteenths, its necessary to translate ⁹⁰⁄₁₂₇" into the nearest sixteenth and interpolate. Finding the nearest twelfth, sixteenth or sixty-fourth to ⁹⁰⁄₁₂₇ is a challenge.
  • Decimal scales are easier to interpolate by eye than fractional scales because there's no need to adjust the divisor.

I reluctantly agree conflating resolution, accuracy and precision is sinful and leave it to Michael to explain the difference! His concern isn't pedantry: in engineering, many words such as energy, work, power, stress, and strain have particular meanings that confuse when used carelessly, as I did with precision. All I can say is 'even Homer nods'. Please be gentle with me and I would like 98 other offences to be taken into consideration!

All I'm trying to say is that rules aren't much good compared with a Vernier or Digital Caliper, and they are inferior to a micrometer. And micrometers aren't the best measuring tools available either.



29/09/2021 11:45:07
Posted by Michael Gilligan on 29/09/2021 10:41:49:
Posted by SillyOldDuffer on 29/09/2021 09:33:56:


Fractional rules aren't a precision system,


crying 2

In your role as a Moderator … Would you please correct that abuse of the word ‘precision’

The system of units has no effect upon the precision of a scale !!

[ Rant over ]


Um, I plead 'not guilty'

I was referring to the precision of a fractional rule in use, not the scale. One definition of precision: The ability of a measurement to be consistently reproduced. Rules aren't much cop for that.

On the ⅛" scale, what's the diameter of this 5p coin? How precise is the measurement in the sense it could be reproduced?


I'd claim no better than about ¹¹⁄₁₆", which is roughly 17.5mm. Official size is 18.0mm; what's that as an inch fraction?





Edited By SillyOldDuffer on 29/09/2021 11:45:40

29/09/2021 09:33:56

I don't believe twelfths were associated with a particular trade, rather it's just a handy scale for rough measuring as might be required in carpentry, dress making, or any other rough work. For this system to work it's necessary for rules to provide several different scales: ⅛, ¹⁄₁₂, ¹⁄₁₆, ¹⁄₃₂, ¹⁄₄₈, ¹⁄₆₄" are common. Late model imperial rules sometimes do ⅒, ¹⁄₂₀ and ¹⁄₁₀₀"

Fractional rules aren't a precision system, and they date back to simpler times when most practical problems could be calculated with fractions to the extent that decimals weren't taught to many Victorian school children. They had little use for advanced maths!

However, progress changed all that. Fractions are clumsy in many situations, especially science and technology. As a system, decimals are much more general purpose, simplifying complex sums, and avoiding awkwardnesses like is ¹³⁄₃₂" bigger or smaller than ⁵⁄₁₂". Another major advantage of decimal arithmetic is accuracy is managed simply by calculating to more or less decimal places. Though fractions have many useful applications, decimals have replaced them for most purposes. Metric measure doesn't use fractions at all and no-one complains...


Thread: Not enoughh CO2 ?
27/09/2021 14:05:15
Posted by Robin on 27/09/2021 11:47:02:


"Overall the globe has cooled substantially since the last El Nino ended in 2016, and it now appears the cooling trend will persist another year as the CFSv2 is forecasting a La Niña to continue into spring 2022".


Robin, that's a blog misusing NOAA data, fake news! The source is actually about forecasting weather anomalies, and climate deniers won't like what it really says about the likelihood of unusually bad weather in the USA next year.

This graph shows global temperature to be rising and is cause for concern because it appears to be accelerating in line with theory, which is bad, bad, bad for everyone.


As climate deniers have successfully delayed attempts to reform our foolish ways over the last 30 years, humanity is stuck with the consequences. Robin thinks CO² helps his garden grow: I'm worried about the risk of Bangladesh flooding. There, rising sea-levels could create 163,000,000 refugees at the same time as North Africa becomes uninhabitable due to desertification.

When the experts predict Climate Catastrophe, they really mean it. I used to think global warming could be managed sensibly into a soft landing, now I believe the future is out of control. The milk is spilt. Prime Minister Macmillan was once asked why governments failed to deliver on their manifesto promises. He replied, 'events dear boy, events...' We are three square meals away from chaos!



Edited By SillyOldDuffer on 27/09/2021 14:05:54

27/09/2021 11:20:22
Posted by Graham Meek on 22/09/2021 18:29:23:

By what I was told today, petrol is also in short supply in certain parts of the country.



Lots of panic buying where I live. Yesterday my local Tesco ran out of fuel and so were the three independents between me and my son (10 miles away). I'm sure no forum members have disgraced themselves by topping-up unnecessarily, but it seems the rest of the nation's drivers are a mob of selfish, hysterical wets! So much for Dunkirk spirit. I think corporal punishment is the answer: six of the best on the forecourt for anyone who queued for less than a third of a tankful!


The problem is due to HGV Driver Shortages and a government minister assuring us there's no shortage of petrol at the refineries. I wonder how many of those queuing realised that electric cars are immune to this problem - they're recharged at home...


Thread: I need to cut chamfers into x64 pieces of mild steel - any advice?
27/09/2021 10:55:39
Posted by John Smith 47 on 20/09/2021 16:20:04:
Posted by Rod Renshaw on 20/09/2021 15:22:43:

Usual advice from the makers of diamond "whetstones" and wheels is to use them only for hard materials (carbide or ceramic etc) and not steels which are mostly "soft" in this context, and to use only very light pressure. Diamond is very hard but rather brittle, too much pressure will either fracture the diamonds or tear them from the wheel, and as has been said soft materials will clog the surface.


My SHARPAL Diamond Whetstone is specifically designed for use with knives which one tends to find are made out of steel.

I can see no mention of "a very light pressure". In fact I have heard people claim that a light pressure is bad for a diamond whetstone and that they prefer to be worked hard.

Water and a nylon scrubbing brush are suggested for removing of any metal particles that get stuck onto the diamond stone.



Never draw conclusions from a sample of one! In general Rod's advice is correct. Diamond whetstones are designed for hard materials and clog easily when misused. Mild-steel is very soft compared with the stainless steels used to make knives. There's a high risk of failure.

Once a diamond wheel has been clogged by misuse it may or may not be practical to clean it. It's unpredictable - only trying it will prove whether what's wanted in your workshop will work or not and the smart money is on not!

As to diamonds and pressure, this varies all over the place too. It's because abrasive systems are carefully tuned to work well on specific targets. Sandpaper doesn't work well on hard metal, and Emery Paper doesn't work well on soft wood. Diamond drills are designed to take heavy pressure, most diamond files aren't.

Having the right tool for the job makes light work of most problems. Being pushed to extemporise by shortage of space, money and skill can be an expensive time-waster. It doesn't take many purchases of disappointing kit to add up beyond the cost of paying someone else to do the work, or saving up for an appropriate workshop. Keep a sharp eye on cost versus progress!

I use machines to support experimental work rather than modelling and my projects have a high failure rate. The main cause is me. Be even worse if I didn't have a basic collection of effective tools! I make a fair few simple parts that could be made with a hand-drill, hacksaw, files and a vice, but this is impractical. My milling machine is much faster, more accurate and requires less skill: well worth the investment! You have my sympathy - improvising is really difficult, especially for beginners. If it turns nasty, be ruthless - pay someone with the right equipment to do the work.


Thread: Saving the Planet or is it ?
26/09/2021 10:44:20

Posted by JimmieS on 25/09/2021 22:58:24:


And if the facts stated in last 8 minutes of this prog are correct, looking forward to an era of ‘cheap’ energy is a pipe dream.


Humanity has the exact opposite problem: energy prices are about to go through the roof. Fossil fuels are 'free' apart from the cost of extracting, processing and transporting them, plus tax. It's been great: mankind has enjoyed the benefits of marvellously cheap energy since the Industrial Revolution started.

Unfortunately, after 250 years three major problems have emerged:

  • fossil fuels are running out - think 10 years time
  • too much fossil fuel is imported from unreliable countries
  • Carbon Dioxide and other industrial gases are heating the planet. The consequences are off-the-scale, so extreme many reject the predictions as science fiction. The evidence suggests they're wrong.

Ignore Climate Catastrophe though and ask what happens when demand for fossil fuels exceeds supply? Easy, the cost of fossil fuel will rise until most people can't afford it. 'Most people' means you and I - the party is over.

Only the most stupid politician would bank his country's future on burning fossil fuels forever. Green energy is part of the answer, not the enemy. People want energy and don't care where it comes from: remember fossil fuels are just one way of providing it. Finding alternatives to coal, oil and gas is urgent and believing fossil fuels will last forever isn't the answer. Rather than rely on a tired old friend, it's time to change...


Edited By SillyOldDuffer on 26/09/2021 10:45:37

Thread: Material selection or additional process
26/09/2021 09:50:20
Posted by Tony Pratt 1 on 26/09/2021 09:35:12:

T bar is way too long.


Too short is bad too! My genius let me down badly with these:


I thought short, fat adjusters would make it easier to rapidly centre opposing jaws by twirling. Brilliant, until they foul the jaws:


Silly me. embarrassed


25/09/2021 21:30:27

Like Nigel I'm surprised mild-steel twisted: over-tightening or something wrong with the chuck maybe?

As a pair of chuck keys used together are useful for centring a 4-jaw, I made some out of mild-steel for that purpose and they're OK.


I expected to have to remake the keys in Silver Steel but so far no need.


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