Replacement plane iron, standard thickness

[Corneel]

A similar laminated iron as the one from Axminster can be bought straight from Japan, from "tools from japan". Look under Tsunesaboro planes (or however you write that). It is a lot cheaper and shipping isn't much for such a small item. It just takes longer.

 

[Cheshirechappie]

It may be worth a quick note to the effect that the stiffness of a plane iron, using classical beam theory, is proportional to the cube of the thickness. Thus, an iron 2.4mm thick is almost twice as stiff as a 2mm thick one. (A 3mm thick iron is more than three times stiffer than a 2mm one.)

It's true that the stiffness of the iron is bolstered by being firmly fixed to the cap-iron, but increasing the stiffness one element of an assembly can only help the overall stiffness.

A stiff plane iron is infinitely preferable to a weak and floppy one; too much flexibility means chatter will be much more likely.

It's interesting to note that the older Record irons were a bit thicker than more modern ones. Speculating a bit here, but could it be that iron thickness was reduced as much as they thought they could get away with to save a bit manufacturing cost? I have a feeling that 1.8 to 2mm is about as thin as a Bailey-type iron can go and still give fair performance most of the time. (From personal experience of a replacement Cliffie iron in a Record 07, the extra thickness definitely improves performance on tougher duties.)

Has anybody ever tried irons thinner than 1.8mm in a Bailey-type plane?

 

[Vann]

A similar laminated iron as the one from Axminster can be bought straight from Japan, from "tools from japan". Look under Tsunesaboro planes...

I see they're 2.2mm thick, which has got to be better than the 2.0mm thick Axi irons.

Cheers, Vann.

 

[bugbear]

A similar laminated iron as the one from Axminster can be bought straight from Japan, from "tools from japan". Look under Tsunesaboro planes (or however you write that). It is a lot cheaper and shipping isn't much for such a small item. It just takes longer.

here's a direct link

BugBear (who had to google it)

 

[Jacob]

Hello,

I try to advance from fictive online woodworking to real woodworking at home work. ...

Getting bothered about replacement plane irons and all that jazz is one of the defining features of fictive woodworking.
If you want to do real woodworking you use the blades you have and spend the money on wood instead.

 

[Jacob]

...
It's interesting to note that the older Record irons were a bit thicker than more modern ones. Speculating a bit here, but could it be that iron thickness was reduced as much as they thought they could get away with to save a bit manufacturing cost? .....

No of course not.
Reducing costs by skimping the most important element of the tool would be insane, not least because the amount of material and money saved would be tiny.
The reason for thin blades is that they are easier to sharpen. They save a lot of time. That's the whole point of the Bailey design in nutshell.
There would be some variation as makers tried different set-ups e.g. many Stanley and Record blades were laminated, which I guess might make them thicker.

 

[Cheshirechappie]

The reason for thin blades is that they are easier to sharpen. They save a lot of time. That's the whole point of the Bailey design in nutshell.
There would be some variation as makers tried different set-ups e.g. many Stanley and Record blades were laminated, which I guess might make them thicker.

Why not even thinner, then? How about 1mm, or even thinner? Razor blades?

Is that why chisel makers made thin chisels, so that they were easier to sharpen? Makes you wonder why they bothered making registered firmers, or mortice chisels. And as for the wooden planemakers - well, they spent about three centuries getting it completely wrong, didn't they? Not to mention the infill planemakers. And yet craftsmen still bought their products, right up to WW2 and beyond - Marples didn't cease wooden plane-making until the 1960s.

No, Jacob - if ease of sharpening is a feature of thin plane irons, it's an incidental benefit. It's not the main reason.

 

[Paul Chapman]

Reducing costs by skimping the most important element of the tool would be insane

From the 1970s onwards, Stanley and Record skimped on every element of their tools........

Cheers :wink:

Paul

 

[Jacob]

....

No, Jacob - if ease of sharpening is a feature of thin plane irons, it's an incidental benefit. It's not the main reason.

It is actually.
Plus ease of adjustment, speed of blade removal/replacement; all add up to ease of sharpening.

And as for the wooden planemakers - well, they spent about three centuries getting it completely wrong, didn't they?

They did the best they could with the technology they had, but then were superseded by the improved steel plane. It's a very simple story.

 

[Cheshirechappie]

Why not even thinner irons. then? They'd be even easier to sharpen.

 

[Paul Chapman]

....

No, Jacob - if ease of sharpening is a feature of thin plane irons, it's an incidental benefit. It's not the main reason.

It is actually.

You've been pedalling this myth for years, Jacob. The way most of us hone blades (just the end bit that does the cutting), honing a thick blade takes no longer than honing a thin one. But the way you hone (your dubious rounded under method) involves honing the whole of the bevel, so a thick blade will take longer.

Cheers :wink:

Paul

 

[Corneel]

Some background information about these Japanes irons. It is not like a blacksmith makes each of these individually from a a lump of wrought iron and a bit of steel. In Japan you can get large sheets with a laminated steel edge. These are made in the steel factory and are used mostly for kitchen knifes. The blacksmith buys these and cuts the blade from the sheet. Then he hardens the edge. The base material is normal carbon steel, not expensive and rare wrought iron.

In a Stanley plane, a 2.2 mm iron is plenty thick enough for most work when you make sure that the frog is pulled back so the blade is fully supported on the sole of the plane too, and with the capiron relatively close to the edge. When tearout is a problem this can be controlled with the capiron too, placed very cclose to the edge.

 

[Jacob]

Why not even thinner irons. then? They'd be even easier to sharpen.

Compromise. No doubt experiments were made.
A similar design is the Gillette safety razor where the blade is very thin, but disposable rather then resharpenable.
The similarity is that they both have a thin blade clamped in a blade holding/clamping system, which emulates a thicker blade. They tried thicker blades too in early safety razors, and thinner disposable blades in planes.

 

[Cheshirechappie]

Why not even thinner irons. then? They'd be even easier to sharpen.

Compromise. No doubt experiments were made.
A similar design is the Gillette safety razor where the blade is very thin, but disposable rather then resharpenable.
The similarity is that they both have a thin blade clamped in a blade holding/clamping system, which emulates a thicker blade. They tried thicker blades too in early safety razors, and thinner disposable blades in planes.

Compromise between what factors?

If razor blades work so well in razors, why don't they use them in planes?

 

[sdjp]

It may be worth a quick note to the effect that the stiffness of a plane iron, using classical beam theory, is proportional to the cube of the thickness. Thus, an iron 2.4mm thick is almost twice as stiff as a 2mm thick one. (A 3mm thick iron is more than three times stiffer than a 2mm one.)

Whilst true in principle, when you get a plane iron in actual use, it's a bit more complicated than that approximation. In a Baily style plane, the cap iron is normally clamped to the plane iron with uneven pressure distribution (i.e. the line just behind the edge is the bit you want to clamp hard). Whilst I baulk at trying to calculate the second moment of area of such a system, provided that the cap iron doesn't move in use, then even without factoring a preload force, surely it's the cap iron + iron system that should be considered, not the iron on it's own?

The primary effect of the preload would be to increase the net force before the tip of the iron separates from the cap iron - so provided that there's not a gap in use (i.e. no shavings manage to worm their way under the cap), then surely it's reasonable to consider the thickness to be cap iron + iron; as a closer approximation?

The net consequence of that suggests that the effects given above, as relative measures, will overstate the effect of considering a thicker iron. in isolation. Thicker is, of course, stiffer; but if we're taking even a 1.2mm cap iron into account, then to end up twice as stiff, you have to go from a 2mm iron to a 2.8 mm iron. (Obvious problem here is if the two materials are significantly different materials … that's going to complicate any analysis).

I'm sure that this model disagrees with reality in a number of aspects, of course - but I _do_ think that it gets closer than considering the plane iron in isolation (as that's not how they are actually deployed, in use).

 

[Jacob]

Why not even thinner irons. then? They'd be even easier to sharpen.

Compromise. No doubt experiments were made.
A similar design is the Gillette safety razor where the blade is very thin, but disposable rather then resharpenable.
The similarity is that they both have a thin blade clamped in a blade holding/clamping system, which emulates a thicker blade. They tried thicker blades too in early safety razors, and thinner disposable blades in planes.

Compromise between what factors?

If razor blades work so well in razors, why don't they use them in planes?

I guess it's because a thin razor blade iron would not be stiff enough for woodwork, but OK for most beards.
Then again - the larger a disposable blade the more it costs so the more cost effective it becomes to sharpen them. And so on.

 

[Jacob]

.......surely it's the cap iron + iron system that should be considered, not the iron on it's own?......considering the plane iron in isolation (as that's not how they are actually deployed, in use).

Exactly. The Bailey plane has a composite blade "unit" consisting of frog, blade, cap iron, lever cap; which together emulate (and out perform) a thicker blade.

The "composite" tool is not exactly a new idea: a stick or a stone may each be a tool - put them together and you have an axe or club, with some parts disposable, some sharpenable etc. etc.
A tiny flint arrowhead on it's own would be ineffective. Formed into an arrow and shot from a bow it would be more effective than even a very large stone on its own.
Come to think - there's something very stone-agey about the obsession with thick blades!

 

[Cheshirechappie]

It may be worth a quick note to the effect that the stiffness of a plane iron, using classical beam theory, is proportional to the cube of the thickness. Thus, an iron 2.4mm thick is almost twice as stiff as a 2mm thick one. (A 3mm thick iron is more than three times stiffer than a 2mm one.)

Whilst true in principle, when you get a plane iron in actual use, it's a bit more complicated than that approximation. In a Baily style plane, the cap iron is normally clamped to the plane iron with uneven pressure distribution (i.e. the line just behind the edge is the bit you want to clamp hard). Whilst I baulk at trying to calculate the second moment of area of such a system, provided that the cap iron doesn't move in use, then even without factoring a preload force, surely it's the cap iron + iron system that should be considered, not the iron on it's own?

The primary effect of the preload would be to increase the net force before the tip of the iron separates from the cap iron - so provided that there's not a gap in use (i.e. no shavings manage to worm their way under the cap), then surely it's reasonable to consider the thickness to be cap iron + iron; as a closer approximation?

The net consequence of that suggests that the effects given above, as relative measures, will overstate the effect of considering a thicker iron. in isolation. Thicker is, of course, stiffer; but if we're taking even a 1.2mm cap iron into account, then to end up twice as stiff, you have to go from a 2mm iron to a 2.8 mm iron. (Obvious problem here is if the two materials are significantly different materials … that's going to complicate any analysis).

I'm sure that this model disagrees with reality in a number of aspects, of course - but I _do_ think that it gets closer than considering the plane iron in isolation (as that's not how they are actually deployed, in use).

I agree entirely, and that's why I did say that the iron's stiffness is bolstered by being firmly fixed to the cap-iron. However, increasing the stiffness of one element of an assembly must increase the overall stiffness of the whole assembly, as also stated.

There must be some point at which reducing the stiffness of the assembly (by reducing the stiffness of one or more elements of that assembly) begins to produce a performance that is less than acceptable under most circumstances. I'm not sure that I've ever seen any tests that might show where that limit is concerning the thickness of plane blades, but as nobody has reported finding blades thinner tha 1.8mm, I suspect that's somewhere close to it. Unless anybody can demonstrate otherwise?

Edit to add - There is also the subjective point of what is regarded as acceptable performance. Anecdotal eveidence would suggest that some poeple are happy with blades of 1.8 to 2mm in their planes, whilst others feel that their plane's performance is not quite as good as it could be with such an iron, being prone to chatter when faced with harder timbers, knots or endgrain; but that performance is enhanced (problems reduced)with a slightly thicker iron.

 

[Cheshirechappie]

"I guess it's because a thin razor blade iron would not be stiff enough for woodwork, but OK for most beards."

Indeed. But what thickness of iron IS stiff enough for woodwork, and how do you determine what's acceptable performance?

 

[Paul Chapman]

But what thickness of iron IS stiff enough for woodwork?

It all depends of how demanding the wood is; how demanding your standards are; and the sort of work you are doing.

Just get a plane with a Bedrock frog, a thick iron and a Stay-Set cap iron and you don't have to worry about all this stuff any more

Cheers :wink:

Paul