Thread: Toothing Planes

One of my books on making acoustic guitars recommends using a plane with just a few wide teeth for planing down the thin plates, mostly so that you can make sure you have covered the entire surface of the thin timber evenly - the teeth enable you to see where you have been.

Originally Posted by petersemple

One of my books on making acoustic guitars recommends using a plane with just a few wide teeth

Hi. Sorry to be thick - I'm trying to picture what you mean - 'wide' in the sense of wide apart at the tips? or flattened triangles that don't come to a point? ... or ... ?

(The old toothed blades I have are 30 and 50 teeth across 2 inches.)

Thanks,
Paul

SOrry, what I meant was take a Stanley #4 or #5, and file say 4 or 5 triangle notches out of the blade, spaced evenly across the blade. That way it mostly just planes, but it leaves behind a few hills to that you can see where you have planed and where you haven't. Then you just plane or scrape off the hills.

The Toothing Plane.

The most miss understood , miss described secret of the Cabinet Makers tool chest that exists.

Originally Posted by auscab

The Toothing Plane.

The most miss understood , miss described secret of the Cabinet Makers tool chest that exists.

You're not wrong about the secrecy, Auscab - I certainly have never heard any compelling reasons why I should own a toothed blade. Reading the link above has provided me with the only plausible reason I've heard so far, & that is the claim that they work cranky grain better than a simple blade?

I'll be provocative by declaring that the common myth about these blades, i.e. that they prepare a good ground for glueing, is just plain wrong. While intuition may suggest that the rough surface acts to 'key' the glue, it's not the way glue works, when it's working properly, which is to form molecular bonds with the wood material. This was researched by materials engineers between the WWs., so it's not recent knowledge. It was shown that scuffing up wood fibres actually weakens the glue joint. The strongest glue bonds come from having two clean & closely-opposed surfaces. These guys were taking glue bonds very seriously, at the time, beause they were sticking wooden aeroplane frames together, and they thought it might be a good thing if they remained stuck under the sorts of stresses that furniture is not usually called on to bear outside of the odd bar-room brawl.

Cheers,

Originally Posted by IanW

I'll be provocative by declaring that the common myth about these blades, i.e. that they prepare a good ground for glueing, is just plain wrong. While intuition may suggest that the rough surface acts to 'key' the glue, it's not the way glue works, when it's working properly, which is to form molecular bonds with the wood material. This was researched by materials engineers between the WWs., so it's not recent knowledge. It was shown that scuffing up wood fibres actually weakens the glue joint. The strongest glue bonds come from having two clean & closely-opposed surfaces. These guys were taking glue bonds very seriously, at the time, beause they were sticking wooden aeroplane frames together, and they thought it might be a good thing if they stayed stuck under the sorts of stresses that furniture is not usually called on to bear outside of the odd bar-room brawl.

Cheers,

As you might have anticipated I have to take issue with this Ian. I can hammer modern 1/42" to 3/64" thick veneer without toothing the ground, but > 3/64" (1.2mm) veneer will often spring up if the ground isn't toothed. What you're describing may be related to modern adhesives, but toothing the ground and/or veneer for use with animal glue has been proven to work for centuries.

I wrote a little bit about toothing planes here.

Originally Posted by IanW

I'll be provocative by declaring that the common myth about these blades, i.e. that they prepare a good ground for glueing, is just plain wrong. While intuition may suggest that the rough surface acts to 'key' the glue, it's not the way glue works, when it's working properly, which is to form molecular bonds with the wood material. This was researched by materials engineers between the WWs., so it's not recent knowledge. It was shown that scuffing up wood fibres actually weakens the glue joint. The strongest glue bonds come from having two clean & closely-opposed surfaces. These guys were taking glue bonds very seriously, at the time, beause they were sticking wooden aeroplane frames together, and they thought it might be a good thing if they stayed stuck under the sorts of stresses that furniture is not usually called on to bear outside of the odd bar-room brawl.

Cheers,

Originally Posted by Woodwould

As you might have anticipated I have to take issue with this Ian. I can hammer modern 1/42" to 3/64" thick veneer without toothing the ground, but > 3/64" (1.2mm) veneer will often spring up if the ground isn't toothed. What you're describing may be related to modern adhesives, but toothing the ground and/or veneer for use with animal glue has been proven to work for centuries.

I wrote a little bit about toothing planes here.

I wonder whether you're not both right? What would you have in the case of hammer veneering? You probably have a ground that is prepared fairly smooth and you may have a smooth thin modern veneer that goes as limp as a boned fish when moistened with hide glue, so once it is hammered down there aren't many forces at work that the thin layer of hide glue can't overcome. But if you have a thicker veneer, it may want to distort and carry on when moistened with hide glue even if it is sized and the thin layer of glue may not be able to retain it (somewhat akin to overclamping starvation). But if the ground is scarified with a mesh of very fine trenches, there would be retained between the veneer and the ground a network of hide glue with more holding power, ie the toothing makes it impossible to starve the veneering of glue, no matter how thorough you are with the hammer. (?)

Originally Posted by mic-d

I wonder whether you're not both right? What would you have in the case of hammer veneering? You probably have a ground that is prepared fairly smooth and you may have a smooth thin modern veneer that goes as limp as a boned fish when moistened with hide glue, so once it is hammered down there aren't many forces at work that the thin layer of hide glue can't overcome. But if you have a thicker veneer, it may want to distort and carry on when moistened with hide glue even if it is sized and the thin layer of glue may not be able to retain it (somewhat akin to overclamping starvation). But if the ground is scarified with a mesh of very fine trenches, there would be retained between the veneer and the ground a network of hide glue with more holding power, ie the toothing makes it impossible to starve the veneering of glue, no matter how thorough you are with the hammer. (?)

That indeed is my understanding. I'm not very familiar with modern (at the time of the early twentieth-century tests Ian cites) adhesives, but I can see how they might not work as well with toothed surfaces because – in my limited experience – they're not sticky and dry/set-up completely differently to animal glues.

Originally Posted by Woodwould

As you might have anticipated I have to take issue with this Ian. I can hammer modern 1/42" to 3/64" thick veneer without toothing the ground, but > 3/64" (1.2mm) veneer will often spring up if the ground isn't toothed. What you're describing may be related to modern adhesives, but toothing the ground and/or veneer for use with animal glue has been proven to work for centuries.

I wrote a little bit about toothing planes here.

WW, I can't dispute your empirical results, but if I understand you correctly, you are talking about short-term problems with the veneering procedure, not the ultimate strength of the bond when the glue has cured? If so, the explanion seems highly unlikely that toothing is 'keying' the glue. I would think that a major part of the effect comes from the toothing altering the surface qualities of the ground and allowing it to take up more water, which exits via the veneer, & keeps it softer & more flexible as the glue cools & sets. Toothing the veneer itself probably increases the flexibility of that, too.. Once cured, I can't imagine bond strength being an issue for well-laid veneer, because the amount of surface area is so large in proportion to the wood that even a bond that achieves only 50% of the theoretical maximum strength is probably way more than necessary to hold the veneer in place (unless you take the piece off to Darwin in the wet season.. )

The work I weas referring to was done in the 30's & 40's and didn't include any of the popular 'modern' glues. Their findings held for several glues, including hide glue, and they were investigating both solid wood-to-wood joints and moulded plywood joins. IIRC, they used a casein (milk-derived protein) glue to stick the early Mosquito bombesr together, but later switched to urea formaldehyde. Not because it was 'stronger' but because it was less prone to fungal & bacterial attack under the damp conditions experienced in many operational areas.

Many procedures that have been evolved over time by trial & error manifestly work, but the reason they do so may not have anything to do with the popularly-accepted explanation. When carefully controlled experiments show roughing/toothing does not improve the strength of the (cured) joint, and actually reduces it, it is certainly food for thought, if nothing else. All wood glues work by the same principle, whatever their actual chemical composition, and that is by establishing molecular bonds with the base material. These bonds are powerful, but operate over very short distances, which is partly why maximum bond strength is achieved by having the closest possible contact between the two bonded surfaces (the other part of the equation is the tensile strength of the glue materiaal itself).

Forgive me if I over-react to the 'keying' myth, but I have too often seen it used to excuse poor surface preparation.....

Cheers,

Edit: Micahael beat me to it, but we seem to be thinking along the same lines...

Originally Posted by IanW

WW, I can't dispute your empirical results, but if I understand you correctly, you are talking about short-term problems with the veneering procedure, not the ultimate strength of the bond when the glue has cured? If so, the explanion seems highly unlikely that toothing is 'keying' the glue. I would think that a major part of the effect comes from the toothing altering the surface qualities of the ground and allowing it to take up more water, which exits via the veneer, & keeps it softer & more flexible as the glue cools & sets. Toothing the veneer itself probably increases the flexibility of that, too.. Once cured, I can't imagine bond strength being an issue for well-laid veneer, because the amount of surface area is so large in proportion to the wood that even a bond that achieves only 50% of the theoretical maximum strength is probably way more than necessary to hold the veneer in place (unless you take the piece off to Darwin in the wet season.. )

The work I weas referring to was done in the 30's & 40's and didn't include any of the popular 'modern' glues. Their findings held for several glues, including hide glue, and they were investigating both solid wood-to-wood joints and moulded plywood joins. IIRC, they used a casein (milk-derived protein) glue to stick the early Mosquito bombesr together, but later switched to urea formaldehyde. Not because it was 'stronger' but because it was less prone to fungal & bacterial attack under the damp conditions experienced in many operational areas.

Many procedures that have been evolved over time by trial & error manifestly work, but the reason they do so may not have anything to do with the popularly-accepted explanation. When carefully controlled experiments show roughing/toothing does not improve the strength of the (cured) joint, and actually reduces it, it is certainly food for thought, if nothing else. All wood glues work by the same principle, whatever their actual chemical composition, and that is by establishing molecular bonds with the base material. These bonds are powerful, but operate over very short distances, which is partly why maximum bond strength is achieved by having the closest possible contact between the two bonded surfaces (the other part of the equation is the tensile strength of the glue materiaal itself).

Forgive me if I over-react to the 'keying' myth, but I have too often seen it used to excuse poor surface preparation.....

Cheers,

Edit: Micahael beat me to it, but we seem to be thinking along the same lines...

Again, I must take you up on your comments. You initially claimed "...the common myth about these blades, i.e. that they prepare a good ground for gluing, is just plain wrong." which I repudiated. Latterly you talk about long term bond strength.

Toothing the surfaces when laying thick veneer is more often essential to create a decent bond when hammering with animal glues (not necessary when clamping in cauls). I am aware that some if not all modern adhesives require clamping at considerable pressures to affect a serviceable bond, but the opposite can be the case with animal glues. It is possible to over-clamp a joint and starve it of animal glue. Likewise, it's possible to over-hammer veneer, excluding too much glue from the mating surfaces.

Now that we're talking about long term bond strength however, I can report I have noticed absolutely no difference in the longevity of toothed or un-toothed animal glued veneer.

There are dozens of dubious procedures in woodworking; many dependent on tradition/personal preferences/ignorance, but when thousands of woodworkers worldwide adhere (pardon the pun) to a regimen, then I suspect it deserves due recognition. Gluing narrow wooden aircraft ribs together is not a valid comparative test in my view. I believe Cascamite (casein) glue is indeed what was used for sticking Moskitos together.

Originally Posted by Woodwould

Gluing narrow wooden aircraft ribs together is not a valid comparative test in my view. I believe Cascamite (casein) glue is indeed what was used for sticking Moskitos together.

Mosquito bombers for most of their production time were actually glued with urea-formaldehyde glue, see ref from an article in Wikipedia (de Havilland Mosquito - Wikipedia, the free encyclopedia)

"The type of glue originally used was Casein resin, which was later replaced by "Aerolite", a synthetic urea-formaldehyde, which was more durable.^{[64][nb 8]}"

Only reason I picked up on this is that a company I worked for sold large quantites of urea-formaldehyde glue to the plywood and veneered sheet industries.

One of our sales pitches was the u-f glue was specifically developed for the production of the Mosquito bomber.

There you go, bit of (useless?) trivia for you.

Originally Posted by Woodwould

Likewise, it's possible to over-hammer veneer, excluding too much glue from the mating surfaces.

Now you've done it, I'm going to have nightmares for weeks... again.

Originally Posted by mic-d

Now you've done it, I'm going to have nightmares for weeks... again.

As long as your glue wasn't too thin everything should be fine.

Originally Posted by Woodwould

As long as your glue wasn't too thin everything should be fine.

Oh yes, the sixteeth time everything went swimmingly, everything's fine now :twitch twitch:, the drugs and therapy are helping. However, the first fifteen times may have taken their toll on my sanity :twitch twitch: