Cap iron setback and shaving thickness

Re: Cap iron setback and shaving thickness

David Weaver

These are shaving thicknesses, right?

They will correspond to less than the thickness in actual cut depth if you measure the board itself. I just don't know a reasonable factor, because I've never taken a dataset from various boards, but it wouldn't take long. I'd guess 4/5 or 3/4 as a starting point.

Some measured this, but I can't remember who.

Brian clips corners on a Japanese plane because the abutments go all the way to the mouth and the cap iron is only as wide as the abutments, they are a different case.

Hanks for taking this and running with it. I still think when the dust settles, we'll find no cut without evidence of smashing when the cap is below the sole or even just even with it.

Re: Cap iron setback and shaving thickness

Warren in Lancaster, PA

You want a nice even radius on the iron, in proportion to the usual depth of cut. Not just rounded corners. And you want this nice even curvature on the cap iron also.

Over the last dozen years a lot of guys on this forum have thought that their little experiments in their basements must certainly make them more knowledgeable than Peter Nicholson. But Nicholson worked in London at a time when figured exotic woods were the rage and carving and moulding were not. He was a brilliant man and he worked in a community where everyone was using these double iron planes. His 1812 book was written for amateurs, so it is somewhat "dumbed down" for their benefit, but guys have made fools of themselves suggesting he did not know what he was talking about.

Re: Cap iron setback and shaving thickness

david weaver

I'd be curious to find out why he thought the radius was an advantage.

If Patrick confirms that he was measuring shaving thickness and not the reduction in board thickness, he's still going to come to the conclusion that he's not using the cap below the sole, and even at the sole is a recipe for fuzzy wood.

re: nicholson, there's no guarantee that every single thing in his book is optimal. Certainly on the whole, it's far above where I'll ever be, and perhaps I know one person who I'd rate at his level (George) as a craftsman.

I'd be willing to defer on the radius in a non-flat sole or as a matter of solving feeding problems in less than perfect planes, but as a matter of tearout reduction, it's functionless, and potentially backwards. But maybe not materially enough so that anyone would notice the difference (as in, the shaving thickness at the corners is thinner, and that can cause feed problems if a plane isn't properly set).

That said, if you can't tell me why it's better (to radius the cap), i'm inclined to believe I'm right in this case, or at the very least, not materially wrong. A vague explanation or reliance on craftsman's subtlety isn't going to suffice. Proving why the cap iron is such an advantage (especially if we go beyond just smoothing) has not been very difficult to explain or prove.

Perhaps you can elaborate to me why a thinner shaving spanning the same distance to the cap iron is better than a distance that varies based on shaving thickness.

(we don't see this radius on any japanese planes, either - but they wouldn't have the corner feed problem, because the cap iron is between the abutments and not under it - and to be honest, I haven't seen a lot of old japanese planes with much radius, but the ones I have gotten have been in such disrepair that maybe they were last used in rough construction).

Re: Cap iron setback and shaving thickness

John Aniano in Central NJ

David,

I'm sure I'm preaching to the choir, and by no means disrespect - maybe I'm not understanding your question, i.e. radius of the blade or radius of the cap iron, but...

I always assumed that the "nice radius" of a smooth plane was so that the finished planed surface would have a smooth-to-the-touch feel. With a blade with clipped corners, there is the distinct possibility that the finished planed surface would have faint furrows caused by those corners. As a bow maker, I often run my fingers along a curved edge to sense if there is a discontinuity - you often can't see it, but you can feel it. A faintly fully radiused edge would be less prone to furrows, leaving a smoother finish. After all, except for the shaving measuring "Kez" folks and tool researchers, the reason we use a hand plane is to dimension and flatten wood to a smooth finish, right?

John

Re: Cap iron setback and shaving thickness

david weaver

Hi John - that's exactly right. The iron has the curvature you're talking about, but there's no real functional reason for the cap iron to also have it unless the sole profile is the same radius as the iron.

I'm making the case here that we don't plane with the cap iron projecting through the sole of the plane (doing so results in enormous pressure required to move a plane, and a substandard "furry" surface as Patrick found out).

If the cap iron is not below the surface of the plane, then there is no functional reason to radius the cap itself unless there is an off chance that someone really had a desire to adjust the blade laterally and cut with only one side of the plane. I really don't see a reason for something like that and have never done it.

In short, the projection of the blade past the cap iron is dependent on shaving thickness. As the projection is around 1 or so, we find exponentially increasing pressure required and a surface that show defect from the shaving being smashed ahead of the iron because it can't travel over the surface of the cap iron smoothly without being crushed into the wood. As the projection gets close to 2x the shaving thickness, the cap iron begins to lose its effectiveness.

So, if we radius a cap iron to match the iron itself (in my opinion, we always want the radius on the iron, as you describe), the center of the iron is going to be in the 1-2x range in terms of distance from the cap iron (I have never measured these, so I can't say for sure what the exact numbers are). As we travel to the edge of the iron, the shavings will thin and they will become too far away from the cap iron for the cap itself to be effective in reducing tearout. They may be so thin that it doesn't matter, because they don't have the strength to lift (which is why I said that the difference may be immaterial, and in that case, it's no more harmful than just being a waste of time _unless_ the extra room at the corners allows a plane with a defect to continue feeding rather than addressing the defect).

There is detail not provided by Nicholson, but in that detail is the reason that he's radiusing the iron. If it has anything to do with reducing tearout, it doesn't have merit. If it has to do with ease of feeding, maybe it does. When I make wooden planes, the last troubles are usually at the edges (and I leave my irons square for that part, because it makes the most trouble there), and I have to do some wear adjustment or cap iron adjustment (thinning the bend slightly right behind the point of contact) to eliminate those edge problems. Relieving the cap iron at those corners may also do that, but I'd rather adjust the plane. If I have a feed problem again over time (which hasn't occurred with any of the planes I've made), then I can go back and adjust the plane based on the fact that I've had to learn with varying cap iron geometries.

That learning about the wear vs. the front bit of the cap iron is why I made the comment that i probably know more about this specific aspect than Nicholson did, unless somewhere in the text is a discussion of him making a bunch of planes and experimenting with different things.

The conclusion of all of that as far as I've come up with is that the best design for the cap iron is to match it to the sole of a plane. I can come up with all kinds of little straw scenarios that can poke holes in it, but each is suboptimal in the grand scheme of using planes (for example, laterally adjusting an iron a significant amount - i'd rather keep the iron cutting in the middle of a plane and noticed that the better older planes really didn't have much initial lateral adjustment, so that is out).

Re: The other issue...

david weaver

...with this is that it's often a beginner who comes along and asks if they should start hacking the sides off of a cap iron edge, and from time to time, someone answers "yes", and the follow-up work involves all kinds of things that could ruin a cap iron in the hands of a beginner.

There is a conceptual issue that causes a beginner to think that the projection should be the same along the entire radius of the iron, and that is that said beginner isn't accounting for the varying shaving thickness that keeps the shaving at the edges from causing a jam at the shortened projection of the iron at those same edges.

The same person is probably also not aware that the cap iron is probably ineffective in any critical case when the shaving thickness deviates too much from 1/2 of the iron projection. And, they believe that the part of the iron that is either behind the cap or even with it is somehow going to end up below the sole of a plane and be in the cut - and that's not the case.

Conclusion - if there isn't an explainable difference, a material one, too, then there's no reason to radius the cap iron laterally, but there is potential trouble in doing it.

Re: Cap iron setback and shaving thickness

Patrick Chase

Yes, shaving thickness.

I measured board thickness before/after a selection of cuts to check for what you outline. The difference was about 15%, i.e. actual board thickness loss 85% of shaving thickness. I should have adjusted my results based on that, but forgot to when I wrote up. Interestingly it doesn't change the conclusion much - 4 mils is right on the edge either way.

I also successfully pulled a cleran 5 mil shaving after I did the writeup. Pretty impractical IMO due to the forces involved, but it's nice to see that I can in fact more or less recreate the Kato/Kawai geometry.

Re: Cap iron setback and shaving thickness

david weaver

Impractical is the important thing. As the cap iron protrudes below the sole a thousandth or more, you should start to be able to see it.

You may wonder why I'm so sure about all of this. The reason is pretty simple. In five years (five and half?), I've never encountered a situation where it's beneficial to have the cap iron below the level of the mouth, and though on my jack plane, the cap iron will easily overlap some of the iron if it has to be set close, I've again, never been able to set the iron at the mouth or below and found it to be productive.

I think it's only been twice that I actually had to set the jack's cap close when thicknessing something, and it makes you appreciate the wood where you don't have to set it close a whole lot more. Perhaps doubled the time over a straight grained stick (and doubled the effort, for certain). We'd normally just change direction of work, but curly cherry that's quartered sometimes won't thickness easily in any direction, and if the board is not wide, there's no real choice other than to address the tearout.

Re: Cap iron setback and shaving thickness

Warren in Lancaster, PA

It has been over forty years since I used a cap iron that did not follow the curve of the iron and I long ago forgot what I was thinking at the time. Here is what I would say today:

(1) It is a lot easier to judge distance if there is a uniform strip between the iron and cap iron. (2) There is less danger of sliding the cap iron over the edge. (3) If the iron is slightly crooked there is still the same presentation of iron and cap iron. Altogether a lot less clumsy.

Proving why the cap iron is such an advantage (especially if we go beyond just smoothing) has not been very difficult to explain or prove.

You can't imagine how much effort it was to bring people around on this issue. It took four years to get the first convert (Bob Strawn) and another two years before he had the guts to admit it publicly. In the meantime many people, some of whom are still held in high regard, suggested I was lying and called me names. Some moderators thought I deserved to be called names.

The Kato material was discussed on this forum in December 2007. At that time I wrote: My feeling is that anyone who does not see the value of the double iron system probably does not understand how to use it. Do I need to remind you what others said at the time?

Re: Cap iron setback and shaving thickness

david weaver

beginning of your write up, is it 5.7 or 5.4? guessing 5.4 based on the 3.8 number.

That would put a shaving equal to the sole at 3.82/0.85 = 4.5 (about).

You mentioned that at 4, you started to notice significant resistance. At that point, surface improvement will stop, and it's also at that point where you don't want to advance the cap iron closer or the iron deeper into the cut because the effort won't be less (and that counts if you're going to dimension 20 board feet of something before you take a break - and if you were to work all day - it would really count).

If even with the sole is 4.5 and 4 is where you'd practically stop, that pretty much matches what I'd see. I would guess (by shaving thicknesses and resistance) that I never really set the cap iron closer than that. If there is still a problem with tearout, I take one full bore shaving (which would be equivalent to your 4 mil, potentially a couple of more until the surface is as good as it will get at that setting), and then back off the thickness and finish the work.

It's a very rare case that doing what I just mentioned will not finish a surface appropriately, and when it occurs, it's something like dead quartered cocobolo, which has a very soft earlywood and hard late wood. Even then, it's a fraction of those pieces of cocobolo that are quartered that cause a problem. The early wood crushes to dust or tears out easily. the former causes the wood surface to crush and break out under a close set cap iron, and the latter causes it to break without a close set cap iron.

You plane it as well as you can and then scrape it, and only if it's showing. In my case, it was showing (the side of a plane). Sanding is a reasonable option in that case, too - nobody would build furniture from it because that kind of early wood is fragile and the surface of the furniture would sustain very uneven wear over time.

Brian's plane also had that sort of behavior, but in beech, it's manageable. You just have to remember on something of that sort that you can't take a hogging shaving on the first pass unless you want to spend a lot of time cleaning it up.

Side comment in all of this, too, regarding cap iron engagement. The surface quality on harder woods actually improves with a less than perfect iron when the cap is engaged. As in, if I were to sharpen an iron with a 1k diamond hone, set the cap at 5.7, and then take two shavings - one at a shaving thickness of 4 and one at 2, the surface quality from the thickness of 4 would be better than the one of thickness 2. That can be handy once in a great while if you're working with an iron that's sustained a tiny nick.

Re: Cap iron setback and shaving thickness

david weaver

I recall those, Warren, but you are afflicted with something (or perhaps it's intentional) that prevents most people from picking up on what you're saying and that is the following:

* quite often, your responses make you appear to be contrarian in nature. I don't think that's necessarily the case, but it looks that way when most replies are in conflict with something that's been said rather than before that

* your descriptions of things are often vague or incomplete. like "it's subtle, it takes many years to perfect".

I barely remember the first time the K&K stuff came out (before the videos were available) because they got little press. At the time you were arguing in favor of the cap, only Todd was also arguing with you. Todd's explanations weren't complete, either. Larry's were, but they were erroneous (double iron planes can't feed at the corners so you lose effective width and that's why double iron planes are wider, you can't reliably set the cap iron at the right projection, ...).

I doubt anyone would've believed anything I said, either, even in detail - without the video following shortly after (perhaps that was february 2012 and the video came out in march?).

The one thing that led me to persist was the fact that nobody else said they were dimensioning by hand, except for you, and when I dimensioned with single iron planes, it just seemed like there must be a better way to go that wasn't so directionally sensitive. I don't recall at all what I expected for specs (I don't think I had any), but figured if I set my planes aside and used a cap iron for two weeks, I'd figure out how to use it just by need. That turned out to be true (I don't think it took two weeks to see a benefit over single iron planes - it may have been a small fraction of that). Summary of that, it wasn't anything that you said that led me to learn to use the cap iron, it was the belief that you were probably right whether or not I could figure out what you were talking about at the time.

You know as well as I do, if you're having a discussion about any of this with someone who planes machine planer marks off of a board, they're not likely to grasp why any of it is really that important.

In this case, I asked a very specific question about why tearout reduction would be improved. As you say, maybe it's easier to set the cap if you can see a uniform projection. I don't need that, but maybe in the future I would appreciate it. For what I've seen so far, it's solving problems that I don't have, and none of them are tearout related, or effort related.

I never close the book on a question ala Larry, so I'm going to read with interest any time someone can express the benefit in setting a cap iron to match the profile of an iron when the sole doesn't match the profile. I wish Nicholson would've done it, but maybe the audience wasn't appropriate.

Re: Cap iron setback and shaving thickness

Patrick Chase

It's 5.4.

I initially measured 5.7 in a 1X magnification image, but then discovered that this particular lens' "1X" isn't exactly as specified. I then reshot with a scale in the image and remeasured at 5.4.

As I said in my writeup, I view these results as ambiguous. The planing forces certainly start to increase significantly as the cap iron approaches the sole, so as you say there is a question of practicality here. With infinite force (i.e. a supershaper or the Kato/Kawai setup) I'm sure that I could get good results with the cap iron edge significantly below the sole, but as you've said in the past that isn't particularly relevant to hand planing.

The thing that gives me pause is that cap iron placement and lateral tilt are not exact. Even at 3.5 mil shaving thickness (which worked well) the cap iron is less than a mil from the sole, so it wouldn't take much tilt at all to get into trouble at one of the corners. I therefore think that a reasonable argument can be made for profiling the cap iron, not because it's a good idea to set the cap iron nominally below the sole, but instead to add tolerance when setting it nominally close to the sole.

That's really all I need to know to conclude that Nicholson isn't out in the weeds here, to be honest. It's probably worth noting that in borderline cases like this it's entirely normal to find that different people have worked their way to different (and ~equally valid) solutions.

Redoing the test

Patrick Chase

One thing I noticed was that the difference between depth and shaving thickness wasn't a constant 85%, but seemed depth-dependent. I only caught onto that at the end of my experiment, so I'll redo it today measuring board thickness instead. That should eliminate a fair bit of uncertainty.

As we all know type-2 shavings are also typically shorter than the board they come from, so I suspect there's some lengthwise "compaction" going on here, that may depend on the degree of cap iron engagement.

Re: Cap iron setback and shaving thickness

david weaver

Here's what makes it easy not to screw up with the cap iron set. It's exceedingly rare that a set that I have would vary more than a thousandth, but I still have good eyes. age may take that away (and I have rounded the initial part of my caps, which makes it easy to see the contrast - if it's not, I gun blue the cap iron so that it can contrast well against the iron).

If you have camber on an iron, the issue is very simple - your cap is either going to be somewhere just set off of the edges. If the camber is some number of thousandths, then maybe at the edge, it's only about 2 or so at the edges, maybe.

Perhaps in your example, the center would project 5 thou, the edges 2. The 2 is very easy to see. In a more heavily cambered iron, you can pretty much set the sides of the cap even with plane iron unless you've really gotten out of shape sharpening the iron - that's something to correct with each sharpening.

I never have a cap overlapping edges, except perhaps once in a great while on a jack plane.

The subtlety in this case, then is maybe more in the sharpening than the setting. the squareness of the edge has to be in line with the profile of the cap iron and the iron. if they get too far off, the cap sits askew. On a stanley, maybe that's just an annoyance. On a wooden plane with not too much lateral space, you either correct the cap iron or the iron. But there is a benefit to this that is not often described, either. A quick look at the iron and cap together along with the edge will tell you if you need to bias a little in honing to get things back in line. You never need to check squareness on the iron because a proper fit with the cap ensures it - or ensures that the version of squareness that you need with your plane is there.

This is maybe another reason that the washita is so nice to use - point and shoot. If the washita isn't quite enough, a once or twice over with a trans ark or black arkansas on the same profile can remove the work of the washita, and there is no multiple bevel arrangement to work through - but the washita itself maintains the correct profile.

This is long winded in text but extremely simple in practice. If things don't look right, you correct them so that they do. If my plane is a stanley 4, and I notice things get out of whack just a little, I don't try to correct them all in one shot (after all, the plane was working fine), I correct them a little with subsequent honing. The only time there is a large correction is with a new wooden iron and cap iron set (and that happens some, but I don't make many wooden planes these days because I have no outlet for them. When I make one for someone like brian, I correct all of that before the plane goes out. Brian is a better woodworker and planer than me, so I don't have to think too much about whether or not my setup will be maintained).

Anyway, if you're concerned about the evenness of the set, focus on the edges.

We can speculate on what Nicholson knew or didn't given the brevity of the section on caps, but without reasoning, we don't really know what the issue could be. As I'm prone to hyperfocus, even though I don't agree with it, I'm still going through iterations about what the reason could be. So far, I think these things (because tearout reduction is not an improvement that will happen with his setup vs. mine):

* visual cue to honing the iron and setting it (even though I don't think that's necessary if you can just make the edges even)

* perhaps with a coarser plane, there is a lowering of the effort needed for a close set if the edges are relieved (and by that, I mean in a constant radius and not just the corners - i never liked "clipping" the corners as Chris Schwarz describes - you can still see tracks.

* relieving the sides laterally may make for better feeding with planes that aren't quite done right or set up right. I am sure that there were planes that were delivered in a state such that they weren't feeding well. In the event that some work is done to relieve the sides of a plane, a wedge may end up with fingers that aren't sprung against the sides, etc.

It really could be any of these things, but I'd like to know. I have gone way deep into this cap iron stuff, and every time I think I'm set, I run into a wooden plane that I've made where there is something like a butcher cap that has a fat rounded front profile and requires me to do a bunch of fitting. I *think* I've gotten the making and feeding down now, and most of what Larry has said, I've dismissed.

Steve is at an advantage compared to me with this stuff because his materials are more uniform, plus he's probably made 10x as many planes and probably really has the system down. I'm still banging them out pretty freehand and none really matches the next (it pleases me to do them that way - feels good). But we've had discussions about the wear, and I'm sure Steve has banged around in his head what's necessary to make sure that a plane that he puts in someones hand will feed well even with a little user error.

I haven't made one in a while. All of this discussion caused me to clear off my bench last night. It's time to make a couple. You have one?

Re: Redoing the test

david weaver

This might be esoteric (our discussion about this and wanting to know just what it is, you don't really ever have to know if you use your planes a lot - you just get familiar)...anyway, it might be esoteric, but it's something trivial that I'd like to know.

Re: Cap iron setback and shaving thickness

Patrick Chase

To be clear, and I realize that I wasn't in my original post, I didn't see furriness until the cap iron was well below the sole, as in 5+ micron cut depth (6 um shaving thickness).

The immediate limiter to cut depth was ridging, resulting from high planing forces and my resulting inability to keep the plane moving continuously through the cut. As I did say in the original post, I only considered a setting successful if it yielded clean cuts from end to end.

Re: Cap iron setback and shaving thickness

david weaver

John, I hope you don't ever feel like you (or anyone else) owes me any amount of respect at all, or that I'll be slighted. I go way deep into these things like this because of curiosity, but I'm still a piker. The amount of detail that I respond with may make it seem like I'm bullying, and that's not really the case - just my process of understanding things in print and discussion.

Glossing over something trivially and then learning something from it (and remembering what i learned without a "why") is not my strong point.

Re: Cap iron setback and shaving thickness

david weaver

Ridging is pretty severe. Generally, if I think it's remotely painful to finish a cut, I'll back off on shaving thickness.

I think in your setup (keeping in mind that I've never measured anything, so I'm ballparking), I'd probably end around 4. Even at that, when you look at something like softwoods, you can see evidence that a cap was set close.

I'll bet Warren would spot that kind of thing in a second (the evidence of crushing), but I'm not sure many other people would. When I first started, I leaned a little on the too close side to try to ensure no tearout and I do recall Warren suggesting that it was on the less practical side of things. That sort of came from what I said above, that you can eliminate tearout really quickly. It's the rest of the subtle things that go with cap iron use (using it to your advantage to make planing pleasurable as well as efficient and sustainable - not to mention predictable and dead accurate) that take a little more time to nail down. All of the really significant advantages come out of that - and those were the things that I was lacking when I was using a long plane from the early 1800s to do my middle work - one with a single 50 degree iron. A beautiful plane, by the way, but it taught me what I wanted.

By the way, which maple are you talking about - western bigleaf maple?

Contrariness

Patrick Chase

In re: contrariness I'm sensing some "hot pot-on-kettle action" here :-).

I'm really enjoying this conversation FWIW, so don't take that as criticism. It's hard to make real progress without some level of contrariness. I do think that the participants in this discussion are somewhat self-selecting for that particular trait though.

I do think that there are many standards that we can use when evaluating somebody else's statements (be it Warren or Nicholson or whomever). David, you seem to be evaluating based on whether their claims align with your specific experience and the techniques you've come up with as a result. In contrast I'm intentionally trying to ask whether there is some way the claim could be valid, even if it doesn't apply to my own situation or experience. Both standards are fine, but both address different questions.

FWIW I still grind my cap irons straight, and I'm not ready to change (yet). With that said I'm now becoming convinced that the idea is fundamentally reasonable, probably enough so to be worth experimenting with at some point in the near future.

Re: Contrariness

david weaver

By all means, I'm not exempt from the contrarianism criticism.

(by the way, it's not just my experience, but a lot of it is based on that. Otherwise, quite a bit of it is based on the K&K video showing us a reasonable range where the cap will work effectively in difficult wood. If there's a logical hole in that, I'd sure like to know what it is. If the radius is for a different reason, I'd like to know that, too).

Kato and Kawai

Patrick Chase

The best configuration in K&K was 0.1 mm setback, 0.1 mm cut depth, and 40 deg bed angle. See about 10:50 in the video.

In that configuration the cap iron leading edge is 0.1 - 0.1*sin(40) = 0.36 mm = 1.4 mils *below* the surface of the wood. If anything K&K completely disproves your claims about surface quality, because it shows ideal results from a configuration that you claim to be completely unworkable.

As we've previously agreed K&K is unrealistic for handplaning because it basically assumes that infinite force is acceptable/available.

Re: The other issue...

Patrick Chase

Yeah, I completely agree that you could end up way off in the weeds if you tried to start with something like cap-iron profiling before getting the fundamentals sorted out.

I've only ever messed with the corners/sides of one cap iron, and that was for a 10-1/4 (a jack-sized bench rabbet). The cap-iron's leading edge was ever so slightly crooked, to the point where its side stuck out a tiny bit past the plane's sidewall when evenly set. That's a bad thing in a rabbet plane for obvious reasons, so I ground in a bit of a lengthwise taper (entirely behind the edge) so that it could be rotated a tiny bit relative to the iron without sticking out.

The point I'm making by example here is that even if you know something is OK to do in principle, it's probably not a good idea to actually do it until you have a concrete reason. OTOH "because Nicholson/Warren said so" does carry some weight :-)

Re: Kato and Kawai

david weaver

If you watch that video, you can see some "hair" standing up behind the iron, but the smashing is a little less than i expected - though I can't tell much from the video in regard to surface quality or "smashing", which is evident in something like pine as a bit of waviness or almost a miniature looking level of figure.

I calculate that to be a 4 thousandth depth removal, so the shaving is probably in the neighborhood of 5 thousandths. I think it's probably more useful to do this test with a plane, but back to the original need for a conclusion:

Is there any reasonable setting where you will use a hand plane with the cap iron below the mouth, and even more important, is there a setting where you'll use the cap iron below the mouth and with the cap iron overlapping the edge of the iron. The answer to that is no.

5+ years ago when I tested a bunch of different sets with a bunch of different planes, I watched the video and assumed that I could blunt the edge of a japanese cap iron to 80 degrees and I'd be pretty much home free - 8/10bu shininess and perfect tearout control, but it turned out to work like crap. It was very sensitive to set. Point being, I'm not sure the video is nearly as practical as just intentionally setting the cap iron below the mouth with a 50 degree leading angle (which is about as low as you'd want to go for effective tearout control).

The makers of the video were pretty direct about it not being instructive for hand planes in general.

I'm insisting on two things for a good conclusion:

* these things be tried instead on a hand plane

* that they be used in context of actual work, vs. what is potentially possible if you are really going to bulldoze your planes. That's important because this expands out to what you can do for a while, and a while means for an hour, for a day, for a week, for a year, for a lifetime of work

Not to mention, if there is a need for a set below the mouth, we can identify it by showing a sample stick of wood that is representative of work we'd do and that can't be planed cleanly with the cap level with the mouth or above, but can be planed cleanly if the cap iron is shoved below mouth level. I think the sample that fits that will be zero or near zero, and if the latter is the only successful method, it's going to need scraping after the fact.

I sanded my cocobolo plane to solve the problem and then scraped it. Not intellectually honest for someone like me!! But it was a rounded surface on a smooth/coffin plane and you can only do so much. I'm confident that the woods that cause me problems cannot be planed reasonably by anyone on this board. I'm also confident that if you really wanted to take a single iron plane and sharpen it to the Nth degree and move the cap out of the way, you might be able to plane the sticks I talked about causing me trouble. But woe be to the person who takes a single shaving a little too deep, or who takes a shaving with the iron just a bit too dull. That kind of thing isn't at all practical. It might take half a day to finish plane a table top made like that, and I wouldn't struggle through it.

This is interesting to us, because I know you like to get into the weeds. I had broken myself of the habit mostly, but I'm easily dragged back into them! I don't think there will be a time, though, no matter how long I live, that I'll plane with the cap iron below the mouth. BTDT, and that very thing is actually what sent me in the wrong direction many years ago.

I recall warren saying something about the cap iron, and it may be 2007 or so. AT the same time, I had just seen Charlesworth's video about setting a microbevel on the back of an iron for a 70 degree effective pitch to plane santos mahogany. So I set the cap iron way too close, it was about as hard to push as charlesworth's version and the surface quality was the same. I know I came back on here and whined at Warren about it. I'm not sure he remembers that, but he doesn't forget much! I am not successful using the search function on here, so don't know exactly when it was, but that sent me going the wrong way for another 5 years or so, only to be bothered by the topic again just before the K&K video came out (by chance) because I figured there was something Warren knew about dimensioning wood and I knew me and my JT brown long plane weren't going to have a relationship doing it.

Re: Radius of cambered blade - some #'s *LINK*

John Aniano in Central NJ

Hi Patrick,

I thought I'd give some actual numbers to the blade camber radiuses you/we are talking about here. I was curious...

Used the formula for a circle's sagitta "x" which is the perpendicular height above a chord of a length "y". See the Wikipedia link below for the drawing. It's a bit down in the Wikipedia entry under "Properties" of a circle.

r= (y^2/8x) + x/2

Let's assume a 2" wide plane blade that when radiused, will just barely cut at the edges. Patrick, if I understood you correctly, you suggested that it was difficult to push your #6 jack plane with the blade and chip breaker projecting 0.005" (5 mils) from the sole of the plane. Plugging in the values of 0.005" for x and 2.000" for y one gets a blade camber radius of 100" or about 8 feet. Pretty large!

Of course, you can make a smaller radius and more blade would be projecting out at the center, but, it would be harder to push the plane. Conversely, you could make the radius smaller, but not have the blade cut at its edges.

Food for continued thought!

John


https://en.m.wikipedia.org/wiki/Circle