Wooden Straightedge ?!?

[Boxer]

I am currently reading and enjoying "The New Traditional Woodworker" where Jim Tolpin encourages woodworkers to construct their own marking out tools.

Having a bit of a bench engineering background I am probably a bit too hung up on fine tolerances so the idea of making prime reference tools out of a material that expands and shrinks according to humidity and may be prone to twisting is a tough one for me.

Do people here use their own-made wooden straightedges and squares, and do they stay true throughout use.
And if so any recommendations for which are the best types of wood to make them from ?

Cheers
Chris

 

[Fromey]

Perfectly serviceable metal ones are relatively cheap so I've never been tempted. But according to Chris Schwarz, the reason wooden ones are shaped the way they are on the upper edge is to regularise the amount of moisture entering and leaving the wood (the majority coming in through end grain) and so in that way help maintain their uniformity. After all, they've been used for many a year to make excellent and exceptional furniture.

 

[marcros]

plenty of people make a wooden straightedge for running the circular saw/jigsaw down. Not quite what you meant but...

 

[Cheshirechappie]

The 'traditional' woods seem to be walnut and mahogany, both of which are fairly stable. They were also fairly readily available as offcuts in the older cabinet shops.

One way of overcoming the problem of knowing if the straightedge is straight is not to make one, but to make three. Then, using the old principle for generating flat surfaces by comparing the three against each other, they can be quickly checked.

For those not familiar with this trick, it works as follows. The three straightedges are labelled A, B and C. They are all planed up as true as you can get them by eye. Then, compare A with B by putting their reference edges together and seeing where light shines between them. Adjust accordingly, then check A against C. Adjust again. Compare B against C, adjust again. Keep going like this until all three show no light when tested one against the other. For the minor adjustments, a scraper may be more sensitive than even a fine-set plane. You need to keep the compared edges very clean; a speck of dust will throw things out by enough to show a gleam of light.

This works because A may have a slight convexity that precisely fits a concavity on B. However, C may have the same concavity as B, and thus fit A perfectly, but it cannot fit B because both B and C are concave. The only condition in which all three can fit each other perfectly is when all three are dead straight.

The beauty of this method is that the three can be checked against each other at any time, and adjusted if needs be. No expensive reference straightedge needs to be kept on hand, and pampered to keep it true.

 

[deserter]

I use my own squares all the time, mine are beach blades and rosewood stocks. They stay true most of the time but on the odd occasion they do go out of square it only takes 2 seconds to true them up with a plane.
Personally I just push the stock against a known square edge I.e. a freshly cut piece if MDF and then use the other side of the corner as a shooting board for the blade. Hope that makes sense easier to do than type.


~Nil carborundum illegitemi~

 

[No skills]

I have considered this several times and come to the conclusion that if you like to make your own tools then yes make up straight edges and squares a plenty and enjoy it.
I also came to the conclusion that even if you dont like making your own tools you should still have the odd wooden straight edge handy - whys that? - because their just handy, thats why. Doesnt matter if they move a bit with the weather - doesnt matter if their not straight to the nearest to the nearest thou (or whatever daft micro measure your working to) - and whys that?.. because its wood work.

No offence ment, just having a bit of a Jacob moment.

 

[carlb40]

I have considered this several times and come to the conclusion that if you like to make your own tools then yes make up straight edges and squares a plenty and enjoy it.
I also came to the conclusion that even if you dont like making your own tools you should still have the odd wooden straight edge handy - whys that? - because their just handy, thats why. Doesnt matter if they move a bit with the weather - doesnt matter if their not straight to the nearest to the nearest thou (or whatever daft micro measure your working to) - and whys that?.. because its wood work.

No offence ment, just having a bit of a Jacob moment.

So do we need to have a rounded bevel on one edge? :lol:


I often use home made straight edges, well ply/mdf. But those are for cutting guides etc not marking out.

 

[No skills]

Why not, save cutting yourself on anything sharp..

 

[Jelly]

Never made a straightedge or try-square, but I have about half a dozen different refernce angles cut into blocks of 12*50mm PAR Keruing

There is some potential for moisture movement to alter them slightly, but the exceptional resistance to glue, impact, and snapping is ideal for something which needs well defined corners which could be vulnerable to damage.

 

[bugbear]

For those not familiar with this trick, it works as follows. The three straightedges are labelled A, B and C. They are all planed up as true as you can get them by eye. Then, compare A with B by putting their reference edges together and seeing where light shines between them. Adjust accordingly, then check A against C. Adjust again. Compare B against C, adjust again. Keep going like this until all three show no light when tested one against the other. For the minor adjustments, a scraper may be more sensitive than even a fine-set plane. You need to keep the compared edges very clean; a speck of dust will throw things out by enough to show a gleam of light.

This works because A may have a slight convexity that precisely fits a concavity on B. However, C may have the same concavity as B, and thus fit A perfectly, but it cannot fit B because both B and C are concave. The only condition in which all three can fit each other perfectly is when all three are dead straight.

It's all greek to me. :lol: :lol: :lol:

ETA: http://home.comcast.net/~jaswensen/mach ... _edge.html

BugBear

 

[GazPal]

I normally make my own straight edges, winding sticks and travellers using quarter-sawn stock in whichever timber I have on hand at the time, because it's less likely to distort, but seldom make squares. At most I've made two squares in the shop during the past 47 years and the last one must have been at least 25 years ago, although making larger scale setting-out squares for site use used to be normal practice.

Rather than produce three straight edges as cross reference pieces, I tend to make one piece and reference it's working edge against a known straight/reference edge. Typically one of my longer spirit levels.

 

[Cheshirechappie]

It's all greek to me. :lol: :lol: :lol:

ETA: http://home.comcast.net/~jaswensen/mach ... _edge.html

BugBear

I've no idea who came up with the original theory. May well have been the Greeks - they did know a thing or three about geometry. As far as I'm aware, the first person to use it in practice was Henry Maudslay (or possibly Joseph Whitworth whils apprenticed to Maudslay) in his quest for mechanical improvements of plane surfaces for machinery construction. He first produced surface plates by this method in the 1790s, along with the machine-cut reproducable constant-pitch screwthread, and the slide-rest for lathes. Very gifted and inventive workman, was Henry. His contribution to the advancement of civilisation was immense; sadly, he's rather under-appreciated.

That link's a good one.

 

[bugbear]

It's all greek to me. :lol: :lol: :lol:

ETA: http://home.comcast.net/~jaswensen/mach ... _edge.html

BugBear

I've no idea who came up with the original theory. May well have been the Greeks - they did know a thing or three about geometry. As far as I'm aware, the first person to use it in practice was Henry Maudslay (or possibly Joseph Whitworth whils apprenticed to Maudslay) in his quest for mechanical improvements of plane surfaces for machinery construction. He first produced surface plates by this method in the 1790s, along with the machine-cut reproducable constant-pitch screwthread, and the slide-rest for lathes. Very gifted and inventive workman, was Henry. His contribution to the advancement of civilisation was immense; sadly, he's rather under-appreciated.

That link's a good one.

Maudsley was first, but Whitworth (who used scraping, not Maudsley's lapping) was the true "zero point" for accurate engineering, standards, gauges, all that kind of stuff.

As you say, Maudsley has his own claims to fame.

One might say (very, very loosely) Maudsley made, Whitworth measured.

(Edit; I found Whitworth's famous paper online

http://en.wikisource.org/wiki/Miscellan ... rue_Planes

)

BugBear (who has gazed humbly at both men's artefacts in the Science Museum)

 

[twothumbs]

I may be terribly wrong...but I have made wooden squares for marking out sheets and pieces wider than a metal try square by making them up and checking for final clean up by putting the square against an edge of say a board or something like that and adjusting until happy with it by flipping it over and repeating. Straight edges and winding sticks I have made up and then checked by drawing a line on the chosen edge against abit of paper (lining paper is good), reversing the stick to show any deviation and so on until happy. You have to use the pencil carefully but t seems to work for me...now going to go out to the gaarge when the snow stops and check! Made in Mahogany, straight pine, mdf, etc. My squares, I have make out of strips glued of same thickness wood (say 6- 8mm) which means the corner joint is an easy slip in and three dowels to hold it. Look forward to comments as the 'other' ways look very complicated. Best wishes to all for so much ideas and thoughts shared.

 

[bugbear]

Look forward to comments as the 'other' ways look very complicated.

The other way are means towards rather more exotic ends than woodworking. :lol: :lol: :lol:

BugBear

 

[Cheshirechappie]

I may be terribly wrong...but I have made wooden squares for marking out sheets and pieces wider than a metal try square by making them up and checking for final clean up by putting the square against an edge of say a board or something like that and adjusting until happy with it by flipping it over and repeating. Straight edges and winding sticks I have made up and then checked by drawing a line on the chosen edge against abit of paper (lining paper is good), reversing the stick to show any deviation and so on until happy. You have to use the pencil carefully but t seems to work for me...now going to go out to the gaarge when the snow stops and check! Made in Mahogany, straight pine, mdf, etc. My squares, I have make out of strips glued of same thickness wood (say 6- 8mm) which means the corner joint is an easy slip in and three dowels to hold it. Look forward to comments as the 'other' ways look very complicated. Best wishes to all for so much ideas and thoughts shared.

You're not terribly wrong at all - nothing wrong with that approach! It'll be more than accurate enough for about 98% of woodworking tasks.

One of the good things about threads like these is that different people lob different ideas and approaches into the pot. Other people can weigh up for themselves which idea suits their particular circumstances and situation. For example, sometimes just going to the scrap pile, picking out a stick, sighting along it to see if it's near enough straight, and getting on with the job will be plenty good enough - horses for courses.

Just because you know of a trick, technique or wrinkle doesn't mean that you have to use it. On the other hand, if you don't know about it, you can't use it. Knowledge, used wisely, is power.

 

[twothumbs]

Yes CC. Somethings are so obvious once you are told but the knowledge available here is without favours. You can pick up so much and good stuff. I do and long may I learn. Stilll too cold to venture out and check my squares are still square ...been droped a few times! ......in the garage. Best wishes.

 

[GazPal]

Just because you know of a trick, technique or wrinkle doesn't mean that you have to use it. On the other hand, if you don't know about it, you can't use it. Knowledge, used wisely, is power.

Precisely :wink:

75% theory:25% practical. IMHO the greatest influencing factor is how you convert sound theory into good practical results.

 

[bugbear]

Yes CC. Somethings are so obvious once you are told but the knowledge available here is without favours. You can pick up so much and good stuff. I do and long may I learn. Stilll too cold to venture out and check my squares are still square ...been droped a few times! ......in the garage. Best wishes.

Look out for paints spots and glue spots on the stock face - they're easily big enough to cause significant (*) errors.

BugBear

(*) for some value of "significant"

 

[twothumbs]

Hi Bugbear. No paint splashes on me, as I have them hanging on the wall on two pegs! Always look after my tools but when you make them yourself when you can least afford time or money then the home ones remain treated like gold. For some reason I have always been embaressed by even a thin paint mark or dirty hand mark on anything, as the sign of a poor worker or one who didn't care. I still have much covetted bits and pieces from when I was 16 and a very poor appprentice. It wasn't easy come, easy go at that time. Lose something and you didn't have it anymore.

Enter the violins playing softly. Best wishes.