Plane Sole Flattening

[xy mosian]

Thanks Philly.
I seem to be able to plane a sufficiently flat surface as required. I was having a problem with the geometry etc. of the discussion. The 'minimum requirement' points help a great deal.

To me your co-planar three points reminded me of a Furring? plane. Of course now I refer to Salaman his image shows a Furring plane with the mouth area and the tail in contact with the stock.

Thanks again.

xy

 

[bugbear]

The theoretically inclined may enjoy this:

http://swingleydev.com/archive/get.php? ... =1#message

BugBear

 

[Mikey R]

XY
As long as the front of mouth area and area directly behind the mouth are co-planer as the plane reached the end of the board the cut is still supported by the area behind the mouth.
Japanese smoothers can have their soles relieved behind the mouth - the plane is used with a very quick stroke, whipping the plane off the workpiece at the end.


As an afterthought - this talk of having only certain areas in contact. This is a minimum, no a goal to achieve. Ideally, the complete sole would be flat and all areas co-planer - but this is difficult to achieve and retain. So when maintaining your plane, this three point approach is the minimum to aim for.
Hope this helps
Philly

Philly, Ive been thinking, that only holds if your workpiece is longer than your plane sole. If your workpiece is smaller, then the coplanar part of the plane will be out in space, and wont be contributing to the action of the sole - from the point of view of the workpiece, the sole will be convex.

 

[bugbear]

XY
As long as the front of mouth area and area directly behind the mouth are co-planer as the plane reached the end of the board the cut is still supported by the area behind the mouth.
Japanese smoothers can have their soles relieved behind the mouth - the plane is used with a very quick stroke, whipping the plane off the workpiece at the end.


As an afterthought - this talk of having only certain areas in contact. This is a minimum, no a goal to achieve. Ideally, the complete sole would be flat and all areas co-planer - but this is difficult to achieve and retain. So when maintaining your plane, this three point approach is the minimum to aim for.
Hope this helps
Philly

Philly, Ive been thinking, that only holds if your workpiece is longer than your plane sole. If your workpiece is smaller, then the coplanar part of the plane will be out in space, and wont be contributing to the action of the sole - from the point of view of the workpiece, the sole will be convex.

I think it is presumed that the three contact points are in contact, hence the name

BugBear

 

[ivan]

I think "How flat is flat for a plane sole?" depends on the plane.

A short smoother is much stiffer than a number 8, and a small error will prevent the plane taking a full length fine 1 thou shaving from a "flat" board (fresh from the properly set* surfacer, say: when setting up tables two 4' edges have about 2-4 thou between them, so "flat" is about 2 thou concave over 3-4')

The No 8 is more flexible and a lot longer, so an error which stops the smoother cutting full length will not affect it so much.

Both planes' errors will add some unwanted curvature to the work. For the same amount of error, the longer plane will produce less curvature in the work than the smoother.

In all the above, the error is considered to be along the length. Hollowing across the sole can lift the mouth and lead to tearing or uneven depth of cut; convexity will make the plane wobble, and so impossible to plane the edge 90 deg to the face.

In practice, I would suggest that "flat" work for furniture, is actually about a couple of thou hollow over the length of the plane. IE over ~4' from the surfacer with 1.5M tables, and over ~2' from your No.8, (by taking stop shavings till it won't cut any more, and then full shavings till you get the first at full length). The work may not stay that flat, but it's flat enough to allow accurate and consistent marking out.

Thus test the work to see if the plane is flat enough! David Charlesworth promotes abrasive flattening on glass or granite as sufficient to achieve this order of flatness in the work.

* From a Felder manual; of course this gets steadily worse till the point that I notice the p/t needs a tweek

 

[Jeff Gorman]

Ivan wrote:

'Both planes' errors will add some unwanted curvature to the work. For the same amount of error, the longer plane will produce less curvature in the work than the smoother.

In all the above, the error is considered to be along the length.'

It is an academic point, but I think it is worth pointing out that even a completely rigid plane can plane a concave curve that is proportional to the square of its length divided by the set. This is why we can plane a slightly concave edge for a cramped butt joint.

This relates to the formula (forgotten it!) that relates to the sagitta (sp?) of a curve, ie the distance between the crest of the curve and its chord.

Jeff Gorman
www.amgron.clara.net

 

[ivan]

I think that's what you may head towards if you keep taking full length shavings. Although as often drawn in textbooks, with only heel, cutting edge, and toe touching the job, the plane couldn't actually cut, so this might be an oft repeated armchair supposition. Presumably that's why "stop shavings till no cut + full pass until first full length shaving" was invented, to ensure you arrive at a given, repeatable degree of very slight hollow.

Edit: be nice if some intrested IT woodworker programmed a model to examine this!

Interestingly, on the box the other day there was a piece of historical black and white film shown. What the programme was about I forget, but I was transfixed by a bloke in the background working on site and planing up a piece of stuff about 8' long with a tryplane with a length of more than half his height. (I guess ~4') From the way he was holding it it appeared to have no handle, but of course the background of the shot was slightly out of focus. The Dictionary of Tools puts try planes up to 30" in the 1800s, although coopers had something longer, but this was used upside down (blade up) and the wood moved over the stationary plane. Now all we need is a price from Philly....

 

[bugbear]

Although as often drawn in textbooks, with only heel, cutting edge, and toe touching the job, the plane couldn't actually cut, so this might be an oft repeated armchair supposition.

if the curve were less (wood flatter) the plane would cut more. if the curve
were more the gap from the blade to wood would become larger.

So the drawing is of the stage in the process where the plane has (juuust) stopped cutting, and the wood-blade gap is zero.

BugBear

(no armchairs were harmed in the making of this post)

 

[Philly]

The Dictionary of Tools puts try planes up to 30" in the 1800s, although coopers had something longer, but this was used upside down (blade up) and the wood moved over the stationary plane. Now all we need is a price from Philly....

Funnily enough, I'm building a 30 inch jointer for a customer at the moment.....

Cheers
Philly

 

[ivan]

Looking good! But doesn't look like four feet to me?

 

[TrimTheKing]

Looking good! But doesn't look like four feet to me?

That would be because 30" is two and a half feet, or are you being funny and it's gone over my head?

 

[Karl]

Looking good! But doesn't look like four feet to me?

That would be because 30" is two and a half feet, or are you being funny and it's gone over my head?

Mark - the latter I think :lol:

Ivan enquired earlier on in the thread whether Philly would build a 4' jointer, hence his reference to 30" not being 4'.

Cheers

Karl

 

[TrimTheKing]

Mark - the latter I think :lol:

Ivan enquired earlier on in the thread whether Philly would build a 4' jointer, hence his reference to 30" not being 4'.

Cheers

Karl

Ahhhhh, missed that one

That'll teach me to read more closely :wink: