A planing question.

[Andy Kev.]

Good Afternoon All,

I've noticed a phenomenon which crops up fairly often when planing a board. If there is e.g. a bit of a hump in the middle as you plane along, it is possible by concentrating on that bit to get rid of it and indeed reduce it to a very slight concavity. How can it be then that when you subsequently make full length passes the hump reappears? The same can happen where there's a bit of a drop off at one end.

I initially put this down to my planing technique but I'm not sure that that is the problem as there are some boards which plane nicely square and flat and stay that way, although my technique could be faulty because if I'm doing something wrong then by definition I don't know what it is. I've found that as I become more experienced, I can deal with this sort of thing more quickly but I still don't get it as it seems to defy all logic. Could stresses in the wood itself be the cause?

 

[D_W]

If the sole of the plane isn't concave, it's likely technique. Try to take even full passes after you've got the mild concave dip that you mentioned that you put into the board to relieve the initial hump.

I think what you're describing is fairly common.

 

[essexalan]

What I do is check both sides of the board and plane the side that is concave first you can shim the ends to prevent rocking but I don't bother, plane one edge square and then go after the convex side. No idea if this is the correct procedure but it works for me. Otherwise the convex side will push down in the middle and you will never get it flat. As DW says trying this with a concave sole on your plane is a bad idea and technique is important. Of course if the other side of the board is already flat then it is either your plane or technique, checking for wind will of course be part of this process.

 

[Andy Kev.]

That's my method too and my planes are definitely flat soled and I always check for wind. The fact that some boards plane like a dream lead me to believe that I'm essentially getting the technique right and as I say I do eventually sort out the awkward ones. It's the repeated reappearance of the same "fault" that flummoxes me. Maybe I'm no applying enough downward pressure in the middle of the pass.

 

[D_W]

That's my method too and my planes are definitely flat soled and I always check for wind. The fact that some boards plane like a dream lead me to believe that I'm essentially getting the technique right and as I say I do eventually sort out the awkward ones. It's the repeated reappearance of the same "fault" that flummoxes me. Maybe I'm no applying enough downward pressure in the middle of the pass.

It's not so much the middle of the board, it's getting good even passes so that you're not planing off the ends. When you're doing the final work dimensioning something, and the middle work (try planing, jointing, etc), the skill to develop is definitely taking off an even layer across the board after you've gotten it relatively flat. I'd bet that there are a lot of people who can get a board flat at some point, but who can make it "unflat" as they're working toward final dimension or final finish.

Thicker shavings help (until the final cuts), because you don't lose patience or get tempted to spot remove areas - or lose track of what you're doing because you have to take 100 shavings to remove a relatively small amount of wood. Then final smoothing or jointing is just enough to get continuous overlapping shavings.

I'd suggest finding a problem board, and use a long plane and do the following after you've gotten the board concave:
* start a series of passes holding the plane down at the front knob, pushing only on the handle forward at that point and not down
* finish the cut with your hand off of the front knob so that only the back of the plane has pressure on it

While some wood can relieve itself unpredictably, I would suspect that the issue is down pressure on the rear handle/tote at the start of the cut and down pressure on the knob at the end of the cut.

 

[Andy Kev.]

That's my method too and my planes are definitely flat soled and I always check for wind. The fact that some boards plane like a dream lead me to believe that I'm essentially getting the technique right and as I say I do eventually sort out the awkward ones. It's the repeated reappearance of the same "fault" that flummoxes me. Maybe I'm no applying enough downward pressure in the middle of the pass.

It's not so much the middle of the board, it's getting good even passes so that you're not planing off the ends. When you're doing the final work dimensioning something, and the middle work (try planing, jointing, etc), the skill to develop is definitely taking off an even layer across the board after you've gotten it relatively flat. I'd bet that there are a lot of people who can get a board flat at some point, but who can make it "unflat" as they're working toward final dimension or final finish.

Thicker shavings help (until the final cuts), because you don't lose patience or get tempted to spot remove areas - or lose track of what you're doing because you have to take 100 shavings to remove a relatively small amount of wood. Then final smoothing or jointing is just enough to get continuous overlapping shavings.

I'd suggest finding a problem board, and use a long plane and do the following after you've gotten the board concave:
* start a series of passes holding the plane down at the front knob, pushing only on the handle forward at that point and not down
* finish the cut with your hand off of the front knob so that only the back of the plane has pressure on it

While some wood can relieve itself unpredictably, I would suspect that the issue is down pressure on the rear handle/tote at the start of the cut and down pressure on the knob at the end of the cut.

That's very useful, thanks. I actually follow the technique you describe in the last few sentences but there is one thing you have highlighted that I probably don't do enough and that is taking thick shavings with the jointer. Most authors are quite clear on e.g. rough old shavings with the jack and/or scrub plane and superfine shavings with the smoother but the shavings from the jointer don't seem to get too much of a mention. So I'll thicken up on the jointer tomorrow evening.

 

[G S Haydon]

"I'd suggest finding a problem board, and use a long plane and do the following after you've gotten the board concave:
* start a series of passes holding the plane down at the front knob, pushing only on the handle forward at that point and not down
* finish the cut with your hand off of the front knob so that only the back of the plane has pressure on it"

Good description, David. Just stick with it Andy, it's very easy to make a piece of wood convex. I'm sure the more you practice and review the better it'll get.

 

[Corneel]

A trick to learn how to pressure the plane during a full length stroke is "tryingto dig a hole in the middle of the board". When you do full length strokes with a long plane, then digging that hole really isn't going to happen, but trying to do that helps you to put pressure on the front of the plane on the start and on the back of the plane at the end.

 

[Ttrees]

I use a 5 1/2 and never focus any pressure on the plane.
I have a long dead flat composite bench that I can trust like a surface plate.
To make sure its flat, you need two lengths the same length as the bench, plane them to fine tolerance,matching the benchtop, and you match these two pieces together and see no gap...ok

So, say the bottom of the board is dead flat....and were planing the top side.
I have found with the no.8, it has a tendency to want to dive off the end
making the board not sit on the ends when you flip it over to check.
and the no 4 has a tendency to do the opposite, scooping the timber.
I do take stop shavings, and one full length thin shaving to finish it off.
I use the bench for checking this afterwards to see if it turns like a propeller or is pivoting on the ends .
I would like to try a no5 or a 6 and see what happens.

I test for wind by attempting to rock the corners.
On a plank with a bend, I go back and fourth depending on how much deflection the board has.
always having the board sitting on each end, or dead flat by the time I am close

I found it strange you didn't mention the size of plane you are using.
Maybe I did not read correctly
Tom

 

[woodbrains]

Hello,

Corneel has it, try to plane a slight hollow. You won't, but the action of trying to, by trying to take a thicker shaving in the middle of the board, will counteract the convexity you are getting. If you think about how a plane works, it will always produce a convex edge on a board, and the more strokes taken will make the phenomenon more prevalent. It becomes second nature to increase pressure towards the centre of the board; I don't think about it any more, it is just automatic.

Mike.

 

[matthewwh]

Yep, Corneel and DW are on the right track with the remedy.

The thing to bear in mind is that a plane doesn't make things flat automatically, it provides the ability to make the board more convex - with full length shavings, or more concave with less than full length ones. It's a bit like steering a bike, you need to be able to turn the handlebars in order to steer a straight path and you need to be conscious of the direction you are going and make regular small corrections and counter corrections.

Applying pressure in the correct places as described above, minimises the convexifying effect of your full length passes and maximises the concaving effect of the short ones.

Another solution would be to take mostly short passes interspersed with the occasional full one - you can't hollow beyond the thickness of a shaving without the plane indicating by stopping cutting that it's time for a couple of sets of full length ones. You pass through flat with your first full length full width shaving on the way back from concave, stop there and your board should be within a thou or two.

Admittedly this is a slower technique than the one DW describes above, but I find it is more forgiving of lapses in concentration. Both will provide good results so I suppose the answer is to try both and see which you prefer. If you really want to improve your technique David Charlesworth's recently re-shot DVD 'Precision Planing' covers it all in much greater depth.

I would put the reason for it happening intermittently down to lapses in concentration, I know I have them when planing and realise I need a few minutes break. If 'applying pressure correctly' is a remedy then it stands to reason that occasionally forgetting to do so might be the cause.

The other thing that might help when doing faces three and four is chamfering the waste around the edges down to your gauge line before you start and colouring in the chamfers in with a pencil, a flatter chamfer gives you an enhanced measurement of how much depth you have left to remove, so you can see if one corner is getting low, or if you've got a high spot to address.

 

[Ttrees]

I know I keep banging on about the same thing, and probably tires some folks, as you guys have way,way more experience
than I, and I understand it might not be feasible to refer to your bench every time,
But I have failed to get as flat of a surface, as I can with using the bench.

I have tried the all these theoretical methods mentioned, and keep them in the bank.
Maybe they will would work for me with a no.6, so I won't dismiss them.
I like the no.51/2 for whatever length of piece

Going back to the bench again :roll:
I find it very strange that there is no bench design that is designed to accommodate the sag in a benchtop.
I have very carefully shimmed my benchtop to have the slightest crown along the length, say a thou, or two
Maybe it's not crowned, but it certainly is not the opposite.
I have some salvaged door panels across acting as a shelf, some stacked door rails on that, and two boards
bridging between.
One of these boards has a banana shape, which I kept shaving down to get to the tolerance I wanted.
So in essence it is a sprung shim, or whatever you might call it.

I have a aluminum beam like a long spirit level, that I'll probably use for the time I can't use the benchtop as reference.
That's if I don't get a no.6 first, and it does that theoretical job mentioned, without needing reference.

Tom

 

[Andy Kev.]

Yep, Corneel and DW are on the right track with the remedy.

The thing to bear in mind is that a plane doesn't make things flat automatically, it provides the ability to make the board more convex - with full length shavings, or more concave with less than full length ones. It's a bit like steering a bike, you need to be able to turn the handlebars in order to steer a straight path and you need to be conscious of the direction you are going and make regular small corrections and counter corrections.

Applying pressure in the correct places as described above, minimises the convexifying effect of your full length passes and maximises the concaving effect of the short ones.

Another solution would be to take mostly short passes interspersed with the occasional full one - you can't hollow beyond the thickness of a shaving without the plane indicating by stopping cutting that it's time for a couple of sets of full length ones. You pass through flat with your first full length full width shaving on the way back from concave, stop there and your board should be within a thou or two.

Admittedly this is a slower technique than the one DW describes above, but I find it is more forgiving of lapses in concentration. Both will provide good results so I suppose the answer is to try both and see which you prefer. If you really want to improve your technique David Charlesworth's recently re-shot DVD 'Precision Planing' covers it all in much greater depth.

I would put the reason for it happening intermittently down to lapses in concentration, I know I have them when planing and realise I need a few minutes break. If 'applying pressure correctly' is a remedy then it stands to reason that occasionally forgetting to do so might be the cause.

The other thing that might help when doing faces three and four is chamfering the waste around the edges down to your gauge line before you start and colouring in the chamfers in with a pencil, a flatter chamfer gives you an enhanced measurement of how much depth you have left to remove, so you can see if one corner is getting low, or if you've got a high spot to address.

I'm grateful for your idea of a combination of mostly short and a few long passes. It certainly makes sense in an intuitive way. As I pointed out above, I do use all the prescribed techniques but perhaps don't apply them competently enough.

However, none of this explains the fact that I can get about 20% of boards bang on and in a relatively short time e.g. last Saturday a friend who is very keen on his festool powertools came round because he found it hard to believe that you can get a better surface with hand tools (and he'd never had a plane in his hand). I was able to demonstrate getting an 18" length of Zirbel Pine dead flat on the face side and face edge in well under 10 minutes. Admittedly Zirbel is the easiest to plane wood I have encountered (and obviously that is why I chose it) but by rights I should have had the above difficulties with it too. The key thing being the reinstatement of unevenness having eliminated it. That said, the replies have given me a lot of food for thought and I will be practising this weekend.

 

[bugbear]

A trick to learn how to pressure the plane during a full length stroke is "tryingto dig a hole in the middle of the board". When you do full length strokes with a long plane, then digging that hole really isn't going to happen, but trying to do that helps you to put pressure on the front of the plane on the start and on the back of the plane at the end.

Yeah - shortest version is - "try to plane hollow; you can't but you'll end up planing flat"

Much easier to visualise and do than pushing on the knob at the start of the stroke, and changing to the handle at the end of the stroke, equal pressure in the middle of the stroke, although it's actually the same thing!

BugBear

 

[Derek Cohen (Perth Oz)]

I've noticed a phenomenon which crops up fairly often when planing a board. If there is e.g. a bit of a hump in the middle as you plane along, it is possible by concentrating on that bit to get rid of it and indeed reduce it to a very slight concavity. How can it be then that when you subsequently make full length passes the hump reappears? The same can happen where there's a bit of a drop off at one end....

There are two different issues here: the first is getting rid of the hump, and the second is creating it again.

All planes want to follow the surface unless one makes a deliberate effort to either plane into it or over it. Short planes are more susceptible to this than long planes - short planes follow the undulations of a board more closely.

In your example, you deliberately planed into the hump to remove it. Then you planed over it and created it again. That is down to technique. It is possible to use a short plane to plane flat - Paul Sellers bases all his projects on this. The key is even pressure across the plane - neither more pressure at the toe nor more pressure at the heel. To do this, push the plane from low down on the handle. Avoid pushing near the top - that will force the vector of effort towards the toe. Low down, the vector goes forward only = even pressure across the sole.

Regards from Perth

Derek

 

[D_W]

It's no wonder that many people give up on stuff like this!! We answer a question 8 times, and I am guilty of it, too, so I'm not pointing fingers.

 

[Derek Cohen (Perth Oz)]

Some answer it better, Dave!

Regards from Perth

Derek

 

[Andy Kev.]

It's no wonder that many people give up on stuff like this!! We answer a question 8 times, and I am guilty of it, too, so I'm not pointing fingers.

Not to worry. Every slightly different take has added value in its own way. A synthesis of them with the experience I already have should, I hope, set me on the right road.

 

[Trafalgar]

I've never quite solved this "problem" so I just make a few extra passes in the middle when wrapping up, test with straightedge looking for an ever so slight concavity from these last few passes. Occasionally a workpiece should be dead flat and not a touch concave. I just make fewer passes through the middle. A board with a slight and gradual concavity looks dead flat to the eye.

Simple enough for this Simpleton.

As long as you don't go beneath gauged thickness during the process then it doesn't matter all that much how you get there, unless you're fond of hair shirts and/or an uber-perfectionist. In that case, being a machinist could be the greater calling.

 

[matthewwh]

I think it's wonderful that we get so many different perspectives; possibly confusing for a beginner reading threads like this, but nonetheless it demonstrates that there are many techniques to achieve the same end.

In answer to Ttrees', I'm currently going through a 'hermit woodworking' phase, so I'm operating at the opposite end of the spectrum from you. Having just moved house all of my tools are packed away, so rather than unpacking them I have set about building a new bench with very simple tools, a wooden try plane, marking gauge, couple of saws, two chisels etc.

The temporary bench I'm working on is a rough sawn 3" slab of waney edged walnut, crudely balanced on a cupboard, with a pinch dog hammered into one end for a planing stop. It's fair to say that I wouldn't recommend a wobbly plank as a long term solution, and the thing that I'm building is a flat square stable bench, but nonetheless the components are still coming out square and true.