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17th September 2023, 01:57 AM #31GOLD MEMBER
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17th September 2023, 08:45 AM #32
If you want to see how complex we make measurement and standards, take a look at the International Standards for aviation products, charts, navigation etc the Aeronautical Information Publication
For measurement of Units used
Distance used in navigation, position reporting, etc. Nautical miles and tenths
generally in excess of 2 nautical miles
Relatively short distances such as those relating to aerodromes (e.g. runway lengths) Metres
Altitudes, elevations and heights Feet
Horizontal speed including wind speed Knots
Vertical speed Feet per minute
Wind direction for landing and taking off Degrees magnetic
Wind direction except for landing and taking off Degrees true
Visibility including runway visual range Kilometres or metres
Altimeter setting Hectopascal
Temperature Degrees Celsius
Weight Metric tonnes or kilogrammes
Time Hours and minutes, beginning at midnight UT
The hybrid imperial & metric system does have some practical benefits in specific applications, but like the development of all standards the final product is a consensus decision by a committee representing a multitude of interests, users, manufacturers, systems developers, designers, legislators, commercial and non-commercial operators etc. A vast range of factors are considered, from existing practices, recommended changes, to cost to implement changes etc ....
Simply flipping a decision to go all metric, or all decimal, etc is no easy task. It has huge ramifications for manufacturers, supply chains, right through to making items, products, machinery etc virtually obsolete. How long a change over / transition period is acceptable - well just ask the restorers of fine old Wadkin machinery or any vintage motorcycles, cars, trucks, etc.
Somehow we have to eliminate the major errors such as the lbs to kgs confusion for aircraft fuel loading etc.Mobyturns
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17th September 2023, 09:34 AM #33SENIOR MEMBER
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Isn't DAR timber still in imperial measurements simply disguised in metric to satisfy the metric conversion requirements...?
The middle line of a 19mm thick board is an easy 9.50mm. I s'pose I'm lucky it isn't 9.25mm...
Happy measuring,
Yvan
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17th September 2023, 07:29 PM #34GOLD MEMBER
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It gets worse when you fly from Oz to the USA. They use statute miles for visibility, feet for runway length and inches of mercury for altimeter pressure setting.
Then when you fly to China, they use metres for altitude and metres per second for wind speed. Their instrument charts have speeds in knots and kph, so take your pick!
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18th September 2023, 12:29 AM #35
It is similar with marine navigation.
Distance is measured in nautical miles and cables - a cable is a tenth on a nm. The metric countries have always navigated in nautical miles - in French a nm is a Mille Marin. A nm is equal to one minute of latitude and is conveniently taken from either side margin of a paper chart.
Speed is measured in nautical miles per hour or knots - French noeud. Ship speed, wind speed and current speed are all measured in knots. With ship and currents the direction is where it is going; with wind it is the direction it is coming from. (A southerly wind is blowing from south to north. A southerly current is flowing from north to south.)
Depth is measured in metres and decimals. It used to be measured in fathoms and feet but that was phased out from 1967. American charts still use fathoms and feet.
Directiion is measured in degrees, minutes and seconds. Attempts to metricise direction have not succeeded. Often now, direction is measured informally in degrees and decimals, ditto for position.
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18th September 2023, 08:08 AM #36
Much confusion has resulted in searches etc due to the misinterpretation of position as either DDD.ddddd or DDDmm.mmm or DDDmmss.ss ... no confusion when a 7, 8 or 9 appears in the first decimal .... well ..... still could be mm.mmm or mmss.sss .... argh!
Then we add confusion of chart datum ..... WGS or ..... AGD some 200m (approx) difference in position, on the water not such an issue but in dense bush??? Well it can be an issue marine navigation wise as many have experienced when they run aground or prang into a breakwater sea wall etc.
now back to metric vs imperial bolts .....Mobyturns
In An Instant Your Life CanChange Forever
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18th September 2023, 11:35 AM #37
Unfortunately true, Mobyturns.
But when doing onchart calculations it is much easier to work in degree decimals rather than degrees, minutes and seconds - that is the justification of the metric system.
As to those groundings and errant seawalls, aren't you confusing navigation and pilotage?
Now, back to metric vs imperial bolts .....
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18th September 2023, 05:57 PM #38
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19th September 2023, 06:13 PM #39Senior Member
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Did you know that the USA inch is very slightly different in size to the UK imperial inch?
All due to the fact that in the mid 19th century the UK settled on a definition of a standard inch, but the USA was independent and not subservient to its former masters.New Zealand
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19th September 2023, 08:37 PM #40
THere are so many common items in the world that do not use metric threads. All the other thread types were made for reasons and there are large expensinve things that people won't want to just throw out because they can't get the imperial bolt to fix it. I generally have found already that if I go out to buy a particular imperial bolt or nut they do tend to be far more expensive than the metric ones.
So, if Bunnings don't sell metric fasteners any more I will probably have to do what I did during COVID lockdowns when Bunnings was the only nut and bolt shop within my 5 km Daniel Andrews-imposed radius, and you had to click and collect, and had to sit in th ecar park for an hour and a half to be handed the wrong items. I just made my own on the lathe and mill. Time consuming, not really cost effective but doable.I got sick of sitting around doing nothing - so I took up meditation.
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19th September 2023, 08:38 PM #41
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20th September 2023, 12:13 AM #42Originally Posted by doug3030
I am forced to go to a specialist store - usually Nuts and Bolts in New Town, an inner suburb of Hobart - for a number of reasons:
- Significantly lower prices,
- Much better quality - they do not sell screws with detachable heads,
- Will sell me one screw, not one packet,
- Staff really know their product lines, and
- I trust them and their products.
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20th September 2023, 12:24 AM #43
No, what I meant was that during covid lockdowns Bunnings was the only place within our allocated 5km radius. Buying nuts and bolts from Bunnings never ends well. They hardly ever have what I want anyway and the staff are useless. I normally go to Connekt Fastenings, where their range of stock means I have to make my own less often. Unfortunately they were outside the 5 km radius during lockdown.
I got sick of sitting around doing nothing - so I took up meditation.
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20th September 2023, 01:28 AM #44Senior Member
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I wasn't aware that these are optional.
My experience is that they're standard, along with Phillips head screws that chew out with the slightest force and then can't be easily extracted, with all bathroom, kitchen and other fittings such as toilet roll holders, towel rails, light fittings and everything else that comes with a package of screws and plugs out of China.
Which is why I always use other screws and plugs, often made in China to better specifications and quality control, and usually from Australian suppliers. Sometimes I explain to my customers that I'm not using the rubbish that comes with their often supposedly top quality fittings as I prefer to install things that last for a reasonable time or even can just actually be installed successfully. Or more often I don't bother explaining, because it'll just upset a customer who's spent big dollars on a fitting and thinks everything in the box is quality to finish their expensive reno. I just replace the crap fasteners with good stuff, and craftily conceal the supplied fittings as I sneak them off site.
The farce is that there's rarely even a couple of dollars in replacing the crap with quality. And slightly less when deducting the obviously minimal cost in supplying the packed screws and plugs.
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20th September 2023, 02:13 AM #45GOLD MEMBER
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Bunnings has a huge selection of quality bolts and screws. Especially their SS bolts and screws. Also the high tensile bolts are very good. No, they aren’t cheap. But if you only need a few they are a very convenient option. They also have lower quality bolts and screws. You just need to be discerning.
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