Quantcast

Imperial measurement

UKworkshop.co.uk

Help Support UKworkshop.co.uk:

Templatetom

Established Member
Joined
4 Jun 2010
Messages
77
Reaction score
0
Location
Perth Western Australia
Since I have produced all my topics and plans in the metric system I made an effort to produce a sample of tenon making with my Super jig using imperial method.
I need some advice as to how the details are presented (a) in decimal parts of the inch or (b) fractions on an inch as per the drawing.
 

Attachments

twothumbs

Established Member
Joined
13 May 2011
Messages
394
Reaction score
0
Location
Edinburgh
Fractions of an Inch would be the usual way. Went into my first construction metric exam with the advice from a tutor... remember it is straight forward...an inch is equal 25.4mm. and that was before calculators. I passed.
 

Sawyer

Established Member
Joined
7 May 2011
Messages
581
Reaction score
0
Location
France
It should be fractions, as you have in (b). Usual to use the simplest possible fraction, eg. 3/4" instead of 6/8" and so on. As you have done in (b), so your drawing is spot on.
 

Cheshirechappie

Established Member
Joined
30 Jan 2012
Messages
4,732
Reaction score
17
Location
Cheshire
The general convention in engineering is that any dimension expressed in decimal fractions (1.750" for example) is one that expected to be made to a tolerance of 1/2 thou either way - so 1.750" really means between 1.7495" and 1.7505". That level of precision - or even tighter, sometimes - may be necessary to ensure proper fits between components. Dimensions expressed in fractions (7/8" for example) are not expected to be so precise. Both methods may be used on the same drawing in some instances.

In woodwork, the precision implied by using decimal fractions is not really appropriate. After all, wood shrinks and swells with different levels of humidity, so a piece that may be 1.750" thick at 10 o'clock in the morning may be 1.753" by 2 o'clock in the afternoon if it happens to have started raining! By the same token, if you want 1/4" mortices, your mortice chisel may well not be exactly 0.250" wide. It's actual width doesn't matter one jot as long as it's about 1/4", because you'll cut the tenons to fit. So specifying 1/4" on the drawing is plenty close enough.

Another factor to take into account is what measuring equipment the person reading the drawing will have available. Most tape measures have metric dimensions in metres and millimetres, and imperial in feet, inches and fractions of an inch - 1/4's, 1/8's 1/16's are the usual ones - so it would be sensible to use these instead of decimal fractions of an inch, which would require the workman to make a conversion to something actually on his tape. He can read off 16 7/8", but 16.875" would make him scratch his head. The less chance of errors arising by having to make mental conversions, the better.
 

Tony Spear

Established Member
Joined
6 Apr 2006
Messages
895
Reaction score
0
Location
Hinton Waldrist
Tom,

basically for things like woodwork, housebuilding etc. the norm would be to use fractions.
For anything needing high accuracy (i.e Engineering), you would use tenths. or more specifically "Thousandths."
However, it was not unusal to mix both of the Imperial systems on one job.
During my apprenticeship we used to make hydraulic tipping systems and truck bodies; for the steel fabrication work we used fractions but for the hydraulic pumps and rams we used thousandths, BUT NEVER on the same drawing.

Slightly OT, when the metric system came along it could get really confusing. I did a number of projects for a Nigerian company refurbishing old (mainly British built) water treatment plants. I could be sitting in the UK office and I'd get a fax saying "we need a new valve for XYZ, the meeting flange is 150mm bore diameter and has 4 holes" Knowing the age of the plant I was forever pointing out to them that there were 6 or 8 standard flanges that would fit that criteria! (hammer) (hammer)
 

SammyQ

Established Member
Joined
12 Apr 2005
Messages
2,253
Reaction score
23
Location
A wee house on a hill
Talking of standards that are taken as 'read', I know I'm going to put my foot (in my mouth) with Tony, but criteria are plural, criterion is singular......


Yes, I know, I came across as an irritating pedant, in the Jacob corner perhaps :(, but as a classically educated Latinist and biologist who also wants to throw things at the telly when some talking head says (about a specific species) 'the bacteria has..' GRRRRRRR! "BACTERIUM HAS - BACTERIA HAVE"!!, I feel I have to express a mild whinge!

Tony, please feel free to object to this rant, it's Monday and 9B1 were particularly........challenging today.....

Sam
 

Templatetom

Established Member
Joined
4 Jun 2010
Messages
77
Reaction score
0
Location
Perth Western Australia
Many thanks to all who expressed their reasons for a preferred method. Personally I was brought up in the imperial system (Fractions of an inch) when living in Scotland but on my journey to Australia some 45 years ago I arrived to find Australia were in the process of changing to metric. As I was in the teaching profession teaching technical drawing woodwork and metalwork I had to make some quick changes to my presentations. Then some years later I began cabinet making and then I had to go armed with both Imperial and Metric to explain sizes of cabinets to my customers.
I did make the complete change to metric and when I began writing articles on woodworking I made all the dimensions in Metric.
To this end I have always purchased individual metric template guides for my Makita and Hitachi routers
I have searched the internet to see if there are any boxes of guides for sale in metric and the only ones I have seen are produced by Trend. The manufacturers of the guides (may only be one) have come up with a strange collection of sizes IMHO and I often wonder if they had any idea as to what they were going to be used for when they made their decision as to the sizes they included in there kits as there has been little information included with the purchase.
My thoughts on this matter is that they searched the various jigs available like the number of Dovetail jigs or Finger joint, and found a certain guide was required, and included that in their selection. If I were to ask how many of the guides from the purchased set are used on a regular basis I am convinced the answer would be "Just a couple". Obviously template guides are not widely used by most enthusiasts

I would be interested in more comments on what template guides are used by the average router user
 

JakeS

Established Member
Joined
25 Oct 2011
Messages
947
Reaction score
0
Location
Grantham
I'm afraid I don't have anything to add to the discussion at hand - I was brought up metric so I don't properly understand all these inches and chains and what have you - but:

SammyQ":3uisfrxc said:
Talking of standards that are taken as 'read', I know I'm going to put my foot (in my mouth) with Tony, but criteria are plural, criterion is singular......
Think on the bright side, I saw someone use "criterium" for the plural the other day.
 

Wildman

Established Member
Joined
30 Jan 2012
Messages
929
Reaction score
4
Location
Ilfracombe
In general forums deal with specialist subjects and criticizing someones use of English or Grammar is generally considered bad form. People cannot spell for a number of reasons poor education, dyslexia, old age, and even clumsy fingers like me. To make them feel uncomfortable is not the done thing. If correct English is your bag then good luck to you but please express it on an English pedant forum. Otherwise you might drive away a very clever craftsman who can really add something to the forum.
 

bugbear

Established Member
Joined
16 Jul 2004
Messages
13,074
Reaction score
0
Location
North Suffolk
Templatetom":26qh63zu said:
Many thanks to all who expressed their reasons for a preferred method. Personally I was brought up in the imperial system (Fractions of an inch) when living in Scotland but on my journey to Australia some 45 years ago I arrived to find Australia were in the process of changing to metric. As I was in the teaching profession teaching technical drawing woodwork and metalwork I had to make some quick changes to my presentations. Then some years later I began cabinet making and then I had to go armed with both Imperial and Metric to explain sizes of cabinets to my customers.
I did make the complete change to metric and when I began writing articles on woodworking I made all the dimensions in Metric.
To this end I have always purchased individual metric template guides for my Makita and Hitachi routers
I have searched the internet to see if there are any boxes of guides for sale in metric and the only ones I have seen are produced by Trend. The manufacturers of the guides (may only be one) have come up with a strange collection of sizes IMHO and I often wonder if they had any idea as to what they were going to be used for when they made their decision as to the sizes they included in there kits as there has been little information included with the purchase.
My thoughts on this matter is that they searched the various jigs available like the number of Dovetail jigs or Finger joint, and found a certain guide was required, and included that in their selection. If I were to ask how many of the guides from the purchased set are used on a regular basis I am convinced the answer would be "Just a couple". Obviously template guides are not widely used by most enthusiasts

I would be interested in more comments on what template guides are used by the average router user
I think most people in the UK can "manage" in metric quite well; it's only the USA-ians who'll need the imperial version. (some irony there, surely!?)

BugBear
 

SammyQ

Established Member
Joined
12 Apr 2005
Messages
2,253
Reaction score
23
Location
A wee house on a hill
Wildman? I fully take your point about dyslexia and other similar conditions. As a teacher of 31 years, with a pastoral qualification and 20 years practicising it, I know and empathise with lots of people in this bracket. I was in no way aiming my 'rant' at this section of Humanity, as Tony Spear seemed a reasonably erudite individual, with a similarly reasonable grasp of technicalities and therefore, not vulnerable to ill-considered crtiticism. As a scientist, I have an obligation to use precision of language, just as woodies have in describing joints, faces, angles and components. I was trying - after a trying day - to have a have a mock-serious 'dig' and simultaneously, wake up just someone to this neglected phraseology. I admitted to Tony that I was probably going to be considered foot-in-mouth AND he's quite free to 'dig' right back. I just cringe when I hear something clear and definable mis-used and I was always taught that correction was better than allowing a mistake to be further perpetrated. But then, I am old-school (1963 onwards) and probably NOT in favour of a "dynamic lauguage".


"Practise or practice....?" see above, Sam
 

RogerP

Established Member
Joined
7 Jan 2011
Messages
3,785
Reaction score
2
Location
Gloucester
bugbear":7um67z3z said:
I think most people in the UK can "manage" in metric quite well; it's only the USA-ians who'll need the imperial version. (some irony there, surely!?) BugBear
We are officially metric in the UK but in reality we have a totally mixed system. Road distances in miles, speed restrictions in MPH, eggs packed in half-dozens and soft drinks in the original “6 pack” (half dozen). Pints of beer in pubs and pints or litres of milk on the doorstep. Most people think of their weight in stones. The list goes on ......
 

marcros

(Trevanion)+1
Joined
11 Feb 2011
Messages
10,111
Reaction score
146
Location
Leeds
i have always used metric throughout my education. I now work for an American manufacturing firm (although I am office based) where all dimensions are in inches. I actually prefer to work in inches for woodwork, for some reason it just works better for me.
 

JakeS

Established Member
Joined
25 Oct 2011
Messages
947
Reaction score
0
Location
Grantham
RogerP":387bfv4e said:
eggs packed in half-dozens and soft drinks in the original “6 pack” (half dozen)
I'm not sure these can really be considered a metric thing particularly - the metric system and decimalisation are two very separate things. Most of Europe is entirely metric, and to the best my knowledge they still have two dozen hours in the day and 360 degrees in a circle!

(And surely everyone knows a circle should be divided by two pi radians... ;-) )


I did hear something once - no idea if it's made up or true - about Napoleon trying to decimalise everything from months in the year to degrees in a circle but (thankfully) not getting away with it.
 

nanscombe

Established Member
Joined
3 Feb 2010
Messages
614
Reaction score
0
Location
Kent, UK
I have used both imperial and metric in the past.

Once I dropped a socket set and all of the sockets scattered all over the floor.

I picked them up and started putting them back.

5mm, 6mm, 7mm, 8mm ... No problem. :)

Then I started with the imperial ones.

1/4, 5/16, 3/8 ... Eh? :shock:

I tend to stick to metric for woodworking these days. :wink:
 

Sawyer

Established Member
Joined
7 May 2011
Messages
581
Reaction score
0
Location
France
By the way, even in France, the eggs are still sold by the douzaine. Even Napoleon couldn't get the hens to lay in metric! 8)

Marcros, I too find feet & inches far better for woodwork. There's something 'organic' about it which seems to suit the material. That's just me though...
 

Digit

Established Member
Joined
11 Nov 2007
Messages
10,222
Reaction score
0
Location
Wales
I use both in both wood and metal. If the measurement is 22 mm I'll work with that rather than 0.866 inches.

Roy.
 

Tony Spear

Established Member
Joined
6 Apr 2006
Messages
895
Reaction score
0
Location
Hinton Waldrist
SammyQ":1flouu2f said:
Talking of standards that are taken as 'read', I know I'm going to put my foot (in my mouth) with Tony, but criteria are plural, criterion is singular......
Sam
Actually Sam. my error was in using "that" instead of "those"! :wink:
 

bugbear

Established Member
Joined
16 Jul 2004
Messages
13,074
Reaction score
0
Location
North Suffolk
Digit":bic7nqry said:
I use both in both wood and metal. If the measurement is 22 mm I'll work with that rather than 0.866 inches.

Roy.
Me too. But I really should break the habit. Mixing units is a recipe for cockups - just ask NASA.

BugBear
 

Digit

Established Member
Joined
11 Nov 2007
Messages
10,222
Reaction score
0
Location
Wales
I don't need help from metrics to make mistakes!

Roy.
 

Latest posts

Top