How accurate should wood-working squares be?

Evening all!
I've just bought Screwfix's Combination Set:
http://www.screwfix.com/app/sfd/cat/pro.jsp?id 407
and am a bit concerned about the lack of precision compared with the engineering squares I have.
The square head "rocks" within the centre head and the sole-plate of the protractor head shows light when held against a true straight-edge.
Whilst it's probably as accurate as I can cut when used for marking within three inches of the straight edge of the work it's visibly "off" at 10 inches.
Am I being over fussy for a tool that only costs 15UKP or should it go back?
Is there a British Standard that covers wood-working tools and their accuracy?
(Two years ago I wouldn't even have noticed ... but as skills have improved I'm getting much more demanding of my tools ...)
TIA
Barley Twist (Please put out the cats to reply direct)
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This is what I should have bought:
<drool>
http://www.littlemachineshop.com/products/product_view.php?ProductID 38
</drool>
Barley Twist (Please put out the cats to reply direct)
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Barley Twist wrote:

You pays your money and ... Seriously though , if you bought the expensive one you'd be so terrified of damaging it it would keep you awake at night.. :-)
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It crossed my mind to ask why someone would want one of them things, especially at that price; until I read post II. Then I realised the man's a fool.
Seriously though, where would you use one of them? You couldn't use it on a drawing board could you? Setting some sort of a machine up, perhaps? I have no idea?
You could use it to pry open a can of paint perhaps, not a bottle of caustic soda though. Perhaps you could squeezee the cap in the angle and .... na..ah...
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On 7 Nov 2003 20:55:33 -0800, snipped-for-privacy@hotmail.com (Michael McNeil) wrote:

hmmm - having googled back I see that Mr McNeil falls prone to the odd bit of tool lust too - but he does ask a serious question after the slight insult ...
I'm at an age where my eyesight is difficult - moving from shortsightedness to whatever - always having to take glasses off and then put them back on in the course of any marking out operation.
From *experience* I've discovered that the biggest effect on the precision (and I do know the difference between accuracy and precision!) of the job is in transferring measurements between one tool and another - something that's compromised if I have to take more than a couple of measurements for a given line/point.
I've a couple of small, very cheap, combination squares that checked out very well for both accuracy and precision - they live in a foam lined box when not in my hands. I've found them invaluable for transferring measurements - say the depth of a half-lap joint, the thickness of a component, and then being able to scribe lines at that value. Also for consistent, repeated marking at a particular measurement.
I've a job on at the moment where I'll be working 6 inches away from the true edge, I'd hoped that the larger combination square/set would allow me to carry on using the *proved* technique I've developed.
I think Mr Dingley's response the most helpful:
"Perfectly accurate. They should be the second-most accurate thing you have, second only to your straight edge. Anything less is unacceptable."
... thanks.
I have tracked down the British Standard for such things - It's BS 3322 - which specifies an accuracy of 0.01mm per cm blade length. Fairly easy to check with a long slip gauge on end and a feeler.
Armed with which knowledge 16407 and 16969 will be going back to Screwfix Screwfix
Barley Twist (Please put out the cats to reply direct)
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On Fri, 07 Nov 2003 20:29:12 +0000, Barley Twist

Not much good if you are metricised by the looks of things ;)
PoP
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For 15 I'd send it back and go visit your local tool shop, check before you buy. Even if you can work with the Screwfix thing it's shortcomings will annoy you every time you use it.
Rgds
Noel
noel dot hegan @ virgin dot net
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On Fri, 07 Nov 2003 19:51:34 +0000, Barley Twist
Perfectly accurate. They should be the second-most accurate thing you have, second only to your straight edge. Anything less is unacceptable.
Accurate squares are cheap and easy to get. They're easy to test too. Don't compromise. "Accurate" here means "More accurate than the rest of my marking and cutting process".

I have no real use for combination sets. The protractor head is useful, but not the other two. If I need a square, I'll use a fixed one. If I need a centre finder, I'll use a rough one (or a finger and pencil) because that's a low-accuracy task that I shouldn't perform by dragging my high-accuracy tools around the logpile.

That's the other problem with combination sets.
Basic rules for buying combination sets. They shouldn't work, but empirically they're a good guide to quality:
- Cast iron bodies, not diecast mazak.
- Etched rule, not stamped or printed.
My combination set is a Chinese no-name, bought from Chronos Tools at a Model Engineer show. Cost about 30 and is of high accuracy and reasonably good quality. The adjusting "bolts" aren't as ergonomically designed as a Starrett, and it's probably not as accurate as a Mitutoyo, but it's close enough for jazz. I think Axminster sell something similar http://www.axminster.co.uk/default.asp?part=SMT031

Wobbling clamps and non-flat machined surfaces sound unacceptable IMHO. Apart from that, I'd not expect a 15 combination set to have any real claim on accuracy.
-- Die Gotterspammerung - Junkmail of the Gods
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Very useful tool a combination square. It should be accurate enough so that in normal use - i.e. marking on wood with an HB pencil, no error is obvious. Screwfix cheaper tools are often crap - if you ask for a refund or replacement they don't ask you to return the tool as they also know it's crap. I've got 2 pairs of wire stripping pliers free on this basis but unfortunately they are rubbish. I'll probably give them away as Christmas presents.
cheers
Jacob
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<snip>
<snip>
3 tools in one, so 5 per tool, so YGWYPF.
Also loads of moving parts, with the potential for wear.
If you can't rely on it then what is the point of using it?
If a good one costs $150 (do you get both of those shown in the picture for $150?) and weighs 3.5 pounds (small club hammer?) then 15 isn't likely to do the business.
Depends what you want it for.
If you want the fancy angles then use it for that, and use a seperate good quality square for right angles.
This looks like a JOATMON tool to me :-)
Cheers Dave R
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Send it back !!!!!!!
wrote:

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