What is a measurement?

[condeesteso]

An odd question? But I think it's worth consideration. We're all familiar with the basis of measurement (inches, mm, Bob's Rule etc) so it seems obvious, although I have seen arguments saying stop using a rule as quickly as possible when making anything. There is a thread here about some chisels that seem to maybe come out not exactly the width stated - and this is NOT specifically about that but it did prompt it.
I think a measurement is the exact replication of another dimension. If we need a measurement to travel a long distance we need a common code (a ruler) but in the workshop, the first stretcher is the best ruler to set the next 3, and that basis applies for every repeated dimension. After all, a mortice gauge isn't what we regard as a ruler is it?
In fact, I think rulers are one enemy of design because if you work to dimensions off a ruler, it stops the eye looking at what is right. I like the idea a table top may end up 1476mm long because that looks right when the legs are 773mm high - and neither were ever 'rulered'.
If you are replacing or replicating something, the best reference is the original or the hole it left, a rule only introduces error.
The fact that an American may replicate an old European piece in inches, or European replicate an old American piece in mm serves to remind that a rule is like a currency - it is no accurate gauge of anything, just a reference of length or value.
There is plenty of evidence supporting the fact that a measurement is just a value we can all understand (like currency) and it's a simple language form enabling us to communicate with each other. But it's not a good way to make things. Witness the story stick, for example.

Let debate commence.

 

[clk230]

a measurement allows you to accuratley replicate , wether it be distance, weight ,speed its as simple as that.

 

[Paul Chapman]

a rule only introduces error.

Agreed. I avoid using rulers whenever possible and use rods (or variations on the rod) which helps to avoid mistakes in transferring measurements.

Cheers :wink:

Paul

 

[bugbear]

a rule only introduces error.

Agreed. I avoid using rulers whenever possible and use rods (or variations on the rod) which helps to avoid mistakes in transferring measurements.

Cheers :wink:

Paul

You said "rod " !!

BugBear

 

[Jacob]

a rule only introduces error.

Agreed. I avoid using rulers whenever possible and use rods (or variations on the rod) which helps to avoid mistakes in transferring measurements.

Cheers :wink:

Paul

You said "rod " !!

BugBear

It's catching on. I knew it would! Even Paul has finally twigged :shock: though I'd like to see how he actually works it.

 

[Hudson Carpentry]

To answer the question: Its the size in numerical value in a preferred unit that someone has given reference to or recorded using a measuring device.

Any measurement is accurate to the devices read out, other devices may not show the same value in which case if your that bothered take a few measurements and then work out the average.

When it comes to wood, mm perfect is all you can hope for. Wood moves, expand and change making a perfect true measurement impossible with woods anyway.

EDIT:
As with all devices, a tolerance is involved. Using a rod can be inaccurate in terms of true values. The pencil mark or marker you use can add a mm or more if not done correctly. A rod is a good method but really is just a reference to a point.

 

[Jacob]

It's all here (probably) http://en.wikipedia.org/wiki/Measurement

I have seen arguments saying stop using a rule as quickly as possible when making anything.

The argument is not so much about stopping the use of a ruler, but more about working from full sized working drawings taking marks off directly without measuring. Even more important; without having to do acres of little calculations on the backs of envelopes.
The (almost) lost art of the "rod", surprisingly commonplace in other areas of manufacturing, from making model aircraft or clothes from sewing patterns, and upwards.

 

[Paul Chapman]

The (almost) lost art of the "rod"

Why do you claim that it's almost a lost art? My observations suggest that many woodworkers use rods.

Cheers :wink:

Paul

 

[woodbloke]

It's all here (probably) http://en.wikipedia.org/wiki/Measurement

I have seen arguments saying stop using a rule as quickly as possible when making anything.

The argument is not so much about stopping the use of a ruler, but more about working from full sized working drawings taking marks off directly without measuring. Even more important; without having to do acres of little calculations on the backs of envelopes.
The (almost) lost art of the "rod", surprisingly commonplace in other areas of manufacturing, from making model aircraft or clothes from sewing patterns, and upwards.

I use full size working drawings and rods where required, but in order to make the rod accurately, you have to use a rule in the first place, n'est pas? - Rob

 

[Paul Chapman]

in order to make the rod accurately, you have to use a rule in the first place

Not necessarily - it depends what you are making and what you are measuring.

Cheers :wink:

Paul

 

[woodbloke]

in order to make the rod accurately, you have to use a rule in the first place

Not necessarily - it depends what you are making and what you are measuring.

Cheers :wink:

Paul

Example Paul? - Rob

 

[Jacob]

in order to make the rod accurately, you have to use a rule in the first place

Not necessarily - it depends what you are making and what you are measuring.

Cheers :wink:

Paul

Example Paul? - Rob

You can start a rod simply by pencilling in your first marks taken directly from e.g. the width of an opening (if you were making a door), or the length of a trombone (if you were making a cupboard for it) and then work in all your other components either by eye or by tracing off around timber samples, or by applying dividers, or laying on actual hardware, etc etc. In this way you can design the whole thing without measuring anything. You then take off your measurements directly on to the timber and then make the whole thing without measuring anything.
You might need to measure if you are ordering timber - which is where measuring comes in handy i.e. for distant communication of size information.

 

[Paul Chapman]

in order to make the rod accurately, you have to use a rule in the first place

Not necessarily - it depends what you are making and what you are measuring.

Cheers :wink:

Paul

Example Paul? - Rob

I've just made and fitted some shelves in a cupboard for my daughter. I took all the measurements with a couple of these and didn't use a ruler at all

I fitted them today and they fitted perfectly.

Cheers :wink:

Paul

 

[woodbloke]

You can start a rod simply by pencilling in your first marks taken directly from e.g. the width of an opening (if you were making a door), or the length of a trombone (if you were making a cupboard for it) and then work in all your other components either by eye or by tracing off around timber samples, or by applying dividers, or laying on actual hardware, etc etc. In this way you can design the whole thing without measuring anything. You then take off your measurements directly on to the timber and then make the whole thing without measuring anything.
You might need to measure if you are ordering timber - which is where measuring comes in handy i.e. for distant communication of size information.

Yes, and those arguments are valid and that's the sort of thing that I think we do all the time. But suppose you had a commission to build eight of these (and I did something similar once) to fit an ordinary member of Joe Public, not anyone specific (aka a trombone):

...you would yes, make a set of rods for ease of batch production, but what would you do to make the initial rod(s)? You would have to consult a book to find the correct measurements (remember this for Joe Public 'ordinaire') for seat height and width (say) and then you'd have to use a rule to transfer those measurements onto that first rod...after that, agreed, you wouldn't need to use a rule again, provided the measurements were correct.

Or to swing the question the other way...suppose you had a commission from a designer to make the same batch of chairs, but to fit people with very large backsides, much bigger than standard and you were given a specific measurement for the seat dimensions, a rule would have to be used to find that measurement and set out the rod(s) - Rob

 

[Jacob]

.... suppose you had a commission to build eight of these (and I did something similar once) to fit an ordinary member of Joe Public, not anyone specific (aka a trombone):

,,,,
...you would yes, make a set of rods for ease of batch production, but what would you do to make the initial rod(s)? You would have to consult a book to find the correct measurements (remember this for Joe Public 'ordinaire') for seat height and width (say) and then you'd have to use a rule to transfer those measurements onto that first rod...after that, agreed, you wouldn't need to use a rule again, provided the measurements were correct - Rob

Personally I'd be inclined to look at a chair as a first point of reference.
In fact I've said it many times, no doubt boring the harse of a lot of people :roll: but for designing/making things your best source of information is nearly always other things of the same sort. Books are utterly secondary.
If I was running a furniture course I'd make anatomy of furniture the main, central, compulsory module, with old furniture being brought in and de-constructed on a daily basis!

 

[woodbloke]

Personally I'd be inclined to look at a chair as a first point of reference.
In fact I've said it many times, no doubt boring the harse of a lot of people :roll: but for designing/making things your best source of information is nearly always other things of the same sort. Books are utterly secondary.
If I was running a furniture course I'd make anatomy of furniture the main, central, compulsory module, with old furniture being brought in and de-constructed on a daily basis!

Yes Jacob, I agree with you, but you haven't answered the question (you ought to be a politician :lol: )...how do you obtain the measurement to set out that first rod(s)? even if you look at good examples of the sort of thing you need to make - Rob

 

[Jacob]

Personally I'd be inclined to look at a chair as a first point of reference.
In fact I've said it many times, no doubt boring the harse of a lot of people :roll: but for designing/making things your best source of information is nearly always other things of the same sort. Books are utterly secondary.
If I was running a furniture course I'd make anatomy of furniture the main, central, compulsory module, with old furniture being brought in and de-constructed on a daily basis!

Yes Jacob, I agree with you, but you haven't answered the question (you ought to be a politician :lol: )...how do you obtain the measurement to set out that first rod(s)? even if you look at good examples of the sort of thing you need to make - Rob

For a chair you can of course measure - we are not being obsessive here. But you can also use dividers or draw profiles direct. Dividers are very useful and often handier than a tape for transferring dimensions.
The important thing is to be looking at an example, and sitting on it, and bouncing up and down, trying it with cushions etc etc.

 

[woodbloke]

For a chair you can of course measure.

Hallelujah and praise be \/ ...a breakthrough at last!...I can enjoy me glass of vino tonight :lol:
Now about those rounded bevels :lol: :lol: - Rob

 

[Paul Chapman]

Another example. When I was making a table where the legs were splayed in two directions, it was quite complicated to work out the angles for the legs and rails. In the end I made up my own version of a double-ended sliding bevel which made it easy to transfer the angles. It was a variation on the rod.

Cheers :wink:

Paul

 

[Jacob]

For a chair you can of course measure.

Hallelujah and praise be \/ ...a breakthrough at last!...I can enjoy me glass of vino tonight :lol:
Now about those rounded bevels :lol: :lol: - Rob

I think you have missed the point as usual Rob so I wouldn't hit the bottle too soon!
I've got nothing against measuring - that'd be insane. The main point of the rod system is to eliminate error, where measuring is often the cause, especially the detailed addings and subtractings which go on once things get a even a bit complicated.