Thread: Toothing Planes

Have not used a toothing plane or hide glue but am wondering why veneering required toothing and a good old rubbed joint didn't.

Any ideas?

Cheerio,
Virg.

Originally Posted by Virgil

Have not used a toothing plane or hide glue but am wondering why veneering required toothing and a good old rubbed joint didn't.

Any ideas?

Cheerio,
Virg.

When rubbing glue blocks, their surface area is relatively small and their faces are normally planed flat; therefore there are no forces at play trying to peel the glue block off. Thick veneer can generate significant forces, especially when wetted with glue and will often try and rip itself off the groundwork. If I'm rubbing a moulding onto a chest or table and the length of moulding has taken on a twist or is warped, I will tooth the back of it and the groundwork before rubbing it in place.

I'd say that it depends on the forces the joint will be exposed to. ie. the type of joint.

M&T is an example of where I think keying must help with hide glue.

How I visualise it and its a simple way of looking at it (but hey prove it wrong)......if a mortise is scratched up and the matching tenon has matching scratches and hide glue when set is rock hard keying must help stop the tenon from pulling out ? You've seen hide glue set. Rock hard glues going to be crossing the mortise tenon lines. Its going to be like trying to turn a key that doesn't fit a lock. (pins don't line up)

so toothing has some procedural advantages in hammer veneering. it has no structural advantage in high performance joinery like wooden airplane manufacture. it helps reduce tearout when planing highly figured wood. all good data points. here's a bit of conjecture- before modern glues, and before modern air conditioning, furniture was routinely subject to conditions far more variable than today. the slightly fuzzy surface presented by a toothed surface within a joint gave a lower absolute strength, but a higher resiliency to wood movement. if the joinery alone was adequate to support all loads the piece would see, a somewhat resilient glue line would survive better over time. modern glues and production methods have made traditional joinery like through tenons, dovetails and so on structurally unnecessary. thus the toothing plane has become a bit of a relic from the golden age of veneering, seeing a bit of a resurgence for use preparing figured woods. should traditional hammer veneering continue to gain interest also, toothing planes will likely become far more available, understood and used.

but then again, I may be totally off base.

Bridger

another point that supports keying which I think relates is that porous timbers glue stronger with hide glue. An article I read recently where proper strength tests were done proved it. An example they gave was that hide glueup of old mahogany furniture proved successful because mahogany was porous (thats just what I read)

so porous timber gives places for the glue to fall into..... And isn't that what keying does .....gives places for glue to fall into.

Must help generally imo, for joints where forces run perpendicular to keying.

How Strong is Your Glue? - Fine Woodworking PDF Cover page

It was in here I think about porous timbers gluing better with hide. Betcha porous timber is related to keying. But thats just my theory ( a theory thats no doubt been thought of thouuuusands of times before) . Might be going off track a bit sorry.

Originally Posted by apricotripper

.....M&T is an example of where I think keying must help with hide glue.

How I visualise it and its a simple way of looking at it (but hey prove it wrong)......if a mortise is scratched up and the matching tenon has matching scratches and hide glue when set is rock hard keying must help stop the tenon from pulling out ? You've seen hide glue set. Rock hard glues going to be crossing the mortise tenon lines. Its going to be like trying to turn a key that doesn't fit a lock. (pins don't line up)

Jake, that is the sort of good intuitive thinking that makes us believe roughed-up surfaces must produce a better bond. However, the forces in play with a glue bond (modern or ancient) are working at the molecular level, not the gross level. The bond between glue & substrate can be higher than the structural strength of either material, but this may not translate to a joint that is stronger, because there are discontinuities in the glue & wood which can start & propagate cracks. The thicker the glue, the more flaws there are likely to be in it, which diminishes the overalll strength of the material to well below its theoretical maximum. So joints with thick glue-lines are more likely to fail under load than those with thin glue-lines (all else being equal). The weak point in your concept is the structural strength of the glue, which in thicker sections may be less than the wood, allowing your 'keys' to fail under load before the wood does. I have confused the issue by yakking about maximum bond strength, when what we are really concerned about in day to day woodworking is sufficient bond strengh. Your M&T joint would probably have more than sufficient strengh for practical purposes, just not theoretical maximum strength.

Cheers,

Originally Posted by IanW

Jake, that is the sort of good intuitive thinking that makes us believe roughed-up surfaces must produce a better bond. However, the forces in play with a glue bond (modern or ancient) are working at the molecular level, not the gross level. The bond between glue & substrate can be higher than the structural strength of either material, but this may not translate to a joint that is stronger, because there are discontinuities in the glue & wood which can start & propagate cracks. The thicker the glue, the more flaws there are likely to be in it, which diminishes the overalll strength of the material to well below its theoretical maximum. So joints with thick glue-lines are more likely to fail under load than those with thin glue-lines (all else being equal). The weak point in your concept is the structural strength of the glue, which in thicker sections may be less than the wood, allowing your 'keys' to fail under load before the wood does. I have confused the issue by yakking about maximum bond strength, when what we are really concerned about in day to day woodworking is sufficient bond strengh. Your M&T joint would probably have more than sufficient strengh for practical purposes, just not theoretical maximum strength.

Cheers,

I see your point.

Still think its a general thought thought based on ideal joinery. Still feel keying would help in many situations in the workshop, to help lock a joint.

eg. .... joints arn't perfect, but have to be used anyway.
Timber is greesy. ie. Doesn't glue well normally anyway.

And also, I betcha keying would definetly help in places where one part of the timber is end grain. So you could put a key (in my diagram above) top and bottom of the mortise.....A key shorely be better imo

And its hard for me to also give up just from simply looking at say the squeezeout of hide from glueup. Try and flick a (thick) bead off with your finger. The stuffs seems to retain high density even when its thick. (but thats probably too simplified) . Works like epoxy but is reversable. (If you had one of those sitting on the mortise/tenon line)

also a thought is the key needent be ruff....not sudden sharp points that propagate a crack. Could be smooth. Just an idea.

Anyway, if indeed all instances have been explored on this already, then I conceeeed.

Not wanting to get involved in the conjecture, just an observation... I can't imagine any historical M&T joints where the mating faces would be cleaned up very much, to even approach the fine toothing marks of the sort WW is talking about. That sort of thing surely is the reserve of modern tooling and those OCD people using hand tools.

Nice to create controversy ...

I assume Ian's picture of toothed gluing is of the veneer contacting the 'peaks', and not the 'troughs'.

One way it could make things stronger would be - like machine feather joints - where the troughs and peaks of one material fit into the reverse in the other. In that case surface contact could be close and the effective contact area increased.
Obviously people are not machines so I don't know if that could play any part in it.

WW - when you do the toothing, is there any practice of marking up in matching directions? or is it more 'random' than that?

Thanks,
Paul

Also ... from reading your article ... the three old blades I have seem to be about 15ish and 25ish tpi.
The two fine ones are Alex Mathieson, the 'rougher' one is James Cam.

They are much like these:

A bit more info here ... WPatrickEdwards: More Toothing Plane Info

The guy distinguishes (for tpi) between hard and soft woods.

Also ... in the comments ... says no toothing on sliced veneer, but needed for 'hand sawn' (which is a different type of rough?)

The toothing planes used for hammer veneering are very fine and no attempt is made to match up grooves on veneer and ground. Indeed on thinner veneers you can't even tooth it. The reason for toothing in hammer veneering is simply that the ridges you leave provide a "screed" level, so that no matter how hard you work the hammer, you cannot starve the veneer of hide glue, and the amount remaining in the troughs is sufficient that the initial tack of hide glue can keep the veneer in place until the second curing process takes place.

Originally Posted by pmcgee

A bit more info here ... WPatrickEdwards: More Toothing Plane Info

The guy distinguishes (for tpi) between hard and soft woods.

Also ... in the comments ... says no toothing on sliced veneer, but needed for 'hand sawn' (which is a different type of rough?)

And the reason for that is that sliced veneer is thin so when it is wet with glue it is limp and doesn't fight the glue. Sawn veneers are thicker and as we've said, thick veneers are more forceful when moistened so toothing them helps retain more hide glue so the initial tack is powerful enough to hold it.

The Toothing plane is used to get the best flat surface , so you don't end up with varying thicknesses of glue under your veneer. Hide glue shrinks back, cracks up and crumbles away when as much as possible is not squeezed or hammered out.

You can set your bench plane blades as fine as possible to true up your surface that is to take the veneer , but no matter how much you traverse and then straighten up, and think you have it flat, when the toothing plane is set right it will prove to you how far out you got it . Every time.

The blade must be set fine so that as you traverse it just takes the high tops off, with each change in direction you hear the amount the blade is taking off increase, and you can obviously see it as well . when the ground is totally covered with no more clear spots I give it a few straight passes , and the a light cabinet scrape to take the fur off.

When using a hammer to lay veneer I always size my veneer both sides when using hide glue, it makes a very noticeable difference as to how well it goes down, specially crotch or figured stuff . I don't do this when I press with a caul.

Another thing about "why use a toothing plane " is if you were veneering to a quality hardwood you could get away wit just using a scraper to get a good flat ground , but 90% of veneering is put down on to a softwood , and a lot of softwoods don't liked being scraped.

So in short if someone asked me why do I use a toothing plane ?
I would say because I dont want the veneer falling off down the track, and I dont want imperfections in the preparation of the ground showing up six months later. when using animal glue.