Thread: How did pre-industrial woodworkers check for squareness and flatness?

Once humans got on top of geometry, accuracy and precision were possible in many fields.

Inscribed over the door of Plato's Academy was: "Let no man ignorant of geometry enter here."

Simple geometry allowed craftsmen to work all sorts of Magik. In the 6th century BC on Ionia two working groups under the lead of the engineer Eupalinos dug a tunnel through Mount Kastro to build an aqueduct to supply the capital Samos with fresh water. Eupalinos' 1 km long tunnel was dug from both ends using geometry to guide them.

I have used string to check largish objects for square, flattened tables with a heavy weight, sandpaper and a couple of lumps of rope, and recently used string lines to get the wings and saw of my drop saw cabinet true through two dimensions. When I was a very young man we were laying the foundation for a large pre-fabricated building. Getting the slab flat and true was mission critical, and it was done with a long water-filled garden hose with glass tubes fitted to each end. The five cut method of testing a table saw mitre or sled for square, that we still use today, is simple geometry that ancient scholars and tradesmen would recognise. One of my first woodworking lessons at the age of 12 or 13 was to make a square.

Geometry is an ancient science. The old-timers might not have had our machines, but calculating and drawing out angles, checking for square and plumb, making flat surfaces and many other tricks of the trade are skills that date back to the dawn of recorded history.

Originally Posted by Twisted Tenon

I was wondering about this too Jim. I was wondering how square the old furniture was and how necessary was it. I guess it was as important then as it is today, however they didn't have Starrett squares then, and what passed for square 200 years ago might not be the same today.

TT

TT, I would suggest that what passed for square 200 or 400 or 800 years ago would pass for square today! Even small errors in laying out a large cathedral would have had disastrous consequences, (which sometimes did happen!). For most woodworking purposes, there are sensible tolerances, & these can range from small to generous, depending on the scale of what is being made, & what has to fit in or over it. I think drawer-fitting is an example where you actually had to work to tighter tolerances in the 'good old days', - no wussy metal slides that can tolerate quite large deviations from nominal, and uneven gaps around drawers stick out to al but the least critical eye! Wear & tear & abuse & sometimes poor construction methods have taken their toll, but I'd wager most old pieces were built to as good or better tolerances as any today.

I think a good deal of the current insistence on super squares accurate to astronomical fractions is due to some fundamental misunderstandings of the science of measurement. I don't think you need a Starret square for woodworking. I cannot see the logic in using instruments made to fractions of a thousandth of an inch tolerances to work with material that can move many times more than that in an hour or two if the weather takes a sudden change. A simple, home-made square that is carefully made & set up by the scribe-and-flip method as accurately as the moderately practised eye can do it, will be more than adequate if it is used within the limits of what it's meant to do. As various people have pointed out, you don't use a square to do other than a quick check of a cabinet carcase, because small deviations the square won't pick up, can be very significant if extrapolated over a metre or more. Measuring the diagonals is far more accurate in that case.

You also learn to compensate for inevitable small errors by various means, and practical ways of attaining sufficient accuracy must have been around for a very, very long time. Those Roman aqueducts someone mentioned were built to tolerances that would be the envy of a modern construction firm, I reckon, with theodolites & Dumpy levels still far in the future.....

Cheers,

To add to what you've said Ian(W), I read somewhere that the columns on some of the Greek temples are shaped to allow for perspective to make sure they look straight.

Originally Posted by jimbur

To add to what you've said Ian(W), I read somewhere that the columns on some of the Greek temples are shaped to allow for perspective to make sure they look straight.

Entasis


My post a bit before was a bit vague. I said that we would not feel out of place in a workshop of a few millenia ago. Between the lines, the pursuit of accuracy of measurement goes back many thousands of years. But you don't pursue accuracy if you don't intend to use it. John Samuel explains it more directly. We do have excellent tools with high degree of accuracy capable of very specialist measurements, but you can go a very long way with a piece of string and a bit of knowledge too.

We assume that peoples from long ago were not as "smart" as us, so not as capable as us. Truth is, individuals from then were absolutely as able as modern people, they just didn't have the advantage of access to a couple of thousand years of accumulated knowledge. However, the knowledge they did have was pretty refined. I saw a double action pump in a museum in Spain once, which wouldn't look out of place in a Bunnings or similar. If you asked me to date it I would have said, Victorian age for sure, about 100 years or a bit older. It was Roman from about 2000 year ago.


Regards
SWK

Those "old guys" didn't have the opportunity to use power tools as a means to an end.
We all agree that there's no argument about the finesse of the craftsmanship.
Somewhere, I have a little book which explains how to shape 50-60 different curved church window
frames with no more than a compass and a straight edge.
The medieval siege weapon, the trebuchet can be kept as a length of knotted cord in your pocket.
Power tools or not, I can't get there but it does not stop me from trying.

Some years back, there was a big fire in Buckingham Palace/London/UK.
Major structural damage as you might recall. National Geographic magazine
followed the reconstruction. The oak carvers were stopped, they could not replicate
the original work. UNTIL, it dawned on them that the wood had to be carved green/wet
to shrink to fit.

As a biologist, for setting ecological survey lines, the 3, 4, 5 right angle is stupidly useful.
Ah. Was Stonehenge some haphazard pile of rocks>

Originally Posted by Robson Valley

Ah. Was Stonehenge some haphazard pile of rocks

I'm so glad you asked!

Lots of good arguments and time wasting there, especially with links to astronomy...

Actually, I think it was almost certainly laid out with string and pacing (or maybe measuring rods unique to that site). But there seems to be a good possibility that there is _some_ inherent astronomical measurement involved as well.

Regards
SWK

Originally Posted by Russell Cook

Hi all,

I'm interested in the history of woodworking, and recently as I've been squaring up some pine at home it occured to me that I am totally reliant on my industrially-manufactured carpenter's square as a reference.

So, my question is, how did the ancients go about this? Did they make themeslves a square going my eyesight alone? And related to this point, how did they ensure their whetstones were perfectly flat, in the absence of industrially-manufactured flat reference surfaces?

Thought we should return to the original question ...

BobL gave several examples, including how to make flat surfaces, a subject also addressed by someone else who referred to molten glass or metal allowed to solidify creates a flat surface. We still make flat glass by forming it on a bed of molten tin. To this day a common method of grinding something flat is to glue wet and dry to a sheet of glass.

Timeless explained how to make a square, something boys used to learn at school.

Others mentioned a variety of techniques. Back in the sixties boys were taught these techniques at school and whilst working alongside their fathers and grandfathers. What I find interesting is that none of these techniques is obsolete. I have used them all at one time or another. Recently I discovered the source of one of my problems ... a large steel square that was out my nearly 1 mm over 300 mm. So, I threw it away and made a timber square using the scribe and flip technique to get me out of trouble. Maybe one day I'll buy another large steel square.

It seems to me that the very best engineers and craftsmen I have met are those who understand and use first principles, rather than those who have access to the latest technology. The ancient woodworkers understood first principles because it was absolutely necessary. They did not buy squares, levels, plumb bobs or reference surfaces; they made them in the shop. One of the planes my father used to make spars for our boats was created by my grandfather from a lump of boxwood and a piece of scrap steel.

I love my machines and gadgets. They make life easier, but I also love the jigs, sleds and other things made to meet my needs in the shop. As BobL will attest, to this day hobbyists who want a good dust collection system need to understand first principles because they must make their own hoods and shrouds, much like the ancients. The machine manufacturers either don't make them at all or make such a poor product that it must be heavily modified or replaced to build a sound, working system.

Russell, if you have not already done so, find some nice hard, stable timber and make a square. It takes no time at all, and you might surprise yourself at just how precise your instrument is. If you have a table saw make a new mitre and a crosscut sled. I love my sleds, and my shop made mitre is a joy to use. You already have the necessary skills.

Originally Posted by John Samuel

... a large steel square that was out my nearly 1 mm over 300 mm. So, I threw it away and made a timber square using the scribe and flip technique to get me out of trouble. Maybe one day I'll buy another large steel square.....

Or make one, John....

As you say, this is all old technology. Making a calibratible square with a steel blade is relatively easy, Colen Clenton didn't invent the style (but he does do them well!) so you are not infringing any patents. You can keep it pretty simple, or add as much brass or other bling as you like.

14 inch square.jpg

The blade of this one is 350mm & cut from a Bunnings scraper blade (no longer available, it seems) but there are other sources of suitable spring steel:

Never underestimate the power of the human eye. I've seen the late Les Miller cut a piece perfectly square both ways, with not even a pencil line, just a to show it could be done. Mind you, he'd had a bit of practice.

The old apprentices used to work 6 days a week, 12 hours or more a day, for 7 years. That's about 25,000 hours. It's said that it takes 10,000 hours to become an expert at something, so it's no wonder that they became pretty good at their trade.

Alex, being nearly my age you'll remember slide rules. For real accuracy your eye had to read between the graduations.

There are old temples that spread across south america an into the north built ages ago that were measured from space to be exactly spaced apart and set out according to the Inca Cross. Also try explaining the Nazca lines?? Some of these civilisations are over 2000BC and I doubt we will ever know how it was done or be able to replicate it. On the flip side I think also there were the elite craftsmen and the layman. These would have different expectations of square. As for draws in a farmers cottage I doubt they would have met a high standard but as long as they were functional were good enough.

Things would have also been measured by story stick for repeatability rather than measured and measurements weren't so accurate for a long time with , feet, spans etc as the units which differed based on each persons physiology. Set out by dividers for units and arcs can create very complex set up.

It is great hearing home many of you were taught these things either at early schooling or it was passed down by family……….I ask you now how many of your kids etc have learn this??? It needs to be passed on before they are wondering how it was done the same as we wonder on the Egyptians and Incas did it.

Originally Posted by IanW

Or make one, John....

As you say, this is all old technology. Making a calibratible square with a steel blade is relatively easy, Colen Clenton didn't invent the style (but he does do them well!) so you are not infringing any patents. You can keep it pretty simple, or add as much brass or other bling as you like.

14 inch square.jpg

The blade of this one is 350mm & cut from a Bunnings scraper blade (no longer available, it seems) but there are other sources of suitable spring steel:

Great idea, Ian.

So far I have not found suitable components. The square I ditched was a one piece 400 mm x 600 mm unit. I have another like the one in your pic, and would likely use a similar construction method if I can get a piece of spring steel about 600 mm long.

Originally Posted by IanW

TT, I would suggest that what passed for square 200 or 400 or 800 years ago would pass for square today! Even small errors in laying out a large cathedral would have had disastrous consequences, (which sometimes did happen!). For most woodworking purposes, there are sensible tolerances, & these can range from small to generous, depending on the scale of what is being made, & what has to fit in or over it.

You also learn to compensate for inevitable small errors by various means, and practical ways of attaining sufficient accuracy must have been around for a very, very long time.

Yep I think you have got to the nub of it Ian. I believe those old tradesmen worked within created tolerances. As you and John Samuel said it shouldn't be hard to make your own square. I've made myself a couple of isosceles triangles (about 350mm) to square up the inside of a table frame I was building. They don't look classy but they are accurate and i'll have other uses for them as time goes on. A square should be on the cards in the near future
Cheers

TT

Sorry RV, but I think the fire you are referring to was in Windsor Castle sometime in the early 90s.

There was a lesser fire at Buckingham palace in 2002 and the lessons learned form the
restoration of Windsor were certainly applied to restoring Buckingham palace.

When the reconstruction began it was found that in over the entire length of the main hall
the sides were out of parallel by quite an amount - 14 feet from memory.Wonder how they
originally "squared" everything up!!

You are right about the oak carving, and because the walls were not parallel each truss
(I think they were hammerhead trusses) had to be made to fit the width at its point of placement.

A right angle can be very simply obtained by folding paper. I have used this method to great
affect before today.

The Egyptian pyramid builders filled trenches with water to get a level from which to work.
Measuring sticks with a string stretched between them were then used to set heights.

As for straight lines over long distances, eyesight is hard to beat. The dingo and rabbit fences
were often sighted at night between fires.