General Category > General Discussion
Metricification of Imperial measurements.
Bryan Milham:
I'm of an age where I am quite happy working in just about any measurement. From Miles through Barleycorns (1/3") to 'thou's of an inch, and from Kilometres to Millimetres and fractions thereof.
So a simple question. When should we not convert between them?
This question is raised by this months Woodturning magazine article on making a pocket pipe. In it the instructions say drill a hole 3.81mm diameter (Do What!). Now I'm quite lucky in having closed several workshops and 'acquired' many twist drill bits, including several 3.8mm, but what is a 3.81mm?
So I set to working it out, nope, not 16ths, nope not 32nds and not 64ths, I even tried 128ths, a drill size I've never even heard of (and it wasn't one of them either).
So I worked it backwards 25.4mm / 3.81mm = 6.66667, ah, It's a 1/6 of an inch. Now that is probably a drill bit size but I can't find one. It's bigger than a (Old English) size 'V' at 3.77mm and smaller than the size 'W' at 3.86mm. And I can't see one listed in any Drill Chart either!http://www.csgnetwork.com/drillsizeconvert.html Anyone seen or got one?
So the instructions are telling us to use a metric equivalent of an unobtainable English size!
Are there times when we should not convert from one measurement system to another, or an I just being grumpy?
thebowlerhattedturner:
No I think you are just being grumpy. :D
Those of us of a certain age and over have the ability to work and think in many different measurements.It is not unusual for me to combine 2 different measurements(ie. 3 foot 7mm)As long as I know what I mean that's all that matters. In joinery we used to work to the nearest 32nd (these days I think they work to the nearest 1/4.)!! If it didn't fit hit it harder. It was only when you worked on cabinetry that the measurements got more critical, things like inlay work and fine furniture had to be a bit better. When I turn things like newel posts I can quite often work all day without taking any measurements with a rule or tape,I do comparative measuring and work to the sizes of my tools, obviously diameters have to be more accurate. If you think of how much the wood can move being that accurate may cause problems in the future, how many times have you made a pot and put it on the table only for the lid to pop off once it starts to move?
I don't want to convert for the same reason that I don't want to have currency in my pocket without having the Queen's head on it.
Who being grumpy now then? ;D
Regards
John BHT
Bryan Milham:
Ah, the old,
Measure Twice, Cut Once and beat into Place trick!
The other one I heard was,
Cabinet Makers work to the thou',
Joiner work to the 64th,
and Carpenters work Monday to Friday!
woodndesign:
--- Quote from: dr4g0nfly on January 31, 2013, 06:43:34 PM ---Ah, the old,
Measure Twice, Cut Once and beat into Place trick!
The other one I heard was,
Cabinet Makers work to the thou',
Joiner work to the 64th,
and Carpenters work Monday to Friday!
--- End quote ---
:) .. :D .. ;D ... There is always room for a smidgen and if there's ever a spanner in the works ... it Metric ... ;D ...
I still even at my age see readily Imperial measurements, maybe from cutting, matting and framing, it's as John put it: 'work to the sizes of my tools' I find it the same when all you use are imperial, fine for laying out, sizing, but add in metric, however much they try telling us it's the same .. 1" is not 25mm .. since 1959, the inch has been defined and internationally accepted as being equivalent to 25.4mm ... that's when it's not as with most conversions given as cm ... :( .. then timber is metric, blanks are often imperial-ish, so which do anyone of us use, which ever works best for what your doing or what someone else may what, like a newel as long as the ends are correct, you less whatever the lenght it is in the middle.
Ok from another grumpy .. ;D .. David
Tim Pettigrew:
--- Quote from: dr4g0nfly on January 31, 2013, 03:59:40 PM ---
This question is raised by this months Woodturning magazine article on making a pocket pipe. In it the instructions say drill a hole 3.81mm diameter (Do What!). Now I'm quite lucky in having closed several workshops and 'acquired' many twist drill bits, including several 3.8mm, but what is a 3.81mm?
--- End quote ---
Sounds to me as if someone has let a typo slip through the magazine proofreading ::)
Tim
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