Video of a cap iron at work..and discussion about the cap

[David Weaver]

Bill Tindall, over at wood central has gone to great lengths recently to find information about the planing test that was done around 1980 at Yamagata University by two professors that none of us have probably ever heard of, professors Kawai and Kato.

I suspect this video is going to be popping up all over the place as a result of Bill's efforts in general, and you may have seen a link already at wood central to the video posted elsewhere.

What it describes in motion is what is going on below the cut line based on different cutting conditions and different combinations of cap iron projection and effective angles of attack (as well as without them). You have probably seen some pictures from this video, but to see the wood fibers moving in video is a lot more instructive. What it describes in general is that with the cap iron set properly, we're probably not ever going to need anything other than a basic bench plane to plane anything at all. The settings in the video, I think range from .004" from the edge to .012" to the edge (perhaps only .004" and .008" are included).

This is the direct video link to the video at Yamagata University, and if it changes, I will post a link from elsewhere, but this is the best quality of the video I've seen (it's large). Start around 3:00 if you don't want to watch particulars about the machine. This is a direct link, and it will pop up a video screen.

Original Cap Iron Video

And the credit that goes with the video (please do not repost the link to anyone without providing this credit - the video is not public domain):
Educational Video on "Influence of the Cap-iron on Hand Plane."　
Created by Professor Yasunori Kawai and Honorary Professor Chutaro
Kato, Faculty of Education, Art and Science, Yamagata University.
Video taken in Yamagata Prefecture, Japan.

There are other ways to control tearout, like
* steeper pitch
* very tight mouth (note the video is done totally without a simulated mouth ahead of the iron, the cutting effect is entirely due to the cap iron and the iron itself)
* sharper iron and thinner shaving
* discretion in picking wood, skewing a plane in a cut across quartered grain,
* planing with the grain regardless of what it takes to do that

But to do what is shown in the video is probably free, and it can be done with very inexpensive planes as well as expensive planes will do anything. No 55 degree frogs are needed, no 3 or 4 thousandth mouths.

Bill's excellent detective work to track this stuff down came with perfect timing, right along with when I was drawing conclusions from playing with an $11 common smoothing plane ($14 if you include the spare iron) vs. one that cost me $300 in materials to make. I still have more to learn from using the cap iron, like when I can back off of it some to improve the surface, but needless to say that when it is set tight, it has still given a better brighter finish than my 55 degree infill smoother on everything that I've tried. It does not have the same cadillac feel in all wood (that's a weight issue), but for sure the surface is a bit better.

It's worth the trouble to learn to use the cap iron properly, even though it doesn't make us feel as warm and fuzzy as buying more planes (and if I'm not chief indian in the pack of plane buyers, I'm first assistant to the chief).

Maybe we can get a productive discussion going, and save a few people some bucks. It only takes a couple of weeks of use to learn to set the chipbreaker as tight as these videos without accidentally running it past the edge and over it (dinging up the edge in the process).

[Chris Griggs]

Thanks a lot Dave. Geez, I've spent several years convincing myself that my Stanley No. 4 is inadequate, and that I need a premium smoother, and you had to go throw a wrench in my logic. I've had it with you

Actually, I'm glad you posted this Dave. I finally saw the video, not just the pics last week (I've been lurking at WC lately and saw the link). It really does show sooooooooo much more than just the pics alone.

I've been messing with this too, and it does seem to work. What I like about it is on a standard BD plane its easier to adjust the cap iron than the frog/mouth. I don't always need the cap iron to be that close, but if I do, its quite easy to move it up.

As you said, there are a lot of ways to reduce tearout, and while I still don't think cap irons are essential they are a good option. And they cost you no extra money.

The other funny thing I'll mention is, that since I started setting the cap iron really close, I've come to prefer the old style better. Becasue they have a relatively fine edge, and they are made of soft metal, the modern ones will chip and crumble if you hit knots/hardened sap when they are finely set. As, I mentioned to you in a previous discussion, I went back and actually blunted/rounded over the leading edges on my modern CBs. The old style ones have a steeper rounded over edge on them already.

(I am still going to buy at least one premium smoother one of these days)

[David Weaver]

I think I like the older ones better, too. I don't know what the angle of attack is on an old stock chipbreaker, but it works well.

There is another very big side benefit of setting the chipbreaker close, and that is that a stock or stock thickness iron is completely stable, even in very hard wood. No chatter on anything, no need for a super thick iron, no need to file the mouth bigger, etc.

I'm almost embarrassed that I was such a big pusher of everyone should go out and make a 55 degree infill and file the mouth to 4 thousandths of an inch so they could disregard planing direction (still can, but it's expensive for the materials and takes time to do it). It's still a good pleasant to use option, but it's definitely no smoother for white pine to set one up like that, either.

I have a cap iron that I set up just like you're talking about (it's unavoidable for me to use it, since it's on a spiers reproduction panel smoother), except that I gave it a primary bevel of 25 degrees and made a tiny secondary bevel of 80 degrees or so. It works pretty well and feeds in a plane that otherwise wouldn't feed because of an oversight I made.

The benefit of all of this is obviously we can smooth anything without getting into any real trouble, regardless of what we guess on grain direction. No more flattening a panel and finding tearout in the final smoother pass, finagling the plane in all different directions, etc. Just straight through strokes to get a good surface.

The original stanley design with a frog that goes all the way to the casting is genius design, more than we probably have ever given it credit for. It provides a bright finish on softwoods, and with the stock hardware, can smooth anything that back bevels and steep irons have been recommended for.

[Chris Griggs]

There is another very big side benefit of setting the chipbreaker close, and that is that a stock or stock thickness iron is completely stable, even in very hard wood. No chatter on anything, no need for a super thick iron, no need to file the mouth bigger, etc.

Yep. I actually pulled the Hock iron out of my no. 4 a couple weeks ago and put stock blade in just to test this. The stock blade is still in my smoother and working wonderfully. The hock is waiting to be reground with a jack plane camber, and will be used for rougher work, where I've come to find blade mass matters more, and where the CB cannot be placed as close to compensate for a lack of blade mass.

[Jonathan McCullough]

Interesting. So how can we ensure that the chipbreaker is set back .1 mm along the length of the iron in a shop environment? A jig that lets you run the CB to the blade against a flat surface, then some sort of stop along the back edge of the iron with a .1 mm shim, then remove the shim and move the CB back against the stop again so the CB is set back exactly .1 mm? What about eased corners so you don't get streaks in the work? I guess you'd have to ease the CB at the same time you ease the corners on the iron, then sharpen the iron and put the roundover on the CB. I'm not sure the video indicates that a higher bedding angle for the iron wouldn't reduce tearout. It seems like the fibers lift off the surface, but the CB curls them up before they get a chance to move vertically. Seems like a higher iron bedding angle would also promote the shearing of the fibers before they got a chance to lift up vertically, slightly more so than at the 40º angle.

[Chris Griggs]

Yes. A higher bedding angle wood also do that. The CB is just another option (an option that until very recently I thought was completely absurd and finicky to the point of being a waste of time). Daves point in bringing all this up lately isn't too say that higher bedding angles/tight mouths don't work, or that single iron planes don't work. Rather he is ponting out something that anyone with a reasonably well tuned bailey style can try without going out and buying anything new.

As far as setting it, its not something you want to or need to be scientific about. You just get it as close as you can and still see a gleam off reflection of the blade. No loop, no microscope, or other crazy gentleman woodworker esotera. It's quite easy once you've done it a couple times. On my smoothers the corners are so slightly eased that it has zero impact on setting the cap iron. I guess if you clip the corners heavily with a file, than this method probably would't be the thing for you.

[David Weaver]

The video definitely doesn't indicate a higher bed angle doesn't work, because it does work. It indicates that it's not the only way to mitigate tearout.

Setting the chipbreaker close to the edge is actually pretty easy, and the corners on a smoother, regardless of how they're rounded off or cambered doesn't really make a difference as long as you're setting the chipbreaker based on the depth of cut at the middle of the iron. If the corners are really relieved abruptly, they'll not ever touch the wood, anyway, and if you are bottoming out the chipbreaker and getting bulled around, either the cut is already too heavy or the chipbreaker set too close.

It is surprisingly easy to set the iron closer, actually, than .004, and you'll be able to tell you did that by the fact that the plane will bull you all over the place if you do it, even on a 2 thousandth thiick shaving, while still cutting a shaving (plus, the shaving will look bunched up to some extent). The surface will be fine when you do that, though, it's a no harm foul.

It takes a week or two to get used to setting it close for a smoother shaving depth, but not too close. You can just see a strip of bright metal off the back of an iron when it's set right for a light smoother shaving. There's no need for a jig, etc, just look for a uniform reflection from the iron.

Anyway, you definitely don't want to ease the edges on the chipbreaker. There's no need to worry about where the chipbreaker is over a part of the edge that's not cutting.

This is one of those things where cleaning up the front edge of the chipbreaker and trying it relieves a lot of questions. Once you're at "tearout proof", then you can back it off some to find out what works. But everyone who works with hand tools should have a go-to for smoothing that will remove no more material than you need to and at the same time make no threat of tearout and extra work.

[Jonathan McCullough]

Ah okay I see. Could you elaborate on the adjustment? I've been doing it by eye, and have found that moving the CB too close gives odd chips and suboptimal performance, so I've backed off the CB to about 1/32", maybe a little less? and have found that to be a sweet spot that gives consistent results. I've also found that going over the edge of the CB with a buffing wheel makes for better chips. Also have been known to put the CB in a vise and bend it just a little to close up any gap between the edge of the CB and the iron.

Chris, although sarcasm is my second language, I was being earnest. I'm familiar with machining tolerances and usually find them to be incompatible with most woodworking. But the video demonstrated different adjustments between .1 and .3 mm, so I was seriously asking--how does the average bear recreate those nice lab results in a shop setting without screwing around too much with micrometers? I've been making those adjustments by eye, but maybe I'm missing something or could be doing it better, so if adjusting a CB calls for repeatable results with .1 mm resolution every time you sharpen, why not a jig?

[Jim Koepke]

David,

Thanks for doing the work of finding and sharing this video.

I'm almost embarrassed that I was such a big pusher of everyone should go out and make a 55 degree infill and file the mouth to 4 thousandths of an inch so they could disregard planing direction (still can, but it's expensive for the materials and takes time to do it).

At least you are still open to learning things that may not agree with what you previously felt was the way to go. It has happened to many of us. I know it happens to me.

I like my old Stanley/Bailey bench planes. They can do great work. They are not as nice as a brand new LN bench plane, but they can do the same work when set up properly.

That is why my position is that someone with more time than money should look for older planes. The other side of the coin is some folks do not have much time, but the paycheck is fat enough to buy a new premium plane. In that case, a premium plane will allow them to get to work as soon as it arrives.

jtk

[Chris Griggs]

Chris, although sarcasm is my second language, I was being earnest. I'm familiar with machining tolerances and usually find them to be incompatible with most woodworking. But the video demonstrated different adjustments between .1 and .3 mm, so I was seriously asking--how does the average bear recreate those nice lab results in a shop setting without screwing around too much with micrometers? I've been making those adjustments by eye, but maybe I'm missing something or could be doing it better, so if adjusting a CB calls for repeatable results with .1 mm resolution every time you sharpen, why not a jig?

My bad! Sorry, I shouldn't have assumed. I speak the language of sarcasm quite fluently as well, and I thought you were being goofy (as I often am). Original post edited.

I actually tried at one point to use a sheet of paper to offset the CB about .004", but it didn't work, though admittedly I didn't mess with it for very long. I would say just keep playing by eye. I think you'll pretty quickly be able set it where you want it with just some practice. You can tell when it's set right, because 1) the surface is tearout free against the grain 2) the shaving changes... it holds together more (less gauzy but equally thin)... it sometimes has little wrinkles where I think it's breaking (type II chip?) 3) BUT the plane doesn't as Dave said "bull you around" and the shaving still ejects nicely

I'll add, that while learning to set the CB has in some ways made me feel less of a need to buy new stuff, it has really made me want a clifton stay-set chipbreaker (and by extension a clifton plane ). It makes a lot of sense if you are using a very closely set chipbreaker. And yes, I realize I can get a Clifton CB without purchasing the whole plane....

[David Weaver]

I guess if you could come up with a jig that was easy to use, it wouldn't be a bad idea. But a week or two of setting the iron should under half tension and then moving it to where you want it and tensioning it the rest of the way should take care of things, and it might become a jig that you wouldn't use much.

If you have a light source (even just looking toward a window or whatever), you'll be able to get it as close as you want it. If a polished edge on the chipbreaker makes it hard to see, blue (if you have any blue around) the edge of the chipbreaker or marker it. A couple of years ago, it seemed like tedium to me (after seeing the pictures somewhere on the web - from that video), I ran the chipbreaker over the edge a couple of times and swore it off until not that long ago and decided I'd do it for a couple of weeks no matter what. That sort of solved the problem.

Setting it partial tension and then moving it where you want it and then hitting full tension helps to set it close and tight (without setting it right on the edge or going over). If someone has trouble with that, they can set it partial tension and then lightly tap it into position.

[Jim Koepke]

Ah okay I see. Could you elaborate on the adjustment? I've been doing it by eye, and have found that moving the CB too close gives odd chips and suboptimal performance, so I've backed off the CB to about 1/32", maybe a little less? and have found that to be a sweet spot that gives consistent results. I've also found that going over the edge of the CB with a buffing wheel makes for better chips. Also have been known to put the CB in a vise and bend it just a little to close up any gap between the edge of the CB and the iron.

Chris, although sarcasm is my second language, I was being earnest. I'm familiar with machining tolerances and usually find them to be incompatible with most woodworking. But the video demonstrated different adjustments between .1 and .3 mm, so I was seriously asking--how does the average bear recreate those nice lab results in a shop setting without screwing around too much with micrometers? I've been making those adjustments by eye, but maybe I'm missing something or could be doing it better, so if adjusting a CB calls for repeatable results with .1 mm resolution every time you sharpen, why not a jig?

The "sweet spot" is something that everyone has to find for themselves based on the wood, grain and how deep of a cut is being taken.

The CB should not have any gap between the edge of the CB and the iron. It also needs to be free of nicks or "pockets" where chips can get trapped.

jtk

[David Weaver]

If it's used properly, the shaving will change because it's noticeably being worked by the cap iron. Like straighten out some and come straight up out of the plane.

Someone mentioned accordion shavings being an indication that it's too close, but I don't think I've seen anything like that though I've definitely moved the iron close enough that it provides significant resistance, but still cuts. Too much resisitance is probably too close, and in soft woods is almost definitely too close (straight soft woods probably don't require the cap iron at all unless poor orientation of the boards forces planing seam where wood goes opposite directions).

[Chris Griggs]

I find the hard core accordion shavings (that clog the plane and bull you around) result if the the CB is too close, like all the way at the edge... but also result when you combine a really tight mouth with a close, but otherwise not too close, CB.

To some extent you need to pick your poison.

I do still get some amount of "crinkle" when things seem to be flowing right (though the plane is harder to push), but I still need to play with this some more. Perhaps I am setting the CB closer than is needed at times - I'm still not 100% consistent on finding my sweet spot.

[Darren Brewster]

I have been following the Woodcentral posts, and it is great to finally see this video. Thanks David.