Thread: F-clamp restoration

Originally Posted by IanW

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,

Sadly, this isn't exactly true.

Too many places wood work where error can accumulate and joints are often at 0.1mm or less, for alignment or tight glue joints. We can fudge but that is work too. Measure once cut once - the dream.

At one stage I would not touch any item that was imperial sized, cause it could add another level complexity, but take a more relaxed attitude these days, even if I occasionally stuff up my translations.

Originally Posted by GraemeCook

The concept of a a thirty-second of an inch does not exist in the metric world. They would just choose suitable whole numbers of millimetres, or halves, such as a set of drill bits:
2, 2.5, 3, 3.5, 4, 4.5, 5, 6, 7, 8, 10, 12, etc.

My drill bit set is graduated in 0.5 increments from 1.0mm to 13.0mm

Originally Posted by MartinCH

Sadly, this isn't exactly true.

Too many places wood work where error can accumulate and joints are often at 0.1mm or less, for alignment or tight glue joints. We can fudge but that is work too. Measure once cut once - the dream.

At one stage I would not touch any item that was imperial sized, cause it could add another level complexity, but take a more relaxed attitude these days, even if I occasionally stuff up my translations.

avoiding measurement stuff-ups is the reason I maintain two near complete sets of rules.

Metric, sized at 150, 300, 600 and 1000mm and graduated in 0.5 and 1.0 mm
imperial, sized at 4", 6", 12" 18", 24" and 36" and graduated in quarters, eights, sixteenths, 32nds, and 64ths. I only very rarely use the 64ths, and try really really hard to never convert between measurement systems. If I need to measure 3/8ths of an inch I use the rule graduated in 8ths or 16ths, rather than try and interpolate the measurement on a metric rule.


When it comes to machinist and combination squares, the actual stock of the square doesn't care if it is fitted with a 300mm or 12" or 18" rule as the rules are interchangeable.
Ditto with 150mm/6" combo squares which come with narrower and thinner rules.

All hail the inch, who knew we would end up with Randall Carlson, whilst discussing clamps!
https://www.youtube.com/watch?si=prkw4B-k-HSszpw_&t=3153&v=IMFvB1_2wbs&feature=youtu.be

Hmm, since religion is one of the "forbidden topics" here, I won't comment on that video other than to say such claims of matching dimensions are usually based on some pretty generous rounding!

But before we get into yet another debate on the superiority of metric over Imperial or vice versa, can't we just agree that it's not what you've got but what you do with it?

Perhaps it's because I was schooled by old-time cabinetmakers, but I don't use units of either system all that much in woodworking, it's much safer to use dividers, story-sticks or simply mark parts off each other. For e.g. I set a marking gauge off the work, or scribe one bit from another. I set a mortise gauge from the chisel I intend to use (& old chisels can vary by 0.5mm around the nominal size, easily), and divide lengths into equal parts with dividers or compass. More than half the time I couldn't tell you what a particular measurement was, precisely.

Rulers have a couple of inherent problems, the main ones being parallax and the limitations of our eyesight which can resolve down to about 0.1mm if your eyesight is very good & considerably less for chronologically-challenged optics like mine. Those old boxwood rulers are lovely things to look at, but being so thick they are prone to unacceptable parallax errors if used for fine work.

Precision only matters when you are making multiple parts that need to fit in any of a number of possible places for different pieces as on a production line, or something like a casting pattern. In most everyday woodworking all we need to worry about is accuracy , e.g. that part A fits part B and that fit will vary according to the type of job, e.g. the fit of a M&T vs the fit of a drawer. We don't use rulers in these situations, we use methods that remove very small amounts of wood to sneak up on the desired level of fit.

And while I work to tolerances of hundredths of a mm on my metal lathe (or try to!), my woodworking tolerances are often more like a tenth of a mm, or even more on a large piece, i.e. an order of magnitude greater, so I'm certainly not concerned about rounding errors in the thousandths or ten-thousandths of a mm.

Maybe I'm just sloppy.....

Cheers,

Originally Posted by IanW

Maybe I'm just sloppy.....

Cheers,

Doubt you're sloppy, unless talented with photoshop, but then you're not sloppy. Circular. No way out. Sorry.

Of making a picture frame 100mm wide aiming join gap less than 0.1mm then the total combined error of angle and length foreach part meeds less than 0.01mm. Think we are all pretty accurate...

Cheers

Originally Posted by ian

My drill bit set is graduated in 0.5 increments from 1.0mm to 13.0mm

I bought a cheaper set than you.

And if you had bought yours across the US border, they would have been:
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 ... (Thanks Martin)

Originally Posted by ian

avoiding measurement stuff-ups is the reason I maintain two near complete sets of rules. .

Interesting, Ian. My little brain found two systems to just be too confusing, so I got rid of all imperialist measures 20+ years ago. The last to go were tape measures callibrated in both inches and millimetres.

Originally Posted by GraemeCook

I bought a cheaper set than you.

And if you had bought yours across the US border ...

My 0.5 mm increment set was bought in Aus about 20 years ago.

I also have one of those metric / imperial screw sizing gauges that give you both the metric and imperial drill size recommendations.
so in reality have my hole drilling needs largely covered.

Originally Posted by IanW

Hmm, since religion is one of the "forbidden topics" here

But we were created with ten fingers, that is metric!

Originally Posted by GraemeCook

But we were created with ten fingers, that is metric!

Jokes aside, there is a method of counting to 60 on your fingers -- and 60 is divisible by 12 !!

and till the widespread use of calculators, there was a method of doing multiplication using your fingers.

quoting from How high can you count on your fingers? The answer is much more than you'd think | indy100 | indy100
Slightly more advanced people will know you can count up to twelve on one hand, if you divide your four fingers into three sections, with your thumb as the counter – double that for two hands means you can go up to 24.


Similarly, if you keep to one hand, and use the other to count each time you get to 12, you can have five groups of twelve – or 60.

59,048 ?

I used to work with a deaf guy so learned sign language 40 years ago. I remember how to sign up to 999,000 using only one hand but forget what 1,000,000 is now. It has no limit.

Edit. There is no limit to counting on one hand and the deaf worked out a system for it. Probably a long time ago but I don't know the history of that.

Imperial/metric...It's all rule of thumb if you ask me!

Tom

Originally Posted by jack620

I wonder what happened to Adam? I hope he's OK.

I attempted to send Adam a PM but had no success.
Adam has only posted once and I think you need a minimum of 5 posts before you can receive PMs.

For those interested; Adam last visited this site the day after he posted his request and would have seen the first response to his query.