Decent try square

[MikeG.]

If 90 degrees is unobtainable by that argument, then so is every other angle. And the fact that something can't be measured accurately is irrelevant when considering whether the measurement itself actually exists.

Pin two straight edges together at a pivot point. Rotate one. At some point on a complete rotation, the angle between the straightedges was 90 degrees. The fact that it can't be measured does not alter the fact that at some point (well two, actually), those two pieces were at 90 degrees to each other. So, I say again. It is perfectly possible that 90 degree squares exists. What is more difficult is knowing which ones they are.

 

[transatlantic]

If 90 degrees is unobtainable by that argument, then so is every other angle. And the fact that something can't be measured accurately is irrelevant when considering whether the measurement itself actually exists.

Pin two straight edges together at a pivot point. Rotate one. At some point on a complete rotation, the angle between the straightedges was 90 degrees. The fact that it can't be measured does not alter the fact that at some point (well two, actually), those two pieces were at 90 degrees to each other. So, I say again. It is perfectly possible that 90 degree squares exists. What is more difficult is knowing which ones they are.

How could they exist? It's always going to be +/- off by the smallest particle size.

Isn't this similar to Calculus, where your 90 becomes more and more accurate as your unit of measurement approaches zero?

but as a physical item, we can only ever approach zero, never actually reach it as things have a physical size, so you'd never get your perfect 90?

 

[MarkDennehy]

If 90 degrees is unobtainable by that argument, then so is every other angle.

That's entirely correct.
Pick *any* absolute angle and you are *guaranteed* we cannot deliberately manufacture it.

*accidentally* manufacturing it, sure, that'll happen, but you won't be able to make the thing that measures the angle accurately enough to know what the angle is exactly so you'll never know anyway.

Pin two straight edges together at a pivot point. Rotate one. At some point on a complete rotation, the angle between the straightedges was 90 degrees.

So that's not actually provable. It might be correct; it might not; nobody knows.

It's a consequence of the whole quantum theory thing. The universe is not a smooth continuum when you look closely enough, it's made of very very very very very very small discrete steps so there's always some inaccuracies compared to mathematics which is a smooth continuum all the way down.

Yes, that's weird, yes, it makes no common sense (mainly because we evolved as plains apes in Africa and what makes common sense there does not necessarily translate well to 11-dimensional mathematics regarding the underlying metrics of the universe). And yes, physicists have actually gone slightly insane because of this and several (eg. Einstein) never accepted it as making sense, but the evidence in experiment after experiment keeps on saying, beyond our ability to measure it, that the universe is just fundamentally ******* weird.

 

[Andy Kev.]

If 90 degrees is unobtainable by that argument, then so is every other angle. And the fact that something can't be measured accurately is irrelevant when considering whether the measurement itself actually exists.

Pin two straight edges together at a pivot point. Rotate one. At some point on a complete rotation, the angle between the straightedges was 90 degrees. The fact that it can't be measured does not alter the fact that at some point (well two, actually), those two pieces were at 90 degrees to each other. So, I say again. It is perfectly possible that 90 degree squares exists. What is more difficult is knowing which ones they are.

I think the argument you've been putting is theoretically wrong but practically right.

It's wrong because the atoms of the material of which the square is made are in a state of constant agitation, therefore the chance of them all being in alignment at the same time to produce a consistent edge from which 90° (or any other angle) is measured is vanishingly small.

Meanwhile, back on planet earth, you're exactly right: of course a square can be made to be bang on 90°, as measured by any practical means in a workshop. The only thing the woodworker has to do is ask himself whether the considerations of atomic physics or the ability to test for 90° by flipping the square over are more important for getting a couple of bits of wood to fit together in the desired way.

 

[Andy Kev.]

If 90 degrees is unobtainable by that argument, then so is every other angle.

That's entirely correct.
Pick *any* absolute angle and you are *guaranteed* we cannot deliberately manufacture it.

*accidentally* manufacturing it, sure, that'll happen, but you won't be able to make the thing that measures the angle accurately enough to know what the angle is exactly so you'll never know anyway.

Pin two straight edges together at a pivot point. Rotate one. At some point on a complete rotation, the angle between the straightedges was 90 degrees.

So that's not actually provable. It might be correct; it might not; nobody knows.

It's a consequence of the whole quantum theory thing. The universe is not a smooth continuum when you look closely enough, it's made of very very very very very very small discrete steps so there's always some inaccuracies compared to mathematics which is a smooth continuum all the way down.

Yes, that's weird, yes, it makes no common sense (mainly because we evolved as plains apes in Africa and what makes common sense there does not necessarily translate well to 11-dimensional mathematics regarding the underlying metrics of the universe). And yes, physicists have actually gone slightly insane because of this and several (eg. Einstein) never accepted it as making sense, but the evidence in experiment after experiment keeps on saying, beyond our ability to measure it, that the universe is just fundamentally pineapple weird.

Are you sure it' so fundamentally weird? The scale on which the little increments occur are so small and the wobby wave nature of matter involves such tiny fluctuations at such a high rate of knots that they all cancel each other out to provide stability. That's why a piece of wood stays solid to the point where it hurts if you walk into it. Therefore any physicist who is in danger of going nuts while contemplating the universe needs to keep a piece of oak on his desk
(say 18" x 2" x 2") and his lab assistant should be briefed to hit him smartly on the back of the head with it every time it looks like he might be losing his grip on reality.

 

[MarkDennehy]

Are you sure it' so fundamentally weird?

Well, it's weird to us, a bunch of plains apes who learnt to walk upright so we could spot plains cats trying to hunt us through tall grass.
I imagine it'd be a little less anthrocentric to just think of them as being outside our normal range of experience (which for a few tens of thousands of years was entirely defined by speeds from zero to as fast as you could get if you fell off a cliff, by distances defined by how far a horse could run in a day and by altitudes that range from zero to the tip of a spear waved from horseback).
But that's just me, I'm a lefty liberal tree-hugging hippie beatnik.

The scale on which the little increments occur are so small and the wobby wave nature of matter involves such tiny fluctuations at such a high rate of knots that they all cancel each other out to provide stability. That's why a piece of wood stays solid to the point where it hurts if you walk into it. Therefore any physicist who is in danger of going nuts while contemplating the universe needs to keep a piece of oak on his desk
(say 18" x 2" x 2") and his lab assistant should be briefed to hit him smartly on the back of the head with it every time it looks like he might be losing his grip on reality.

The problem is, some physicists know what oscilloscopes are, and have heard of things like the intelsat V telecommunications satellite (launched in 1977) and its successors.
All of which use tunnel diodes which are based on the quantum tunnelling effect, which is where quantum effects basically let you walk through a piece of wood (metaphorically, on the quantum scale, if you're an electron and the P-N junction is the piece of wood).

Look, I said it was weird

Basically, if you twatted someone in the head long enough with that piece of oak, there's a non-zero chance that at some point you'd just swing it through their head without hitting any of the atoms in their head.



It's just that while it's not zero, the odds are very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very close to zero

 

[StraightOffTheArk]

Mark - thanks for that 'robust' explanation - are you a graduate of the 'MC Hawking' school of science tuition?

https://www.youtube.com/watch?v=5bueZoYhUlg

 

[Beau]

On the secondary discussion here I have always found more problems with wood in customers homes swelling in the summer not the winter. I put this down to central heating being on in the winter. Admittedly being here in the SW it's far more humid than it is for those further east so no one right answer for all. I would never trust a square partly made of wood due to the seasonal movement which is not even by the way. Take a piece of very dry 3x1 and put in a very high humidity environment, it does not shrink evenly as wood breaths faster through the end grain so the ends will swell first and the rest will catch up over time.

 

[MarkDennehy]

Mark - thanks for that 'robust' explanation - are you a graduate of the 'MC Hawking' school of science tuition?

Not really, physics was always just interestingly quirky. Theoretical Physics was a Road Not Taken many years ago, but Engineering paid bills so...

 

[D_W]

I fully understand the point you are trying to make: that manufacturing X number of squares and guaranteeing they'll all be 90 degrees is impossible. I agree with this: it is impossible. But that isn't actually what you said.

Many years ago I had a similar conversation with my professor in an advanced calculus course. The subject was converging on zero in an infinite series of halving the distance between two points. The professor, quite correctly, stated that the goal could never be reached mathematically. However, my argument was sometimes close was good enough, and provided an example. I told him that if his daughter was at one end of the room and I was at the other end of the room, and I divided the distance between us by half each time, I am quite confident he will be a grandfather without ever reaching zero.

I get what you're saying, but you're missing the link where you take the limit as a variable approaches infinity. As the variable approaches infinity, the distance will be zero. if it is not infinity, the distance will be something.

I think this trips people up in calculus class, because they always think there will be an n+1 that is large enough but still another measurable variable. Or, they imagine that infinity is a single number, and they're trying to imagine a point where a number jumps from n to infinity.

 

[Stevedimebag]

I love forums.........to infinity and beyond.

 

[D_W]

Somewhere, I got lost in this discussion, but I have a suggestion - a practical one.

If you know someone who has a certified square (perhaps a machinist, etc), all you really need to do is buy an inexpensive square and check it against said person's certified square. If you're looking for machinist tolerance stuff.

That will allow you to have an almost certified level square in your shop that you can use to set up and check other square in the future. This "almost" square can be an indian square or some other low cost device. If you buy from a retailer with a return policy, you can try a couple until you get close. When you get close, if you need closer, you can draw file the blade on a square to make it ideal.

The key is that someone else owns the true certified square.

Friend of mine who is a mechanical engineer bought a starrett certified square, and he'd bought a lot of magazine type products (things like the "incra guaranteed square") assuming that items made for the woodworking world would be what they say they are. The $90 or whatever it was aluminum square from incra turned out not to be close to square (off by an appreciable number of thousandths over 6 inches or so).

 

[Tasky]

I get what you're saying, but you're missing the link where you take the limit as a variable approaches infinity. As the variable approaches infinity, the distance will be zero. if it is not infinity, the distance will be something.

So..... In other words, no matter how much you file each side to try and true up the bloody square, you'll always end up going too far one way or the other, resulting in 'the universe exploding' as you rage-quit and just fling the flippin' thing across the workshop...? :lol:

 

[transatlantic]

Somewhere, I got lost in this discussion, but I have a suggestion - a practical one.

If you know someone who has a certified square (perhaps a machinist, etc), all you really need to do is buy an inexpensive square and check it against said person's certified square. If you're looking for machinist tolerance stuff.

That will allow you to have an almost certified level square in your shop that you can use to set up and check other square in the future. This "almost" square can be an indian square or some other low cost device. If you buy from a retailer with a return policy, you can try a couple until you get close. When you get close, if you need closer, you can draw file the blade on a square to make it ideal.

The key is that someone else owns the true certified square.

Friend of mine who is a mechanical engineer bought a starrett certified square, and he'd bought a lot of magazine type products (things like the "incra guaranteed square") assuming that items made for the woodworking world would be what they say they are. The $90 or whatever it was aluminum square from incra turned out not to be close to square (off by an appreciable number of thousandths over 6 inches or so).

Is that really going to be any better than the draw a line (with a mechanical pencil or even better a knife) and flip over test? I don't think so.

 

[Stevedimebag]

I get what you're saying, but you're missing the link where you take the limit as a variable approaches infinity. As the variable approaches infinity, the distance will be zero. if it is not infinity, the distance will be something.

So..... In other words, no matter how much you file each side to try and true up the bloody square, you'll always end up going too far one way or the other, resulting in 'the universe exploding' as you rage-quit and just fling the flippin' thing across the workshop...? :lol:

and by chance when that thing hits the concrete block wall, it ends up truly square...then the holy grail appears on ur workbench and the messiah returns on ur doorstep. :?

 

[D_W]

It depends on what you're doing with the square. If you're making tools, yes. If you're just putting together drawers or checking joints for square, probably not.

I don't really go for overly perfect furniture work, which may be where you're leading. Work where people focus on perfect squareness, etc, tends to show - perfect little square boring boxes with super tight joints.....that still manage to look boring.

But tools are a different story, as is machine setup for someone using machines. The precision is not absolutely necessary to have, but it's nice to have.

You could say the same thing about a straight edge. I've got two starrett edges I bought new. I like to be able to file my better planes to flatness as well as I can see it with those. It does make them work a little nicer. Is it necessary? No, but it does make for a difference that you can feel. Starrett's straightness guarantee is something like 2 ten thousandths per foot. If you can't get a feeler between the edge and your filed plane sole, you have a pretty good idea regarding flatness.

 

[D_W]

I get what you're saying, but you're missing the link where you take the limit as a variable approaches infinity. As the variable approaches infinity, the distance will be zero. if it is not infinity, the distance will be something.

So..... In other words, no matter how much you file each side to try and true up the bloody square, you'll always end up going too far one way or the other, resulting in 'the universe exploding' as you rage-quit and just fling the flippin' thing across the workshop...? :lol:

I think the guy who is shooting to prove that he can halve his distance from the wall will eventually touch his nose to it.

If I buy an indian square (or an equivalent over here in my case: an English square that's gently used - Starrett is too expensive for knock-about in a wood shop) and it's relatively close, I'm inclined to use it rather than trying to make it perfect. Unlike most, if I bought a square that was not quite right, I'd file the blade until it was close within a thousandth or two, because it'd be a lot faster than buying another one and fooling around with it.

My shop "good" square is a moore and wright 6" try square that was $17 at an antique shop here. Nobody knows what M&W is other than machinists, so once something like that makes it out to the general public, it's cheap. Starrett never is. M&W cannot match the true althol made starrett stuff....it's only about 10 times more accurate than we need for woodworking vs....what...50 for starrett? I'll keep my money.

TTP with the India comment. My English friend here always turns red if I say "I'll spend the money on something American if I need to, but I'd rather buy English or Indian if it's good enough. Same thing". He hasn't lived in England for 35 years, so maybe some of that has worn off, but it gets him riled up every time.

 

[Tasky]

Unlike most, if I bought a square that was not quite right, I'd file the blade until it was close within a thousandth or two, because it'd be a lot faster than buying another one and fooling around with it.

Why unlike?
Or do people not go that precise?
Seems to me it doesn't matter how many milimetres out of square your square is, as long as you can square it up to be close enough for your work... to me, that'd be so square I couldn't see if it was out in the slightest, which is as far as anyone'd need to go for this stuff.

 

[D_W]

When I say unlike, I mean if I buy a low cost tool and I can fix it, I just fix it rather than troubling the retailer looking for a perfect one. I think over here in the states, we started this absurd notion of every retailer owing you something perfect at every cost level, and then being on the hook to exchange something ten times until they finally blow up and tell you that they'd prefer you shop somewhere else.

I think a more reasonable track is to expect what you'll probably get, apply a reasonable range and fix rather than exchange. If you have a master square of a friend to check with, it's awfully hard to do that bad of a filing job. I don't need perfect, but four or five thousandths over 4 or six inches really irritates me. Even on wood. Especially if you start tracing lines around square bits. You've got a sheet of paper or two in error on some things, and it's a potential time waster. Making something that you can't see light through is pretty easy - takes a little time, but less than shopping and exchanging.

 

[bugbear]

M&W cannot match the true althol made starrett stuff....it's only about 10 times more accurate than we need for woodworking vs....what...50 for starrett?

I love that people have a irrational jones for Starrett above all others.

It means I can get vintage Brown & Sharpe or Lufkin stuff cheap. There's some real fancy stuff comes out of Switzerland too.

BugBear