New data. High angle versus chipbreakers.

[Kees Heiden]

In answer to my article about the forces measured in high angle planes and double iron planes (http://planetuning.infillplane.com/h...pbreakers.html), Don McConnell posted this objection:

There are a handful of difficulties/issues which are inherent in this kind of research, and I'm not completely sanguine that those have been successfully addressed in this research. And I'm not entirely sure how I would address them. But I'll forego that discussion in order to get to the basic flaw I see in the design of this research. As I read the article, Kees, your basic preparation of the iron was to grind at 25º and hone at 30º, resulting in an included angle of 30º for the iron when used at common pitch and with a cap iron. It then seems that you simulated the higher angles of attack by adding a back bevel of 5º, 10º and 15º, which would leave included angles of 35º, 40º and 45º. If this is the case, it is not analogous to an iron prepared with a 30º included angle and bedded at 50º, 55º and 60º, respectively, as would have been done with the 18th century single iron planes with higher bed angles. In other words, you've introduced a variable (actually two, with the subsequent difference in relief, or clearance, angles), which you have not controlled for at all. I believe this brings into question all of the comparative data you've generated, at least as it relates to your primary thesis.

I could answer that his objection was only valid for the second part of my research. The first part where forces are measured with a sharp blade, have all been done with high bedding angles, thus also with clearance angles normally found in 18th century high angle single iron planes. But the second part of the article adresses the wear around the edge and its result on the forces measured. Here I indeed choose to use backbevels. So this is a valid objection, especially because the wear of the blade creates a convex wearbevel on the clearance side which could very well be influenced by the clearance angle.

In fact I had done measurements with a plane with a 60 degree bedding, but they weren't a succes. The plane was too small and didn't register very well on the fence of my planing beam. So I had to make a new one.

foto (4).jpg

Then I had to find some time to do measurements with this new plane and process the results.

This I will call diagram 1. It shows how the forces develop over 100 meter planing distance.



This is diagram 2. It shows how much the forces CHANGE over 100 meter planing distance.



The cutting force Fc is the one which is horizontal in a bench plane and which you can feel when pushing the plane. The other force is the normal force Fn, which is perpendicular to the wood surface. When the blade is sharp this is the force of the shaving pressing down on the edge and when the edge dulls this force changes because the convex wearbevel tries to push the edge out of the wood.

When looking at diagram 2 first, it is quite obvious that the extra clearance angle helps to avoid the rapid increase of Fn in the 60 degree plane with only 15 degree clearance. The other values in this diagram seem to suggest that the wear rate of any high angle plane is higher then the double iron plane. But the measured differences are very small, and start to come into the area of the accuracy of the measuring machine. So, based on these results I cannot conclude that a high angle plane wears faster then a double iron plane. I would need much more test runs. The only valid conclusion I can make is that a high angle plane certainly doesn't wear less then a double iron plane.

That brings us back to diagram 1 and to the 18th century woodworker who was testdriving one of these new double iron planes. And this diagram sais it all. A proparly adjusted double iron handplane is easier to push, has a stronger negative normal force which pulls the blade into the wood and this advantage doesn't change when the edge wears.

We can add another conclusion. A high cutting angle with only 15 degree clearance is not an ideal combination when you want to maximise the life of your edge.

I hope this answers your concerns Don.

[David Weaver]

Somewhat predictable. I'm not surprised that the fn is a little better with more clearance, but somewhat surprised that it appears to have made almost no difference in pushing force required. I guess that shouldn't be too surprising, the lack of clearance that's troublesome is probably occurring very close to the edge itself.

In terms of the iron wear, when the kawai papers first came out, they showed additional wear on the back of the iron. This surprised me because I was planing longer with the cap iron than without, probably because the results don't get diminished in terms of avoiding tearout with a thicker shaving. The additional wear is unsightly on a picture, but the clearance is where the wear counts, and though the back of the iron wear looks more significant with a cap iron, it doesn't seem to make any difference in practical use.

[Kees Heiden]

When an edge gets dull, several things happen. The very tip becomes round, a convex wearbevel is formed on the bottom side and a concave wear bevel is formed on the upper side. This is all explained on Steve Elliott's website: http://bladetest.infillplane.com/htm..._profiles.html

The frontal profile, especially the radius of the edge, is what makes the blade dull and this you can feel when you are pushing the plane. The upper and lower wear bevel make the profile more streamlined and reduce the radius of the worn edge. All these combined make or break the planing characteristics. So, drawing conclusions from the shape of the edge is harder then just measuring the effects, the forces as measured in my setup.

Kato published force diagrams too. The double iron plane behaves not too different from a normal 45 degree plane, until you set the capiron too close. You can feel that very well, because the pushing force increases quite a bit and you have to push down harder on the plane to keep it in the cut. But even then the wear characteristics don't seem to change too much in a negative way.

[David Weaver]

Right, I have seen pictures, I think (and maybe steve does) showing the edges themselves in SEM so you can get a better idea for the shape of the edge than a 2d line drawing shows.

I didn't describe what I meant by the above, which was mostly that you can look at the pictures and draw conclusions, but better conclusions are drawn at the bench. A difference that makes no perceived difference at the bench (especially in the context of time, effort expended and results) is not material.

This study shouldn't really be necessary, because anyone with access to both types of planes will find that the true differences that have been shown in the study are easily perceivable by hand. But there are a lot of people who don't trust their eyes and hands, so you could've literally made up study material, showed all of the irons to be the same in every way, and I could feel something entirely different in the shop. I would get shouted out of the forum for suggesting what is obvious at the bench.

Just as my assertion has been all along that an experienced user can get more work done faster, with less effort with a double iron plane without compromising results (and in many cases getting superior results). I don't mean by that such a thing as nobody should work any other way, that's their decision. But as an original defender of the single iron planes, it's become clear to me that I am doing more work faster than I have done with single iron planes, and when I get back to single iron planes (I still do have some), it's immediately clear to me that the conclusion hasn't changed just because I've gained experience on double iron planes.

To top it off, I remove more CCs of wood, no matter how you count them on a like basis (smoothing, jointing, etc) with a double iron plane with an old iron than I did with a single iron plane with a new iron.

An individual using a 60 degree iron plane will find that for practical purposes, it is dull a lot faster than a 45 degree plane, not necessarily because the relative difference with the 60 degree plane has changed so much faster, but that the basic design of the plane is already working against you compared to a double iron common pitch plane, and then as you continue to work it only gets worse until it is completely undesirable and you go to resharpen. The geometry of the edge has been described to prove that in past discussions, and the same occurs for 55 vs. 45, but not as much. I haven't measured the geometry, just the sensation in practical use of a plane bedded at 62 degrees. It was a wrist and elbow punisher, and just a little dullness sent the user leaning over onto it to keep it cutting. It is a plane now that I have no idea what I'd use it for.

[ian maybury]

The question of what effect the included angle has (not sure how its defined above - but i mean the angle between the surfaces comprising the cutting edge) on cutting performance seems to have been lurking around for a while. (common sense says that narrower angles cut more easily - but the reason for that probably opens up another multivariate can of worms too. (see below) Back clearance angle is another variable - but not an independent one because the two are geometrically related.

I'm actually quite sceptical of taking 'scientific method' beyond a certain point in this sort of situation. The basic principle in 'scientific' investigation is that one variable is changed at a time, and the effect noted by a dispassionate and neutral observer. The problem of course is that (a) its typically not remotely possible to control all variables but one, with the result that traditional research methodology gets into all sorts of theoretical back flips by way of statistical methods in an attempt to isolate the effect that's of interest - and (b) that there's not been an uninvolved observer yet. All of which has the consequence of opening an enormous can of worms by allowing the building of all sorts of intellectual castles in the air - and brings into play all the stuff that entails by way of preconceptions etc influencing outcomes. I spent some time around academia, and saw reality ignored many times in an effort to reduce the problem to a manageable form. Usually without the researcher even being aware that they were making choices that potentially determined outcomes.

There's no easy answer to the problem. Reality is a holistic network of many many more and/or less interconnected variables that change all the time. Even the measured Fc and Fn here are the result of a preconception - of somebody somewhere along the line (rationally enough) deciding that these are the components of force that matter. The likelihood though is that they are components of forces rather than stand alone forces of themselves. More to the point there's likely lots of other unmeasured stuff going on that if it was measured and/or down that would tell a lot. Not to mention all sorts of dynamic and transient effects.

My instinct in these situations is to do the best job possible in setting up an experiment, but that after that it's more important to find ways to realistically use the results while keeping the limitations of method in mind. As in well done for your work to date. Pressing for some academically accepted absolute (that usually isn't - they usually just happen to fit the concensus determined by whatever hierarchy calls the shots in the field) just creates the misleading impression that experimental results are more than the spot/sample readings that they tend to be - and opens the way to the creation of all sorts of dogma. Not to mention opens the way the more 'eminent' to take out the opposition by crying foul.

If we're truly in the business of elarning it's not to my mind a matter of invalidating/dumping the results to date, more a matter of using what was learned to evolve an improved or next experiment or as the basis for some practical trials...

[Kees Heiden]

Yes, I didn't invent something new here, just put some numbers to a feeling that must have been very obvious for the professionals who used these planes 100 to 250 years ago. It is always difficult to prove a point when you are only relying on feeling, even if it is more valid to you personally.

And apart from that it is just fun from to delve into a subject like this (occasionally). I think I am now ready again to make some stuff.

[Kees Heiden]

BTW, these things are not generally known today.

For example, a high cutting angle with a low clearance angle creates twice the wear on the clearance side of the blade. People pay extra for special tool steel advertised to be twice as durable but also harder to sharpen, and then put it into a bevel up plane. That's just not logical.

[David Weaver]

Yes, I didn't invent something new here,

Oh, but I think it's necessary if a conclusion is going to be drawn. Not necessary for me, or maybe even not for you, but if it is done as you're doing answering each item point by point, and without contradiction on a similar basis elsewhere (as in tested and data based), then it becomes definitive.

Warren has been giving us definitive statements for a long time, and think how long it took us to follow them, because people won't trust someone, they trust charts and studies.

So, it is necessary to some extent, anyway.

[ian maybury]

I guess David it was the unthinking acceptance of 'stuff' put in a particular socially/hierarchically evolved format (togther with a consistent desire for easy one size fits all answers) that left me very wary of academia. Which in turn is a reflection of the nature of the common mind.

We mostly tend to unthinkingly reject (what we are averse to) or to unthinkingly accept stuff we think we like. (or have been convinced we would like by others that by leveraging our other often societally imprinted beliefs have convinced us to suspend our disbelief/avoid taking responsibility for ourselves) We then proceed to invest in, get attached to and then defend whatever we tied our horse to. (when we treat knowledge in this way it tends to turn around and bite us up the ass) Which all inevitably leads to our becoming so stuck in the resulting synthetic/imaginary reality that we will often defend to the death and even literally die rather than let it go.

I guess the genuinely open person hears all, sees all but swallows nothing prematurely. It's not mistake proof, but it is the strength of the beginners' mind mentioned before...

[Steve Voigt]

The interesting issue that Don's comment, and Kees' additional research, brings up is the difference between a high angle BD and a BU. The rig used in the original test (with the back bevels) may nominally be BD, but when the back bevel gets steep, it may function more like a BU, because the included angle is steeper. If the forces could accurately be measured for the 3 types of planes, I suspect (based on the graphs in this thread) that a high angle BD (what Don and Larry build) would be the via media between the double iron common pitch on the one hand, and the BU with high angle on the other.
It's interesting because Larry (Don's business partner) has often been the guy arguing against double irons, but I distinctly remember him saying that he'd rather see people using old Stanleys than using BU planes. The new graphs would seem to offer some tentative support for that, and also suggest that the difference between a common pitch double iron and a high angle BD single iron might not be as great as some people think (in terms of force and wear).

[Jim Matthews]

This is an epic, in the making.

Very cool, and the "crinkled" graph is telling.

I have to wonder how many passes I make
on typical materials to get to the inflection point
at 50m. It's intriguing, in any case.

[Derek Cohen]

BTW, these things are not generally known today.

For example, a high cutting angle with a low clearance angle creates twice the wear on the clearance side of the blade. People pay extra for special tool steel advertised to be twice as durable but also harder to sharpen, and then put it into a bevel up plane. That's just not logical.

Kees, what would your data say about a BU orientation with a low cutting angle (37 degrees) and 12 degrees of clearance, against a BD orientation (single iron) at a common angle (45 degrees) and between 15 - 20 degrees of clearance?

Regards from Perth

Derek

[Winton Applegate]

effect noted by a dispassionate and neutral observer . . .
(b) that there's not been an uninvolved observer yet.

So what you are saying is the experiments need to be carried out by our wives / significantly uninterested other.

I can’t wait to tell Queenmasteroftheuniverseandbabybunnytrainer that her complete and utter lack of interest in tools in general and hand planes in particular is going to lend an invaluable and irreplaceable je ne se qua to my woodworking. One would be hard pressed to find a person MORE dispassionate toward tools than her.

Well at least the vast majority of the planes I own are bevel down with a chip breaker and 45° pitch, I kept them around because in a high wind they kept the shop from blowing away. Now you demonstrate that they may be sent in late in the game to decidedly tip the scales for a win.

Who'da thought the gangly, uncoordinated, benchwarmer had it in 'im. Sounds like a Disney movie.

I say hurrah ! Well not hurrah exactly (I still enjoy the simplicity, precision and lack of fuss of the unmentionable BU) but at least all that money I spent on BD early on wasn’t a waste as I had first concluded.

(mutter, mutter . . . chip breakers . . . nasty finicky things . . . sheet metal . . . short little fumble screws . . .
sigh . . .
ohhhhhhhhhkahyyyyy)

[Kees Heiden]

Interesting that dip at 75 meter isn't it? I think it is a sign that the curve isn't straight. It is rising quickly at first, then stabilising with a lower rate of decline. That dip might just be a quirk from my machine but it is evident in three plane setups.

The typical shape of the wear curve is well known in literature. First rapid initial wear. Then a long stable period until you get to the point of failure of the edge. As handtool users we never get to that point of failure, we poop out long before. In Kato's study you can also see how the curves flatten out after 75 to 100 meters. He doesn't have ghat typical dip at 75 m though.

[Jim Matthews]

I wonder if there's a concurrent decrease in the shaving depth at that point?

The force drops, and conservation of momentum should imply that a
similar force has decreased in the system.

Kudos