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What Mr. Weaver is claiming is that very thick shavings may be taken without tear-out by setting the cap iron very, very close with a straight edge profile or a perfectly matched radiused edge. Note that the chipbreaker effect is much less apparent as the thickness of the shaving decreases and the beam strength of the shaving diminishes by the cube of its thickness...which is why sharp bevel-up planes have worked so well for so many, provided those wielding them are content to restrict themselves to 0.001"-0.002" shavings in figured stock.

Peeling off a 0.005" - 0.006" shaving from highly figure stick of hard maple would certainly benefit from a properly fitted and profiled cap iron set a few thousandths back from the edge, but my own experimentation suggests that the need to efficiently smooth large surfaces in minimal time is not really that pressing a priority for those working with small, thin, precious pieces of stock. I don't have the upper body strength to manage that sort of shaving thickness with a #4 or a #4-1/2 for more than a few strokes in any case (note: I can use a #4-1/2 as a kettlebell AND a plane...double duty!), so I do what woodworkers have done for centuries - work across the grain with a sharp jack plane (I finally found a nice #5-1/4) to level the stock and waste down to within a 1/64" -1/128" of the line, then finish with a well set smoother and scraper.

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A constellation only takes shape when one maps the whole.
- Beth Brower

What I'm concerned about, is not the thickness of the shaving so much, but more so that the risk factor of tearout is out of the equation.
You can get away with a lesser pristine edge with the double iron set to have influence, so you don't have to test the sharpness every time
like with a BU plane, before you can be sure of the result.
The BU plane iron will dull more readily.
Tomas

As I'm finally done building the mold, I'll planing rosewood sides pretty soon. Mostly quartersawn with little to no figure so I'm not too concerned about tearout. I'd be surprised if I got any.

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Hutch

Get the heck off the couch and go build a guitar!!!!

For more adventurous types .I/ve switched to using japanese smooth planes, especially on softwoods , they leave a smooth clean cut, an sheen on the wood particularly if the blades are super sharp !

If you are a planing nerd, your familiar with this video. I can only add one URL, so piece this one together:

vimeo.com/ then 158558759

And here is a REALLY technical interpretation:

http://planetuning.infillplane.com/html/review_of_cap_iron_study.html

The gist of it is that if you are taking very fine shavings with a sharp blade (.005" = about .1 mm) then no cap iron is needed. Not many of us can do that, so for a thicker shaving, the set-back for the cap iron varies with shaving thickness, and an 80° face on the chip breaker is best.

In the study, it is cool to see the extreme close ups of the tip of the blade to see wear under differing condition.

And if you are experiencing tear out, move to a scraper. If I still have some thickness to go and am getting tear out, I have a box scraper - a heavy blade in a handle that allows you to push down with one hand as well as pull with the other. An aggressive burr and boy does it take off material. Then I move to a scraper in a #80 holder which I find simple and quick to set up and much easier to use than #12, a 112, or a 212.

It is mesmerizing to watch the chip come off the blade in the video,

Ed

They say 80 degrees on the cap iron makes it too hard to push, but it can be set further back from the edge.
David Weaver and others say 50 degrees is about right, I have been having good experiences with this.
Kees van der Heiden (seekelot on youtube) has his cap iron somewhere about 30 IIRC, could be wrong, but this means it needs to be set closer.
Tomas

Mr. Minch - I assume you mean 0.0005"? Given that I've been planing super-curly maple at 0.0007" to 0.0009" chip thickness with both the LN 62 and my little #3 without issue suggests that beam stiffness at those chip thicknesses is not really much of an issue. Sure - the chipbreaker will have a big influence when the chip is thick enough to exert a measurable lifting force ahead of the blade, but a few extra passes at thinner chip thickness does the job for the tiny pieces of wood we use in most luthiery projects if what we have is just the one Lee Valley low angle jack.

Re: dulling - I'm not certain the presence or absence of a chipbreaker makes much difference, although I seem to recall from a prolonged crawl through the badger Pond and Old Tools lists that edge wear increases as the cutting angle and the honed angle increase. Perhaps because the common cutting angles (and related increase in honed angle) for bevel up planes tend to be greater than bevel down planes (usually fixed at 45 degrees, 50 degrees, or 55 degrees), the common perception is that bevel up planes dull more quickly?

For thin chips and most timbers, the bevel-up fellows seem to do quite well, although I cannot claim to be one of the faithful that consider that configuration to be the do-all, Swiss Army plane. It can be argued that surface finish may be a little nicer with a close-set chip breaker and equally sharp blade, but very few guitars are delivered with unsanded, unfilled, minimalist oil finishes thin enough to allow that difference to be sensed.

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A constellation only takes shape when one maps the whole.
- Beth Brower

"Mr. Minch - I assume you mean 0.0005"? "

I would assume Mr Minch meant 0.005" - roughly the thickness of a human hair. 10 times thinner than that you are just planing blue sky- the air molecules off the top of the board.

I shoot for .001 for fine shavings. .005 would be pretty huge in the scheme of things.

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Pat

I watched the youtube on cap-irons and now have much better results planning woods like curly maple. Some really good tips here also, on ds tape release.

A 0.005" shaving would be a fairly thick shaving...0.0007"-0.001" would be more in line with what is usually referred to as a light cut or thin shaving for smoothing. A 0.0005" shaving would be a challenge to produce in some woods, and a 0.005" shaving would certainly benefit from a close-set, well-fitted cap iron, hence the suggestion that a digit might have been slipped.

_________________
A constellation only takes shape when one maps the whole.
- Beth Brower