Thread: F-clamp restoration

Welcome to the forum Adam.

HI Adam and welcome,

Adam 2.9 sounds like 5/16. A spring pin would tipcally be used in this position. They are economical and imperial should be readily available,
Sellock Spring Pin - United Fasteners.

If you cab get one they are easier to install that the suggested creative use of nails.

Cheers

Originally Posted by MartinCH

HI Adam and welcome,

Adam 2.9 sounds like 5/16. A spring pin would tipcally be used in this position. They are economical and imperial should be readily available,
Sellock Spring Pin - United Fasteners.

If you cab get one they are easier to install that the suggested creative use of nails.

Cheers

Martin
sorry to be a pedant, but 2.9 mm is measurably less than 1/8" = 3.175 mm
5/16" = 7.9 mm a very significant difference

Yeah, whoopsie, I am afraid imperial is a foreign language- . It is a bit like roman numerals. You know its number but what number?

Adam - A 1/8 spring pin should still fit - 3mm will be available as well.

Originally Posted by MartinCH

You know its number but what number?

Divide the top number of the fractional inch dimension by the bottom number and multiply by 25.4 to get millimetres.
Works every time.

Originally Posted by jack620

Divide the top number of the fractional inch dimension by the bottom number and multiply by 25.4 to get millimetres.
Works every time.

Yes, thats what I mean- needs a translator.
Going backwards is tricker, is fourth, eighth, sixteenth, thirtysecond, sixty-four, or some other strange numeral, for random reasons to do with someone's foot.

Originally Posted by MartinCH

Yes, thats what I mean- needs a translator.
Going backwards is tricker, is fourth, eighth, sixteenth, thirtysecond, sixty-four, or some other strange numeral, for random reasons to do with someone's foot.

Martin
Here you go
1" = 25.4 mm
1' = 0.3048 m

working backwards;
just remember that if it's imperial -- i.e. made before most of the English speaking world looking at you US went metric -- the typical divisors are:
4 -- giving you 6.35; 12.7; 19.05 mm.
8 -- giving you 3.125; 9.525; 15.875 (which is NOT the same as 16mm, despite what some saw makers); 22.225 mm -- filling in the gaps between the "Quarters"
16 -- giving you 1.5625, 4.6875, 7.8125, 10.9375, 14.0625; 17.1875; 20.3125; 23.4375 mm -- again filling in the gaps between the "8 ths"
32 -- this time I'll let you do the maths,
64 -- again I'll let you do the maths.

If none of these "work", the item's diameter is probably measured in "thou" -- 1/1000" = 0.0254 mm.
Though "thou" is only very rarely used for diameters greater than 1/16" (1.5625 mm)

There are a large number of "letter" and "number" size drill bits, but these are mostly used when drilling holes to accept taped threads and for everyday use can be ignored.

.
.

Interestingly, while the US population mostly uses "customary" units, NASA is entirely metric.
The US military is also mostly metric, as are most auto makers, but both only rarely ever quote dimensions in metric units, preferring to stay with what their customers expect -- the illogical US customary units.


there is, or perhaps was, a regular US based poster who's tag line was something along the lines of "metric system died when my wife refused to cook in metric"

Originally Posted by MartinCH

... or some other strange numeral, for random reasons to do with someone's foot.

actually originally (in England) it was measured in terms of barley corns, as in
"three grains of barley, dry and round, placed end to end, length wise" (date -- 1324)

the inch was effectively standardised at 25.4 mm in 1912, with the multiples (foot and yard) adjusted to suit.


as an aside,
when visiting the German town of Goslar in 1992, I recall seeing the foot being defined as "1/16 the length of the left feet, aligned heel to toe, of the first 16 men exiting the town's church"

I am also fascinated by the derivation of the measuring system(s).

When the Roman legions marched off to conquer Gaule, Britain and the rest of the world, every soldier took steps of exactly the same length - they were marching. When the Centurian said "left" the Legionnaires took one step; when he said "left-right" they took one pace. The distance covered by one thousand legionnaire's paces became known as a "mille" - anglesized as mile. A nautical mille is still used for navigation in France.

Originally Posted by ian

actually originally (in England) it was measured in terms of barley corns, as in
"three grains of barley, dry and round, placed end to end, length wise" (date -- 1324) ...

My understanding is that the barley corn standard was adopted then, but the inch predates that considerably - every town had its own inch.

the inch was effectively standardised at 25.4 mm in 1912 ...

Crazy isn't it. The imperialist standard is actually defined in metric terms.

Why not bypass the middle man and only use metric?

Originally Posted by GraemeCook

I am also fascinated by the derivation of the measuring system(s).

When the Roman legions marched off to conquer Gaule, Britain and the rest of the world, every soldier took steps of exactly the same length - they were marching. When the Centurian said "left" the Legionnaires took one step; when he said "left-right" they took one pace. The distance covered by one thousand legionnaire's paces became known as a "mille" - anglesized as mile. A nautical mille is still used for navigation in France.



My understanding is that the barley corn standard was adopted then, but the inch predates that considerably - every town had its own inch.



Crazy isn't it. The imperialist standard is actually defined in metric terms.

Why not bypass the middle man and only use metric?

Because it is a really easy way to remember some metric numbers - imagine having to learn these...
0.79
1.59
2.38
3.18
3.97
4.76
5.56
6.35
7.14
7.94
8.73
9.53
10.32
11.11
11.91
12.70
13.49
14.29
15.08
15.88
16.67
17.46
18.26
19.05
19.84
20.64
21.43
22.23
23.02
23.81
24.61
25.40
And so on....

Originally Posted by GraemeCook

My understanding is that the barley corn standard was adopted then, but the inch predates that considerably - every town had its own inch.

Crazy isn't it. The imperialist standard is actually defined in metric terms.

Why not bypass the middle man and only use metric?

diving ever deeper into the definitions of an inch

by an act of congress in 1866, the US inch was effectively defined as 25.4000508 mm (with a reference temperature of 68 degrees Fahrenheit) -- this length was based on a conversion factor of 1 metre = 39.37 inches

on the other hand, the UK inch was set at 25.399977 mm (with a reference temperature of 62 degrees Fahrenheit) as as 1/36th of an imperial yard.

In 1912, a bloke called Carl Edvard Johansson started manufacturing gauge blocks in inch sizes. To reconcile the difference between the US and UK inches, Johansson's compromise was to manufacture his imperial gauge blocks with a nominal size of 25.4mm, (with a reference temperature of 20 degrees Celsius).
These reference blocks were thus 0.000023 mm bigger than a UK inch and 0.0000508 mm smaller than a US inch.

Johansson's blocks were so popular, that they became the de facto standard for manufacturers internationally, with other manufacturers of gauge blocks following Johansson's definition of an inch by producing blocks designed to be equivalent to his.

So in effect, the current definition of an imperial inch (at exactly 25.4 mm) is neither metric nor imperial in origin -- it is a rounding compromise between the US and UK definitions of an inch.

The United States retained the 1/39.37 metre definition for surveying, producing a 2 millionth part difference between standard (25.4 mm) and US survey inches. This is approximately 1/8 inch per mile; so 12.7 kilometres is exactly 500,000 standard inches and exactly 499,999 survey inches. This difference is substantial when doing calculations in State Plane Coordinate Systems with coordinate values in the hundreds of thousands or millions of feet.

In 2020, the National Institute of Standards and Technology announced that the U.S. survey foot would "be phased out" on 1 January 2023 and be superseded by the international foot (also known as the foot) equal to 0.3048 metres exactly, for all further applications. This implies that the very slightly longer survey inch was replaced by the international inch = 25.4 mm.


Source for the above is the Wikipedia entry Inch - Wikipedia

Originally Posted by MartinCH

Because it is a really easy way to remember some metric numbers - imagine having to learn these...
0.79
1.59
2.38
3.18
3.97
4.76
5.56
6.35
7.14
7.94
8.73
9.53
10.32
11.11
11.91
12.70
13.49
14.29
15.08
15.88
16.67
17.46
18.26
19.05
19.84
20.64
21.43
22.23
23.02
23.81
24.61
25.40
And so on....

apart from the numbers highlighted in RED, all those numbers contain rounding errors

Originally Posted by ian

apart from the numbers highlighted in RED, all those numbers contain rounding errors

Darn it, these foreign languages are tricky, always catch you out on the grammar..

Cheer up Martin, the rounding errors are more than two orders of magnitude more than the most stringent requirements likely to be required in woodwork (& at least three orders better than I would ever consider important!)

Cheers,