Plane tuning extremes

[Dee J]

I see a lot on this forum about plane fettling - especially truing the sole. - But , of course, in use the plane is never used on a truly flat surface. The wood behind the blade (ie the bit just planed) will inevitably be a bit lower than the wood in front of the blade - the difference being the thickness of the shaving. Obviously the thinner the shaving the less this matters. Anyone ever made a handplane that follows electric plane practice... ie blade set fixed with relation to the aft part of the sole, with the fore part of the sole adjustable to set cutting depth?

Dee

 

[bugbear]

I see a lot on this forum about plane fettling - especially truing the sole. - But , of course, in use the plane is never used on a truly flat surface. The wood behind the blade (ie the bit just planed) will inevitably be a bit lower than the wood in front of the blade - the difference being the thickness of the shaving. Obviously the thinner the shaving the less this matters. Anyone ever made a handplane that follows electric plane practice... ie blade set fixed with relation to the aft part of the sole, with the fore part of the sole adjustable to set cutting depth?

Dee

The Hardt Patent planes, apparently.

Didn't catch on.

It sounds "obvious" that this is a good idea, but it's not needed, as 2000 years of experience demonstrate!

BugBear

 

[studders]

The only reason I can think of as to why Electric Planes are made to work like that is that it would be rather harder to lower or retract the Blade. If the blade was at a fixed projection the sole could be inline and it would work OK, I think?

 

[János]

Hello,

in a hand plane, no real advantage could be gained through such a solution, as the thickness of the shavings seldom exceeds a few tenth of a millimetre, and the wood deforms and flexes under the cutting forces (this is the reason, why you can not cut shavings thinner than a limit /about 0,05 mm/, as the edge is not able to cut into the deflecting tissue of wood). In electric planers the thickness of cut is in the range of millimetres, so a machine made in a "hand plane-like" arrangement would produce hollow/concave surfaces.

By,

János

 

[matthewwh]

so a machine made in a "hand plane-like" arrangement would produce hollow/concave surfaces.

By,

János

Very, very astute!

A handplane is not a flattening tool, it is a hollowing tool capable of approaching flatness to a very fine tolerance. The distinction is often lost on 'flatsflatinnit' people, but truly flat only ever exists as a concept, even the flattest thing in the world isn't truly flat and if it were then as soon as the temperature altered by a fraction of a degree it wouldn't be flat anymore. If you gave an engineer a century of global GDP and asked him to make something absolutely flat he would still ask you to specify a tolerance. The best we can do is approach flat with varying degrees of accuracy. Approach it from the the concave side and it will behave like the 'flatsflatinnit' brigade expected it to. Approach it from the convex side and regardless of how close you get, you just entered 'tentquiteflamateizzit?' territory.

As long as pressure is applied at the front before the blade starts cutting (engaging the toe and the fore-mouth) and at the rear once the tail is on the board (engaging the fore-mouth and the tail) your timber will end up with a slight hollow, less than or equal to the protrusion of the iron divided by the length of the sole (which is why long planes make things flatter than short ones).

The far eastern planemakers come closest to the concept of machine planing by hanging the blade as far back as possible in the body to create the maximum possible length between the toe and fore mouth. For this reason oriental planes should be used with the weight forward until the point where the body disengages with the workiece, at which point the weight transfers to the rear.

 

[Paul Chapman]

As long as pressure is applied at the front before the blade starts cutting (engaging the toe and the fore-mouth) and at the rear once the tail is on the board (engaging the fore-mouth and the tail) your timber will end up with a slight hollow, less than or equal to the protrusion of the iron divided by the length of the sole (which is why long planes make things flatter than short ones).

I disagree, Matthew. In my experience, if you keep planing a piece of wood end to end, you will eventually plane it convex. The only way to plane hollow is to take stop shavings, where you start the cut a little way in from the end and stop cutting before you get to the other end, whatever length of plane you are using.

Cheers :wink:

Paul

 

[matthewwh]

Hi Paul,

I agree entirely, planing within the length of the board until the shavings disappear (i.e. trying to hollow it out but being limited by the sole) and then one through pass from end to end. Sorry, I should have clarified that.

 

[Paul Chapman]

Phew, you had me worried for a minute there, Matthew :lol:

Cheers :wink:

Paul

 

[woodbloke]

I disagree, Matthew. In my experience, if you keep planing a piece of wood end to end, you will eventually plane it convex. The only way to plane hollow is to take stop shavings, where you start the cut a little way in from the end and stop cutting before you get to the other end, whatever length of plane you are using.

Cheers :wink:

Paul

I'm not sure about that Paul. I done plenty of planing over the years and as long as the hand pressures at the beginning and end of the stroke are applied properly, the wood ought to stay flat. I used to demonstrate to the kids in class that the at the beginning, the pressure is applied on the front knob and the tote can just be pushed with the forefinger. At the end of the stroke, the left hand can be completely lifted off the plane and the stroke finished by just pushing the tote. Any pressure in the wrong place at the wrong time will cause the surface to go 'unflat' - Rob

 

[Paul Chapman]

I disagree, Matthew. In my experience, if you keep planing a piece of wood end to end, you will eventually plane it convex. The only way to plane hollow is to take stop shavings, where you start the cut a little way in from the end and stop cutting before you get to the other end, whatever length of plane you are using.

Cheers :wink:

Paul

I'm not sure about that Paul. I done plenty of planing over the years and as long as the hand pressures at the beginning and end of the stroke are applied properly, the wood ought to stay flat. I used to demonstrate to the kids in class that the at the beginning, the pressure is applied on the front knob and the tote can just be pushed with the forefinger. At the end of the stroke, the left hand can be completely lifted off the plane and the stroke finished by just pushing the tote. Any pressure in the wrong place at the wrong time will cause the surface to go 'unflat' - Rob

I think that the only way you would avoid a convexity without doing stop shavings would be to have the sole of the plane behind the blade lower than the front by the thickness of the shaving. But as you can't have that, you have to compensate by doing stop shavings.

Cheers :wink:

Paul

 

[adidat]

the hardt patent plane looks pretty speaical but at 9 thousand dollars bit out of my price range

adidat

 

[David C]

I tried to get people interested in this phenomenon a while ago.

A simple experiment;

Start with two straightish edges as for a hot glue rub joint.

Take ten full length shavings off each edge and see what happens.

Paul already knows the answer, but it would be nice if a few more were prepared to have a go and confirm one of handplaning's important facts of life.

Best wishes,
David Charlesworth

 

[mtr1]

I can confirm that's true, I wondered if it's because you push down hardish at the start, go into a kinda cruise mode through the cut, then push down at the end of the board again? Might be why my grandfather added lead to the front of his no8, to minimise the convexness of shooting by hand?

 

[David C]

Mark,

Thank you. There is some sanity in the world.......

I have tried hard but still do not understand the reasons for this phenomenon.

David

 

[Paul Chapman]

I think the best way to understand the reason for the convexity, is to think of the plane sole either side of the blade as an in-feed and out-feed table - the front of the sole being the in-feed and the rear the out-feed. If the out-feed were lower than the in-feed by the thickness of the shaving, then the wood would remain flat. However, the in-feed and the out-feed are the same level, so the plane pivots around the blade, and the wood ends up convex.

Cheers :wink:

Paul

 

[Alf]

There is some sanity in the world.......

I'm not sure that isn't just a nasty rumour, David!

I haven't deliberately done the ten stroke test pieces, but certainly I can't get a good glue joint without using stopped cuts, and that's a good enough argument for me.

 

[woodbloke]

I can confirm that's true, I wondered if it's because you push down hardish at the start, go into a kinda cruise mode through the cut, then push down at the end of the board again? Might be why my grandfather added lead to the front of his no8, to minimise the convexness of shooting by hand?

What MrC and Paul say may be fundamentally correct, but pushing down at the end of stroke will only compound the convexity...vertical downward pressure should be eased to almost zero at the end of the board - Rob

 

[mtr1]

I can confirm that's true, I wondered if it's because you push down hardish at the start, go into a kinda cruise mode through the cut, then push down at the end of the board again? Might be why my grandfather added lead to the front of his no8, to minimise the convexness of shooting by hand?

What MrC and Paul say may be fundamentally correct, but pushing down at the end of stroke will only compound the convexity...vertical downward pressure should be eased to almost zero at the end of the board - Rob

Sigh.

 

[studders]

However, the in-feed and the out-feed are the same level, so the plane pivots around the blade, and the wood ends up convex.

Cheers :wink:

Paul

Yebbut, why? It's taking the same thickness of shaving from the length of the board so logic says it shouldn't make the board convex.
I'm confused, my head hurts. :? :? :?

Edit
Has anyone taken a full length shaving and measured it to check it's the same thickness along its length?

 

[Paul Chapman]

However, the in-feed and the out-feed are the same level, so the plane pivots around the blade, and the wood ends up convex.

Cheers :wink:

Paul

Yebbut, why? It's taking the same thickness of shaving from the length of the board so logic says it shouldn't make the board convex.
I'm confused, my head hurts. :? :? :?

Edit
Has anyone taken a full length shaving and measured it to check it's the same thickness along its length?

Hi Studders,

It's very easy to demonstrate to yourself what is happening. Take two boards, say 1/2" thick, and put them together in the vice and plane them as if you were jointing them to make a wider board. By using two boards the effect will be magnified so it will be easier to see the problem.

Take, say, 10 or 20 plane strokes from end to end, then take the boards and place the two planed edges together. You will find, I am sure, that the boards have been planed convex so they will touch in the centre and not at the ends.

Try it and see......

To correct the convexity you will need to take stop shavings.

Cheers :wink:

Paul