Help with imperial measurements

[owas]

I just wish the worker I've been lumped with to cut my steel could read a tape

 

[mtt.tr]

So if you were tiling a plane in mm (or decking out a boat) you'd probably round it off to the nearest mm.
I refer the honourable gentleman to the reply I made some moments ago.

As for "naming" a component identical to many others but with the wiggle room required to fit, does anybody else follow RRBuildings on Youtube? He makes very impressive post frame buildings.

Nothing is ever perfect so they might want an eight foot post with a 4 inch rebate and (typically) +1/8" to level to the not quite perfect concrete. He shouts down to the chap by the saw, "add an eighth to that one and just shy of a sixteenth to the other" etc. That's a human sized unit with its own name rather than a series of numbers.

Sounds about the same as "add 3mm to one and just shy of 2mm to the other one" but in the real world, thats more like a list of numbers than the name of a thing. The "thing" is mm and the measurement is just the number of those things. I don't want to overegg it but there is definitely a place for human friendly imperial measurements which can be more easily remembered or spoken than constant lists of numbers.

I think the problem is that the world never really made a firm commitment to wipe out imperial and go all in for metric. Sheets are still 8x4 (or 2440x1220), lumber is still 4x2 or a 6x2 and that is true even if they sell you a 100x50 or a 150x50. If I was on site and asked a lad to fetch me "three four by twos and two six by twos" I might be more confident than asking for "three hundred by fifty and two hundred by one fifty's". Even writing it down is a chore but the chore is the same when the numbers are spoken....

Anything wood gets scribed


I wasnt digging you out your comments are not outrageous, I think the idea somone can mark to 0.05mm laughable which isn't a comment you made

 

[Screwdriver]

Anything wood gets scribed


I wasnt digging you out your comments are not outrageous, I think the idea somone can mark to 0.05mm laughable which isn't a comment you made

Sure I just think there's no benefit to removing imperial units since they are so much easier in "the real world" whereas online and for CNC, metric numbers rule. No pun intended.

It would appear the metric vs. imperial debate is a bit like Mac vs. PC. In both cases, they both do exactly the same thing! Neither is "better" than the other, they do the same job in different ways.

 

[rtcosic]

So are Gnat's Cock and Fag Paper Imperial, American, Metric or SI units?

Are they Absolute, Relative or Context Sensitive units of tolerance?

Does anyone have a suitable measuring instrument?

I don't; yet when doing work on houses my boys and I didn't have a problem working to those tolerances!

I'm 5' 11 15/16" tall, weigh 90kgs and take a size 43 shoe.

These just happen to be the units I find easiest for these measurements. Purist I'm not.
But my favourite tape measure is metric only on both sides and both faces. So whichever way I hold it one set of numbers and markings is sure to be legible. My pet hate is ones in both metric and imperial. Whichever units I set out to work in will always be the one I can't read given the orientation of the tape measure.
I suppose that's why Murphy's Law was passed.

Edit: talking of American units I fell over some saw milling videos on YouTube - as one does.

I heard the miller talking of 'four quarter' and 'five quarter' which seemed logical that given the kerf of the blade and the agricultural nature of the equipment working to a tolerance of 1/4 of an inch seemed entirely reasonable.

But he later mentioned that a 1 inch board wasn't the same as a four quarter board but never explained. Does anyone know? Don't start on board-feet though.

(let's not talk of acre-feet of water or grains per hundred cubic feet on H2S in natural gas. PLEASE!)

 

[Screwdriver]

I think those quarters refer to the orientation and position of the cut, not the size.

 

[cheb]

Not so much just the fluency part, but knowing how to convert between the 2. The rule of 254. i.e. 25.4mm to an inch. Or divide 1000 though by 25.4 is about 39 so 39 thou to a mm. Ish.

Easy for those who are aged about 50 to 60 as they were at school during the changeover in teaching. Even my wife who is 6 years younger than me can't do imperial, but that's no bad thing. Everything nowadays is metric as long as you're outside the USA. Except I recall the railway system still uses miles, chains, yards etc. Oh and the standard track gauge is 4' 8 1/2" Lord only knows where 4 foot eight and a half came from though

What made me laugh a few weeks back was a news article in the US where someone had a hole appear in their floor. The article described it as being "Large enough to fit a washing machine". The first comment was "Americans will do anything to avoid using the metric measuring system"

The one which does rather grate though is when someone describes something imperial as a decimal notation. i.e. 6.5 inches. When did imperial ever use tenths of anything? Halves, quarters, eighths, sixteenths etc but never tenths.

Some drive chains are specced round tenths IIRC and so were some computer chip pin spacings. The latter is a more vague IIRC than the former.

 

[bricol]

So if you were tiling a plane in mm (or decking out a boat) you'd probably round it off to the nearest mm.
I refer the honourable gentleman to the reply I made some moments ago.

As for "naming" a component identical to many others but with the wiggle room required to fit, does anybody else follow RRBuildings on Youtube? He makes very impressive post frame buildings.

Nothing is ever perfect so they might want an eight foot post with a 4 inch rebate and (typically) +1/8" to level to the not quite perfect concrete. He shouts down to the chap by the saw, "add an eighth to that one and just shy of a sixteenth to the other" etc. That's a human sized unit with its own name rather than a series of numbers.

Sounds about the same as "add 3mm to one and just shy of 2mm to the other one" but in the real world, thats more like a list of numbers than the name of a thing. The "thing" is mm and the measurement is just the number of those things. I don't want to overegg it but there is definitely a place for human friendly imperial measurements which can be more easily remembered or spoken than constant lists of numbers.

I think the problem is that the world never really made a firm commitment to wipe out imperial and go all in for metric. Sheets are still 8x4 (or 2440x1220), lumber is still 4x2 or a 6x2 and that is true even if they sell you a 100x50 or a 150x50. If I was on site and asked a lad to fetch me "three four by twos and two six by twos" I might be more confident than asking for "three hundred by fifty and two hundred by one fifty's". Even writing it down is a chore but the chore is the same when the numbers are spoken....

Its been said before - its what you are used to.

To my younger colleagues, your 1/8 and 1/16 mean absolutely nothing - complete unintelligible garabage - but 3.175mm and 1.6mm are perfectly understandable and useable with no thought at all.

Due to my work experience, older parents, etc, both your and their measurements are clear and useful to me - inf-fact, if you'd said 1/8" from this, and 1.6mm to this, I would still know exactly what you mean.

But if you needed to ask me, or them, to modify our components by so much on assembly, someone somewhere would be getting a rollocking for either not creating a correct drawing, or not making it correctly to the drawing!

 

[bricol]

How do you mark out to 0.05mm when the tip of even an ultra-fine line marker is twice that thickness?

Because you don't use a marker, you use a scribe - and decide which side of the scribed line is where you are working to/from.

Of course, if I decide its this side, and you think its that . . .

I'd be quite happy with me abilities, correct spectacles on, in measuring or marking to the nearest 0.05mm on metal.

Without the specs, I'd be quite happy with simply finding the tape measure .. .

 

[Pete.]

Fair play to you is all I can say. I've yet to see a rule or tape measure with marks that close. The finest I've found searching online is 0.25mm graduations.

 

[bricol]

The Americans don't even use " The Imperial system" just their own unique take on an inch based system , this is not helped by them taking the wrong sized bucket so they have ended up with a gallon of 4 litres.

Flipping heck - have they changed the bucket again . . . last time I looked it was a bit smaller than that

It's how I tell my American fellow Dodge enthusiasts to get more mpg - change the displayed mpg from US gallons to UK imperial gallons (which there is a setting for in the computer for some reason, it being a car never intended to be sold here).

Casio scientific calculators of my school era were pre-programmed with various conversion factors (and might still be for all I know - I can't work a modern calculator as you seemingly have to enter things in all the wrong way round) - and they had the US conversion for litres to gallons - did occasionally cause arguements in the office as to the capacity and weight of water in our industrial washing plant.

 

[bricol]

Fair play to you is all I can say. I've yet to see a rule or tape measure with marks that close. The finest I've found searching online is 0.25mm graduations.

I haven't either - but I am pretty confident in my ability to estimate - note I'm talking to the nearest 0.05mm - not to 0.01, 0.03, or 0.06 - I'll happily estimate to 10.2, to 10.25, or to 10.3. One of the Utah red-necks I sometimes observe on youtube likes to mention his "eye-chrometer" - and he's right, you can estimate pretty well with some experience. I've been proven to be pretty right more often than not when rather more sophisticated measurement gear has been used. I wouldn't like to rely on it, or do it all the time, and I don't have to, as its not exactly precise, scientific or sensible.

I was astounded by an American colleague a few years ago - a project requiring a hole punched in the bottom of a can, then it forming into a flare, with some close tolerances required. We'd then trim the can down and inspected the formed hole - he'd eye it up through a loupe and pronounce his verdict on error . . "about 2 thou . . . about 4 thou . . ."

Bol lox!

By eye, with no reference.

So we stuck it on the shadowgraph . . . . 2 thou and just under 4 . . .

Customer spent many thousands on some fancy bit of kit from Mitutoyo to do the same

(always amuses me - I grew up not far from Elland - that such a company as Mitutoyo has a place there)

 

[bricol]

This is probably to simplify cam processing they don't want to be redrawing it in 3d for cam.

Yeah it's simple but they can save time

You'd be a fool to not triple check any non-controlled 3D model exported from someone else's CAD system though. I quite often supply them, but with no surety my exported file is error free, and certainly none that your import of it is also problem free.

That particular part - I could have modelled it in CAD quicker than it took him to call me and wait for me to pick up the phone.

 

[Newlands]

I think those quarters refer to the orientation and position of the cut, not the size.

I’m pretty sure they refer to the board thickness, measured in quarter inches. It’s the finished size of the sawn timber, so if you wanted it planed it would end up as ¾” thick as you lose ⅛” per face to clean it up.
Quarter sawn timber is something else completely and refers to the vertical orientation of the growth rings in the plank. Slash sawn would have horizontal growth rings.

 

[Screwdriver]

Fair play to you is all I can say. I've yet to see a rule or tape measure with marks that close. The finest I've found searching online is 0.25mm graduations.

As it happens due to some anomalous visual issue, I have a problem with repeating lines, strings of zeros etc. so the best I could hope for is to find a 1/16" or a mm line anyway.

But that accuracy in striking a line marked on the ruler is not the advantage of fractional inches I referred to some time ago. It was rounding error. Cumulative error which can creep into real life (not on a computer/virtual model). If you are chopping a workpiece in half and then finding the-middle-of-that, sort of thing.

Whereas not only is 1/4 dead easy to divide by two, there will be a corresponding preexisting mark on a calibrated rule for you to quickly find. I am playing devils advocate because frankly, I use mm all the time unless I'm cutting some larger pieces and the numbers just makes inches easier or the workpiece is clearly an imperial relic. I can see how dividing by three is trickier but then so is dividing anything by three!

Imperial and metric both have their place and it's sometimes nice to have that choice of which unit to play with. Especially if you have to give someone a verbal instruction. In all honesty, the "accuracy" even cumulative is a bit of a non sequitur, since in my (many!) examples I neglect to admit 1mm is way more accurate than 1/16" anyway but it has been fun!

Gratuitous smiley face because today is a good day.

 

[Screwdriver]

I’m pretty sure they refer to the board thickness, measured in quarter inches. It’s the finished size of the sawn timber, so if you wanted it planed it would end up as ¾” thick as you lose ⅛” per face to clean it up.
Quarter sawn timber is something else completely and refers to the vertical orientation of the growth rings in the plank. Slash sawn would have horizontal growth rings.

Yep, got it thanks. Four quarter is an interesting way to say one inch!

Woodbotherers are odd folk...

 

[mtt.tr]

Woodbotherers are odd folk...

They have to be, lot of witchcraft involved otherwise from day to day with expansion nothing would fit.

 

[Pete.]

I haven't either - but I am pretty confident in my ability to estimate - note I'm talking to the nearest 0.05mm - not to 0.01, 0.03, or 0.06 - I'll happily estimate to 10.2, to 10.25, or to 10.3. One of the Utah red-necks I sometimes observe on youtube likes to mention his "eye-chrometer" - and he's right, you can estimate pretty well with some experience. I've been proven to be pretty right more often than not when rather more sophisticated measurement gear has been used. I wouldn't like to rely on it, or do it all the time, and I don't have to, as its not exactly precise, scientific or sensible.

I was astounded by an American colleague a few years ago - a project requiring a hole punched in the bottom of a can, then it forming into a flare, with some close tolerances required. We'd then trim the can down and inspected the formed hole - he'd eye it up through a loupe and pronounce his verdict on error . . "about 2 thou . . . about 4 thou . . ."

Bol lox!

By eye, with no reference.

So we stuck it on the shadowgraph . . . . 2 thou and just under 4 . . .

Customer spent many thousands on some fancy bit of kit from Mitutoyo to do the same

(always amuses me - I grew up not far from Elland - that such a company as Mitutoyo has a place there)

Ok so that isn't setting out to 0.1mm it's extrapolating a position between two marks. I'll accept that a person could do that with a fine enough scribe and a good loupe but let's not call it 'setting out' at least not to that tolerance. If you can scribe one line then use that trick to 'set out' another line to 0.1mm accuracy say 200mm away using a scribe and loupe than that really would be something.

Of course you can't set out to 0.1mm with a tape measure at all because even a Class 1 is +/- 0.3mm over 2m.

 

[mtt.tr]

Ok so that isn't setting out to 0.1mm it's extrapolating a position between two marks. I'll accept that a person could do that with a fine enough scribe and a good loupe but let's not call it 'setting out' at least not to that tolerance. If you can scribe one line then use that trick to 'set out' another line to 0.1mm accuracy say 200mm away using a scribe and loupe than that really would be something.

Of course you can't set out to 0.1mm with a tape measure at all because even a Class 1 is +/- 0.3mm over 2m.

Yeah but it makes a nice story

 

[Screwdriver]

I haven't either - but I am pretty confident in my ability to estimate - note I'm talking to the nearest 0.05mm - not to 0.01, 0.03, or 0.06 - I'll happily estimate to 10.2, to 10.25, or to 10.3. One of the Utah red-necks I sometimes observe on youtube likes to mention his "eye-chrometer" - and he's right, you can estimate pretty well with some experience. I've been proven to be pretty right more often than not when rather more sophisticated measurement gear has been used. I wouldn't like to rely on it, or do it all the time, and I don't have to, as its not exactly precise, scientific or sensible.

I was astounded by an American colleague a few years ago - a project requiring a hole punched in the bottom of a can, then it forming into a flare, with some close tolerances required. We'd then trim the can down and inspected the formed hole - he'd eye it up through a loupe and pronounce his verdict on error . . "about 2 thou . . . about 4 thou . . ."

Bol lox!

By eye, with no reference.

So we stuck it on the shadowgraph . . . . 2 thou and just under 4 . . .

Customer spent many thousands on some fancy bit of kit from Mitutoyo to do the same

(always amuses me - I grew up not far from Elland - that such a company as Mitutoyo has a place there)

The human brain is an extraordinary piece of kit and it's a shame we are so preoccupied with handing over tasks to computers so that people spend a lot less time developing or maintaining its full function. The eye is just a part of your brain that pokes out the front through a hole in the skull. It can quite easily detect the difference between electromagnetic radiation between say 400THz and 500Thz, if it didn't there would be havoc at the traffic lights. That in itself is pretty damned amazing but even human hearing is an unbelievable Fourier analysis of vastly complex vibration which our brain processes instantly, in real time, to allow us to correlate patterns we perceive as individual sounds.

Nobody knows how it works really. It would appear our brains just aren't smart enough to truly understand how it does what it does. The old adage suggests that if the brain (specifically the cerebral cortex) was simple enough for us to understand it, we'd be too dumb to figure out how it worked anyway. Annoyingly, it will almost certainly be an A.I. that gets there first, cue Skynet and all that malarky because by then that A.I. will be a darned site more clever than some dumb apes who will still be arguing about whether or not this thing is "conscious".

It is sort of relevant to imperial vs. metric because imperial was/is a much more human friendly metrology because it has individual names for scales like inch, foot, mile etc. to which you can attach a multiplier. Metric on the other hand is all one unit, the metre. I don't think that helps our brains to compartmentalise or "scale" our real world perception of measured distance since numbers are an abstract concept which do not immediately orient our understanding from a human perspective.

We use a thousandth of a metre as a "unit" but it doesn't relate to the everyday real world scale of objects that might informally require it, like a coffee cup. There are just too many millimetres in them! The room I am in is about six metres long (I think!) which is a nice number but a crude yardstick (sorry!) to measure it from because no part of my body is easily described in metres. I don't relate to it. I'm definitely more than one but nowhere near two (few humans are!) I **think** people generally are comfortable with up to about ten of anything (for obvious reasons) although I have a distant memory of the actual numbers of "things" we can comfortably relate to or visualise accurately and subconsciouly is closer to six.

Apologies for needing to let this out, I woke up today in an odd mood and it hasn't left me yet.

So what is a metre? About three feet...

 

[Dr.Al]

The thing that bugs me most about imperial/American units isn't the inch itself: it's all the other weird and not-so-wonderful ways of measuring things.

Examples include drill sizes (e.g. #40) & sheet metal thickness (AWG or SWG). I like that in a metric world I can measure the thickness of a piece of sheet metal and if (say) it's 1 mm & I want to order more, I order 1 mm. In America, your calipers would tell you that the material was 0.04" so you'd have to order 18 AWG sheet. Also, there's special place in hell reserved for people who say a number followed by the word "degrees" and mean "degrees Fahrenheit".