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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 a nightmare
25/01/2020 10:58:46
Posted by Baz on 25/01/2020 09:23:50:

... I must live a very sheltered life.

Most of us do! One thing I learned the hard way is being expert in one field did not make me good at everything else. A relative served in the Royal Navy, travelled the world, did well in challenging situations and was regularly promoted. When his time was up, bursting with confidence and full of contempt for civvie ways, he left the Navy to make his fortune. 18 months and 3 jobs later he had a nervous breakdown : now he drinks, relies 110% on his wife, and is lucky not to be homeless. I blame military virtues - they put servicemen and women into a well-structured team, with clear leadership and short-term objectives, minimised individual responsibility, justified pride, and positive purpose. A lot of effort is put into training, obeying orders, building confidence, acting quickly, and managing work/rest to maintain peak performance. Unfortunately civilian life often inverts all this: unclear objectives, low status jobs, bad managers, high responsibility, unachievable targets, weak teaming, indifferent training and maybe the job is unpopular as well.

Similar in civilian life: brash confident Englishmen turn into whinging poms in Australia, city folk hate the country, redundant coal-miners don't do well in offices, etc etc etc. Truth is, most people are foolish outside their normal range of experience, hence jokes about Nerds not having Girlfriends!

Crime is the same; honest folk are unlikely to understand criminal techniques and are more likely to come into contact with petty rather than organised crime. We are Babe's in the Wood! It's impossible to protect oneself entirely against crime, but much of it is defeating by taking simple alert precautions. On the internet or when the phone rings, slow down, have a suspicious think, and double-check.

But no amount of clever precautions help when the crime is something like a cloned number plate. Though the effects are painful, Harry isn't the major victim - he's mere collateral damage, an accidental bystander! The car carrying his registration has been stolen from someone, and the thieves are uninsured, possibly disqualified and unlicensed. Likely the clone car is wanted for anti-social purposes, like drug-dealing or burglary. Maybe it will get torched to destroy forensics after the crime in a kiddies playground, costing public money putting the fire out, removing the remains, and fixing the damaged playdround. Harry only gets whacked with parking and speeding fines, everyone else's insurance goes up slightly, but the real pain surrounds the stolen car.

One of my colleagues was married to a senior policeman, second-in-command of a Regional Crime Squad. One evening while he was watching TV, a gang lifted his brand new BMW off his front drive, over a pair of locked gates, and on to a low-loader fitted with a crane. Probably stolen to order and shipped abroad. Maybe someone in the dealership notified the gang, maybe the gang were watching the garage and followed him home. Either way they got clean away with it...

Dave

Thread: scam alert
24/01/2020 17:12:54

Lack of common sense implies stupidity and I wouldn't want anyone caught by a scam to beat themselves up because they got stung. Bad enough to be duped without being made to feel foolish as well. A scam just needs to make sense for long enough to suck someone in - it's not the victim's fault.

Fraud is big business in the UK. During 2017 42,837 people lost £236 million due to Authorised Push Payment scams; fortunately payments amounting to three times that value were detected and stopped by the banks before the money was lost.

There's no such thing as common sense. Banks get defrauded regularly and they're alert professionals...

Dave

Thread: Opinion on using blue Loctite (thread locker) on clocks?
24/01/2020 16:32:04

Thread-locker is best used when vibration or heat-cycling might loosen a thread. Not sure clocks are vulnerable to that, but thread-locker is certainly common on laptops. So it doesn't seem mad to use thread-locker as a way of lightly tightening a screw and still have it stay in place.

Rather than Blue I'd suggest Purple because it's intended for small screws and undoing with hand-tools (Purple is weaker). Not sure a future clock mender would welcome fixing a clock glued solidly together!

Dave

Thread: Desoldering how to?
24/01/2020 14:09:41

Posted by IanT on 24/01/2020 12:56:40:

... It's also usually much easier to clean up & re-solder if you can cut the old component out and then simply remove the old 'legs' of course.

...

Half a century I've been de-soldering and never thought of that! What a good idea.

It helped me to match the pump and iron to the problem. I threw away a pump because it didn't generate enough vacuum. It's slightly larger replacement works much better provided the nozzle is in good nick. When there's space, the new pump works best with a 25W iron. I guess a larger iron melts more solder around the joint and inside plated holes, and then supplies enough heat to keep the solder wet as it's sucked off the joint.

Desoldering isn't my idea of fun, and SMD is too much...

Dave

Thread: scam alert
24/01/2020 13:49:01
Posted by Howi on 24/01/2020 12:57:55:

A little bit of common sense is all that is needed to determine what ios a scam and what is not.

Howi's common sense has failed him this time: TV Licensing does use email. Not Howi's fault because common sense is dreadful unreliable at the best of times. About as trustworthy as Father Christmas and the Tooth Fairy in my experience.

Duncan describes a combination of circumstances that almost got past his defences. That's how scams work. They rely on the victim using his easily fooled common sense rather than double-checking.

Common sense is no substitute for knowledge and understanding. Let's be careful out there!

Dave

Thread: Digital verniers
24/01/2020 13:07:39
Posted by Steviegtr on 23/01/2020 23:06:30:

As I thought at the price they cannot be made in the uk. ...

Steve.

Gosh, even I thought what I'd typed was tedious!  To save further embarrassment I've deleted it!

Dave

Edited By SillyOldDuffer on 24/01/2020 13:12:42

23/01/2020 22:34:53

Pedant alert - no such thing as a Digital Vernier, but we all know what Stevie means - a digital caliper.

I keep a couple of inexpensive calipers for rough work - they're more than accurate enough for most ordinary work, and I don't mind abusing them to scribe lines. Nor does it matter when they get dropped on a concrete floor. The main problem is they don't feel smooth, are little difficult to feel when it's safe to trust a measurement, and they tend to lose zero. Mine have been mildly inferior, with only one that was truly second-rate. When I'm in a hurry, I use a £30 caliper from ArcEuro - not first-class. but it's nicer to use and results are more repeatable. It holds zero better than the cheepies, but isn't totally reliable, hence has to be watched. For best I have a Dasqua, which does hold zero, and has a silky feel. However, calipers aren't ideal for accurate work - for anything better than 0.02mm, an inexpensive micrometer will be about twice as accurate as any caliper, even a fancy one.

Like Dasqua, Moore and Wright are mid-range, probably better than the average home workshop needs. Mitutoyo or Starrett have more expensive models if that's what's wanted. The extra money doesn't deliver better accuracy, just a better feel, improved reliability and then you're paying for features like a coolant-proof enclosure.

Don't get carried away by Brand Names: most stuff today is made abroad and there's no particular reason why it shouldn't be, digital calipers aren't rocket science. If you do buy an expensive instrument, heed Jeff's warning about fakes.

Dave

Thread: Warco lathe feedscrew shear pin
23/01/2020 14:17:50

I can't remember the diameter of the pin on my WM280, but it was about 3mm, not tapered. Whatever it was, the hard part was getting the broken pin out. With the feed-screw fitted to the lathe, I couldn't see the broken pin well enough to drive it out - high risk I was uselessly hammering the screw rather than hitting the pin. With the screw off the lathe and everything in plain view it took about 10 seconds to tap the pin out and measure it.

No problem turning 4mm brass rod down to size by hand with the lathe in bits. Then it was straightforward to tap the pin in when the feed-screw was re-fitted.

Assuming your 290 is like my 280, the awkward bit will be removing the bearing block at the tail end to get the feed-screw off. (If you have to; with luck you can see the old pin and remove it in-situ.) Mine is held in place by two bolts (easy) plus two dowels (tricky). The plain dowels take an Allen Key but they're sort of shimmied out rather than unscrewed. I may have done it wrong by turning with a pulling action with the Allen key tilted to get a bit of grip. Bad language didn't help other than making me feel better. Reassembly is easy - they just slide in.

Dave

Thread: Unimat 3 underpowered ?
23/01/2020 13:52:11
Posted by 34046 on 23/01/2020 12:11:07:

Posted by Julian Saunders 1 on 22/01/2020 17:15:05:.

...

Heartily agree - absolutely nothing wrong with a U3 and well capable of more than clock making.

Jason's engine as above is proof of what it can do

Bill

Not so sure myself! Reading Michael's link and lathes.co.uk I find the motors varied between 40W and 125W. That's a very wide range, enough to make comparing one lathe with another dubious. Beware of chaps advising that their Unimats are wonderful: it's the state yours is in that matters and they ain't seen it cut metal!

My reading suggests a 90W 80% duty cycle Universal AC/DC motor was most common on these machines. (Some are only 60% duty cycle). That's plenty adequate for small delicate precision work, but clearly Unimat's aren't bruisers. Compared with the more suitable 450-650W DC or brushless motor fitted to a mini-lathe, Unimat motors are weaklings.

What a particular Unimat is capable of today will depend on the motor fitted and even more critically on what condition it's in. Over the last 3 or 4 decades, an underpowered Universal motor may have been thrashed, showered in 3-in-1, run on dud brushes or allowed to spark due to a failed suppressor capacitor. The commutator and bearings may be damaged. I wouldn't assume there's anything wrong with the lathe without having a critical look at the motor; maybe it's just filthy and needs some TLC. Unfortunately, if a Unimat motor is done for, replacing it doesn't seem to be cheap or easy. Not sure why - is it because they're a non-standard fitting? Lot's of old lathes accept new motors and a VFD without fuss.

Dave

Thread: Making Rings
23/01/2020 12:48:49
Posted by old mart on 21/01/2020 16:55:00:

In the UK, only coins which are current legal tender are protected by law. For example, the old 50p coins or pound coins are fair game for defacing.

Is that true? I couldn't find anything that confirms it, rather the opposite. For example, even though old pound coins aren't legal tender, they can still be exchanged for pound coins that are. Although the old pound coin was withdrawn because it was too easy to simulate well enough to fool a vending machine, they're still valid at the Bank of England.

Here's how the Bank of England define it: Legal tender has a narrow technical meaning which has no use in everyday life. It means that if you offer to fully pay off a debt to someone in legal tender, they can’t sue you for failing to repay. Curiously, while Banknotes are legal tender in England and Wales, they aren't in Scotland or Northern Ireland! It doesn't alter the price of fish.

I don't think the actual legalities matter in Stevie's case because his offence is entirely theoretical - it doesn't matter, and no one cares, nor are they likely to care. The Bank of England may even be pleased he's saving them the cost and bother of replacing old money. Far more exciting if Stevie was converting scrap into replica WW1 Trench Knives and selling them. Even though there's no law directly forbidding replica trench knives, expect to go to jail.

Good work from Stevie - attractive rings and impressive workmanship. More the merrier!

Dave

Thread: Can we have a really clear distinction between Silver Soldering and Brazing
21/01/2020 17:28:32
Posted by CuP Alloys 1 on 21/01/2020 16:04:09:

Hi folks

Words fail.

There's an expression involving a horse and water but I can't recall it at the moment.

Perhaps I should just keep my thoughts to myself. Is that the bugler playing "The Last Post"?

Perhaps it's me, but I still don't get what's so offensive about this thread? A tendency to wander around subjects and develop ideas isn't exactly unusual on this Forum. No-one is counting angels on pins.

I normally read Cup Alloys posts with considerable interest but today's contribution has zero value. It doesn't address the question or explain what's wrong with the answers. Worse, the Horse and Water comment suggests the writer has a low opinion of forum intelligence: is that the official view of Cup Alloys the business, or just an individual's unfortunate choice of words? Hard to accept the latter given it's followed by 'The Last Post' gibe.

Dave

Thread: Making Rings
21/01/2020 15:42:11

In most countries, legal tender isn't owned by the whomever happens to be holding it at the moment. In the UK, money belongs to the Crown, and Subjects are lent it to use as a medium of exchange. When coins had actual monetary value being made of Gold, Silver, Bronze, etc. it was common for the actual value of the metal to exceed its notional value. Therefore it was possible to profit by melting down coins whenever metal values were high. Doing this is very bad for the economy because everyone's ability to exchange goods reduces as the coinage disappears and because prices rise unecessarily because there's a shortage of coins. It's doubly bad if the metal is sent abroad. This is where the severe punishments come from, echoed today by the penalties for counterfeiting paper money.

Another potential offence is that defacing coinage is a way citizens in the past have shown distaste for their leaders. As Leaders tend to have delicate egos, it's often illegal to deface their images, even if they've been dead a century or two. Be careful abroad. Some countries will react if a tourist draws a moustache on a banknote!

In theory punishments for messing with coinage are severe, once including death sentences, transportation, and long prison sentences. But since about 1925 coins aren't normally made of metal having any real value. They really are just tokens. Melting down tons of current coins for their scrap value might get one into big trouble, but in practice no-one really cares. This is doubly true of coins that are no longer legal-tender. Unlikely anyone will mind if a few old coins are turned into something else.

But beware of modifying old coins without checking. A friend of mine found a Young Victoria Gold Sovereign in his back garden and drilled a hole in it to make a necklace for his daughter. Out of curiosity he showed it to a local Coin Dealer, who said without the hole it was a rare collectable in Extra Fine condition worth about £1500, probably considerably more at auction. With his hole, scrap value only...

Dave

Thread: Can we have a really clear distinction between Silver Soldering and Brazing
21/01/2020 14:44:31
Posted by Clive India on 21/01/2020 13:08:25:
Posted by Michael Gilligan on 21/01/2020 12:30:19:

So ... The answer to the question posed by Chris is NO. MichaelG.

I agree - but it was good to watch the willie-waving!

Well, I disagree. Reading the submissions I see a good consensus about the main differences between soldering and brazing, with examples, and contributions usefully explaining how and why the terminology is a bit wobbly. I didn't spot any competition between answers, let alone willy waving.

Is this a theory vs practical thing? Some technicians lose interest as soon as an answer allows them to get results, even if it's inaccurate. After that, I suppose any extra information might be considered boastful. Fair enough, but engineering progress depends on building understanding, not just repeating old tricks, however effective they are! And over-simplifying is dodgy on a forum like this because members come from so many different fields. In this thread for example we learn the Silver Solder used in electronics is completely different from the Silver Solder used in Brazing.

Dave

Thread: Buying metal - caveat emptor.
21/01/2020 13:44:51
Posted by Mick B1 on 20/01/2020 14:45:00:
Posted by SillyOldDuffer on 20/01/2020 11:02:09:

...

Can't agree with Mick's suggestion the cause is 'inclusions of different steel types in a cheap gash melt', because it implies steel is made haphazardly in small quantities.

...

SOD:- Well, it was a long time ago, but I can remember prising out bits that looked a lot like broken gear teeth from a bit of what'd been held in RM stores as EN3B, that I was trying to turn. Describing the proper processing doesn't mean it always gets followed.

wink

...

Maybe, it might have been made in a British Furnace like this, first built in 1711 and closed after various upgrades in 1966, long after it was obsolete:

800px-backbarrow1.jpg

Picture Attribition Wikipedia: The photo is of a small manual producer, not very scientific, with quality depending mostly on the skill of the individuals operating it. Capable of good results, but not when the skilled operator is drunk, ill or on holiday! Or his boss insists on cutting corners. This sort of 'stirring scrap in a pot' operation may be what chaps imagine goes on in the Far East. Very unlikely!

Far more typical of modern steel-making is the British Steel plant at Scunthorpe:

scunthorpe.jpg

Plants like this are highly mechanised, highly efficient, with most sources of human error removed. This is the sort of operation unlikely to make steel containing unmelted inclusions, or steel outside the target specification.

Sadly the Scunthorpe Steelworks was sold for £1 in 2016 and went into receivership, bankrupt, last year. Nothing wrong with quality, the problem was cost. This relatively small steelworks relying heavily on imported materials and an expensive workforce, couldn't compete with the really big boys. No profit in it.

To give an idea of scale, 1,808,000,000 tons of steel were made in the world during 2018. China made 928,300,000 tons of it, and the second largest producer was the European Union, at 168,200,000 tons. In 2018, the entire British steel output was 7,700,000 tons, or 0.43% of the world total, slightly less than Egypt. Of course quantity isn't everything, in 2020 steel made in Britain will be something special, high-quality, made in an electric furnace for very demanding applications.

China's dominance of steel isn't entirely wonderful for them because the market for steel is ferociously competitive and very vulnerable to sudden drops in demand. Large inflexible enterprises catch bad colds : about 2 million Chinese steel workers have been made redundant since 2018, which makes British job losses in the steel sector look like chicken-feed, agonizing though they were. (In the UK, about 250,000 lost jobs since 1967, or roughly 50 years). Change in the steel industry, wherever it happens to be located in the world, can occur quickly. British steel production peaked in April 1970 at nearly 2.9 Million tons, but collapsed to 0.13 Million tons in February 1980.

It's not that I believe inclusions are impossible, only that modern steel production methods make them far less likely than in the past. Can anyone post a photo of a recognisable inclusion found by them in a bit of modern metal? Slag is far more likely than ball bearings and gears!

Dave

Thread: Arc Euro Trade website down
21/01/2020 11:23:02

Oh dear, still poorly at 11:18 -"Server Error in '/' Application."!

By this time Ketan's blood pressure must be through the roof. Perhaps we should all order something by phone! Now were did I leave the Catalogue?

Hope it's fixed soon - nightmare.

Dave

Thread: Can we have a really clear distinction between Silver Soldering and Brazing
21/01/2020 11:12:34

My understanding is the difference can be decided almost entirely by temperature: below 450°C it's soldering, above 450°C it's almost certainly Brazing.

Both processes rely on melting a filler metal at below the joint metals melting point. Filler metals that melt below 450°C include Bismuth, Zinc, Tin and Lead. As Bismuth is expensive and poisonous and Zinc evaporates easily and the fumes are poisonous, most solders are alloys of Tin and Lead. Tin melts at 232°C, and Lead at 326°C, but alloying them reduces the melting point. A solder containing 60% Tin and 40% Lead melts at 182°C making it highly suitable for electronic work. It can be precision melted with an electric iron that's not a fire risk, and the solder usually comes with built in flux. The flux is relatively weak and depends on the joint being clean.

Plumbing solder requires considerably more skill because operations are on a much grander scale. The operator has to choose and apply his own flux, and carefully judge the heat. Copper pipe isn't too difficult, but soldering Lead Pipe is skilled work. Plumbers are trained to do it and some become specialists. In the good old days power cables and communications wiring were often protected by lead sheathed cable that had to be carefully soldered at the joints to keep water out: this also is skilled work.

The disadvantage of soldered joints is they aren't mechanically strong.

The words 'Braze' and 'Brazen' both point to the main filler metal used above 450°C - Brass. Brass is an alloy of mostly Copper and Zinc. Pure Copper melts at 1085°C, but alloying it with Zinc drops the melting point. High Zinc Yellow Brass melts at about 900°C. This is very convenient for jointing Iron and Steel; it's much easier than welding, and done quickly the heat doesn't alter the steel. The disadvantage is that, although considerably stronger than solder, Brazed joints are weak compared with Welded or Rivetted joints. In the past, Brazing was associated with cheap and nasty car repairs - I vaguely remember it being made illegal for garages to mend cars by brazing.

Brazing was originally done with ordinary Brass Filings, and still can be, but 900°C is an uncomfortably hot working temperature. The melting point of Brass can be reduced by further alloying it with other metals notably Silver (expensive) or Cadmium (poisonous). Cadmium has been banned for all but special purposes, shame because it's not particularly hazardous in small workshop quantities. It turns nasty when people have to work with it all day every day, or live downwind of a plant, and if it leaks into the water. Silver solder is good stuff, some alloys melting as low as 620°C. As some Brazing alloys containing a lot of Cadmium melt below 450°C, and some solders melt above 450°C, the border isn't rock solid.

Whilst scientists and engineers try to use consistent technical terms, the same can't be said of trades and practical men! Don't be surprised to find the same word meaning several entirely different things (like Alum), or definitions being blurred as with 'Soldering' and 'Brazing'. Despite the name 'Silver Solder' is usually a Brazing material and process. Some trades say 'Soft Soldering' for less than 450°C, and 'Hard Soldering' for above that. In effect 'Hard Soldering' = 'Brazing'.

Keeping it simple:

  1. Soldering - low temperature, mostly easy to do with low tech equipment but joints are weak.
  2. Brazing - harder to do, needs more equipment and much more heat, and the joints are medium strength.
  3. Welding - Hardest to do, requires special equipment, high temperatures and skills. Properly done, joints will be as strong as the base material.

As always, engineering is about balance. Fit for purpose is the goal. Model Locomotive Boilers are a good example; the Codes all discourage Soldering because soldered joints are borderline in terms of strength. Probably wouldn't go bang, but why risk it? Likewise the Codes discourage Welding because amateurs are likely to make a mess of it in non-obvious ways. It's difficult to prove welded joints are sound, especially when they can't be seen. Brazing is recommended because it's reliable - more than strong enough for the job, relatively lenient, and easy to spot and fix mistakes. A boiler brazed by a skilled expert will be a work of art but I think I could just about make a simple one. (Probably ugly and only after much wasted time and materials. I can't see me ever putting the effort in needed to become proficient!)

Dave

Thread: Sent lathe back
20/01/2020 20:37:04
Posted by Derek Allum on 20/01/2020 19:14:33:

The chap I purchased the Unimat lathe off decided to have the lathe back and refund my money, So I have bitten the bullet and purchased a Cowells 90ME ( I think I need to have a lie down).

...

Thanks Dell

Hurrah, that's a good outcome. A hard-nosed seller might have held you to the contract, but this chap has done the decent thing.

Is this a new Cowells you've bought, about £3000 with no accessories? Quite a jump from a second-hand mini-lathe! Nice machine, please share how you get on with it.

Dave

Thread: A change of scale.
20/01/2020 20:05:48
Posted by JasonB on 20/01/2020 19:03:24:
Posted by SillyOldDuffer on 20/01/2020 18:07:27:

A lot more dimensions on a simple plan would have me tabulating them in a spreadsheet and applying ×12 ÷ 8 to the whole lot. (Less error prone, but have to know how to drive a spreadsheet. Another advantage is the figures are stored, can be checked by someone else, and corrected later if mistakes are found.)

Not sure if that is less error prone Dave as x 12 divided by 8 would give a bigger modelblush

...

Well that's embarrassing! Good job I said 'Another advantage is the figures are stored, can be checked by someone else, and corrected later if mistakes are found'.

Thank god I don't do this stuff for a living!!!

nocryingembarrassed

Thread: Silver Soldering Brass
20/01/2020 18:41:19
Posted by Chris TickTock on 18/01/2020 16:01:20:
Posted by JasonB on 18/01/2020 15:39:00:

...

... Also apparently if you connect a propane cylinder all you need is a camping type regulator don't understand how pressure is maintained, is that a property of the cylinder being compressed if so surely it diminishes at some point?...

All the fuel gases (apart from Acetylene) are compressed to liquid form inside the container. A certain pressure is needed achieve this, between 500 and 800psi depending on the gas. When the container is opened, the gas boils by absorbing heat, and the characteristic high pressure is maintained until most of the liquid has evaporated.

A regulator works by counter-balancing the internal pressure against a diaphragm with a spring; when the pressure on the customer side drops below a certain level, a valve opens briefly allowing a puff of gas to expand into a receiver, before closing the valve again. The receiver is kept full of gas at customer pressure and recharged as necessary from the high-pressure side. Provided the right regulator is fitted to suit the gas and pressures, it's a trouble free system : connect it up and it 'just works'

Acetylene is very unstable, with a number of ways of exploding. It's illegal to liquefy it, instead the gas is forced to dissolve in Acetone or other absorbant, and bubbles out when the pressure is released. Inside the bottle it behaves like lemonade, but from the user point of view it just needs a particular type of regulator. Under no circumstances use an ordinary regulator on an acetylene cylinder. One of the gases endearing features is reacting with Brass to form Copper Acetylide which is a sensitive detonating explosive. No joke if it explodes taking the top of the bottle with it - even a small cylinder contains enough to energy to destroy a workshop and burn the occupants.

Dave
Thread: A change of scale.
20/01/2020 18:07:27

Anyone got any suggestions as to how best do the conversion work? I think it depends on how many dimensions there are to do and how complicated the plan is.

For a small number of dimensions and a simple plan, I'd incline to a paper pad and pocket calculator × 0.66666, double checking before cutting metal. (Error prone, but not as bad as pencil and paper.) If one is available, slide rules are excellent for this sort of conversion. After setting the slide to × 0.666, all the answers can be picked off by moving the cursor. (Disadvantage perhaps only good to 2 places of decimals, which I think is plenty good enough.)

A lot more dimensions on a simple plan would have me tabulating them in a spreadsheet and applying ×12 ÷ 8 to the whole lot. (Less error prone, but have to know how to drive a spreadsheet. Another advantage is the figures are stored, can be checked by someone else, and corrected later if mistakes are found.)

A complicated drawing would have me redrawing the plan in the original scale in a 2D CAD package. (I like QCAD, others available.) Then I'd rescale the whole drawing × 0.666666 in one go. This method highlights errors very effectively, including mistakes in the original drawing. Disadvantages are the time taken to re-draught the plan and needing to know a CAD package. But it is fun making an entire drawing change scale at the push of a button!

As an ex-computer programmer I'd love to write code to do the job, but that's hard work for very little return in this case. Spreadsheets are a far better tool unless the number of dimensions to be converted is enormous (millions...)

Dave

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