Center join

[fiddlesurgeon]

For the non-rubbers, some simple to make plate clamps. Sorry, don't know

who to credit for this design.

Plate halves are demonstration only, no center join yet.

I use my 6" power joiner. I first flatten the wide surfaces

of both halves. Then hold them together tightly with the wide

edges together and aligned and join the pair.

[nathan slobodkin]

I have always been curious about this approach.  Nathan, if you read this and can explain the logic, I would appreciate it (or anyone else, of course).  One friend of mine from the Chicago School gave me an explanation that either didn't register or I have forgotten.  I have wondered whether the gap is arrived at by a gentle deepening from the very ends.  I know since it is done by fine makers and it holds it CAN be done, but I'm afraid of it for myself, considering my skills and eye.

The theory behind leaving the dry joint slightly hollow is that a dead straight and flat joint swells slightly when the glue is applied forming a gap at the ends. The hollow is very gradual and increases from tight at the ends to about a quarter of a MM in the center. If you put one half of the plate in a vise at one end (I support the free end on a stool) place the other half of the plate on top and shine a light behind it you can easily see the gap. If you place a clamp at the center with the bar against the peaked side and tighten slowly you should see the gap close evenly from the ends until it closes completely as the clamp gets to "finger tight". When you actually glue it of course you can use a bit more pressure until the excess glue squeezes out all the way along.

[Stephen Faulk]

For the non-rubbers, some simple to make plate clamps. Sorry, don't know

who to credit for this design.

 

The ancient Egyptians maybe? 

[Michael Doran]

I was curious how thick my plane shavings are when I'm joining plates. So I grabbed a random piece of flamed maple of about the right size and got out my jointer plane and my micrometer.

The top shaving (.043 mm) is about the thickest I would ever take for a finishing cut. The shavings are very delicate and easy to see through.

If I went thinner than the thinnest one (.039 mm) I started to feel like I wasn't taking a cut completely across the surface of the edge.

-Michael

[tango]

So makers who rub and glue without pressure are in the very rigth way because there will be no twist between halves ¿ok?

Tango

[Evan Smith]

The theory behind leaving the dry joint slightly hollow is that a dead straight and flat joint swells slightly when the glue is applied forming a gap at the ends. The hollow is very gradual and increases from tight at the ends to about a quarter of a MM in the center. If you put one half of the plate in a vise at one end (I support the free end on a stool) place the other half of the plate on top and shine a light behind it you can easily see the gap. If you place a clamp at the center with the bar against the peaked side and tighten slowly you should see the gap close evenly from the ends until it closes completely as the clamp gets to "finger tight". When you actually glue it of course you can use a bit more pressure until the excess glue squeezes out all the way along.

I was taught this way also,

But the explanation was different.

That it had to do with the extra pressure on the ends helping to hold the wood together

so that through the years it will not open back up as it shrinks ,,which never made any sense to me,

because as soon as the plate is thinned there is no extra pressure anyway.

I have always done it ,,it just feels like a tighter joint,, and you explanation just hit the spot.

Kind of like putting a slight side to side hollow on top of the neck gluing surface.

I thought about trying to reply to this,,,

I am glad that I for once kept my mouth shut.

[Craig Tucker]

And, I'll have to add once again, that it doesn't matter in the least, what anyone does to correctly join their plates...

A perfectly flat joining surface. A very slight gap, closed by clamp pressure.

Who really cares? As long as our particular prerequisites are appeased.

...and - any reliable historical data for a preference, will maybe (but probably not) show up - long after we all go the way of the dial telephone. 

Because IT DOESN'T REALLY MAKE ANY DIFFERENCE - BOTH METHODS WORK EQUALLY WELL.

When correctly done.

[Michael_Molnar]

Michael,

Thanks for the data. Nothing like measurements to satisfy an experimenter!!

Mike

Craig,

We agree.

Mike

[Matthew Noykos]

Does anyone put a slight toenail on their jointer blade or do most just sharpen it dead flat?

[Matthew Noykos]

Daryl,

I love that Japenese planing video! Thanks for that.

[nathan slobodkin]

Does anyone put a slight toenail on their jointer blade or do most just sharpen it dead flat?

If you mean a slight curve along the edge, yes I do, for the same reason that I hollow the joint end to end.

[Will L]

Thanks, Nathan.  And Evan.

[Craig Tucker]

Does anyone put a slight toenail on their jointer blade or do most just sharpen it dead flat?

 

I had to stop and think about this post for a minute or two...

 

Slight toenail on the blade or sharpen it dead flat? Yes I have to cop to a slight lenghtwise toenail on my plane blade. Which I have always gotten from the hand sharpening process - even though my intention is to keep the leading edge as flat as possible. I was not posting about this point in this post at this time because there have been so many other things to post about and discuss, but yes, I do have this also. 

 

I believe it (the curve) is so infinitesimally small, that it doesn't make a great working difference. Still, when I think theoretically, it might be the cause of a slight lengthwise hollow, that isn't visible when looking, but which allows a slightly larger amount of glue to exist on the join surfaces?

 

Sorry about the delay in answering, but this is a really good observation, and no one has brought up this point or this possibility yet. Thanks Matthew, as I believe that this is probably commonplace.

I had meant to bring this observation up myself but never got around to it!

[arglebargle]

How about scrapers!?

 

I've used them before to put the slight hollow in the surface, both along the length and width. 

[Craig Tucker]

 .

[Craig Tucker]

So, I just went into the shop and took a quick shot of the blade. (previous post) You can see the area that is most in use for planing the plates - its the center portion (the light area, where the plates slide along the bottom when the plane is in the "jig".) - it is intentionally  where I feel the flattest part of the blade is, but there's still a SLIGHT, perhaps even microscopic curve to the profile of the blade.

 

Interesting point.

 

(BTW - the red on the top of the blade is a reflection only)

[David Burgess]

(BTW - the red on the top of the blade is a reflection only)

Are you sure it's not glowing red-hot from speed-planing?

[Craig Tucker]

Are you sure it's not glowing red-hot from speed-planing?

 

Geez - I wasn't going to mention THAT specific point, but yeah, that's EXACTLY what just happened... I thought only I did that?

[Matthew Noykos]

I brought up the toenailed blade thing because I'm curious to know what is commonplace. Originally I was taught to make it dead flat, but now I make it slightly curved. The curve I get from the pressure of my fingers while sharpening by hand, so it's not a lot but it's there.

The way I understand it is that the glue will dry faster on the outside of the joint, so having things slightly more snug on the outside creates a better joint. The joints I make now seem better, but that could be due to increased skill over time too.

[robertdo]

The theory behind leaving the dry joint slightly hollow is that a dead straight and flat joint swells slightly when the glue is applied forming a gap at the ends. The hollow is very gradual and increases from tight at the ends to about a quarter of a MM in the center. If you put one half of the plate in a vise at one end (I support the free end on a stool) place the other half of the plate on top and shine a light behind it you can easily see the gap. If you place a clamp at the center with the bar against the peaked side and tighten slowly you should see the gap close evenly from the ends until it closes completely as the clamp gets to "finger tight". When you actually glue it of course you can use a bit more pressure until the excess glue squeezes out all the way along.

What I don't understand is how you can get such a curve along the piece of wood other than getting a sligthly curve sole of the plane? If the blade itself if convexe (or concave) what you should have is a convexe or concave wood but from one edge to the other (across the width), while being perfectly flat from one side to the other?

[Michael_Molnar]

Matt,

 

The long arch runs along and down into the glued joint. What you do opens the possibility of having a visible seem along the arch.

[Matthew Noykos]

Mike,

I'm not talking about a millimeter or something. It's really just a sliver of light that comes through.

[Matthew Noykos]

I think there is a little swelling of the inside from the glue that contributes to everything like Nathan described.

[DarylG]

Does anyone put a slight toenail on their jointer blade or do most just sharpen it dead flat?

 

http://www.maestronet.com/forum/index.php?/topic/329038-centre-joint-questions/?p=597075

[Matthew Noykos]

Thanks. It's impossible to keep up with all these threads. Sometimes I don't even comment because I figure it's been covered before.

David explained my thoughts well. I suppose I probably got the idea from him indirectly.