Subtleties of shaving deflection

[John Walkowiak]

Regarding having the cap iron slip when tightening. I use infill and wooden planes and that happens often on the thick irons/cap irons. On one Spiers plane some years ago I noticed a previous workman's attempt to solve this problem. He used a cold chisel and struck a cross hatch pattern into the back of the screw and along the slot in the iron. I have since done this to problematic irons. I use a 1/2" wide chisel, and center it on the slot at a 45 degree angle, striking about every 1/16". Just after doing this the surfaces will be very rough and that will make the cap iron move. Tighten and loosen the screw, working your way as far down the slot as you have gone to smooth out some of the roughness. It does improve or eliminate the slipping problem on these thick irons when placing the cap iron extremely close to the edge.

[Steve Voigt]

Yes, let's dive into the history of the double iron plane again.
The capiron was invented somewhere in the second half of the 18th century. That was long before the general decline of the planemaking trade. I have some early 19th century moulding planes from Higgs which are top quality, much better then any other wooden plane in my shop. So I kind of doubt the theory that the double iron was supposed to replace craftsmanship.

I certainly didn't mean to imply that the double iron was a replacement for craftsmanship, merely that it was no longer necessary to spend a lot of finicky effort on getting the mouth size just right.

By the way, it took me about half an hour this morning to verify that, just as you showed, the chipbreaker thing works with woodies. I'm making--what else-- a plane out of padauk, which is not as bad as your ribbon-striped jatoba, but still it would have given me fits in the past. I have a little 50* smoother I built this summer; the mouth is about .030", which is not huge but is too big to prevent tearout on its own. I honed a very narrow (about 1/64") bevel on the chipbreaker at around 45* just eyeballing. Set the chipbreaker really close; in fact I thought it was too close, but I tried it anyway. Absolutely zero tearout, cut beautifully. Man, was I pleased!

[Kees Heiden]

Nice isn't it

Learning to love my wooden planes wasn't always easy with all the usuall troubles, setting with a hammer, clogging, wobbling blades and ill fitting wedges, etc etc. But learning this little trick with the chipbreaker was one of the major steps in learning how to succesfully work with wooden planes.

And I think you are right about the mouth in wooden planes. That must have been a factor in the popularity of the double iron too.

[David Weaver]

Yes, let's dive into the history of the double iron plane again.
The capiron was invented somewhere in the second half of the 18th century. That was long before the general decline of the planemaking trade. I have some early 19th century moulding planes from Higgs which are top quality, much better then any other wooden plane in my shop. So I kind of doubt the theory that the double iron was supposed to replace craftsmanship.

I don't know how the british woodworkers worked before the double iron plane, but in Germany they used a very steep pitched plane for difficult woods, with a 65 degree bedding. Such high angles are not very healthy for the edge, they dull a lot quicker. With the double iron plane at 45 degrees you have a normal rate of wear again. I think that played in role too in the popularity of the double iron plane.

I'm not really sure I ever thought hard enough to try to figure out who was right in the whole discussion, but I argued with Todd Hughes a long while ago (like 6 years ago) when he said that the fact that people would pay extra for it was proof enough that it works. I'm pretty sure I was wrong in that argument!!

It definitely existed alongside good single iron planes. I have a JT Brown Jointer that is made somewhere between 1820 and 1840. It's bedded at 50 degrees and it is precisely made and I was lucky enough to find it on ebay listed as a "doorstop" and don't believe it was ever actually used, and if it was, it was very little because the iron is still in good fresh shape, including the bevel. I think someone slathered it either with tallow or oil and put it away.

But the truth about it is that a decent condition later-made more common and less precisely made double iron plane would match it in everything and exceed it in most things.

I believe it won out on its merits. Whether it drove planes to be cheaper and less accurately made, I don't know, but if it did, that's an even bigger endorsement of its usefulness.

I care most that it works, though. It has eliminated my spending on expensive planes, and it's also eliminated my use of my steel shop made infills I'm still going to make more infills, but they will be double iron and either common or norris type pitch. Even went so far as to find one of the old ulmia double iron rabbet planes.

[Steve Voigt]

I'm still going to make more infills, but they will be double iron and either common or norris type pitch.

I'm wondering if a double iron plane pitched at 50* might not be having your cake and eating it too. While the chipbreaker technique is a godsend on gnarly woods, I'd rather set the breaker a 1/16 from the edge (rendering it basically non-functional), if I can get away with it. And I can get away with it most of the time, on straight-grained pine, cherry, walnut, etc, even with a common-pitch plane. It's only when the wood gets nastier that I need to bring the breaker into play. Now, it seems to me that a 50* would increase the number of situations in which you don't need to set the chipbreaker close, yet it's there for you when the wood gets ugly.
What I don't know yet is whether the close-chipbreaker technique really does work as well at 50* as it does in common pitch. It worked great for me this morning, but that's hardly an exhaustive or conclusive test. Definitely going to do some more experimentation on this, though.

[Derek Cohen]

What I don't know yet is whether the close-chipbreaker technique really does work as well at 50* as it does in common pitch. It worked great for me this morning, but that's hardly an exhaustive or conclusive test. Definitely going to do some more experimentation on this, though.


Hi Steve

I posted some of the research I did in this area quite a while back. One of the areas was experimenting with a close set chip breaker on a 55 degree bed LN #3. I was able to demonstrate that the the two are additive: the performance ramps up a notch. The wood I was using was particularly interlocked and hard, only a little more difficult than the usual local fare, so the test conditions were realistic. A 55 degree smoother was not high enough for this wood, with 62 just doing it. When the chip breaker was tuned in the smoother, the result improved noticeably.

This should not come as a surprise. Both the close set chip breaker and the high angle plane are doing the save thing, that is, bending the shaving before it can create any damage. I have previously likened the close set chip breaker to adding cutting angle - perhaps we should now refer to the angle the the leading edge of the chip breaker as the "bending angle".

Regards from Perth

Derek

[Derek Cohen]

I posted this over at WoodCentral where Kees started the same thread.

In a nutshell, what we are achieving with the combination of a close set chip breaker and the angle at its leading edge is a bending of the chip close to the edge of the blade. This we all know.

We also know that there is a relationship between the distance to the blade edge and the angle at the edge of the chip breaker. Borrowing from aerodynamics, we can understand this relationship as follows ...

Think of a sports car being tested for "slipperiness" in a wind tunnel. First we have a vintage sports car ...





What we see here are sudden uplifts of airflow when hitting the vertical sections (such as the grill and the windscreen). One would expect that this extra drag would slow down the car. Where the airflow passes over the more horizontal sections of the body (such as the hood and the roof), there is little interruption, with greater speed and/or efficiency expected.


Here is a more modern sportscar with more advanced aerodynamics ...





Another way of looking at the way the chip breaker interacts with the shaving is as an air break or wing flap on an aeroplane ...





As the air hits the flap, it is slowed down. Similarly, as the shaving hits the leading edge of the chip breaker, it is slowed down and forced upward, and forces the blade down (equal and opposite reactions).

There are three corollaries that follow:

1. the closer the chip breaker is to the edge of the blade, the greater the down force at the blade edge, and the greater the effort to push the plane.

Greater down force should also lead to increased blade wear.

2. the higher the angle at the leading edge, the greater the "braking effect" ... aka greater "bending effect".

K &K recommended an 80 degree leading edge on a 40 degree bed as optimum. It follows that the leading edge for a 45 degree bed smoother would be 75 degrees, for a 50 degree bed smoother it would be 70 degrees, and for a 55 degree smoother it would be 65 degrees.

3. a lower angle at the leading edge will reduce the bending effect, and do so progressively the further from the edge it is placed. It will also reduce the effort to push the plane.

The aim of the chip breaker effect on a bevel down plane is identical to that of a bevel up plane with a high included angle: the creation of a sudden bending effect, which is also known as a Type III chip formation ...




It is the suddenness of the bend that reduces tear out. Tear out is created when wood fibres are allowed to bend slowly and progressively, breaking ahead of the blade's edge. This is also known as a Type I chip formation ...




While some woods tolerate the slow and progressive bend, namely those with evenly formed and upward running grain, those woods with uneven and erratic grain require a plane that bends the shaving in a sudden action.

Regards from Perth

Derek

[David Weaver]

We're getting a little too far into the details - details that are hypothetical and not based on practice, I think and it isn't nearly as important as what happens when you actually apply the method with a plane.

At the risk of sounding like Warren, the whole purpose of using the cap iron instead of high angle (and the reason that I do) is that the surface left by planes at 55 degrees plus leave something to be desired if the wood is not something very hard. If we're talking about hard maple, it hardly makes a diference. If we're talking about pine with knots in it, there is a very large difference, and if we're talking about cherry, there is a fairly substantial difference.

My standard bench planes will outdo my infill plane on everything I've planed so far by just a bit - it's very hard to induce tearout with either of them. But the infill is limited because the mouth is between 3 and 4 thousdanths. I'm pretty sure every single beginner would use the two and immediately declare the infill a much better plane. It's dead simple to use. But it has been on the shelf now for months and months, because I have been planing cherry (some not such great quality) exclusively and I need to final thickness something that comes off of the planer with a little bit of tearout. And on the face side, I've been jointing the face and only thickness planing the opposite side.

I would really not enjoy at all taking a 6 thousandth plus thick smoother shaving with a 55 degree plane, or a thicker shaving with a 55 degree jointer. I don't consider the bench plane any harder to use than the infill at this point, I can't remember the last time I had a "failed setup" with the bench planes, and the surface is just brighter. I have had a few inklings of selling every single plane I have except for stock vintage bench planes, and every single stone that I have that is synthetic. If I could snap my fingers and have cash in hand in exchange, I probably would have. That would leave me with one premium plane, I suppose, which is the LN jointer, and I could easily make an O1 iron for it out of bar stock.

At any rate, I think the secret is at the bench, and in this case, too much thinking consciously and not enough tactile experience is a detriment.

I have found one board in my shop that I cannot plane cleanly. I can't do it with any plane. It is a very dry piece of dead quartersawn cocobolo and no matter what you plane or scrape with it, the earlywood goes to dust and leaves an undesirable appearance - no matter what plane you use and no matter how sharp. It planes perfectly well along the edge, though. The good thing is, I won't ever build anything but planes out of cocobolo and the quartered side would be covered (by metal) or profile sanded if I did.

[Derek Cohen]

At the risk of sounding like Warren, the whole purpose of using the cap iron instead of high angle (and the reason that I do) is that the surface left by planes at 55 degrees plus leave something to be desired if the wood is not something very hard. If we're talking about hard maple, it hardly makes a diference. If we're talking about pine with knots in it, there is a very large difference, and if we're talking about cherry, there is a fairly substantial difference.

Hi David

I only work with hardwoods, and I see no disadvantage in a high angle plane in such circumstances. Indeed, I only see advantages (such as ease of set up). Soft woods? I would anticipate that a lower pitched plane would sever the wood more cleanly. A lower pitched plane is preferred there. Never doubted it, never said otherwise. I am not sure why you raise these points now???

My post above is about chip formation changes caused by the chip breaker, and not about the cutting angle of the blade.

Regards from Perth

Derek

[Chris Griggs]

To David's point (but not intended to contrast Dereks) more and more I'm seeing how many of the only moderately hard North American hardwoods do indeed look much better using a standard angle and a cap iron.

Once recent example that really jumped out at me occurred at the LN show I attended this past weekend. I was watching one of the demonstrators plane some QS Sycamore. Its an interesting wood in that it not all that hard (770 janka) but has interlocked grain. I love sycamore as its actually quite easy to plane , generally a pleasure to work with handtools with grain direction that is easy to read and pretty consistent. BUT if/when you do hit a reversal or misread the grain it will tearout fairly badly. Anyway, I was watching the demonstrator show off a 55 degree frog on this stuff as an example of how well the higher angle works to prevent tearout. Well the surface was indeed tearout free but it looked like it had been hit with a dull scraper...just very dull and fuzzy. No disrespect intended to the demonstrator who was very friendly and knowledgeable...but it just wasn't the ideal way attack that particular wood.

All that is to say that I'm finding increasing benefit to using a capiron in things like curly cherry, QS syscamore, or walnut that has a bit of figure, where a a high angle just isn't the ideal.

IF I was working mostly really hardwoods, I might be more inclined to use high angles. In something like hard figured maple, my LA Jack with 55 degree included angle does beautiful work, and the rock solid simplicity of the thick single iron does make it a pleasure to use. Its rare that actually use it that way, but when I do, I definitely understand the love people have for a high angle and a single iron.

Of course, if one is going to sand afterwards, than the dullness or sheen of the surface is a moot point. While I very often do follow planing with a bit of 220 and it is often moot to me, I'm just more comfortable with BD planes. And I love that fact that I can go from planing pine to curly maple using a standard angle and cap iron without compromise if an unsanded surface is desired.

[Matthew N. Masail]

Derek that was too cool. However the spot light of the info in your post was lost to that amazing VINTAGE sports car.... yeahhh man - that's an infill! the modern one must be made by LV ?

[David Weaver]

Hi David

I only work with hardwoods, and I see no disadvantage in a high angle plane in such circumstances. Indeed, I only see advantages (such as ease of set up). Soft woods? I would anticipate that a lower pitched plane would sever the wood more cleanly. A lower pitched plane is preferred there. Never doubted it, never said otherwise. I am not sure why you raise these points now???

My post above is about chip formation changes caused by the chip breaker, and not about the cutting angle of the blade.

Regards from Perth

Derek

I could be getting conversations mixed up, and my point of view (unless it's obscured sizing cocobolo blocks or something for planes) is usually tempered by the woods someone who works entirely by hand is likely to work here. But I bring it up because the implication above is that the chipbreaker and steep angle achieve exactly the same thing, but they do not. The high angle smashes the chip over and scrapes it off right at the point of attack, and the chipbreaker holds instead pushes the chip back down into the plane surface and cuts it with a lower angle.

All of the "Type" discussion that happens, and I don't know who popularized it, but the type discussion doesn't do a service to a beginner because it replaces a concept with a label. When I first started, there were several people telling me I wanted to get a "type __" chip, which didn't help me out because I didn't have a translator key to have any clue what they were talking about. I'd suspect none of those folks really had a clue what they were talking about, they were just repeating what they saw in videos. I have to imagine that substituting a label for something that is easy to discuss (mechanically) without the label is not helpful to beginners now, either.

Chris brings up a point that irks me. There is nothing about a 55 degree frog on an LN bench plane that is better than a common pitch plane with the cap iron set (at least in the united states, and that's my point, not Chris's). I don't instruct beginners, but I'm pretty sure I could teach people to set the cap iron properly in less time than it takes for them to learn to sharpen, but there are a bunch of iron planes running around with 55 degree frogs (because they are being marketed for lack of good advice or lack of patience on LN's point - wanting to have a good "wood show" tool), which in the long run is a pretty limited tool when the basic common pitch design that LN copied is capable of much more versatility. By wood show tool, I mean something that someone can walk up and take an "ooooh....ahhhh" thousandth inch shaving with a heavy plane and assume that what you see in 2 minutes of use at a wood show translates into better use indefinitely. There was a point in time where you got tools from LN, but they didn't give advice on their use, in general. I liked them better when that was the case. Now they push high angle frogs with all of their planes and put up videos telling folks not to use a grinder to maintain tools. It just reinforces that their focus is to sell tools to beginners, which irks me a little, but in terms of functionally collecting revenue, it's probably true that beginners are the market you have to sell to stay in business. But it irks me the most when a beginner asks me for advice and then says "Chris Schwarz says the cap iron just holds the iron, you don't know more than he does" or "deneb says that's too fiddly and you should use a high angle frog". Chris has changed his tune - fill that in with the name of anyone, Cosman has been cited to me, too- that's just an example of the kind of stuff I hear.

There may be woods in australia where you can create some problems with a cap iron on a common pitch plane, but not here, and it nearly makes advice suitable for 2200 hardness woods bad advice for north american woodworkers.

In my opinion, a common pitch plane with a cap iron is ideal for people working north american woods. Ideal as in a better option than anything else. It controls tearout, it gives you a better finish, it's available cheaply, and you can choose stock iron or get something hard. I don't think it's an accident that eons ago when people were planing wood for a living, that's the design that dominated. It's not quite a "wood show" tool, you have to learn just a little bit to work it as opposed to ("look how much easier it is to push two shavings out with this plane that's twice as heavy"). At one point, high angle was the way to go because "you need it to smooth figured woods". Well, that's not true, and then the other side of the discussion is if you don't need it to do smoothing work, maybe it's better for heavy work? That's definitely not the case, either.

Perhaps the depth of this discussion is also tempered by the fact that I never use a powered jointer and I rarely use a thickness planer unless I'm doing something dull (like making kitchen cabinets), and there is a big divide between that and running planer chatter off of already dimensioned boards (which is probably the fate of most planes sold these days, vintage or new).