Really stupid question about hand planes.

[John Brown]

Forgive me for having to ask, but I can't get my head round this.
On a power planer, even a hand-held one, the table, or the sole? in the case of a hand-held electric planer, is at a different height in front of the cuting edge compared to behind the cutting edge. Indeed, if I want to set up my router table for jointing, I have shims that move the outfeed fence relative to the infeed. This makes sense to me.

In the case of a hand plane, with a flat sole?(if I have the terms right) I would have thought that the piece being planed would end up with a slight curve, as the back end of the plane dropped down onto the section that had already been shaved.
Why is this apparently not a problem? Is the effect too small to matter, or am I missing something?

John

 

[Jacob]

Forgive me for having to ask, but I can't get my head round this.
On a power planer, even a hand-held one, the table, or the sole? in the case of a hand-held electric planer, is at a different height in front of the cuting edge compared to behind the cutting edge. Indeed, if I want to set up my router table for jointing, I have shims that move the outfeed fence relative to the infeed. This makes sense to me.

In the case of a hand plane, with a flat sole?(if I have the terms right) I would have thought that the piece being planed would end up with a slight curve, as the back end of the plane dropped down onto the section that had already been shaved.
Why is this apparently not a problem? Is the effect too small to matter, or am I missing something?

John

It is a problem - you are quite right.
It is possible to take a shaving from a thin edge (narrower than the blade) and to leave the edge flat and straight.
But it's impossible to pass a plane (power or hand) over a wider flat surface and to leave it flat. It will take out a scoop or a trough approximating to the shape of the projecting blade, or the amount of cutter presented on a power plane.
To actually flatten a surface you have to join up these troughs side by side leaving high points between, and then take these off, with gradually diminishing depths of cut, working towards flatness but without ever getting there, but hopefully getting near enough.
Any planed surface on a wide work piece will show plane marks, under a strong and focussed light cast across the surface, unless it is also scraped and sanded. These in turn leave their marks but with ever decreasing visibility.

 

[Cheshirechappie]

Jacob has about nailed it, but just to add a bit. A long plane (22" try plane, say) with a fine set (taking a shaving of about 5 thousands of an inch or less) will indeed plane a slight hollow. Clearly very slight. By good technique, it can be almost eliminated. However, it can be useful - if you want to edge-joint two boards, you don't want gaps at the ends, so you plane the mating edges to a very slight hollow, the cramping pressure will close the tiny gap in the middle, and the ends will be and remain tight together.

The hollowing effect is worse with shorter planes. It doesn't matter in the early stages of stock preparation because the longer planes will remove (most of) the hollow. It doesn't matter much with a smoothing plane because it should be set very fine anyway.

By the way - bad technique results in a surface being planed with a hump in the middle, despite the plane geometry. You have to exert downward pressure on the plane sole to avoid this - at the toe of the plane when the stroke commences, and at the heel when the stroke finishes, transferring pressure as the stroke progresses.

 

[AaronWright]

on an electric hand plane the rear sole plate has to be at 0 behind the cutter block and the front plate moves up and down to give u your cutting depth. If the plates where set to the same heights the planer would not work as it is designed to. On a hand plane the sole needs to be flat to produce a flat surface . On a jack plane the blade should microscopic round and on a smoothing plane the blade should be straight with the corners taking off to stop producing tram lines

 

[Digit]

I can't see it. Must be me.
Assuming you have a straight edge to begin with, and you are using a long plane, and you keep the front part of the sole on the edge, the edge must remain straight till the iron drops off the end?

Roy.

 

[David C]

John,

It's a very good question.

A previous poster suggested that bad technique causes a hump in the middle of the length.

I think this is one of the great woodworking myths. A hump may be produced by bad technique but a small hump is certainly produced by the geometry of the handplane. i.e. A flat sole with a blade sticking out a few thou". The notion that good plane technique alone will produce or preserve flat lengths is wrong. We must work and take stop shavings to avoid the inevitable hump.

My edge planing experiment goes like this. Start with a straight square edge about twice the length of your plane. Take ten full length, fine shavings and see what you have got. I predict a slight hump in the length. (If you don't have a precision straightedge use two boards with two edges, which can be compared to each other.

Planing straight or slightly hollow in the length is achieved with stop shavings, and through shavings. Stop shavings do not remove the start and end of a surface. Straight and minutely convex plane soles work, significantly concave in the length does not work at all.

best wishes,
David Charlesworth

 

[Digit]

My technique is to have a piece of timber at start and finish so the piece I'm interested in is effectively the centre of a longer board.
As I make my own planes I also fit the iron further to the rear than is conventional and keep the weight ahead of the iron.
Works for me.

Roy.

 

[GazPal]

John,
I think this is one of the great woodworking myths. A hump may be produced by bad technique but a small hump is certainly produced by the geometry of the handplane. i.e. A flat sole with a blade sticking out a few thou". The notion that good plane technique alone will produce or preserve flat lengths is wrong. We must work and take stop shavings to avoid the inevitable hump.

My edge planing experiment goes like this. Start with a straight square edge about twice the length of your plane. Take ten full length, fine shavings and see what you have got. I predict a slight hump in the length. (If you don't have a precision straightedge use two boards with two edges, which can be compared to each other.

Planing straight or slightly hollow in the length is achieved with stop shavings, and through shavings. Stop shavings do not remove the start and end of a surface. Straight and minutely convex plane soles work, significantly concave in the length does not work at all.

best wishes,
David Charlesworth

Hi John,

I think David and Jacob both covered most aspects very concisely and leave little for me to add apart from consistent practice and use of sharp blades/irons will bring you ever closer to your end goal.

There's no such thing as a stupid question. :wink:

 

[Cheshirechappie]

John,

It's a very good question.

A previous poster suggested that bad technique causes a hump in the middle of the length.

I think this is one of the great woodworking myths.

Well, I don't know whether it's a myth or not, but it certainly happened to me before I knew better. The plane seemed to knock the ends off (mainly because I didn't apply pressure inboard of the workpiece, but tried to hold the plane level - unsuccessfully) leaving a hump. Once I learned better, and learned to apply pressure where I should, the problem ceased.

As you say yourself, with the 'ten full shavings' experiment, a slight hump may well result. When flattening a board with handplanes only, you get there quicker by constant checking with straightedge and winding sticks to find high spots, and just attacking those. The 'stop-shaving' technique on edge-planing (which I agree is a good one) is basically the same approach.

 

[matthewwh]

Roy, your thinking is entirely rational and corroborated by Asian plane making traditions.

 

[Digit]

In the past I have many hours flattening soles etc and yet I have to say that I think it was wasted, I also note that, like my home made planes, the Japanese have the iron set well back compared with European ones.

Roy.

 

[David C]

Roy,
Your planes have a different geometry to the western metal bench planes. If they have no tendency to round the length, that is a huge advantage, as metal planes all do.

On sole flattening;
A bump of two thou behind the throat prevents the plane from taking a one thou shaving.
Slight convexity of length and straight work, significant concavity does not.
Twisted is not good.

Surely your time was not completely wasted as the above faults were very common? Certainly between 1970 and 2000.

best wishes,
David Charlesworth

 

[Jacob]

In the past I have many hours flattening soles etc and yet I have to say that I think it was wasted, I also note that, like my home made planes, the Japanese have the iron set well back compared with European ones.

Roy.

I had a 7 which was slightly concave. It was impossible to get a straight edge with it using it normally. Possible to do by skewing it across and other manoeuvres. The time required to flatten it was impossibly long so I dumped it on ebay and got another one. This was the only plane I've ever had which really needed flattening but I couldn't be bothered.
As for the hump - this is a beginners problem: If a plane is clumsily handled, badly set, blunt etc. it's easier to get it to cut at the start and the end of a cut but to float over the middle. Bin there dunnit.

 

[David C]

Your last comment is the myth.

Why not try the experiment? Your edges will not be flat after 10 shavings.

David

 

[Jacob]

Your last comment is the myth.

No it's not. It's what happens. But we may be talking of different humps.

Why not try the experiment? Your edges will not be flat after 10 shavings.

David

I expect you are right. If you plane blindly, without checking continuously as Cheshirechappie describes, it'll come out wrong!

 

[Phil Pascoe]

Digit---don't forget that Japanese planes are pulled , rather than pushed; I assume that would affect the position of the iron.

 

[John Brown]

Well, there's a lot for me to read here. When I asked the question I was explicity thinking of the situation where one is trying to obtain a straight edge for jointing boards, so I was picturing the workpiece being narrower than the blade. However, the replies have probably covered this situation as well as most others.
It'll take me a while to read and digest all of this, but in the meantime, thanks to everyone who has responded.

John

 

[Digit]

To answer a number of questions.
Firstly flatness. To me as an engineer flat means flat! The result then was a tendency for metal soles to stick and become harder to push, grooved soles?
I salvages a number 5 on one occasion with a rusted sole, I flattened it but not to the extent of a mirror finish, much of the pitting remained. It worked well.
Geometry, I pull some of my planes and yes, it does affect the result I find. I find it easier to prevent rolling from side to side on narrow edges, which leads me to my method.
Some time ago I needed to produce some fielded panels in Oak. They were to be about 9-10 mm in thickness and two pieces to each panel.
Their thickess meant a rubbed edge and a floating panel, now I find trying to produce a straight edge on a panel that narrow difficult as the plane must produce a straight edge that is not rounded across the width.
I clamped a longer piece of 2 X 1 to the panel and set the lot in the vice. I now had an edge to plane that was longer and wider than the finished panel, and the plane had better support.
That was 8 yrs ago and the panels still show no sign of separating.

Roy.

 

[Phil Pascoe]

I've got a no4 and a no6 with corrugated soles, that I use most of the time. I think they are easier to push than flat soles.

 

[Jacob]

.....
I salvages a number 5 on one occasion with a rusted sole, I flattened it but not to the extent of a mirror finish, much of the pitting remained. It worked well....
Roy.

Rusted sole and pits no prob (within reason) once it's cleaned off the flat bits. If corrugated soles are an improvement then rust pitted ones should be too.
It's the (very unlikely) opposite of pits which could cause difficulty i.e. sticking out bits. Think "rasp"!

re 10 strokes to a hump. Just did this. It seems I can get what I like - a hump or a hollow depending on how I distribute pressure. I kinda knew this already! To get "flat" you just have to watch what you are doing and react accordingly.
So the accidental hump DC describes is a beginner's problem I think. This could include not knowing that a concave sole makes life difficult. Flat to convex is OK. In fact convex probably gives you slightly more control