Thread: High angle, bevel up, back bevels

Well, I wish I could give you a simple answer, yoboseyo, but I haven't found any myself, so that's not going to happen any time soon!

Lets discuss the cap-iron/back-bevel scenario you propose, first. A finely-set cap-iron or a back-bevel on a BD plane are essentially the same thing, in principle, the idea is to turn the shaving & rupture the fibres before tear-out can happen. If you put a back-bevel on a blade which normally has a cap-iron, you won't be able to set the cap-iron any closer than the back of the back-bevel. By the time the shaving reaches the cap-iron, the back-bevel should have done all the work, & the cap-iron won't contribute much, if anything to the surface quality. So go with one or the other, imo.

Does high-angle BD trump low-angle bed with bevel up ground to a high angle, or vice-versa? I think there are too many ifs & buts to give a definitive answer. Theoretically, it should mostly boil down to the cutting angles. (And just to be clear, the cutting angle is the angle of the leading side of the cutter relative to the planed surface). With BD planes, you can only vary cutting angle with back-bevels, whereas with BU planes you can change cutting angle at will by altering the grind/hone angle.

Now a BU plane with a bed angle of 15 degrees, and a blade honed at 30 degrees (which is not atypical for modern tool steels), has a cutting angle of 45 degrees, but in my shed, the low-angle BU plane will almost always cause far more tear-out than a 45 degree BD, even with a not-so-close-set cap-iron, but in other situations, high cutting angles alone do a superior job. I have a very solid infill with a massive blade set at 60 degrees, which can manage almost anything you throw at it, but not quite, and the surface it leaves, though tear-out free, is often not glossy smooth. And sometimes, for reasons I'm yet to fathom, a bog-standard 45 degree Bailey just eats all competition. A few days ago I was trying to smooth a chunk of Gidgee, and my #4 did a better job than the high-angle plane. Normally it would've come a poor second on that sort of wood, so there you go.

Then there's the extra effort pushing high-angle blades through hard woods. Maybe it's my advancing years, but I sure notice the difference if there's more thn just a few minutes work to be done. I won't get into the argument about whether high-angle blades wear quicker, there are too many variables to ever settle that, I reckon.

So the bad news is, I'm no help to you at all - my solution is to try several different planes whenever I strike 'orrible wood, & see which, if any, does a good enough job. I would never take a bet on which one will it will be!

The good news is, it's a legitimate excuse to own a range of planes......

Cheers,

Originally Posted by yoboseyo

These are all ways to increase the cutting angle when dealing with interlocked grain, but what's the difference? Much of a muchness? The difference in cost can be dramatic, i.e., putting a back bevel on is free, a Muji high angle smoother is cheap, and a LN/LV low angle jack is expensive.

For background, I am working with some hard hardwoods, and my smoothing solution is between planing and ROS. I prefer the finish of a plane, but I understand that I'll be sharpening every 10 minutes. That's ok though, as I'll be looking to take as thin shavings as possible.

What I'm thinking, is that perhaps if I put a back bevel on, will it be harder to get the cap iron very close to the blade? Will it be harder to close the gap? Will I get too much chatter?

My experience has some similarities to those of Ian, but also some differences.

All things held equal, the lowest cutting angle should leave the clearest surface. However there is so much in the way of this.

Here in Oz we have more than our share of hard, interlocked timbers. They do not play nicely. There are a number of ways to tame reversing grain with hand planes.

The absolutely best way is a closed up chipbreaker. By this I mean that the chipbreaker is around 0.4mm from the back of the blade. I had used high cutting angled planes for about 20 years, and then began using the chipbreaker seriously in 2012. It took some while to master, and you have to be able to do so to appreciate just how powerful a method it is. It is finicky to learn, and this it clicks and becomes straightforward. My (bevel down) Veritas Custom Plane has a 42-degree frog, and this is a superb smoother. You really appreciate the ability to plane any grain direction when you are smoothing book matched panels.

Let me compare two high cutting angle planes. One is a Veritas BU Smoother (12 degree bed) with a 50 degree bevel (=62 degree cutting angle), and the other is a (bevel down) HNT Gordon Smoother with a 30 degree bevel (and a 60 degree bed = 60 degree cutting angle). These two planes will perform the same - the Veritas because it is has a low centre of effort, and the HNT Gordon because it has a slippery wooden sole. Which to use will depend on your preference for plane type.

Now if you compared these two planes with a Stanley or LN with a common angle frog (45 degrees), which uses a 15 degree back bevel (=60 degree cutting angle), you will notice that it is much harder to push. It is not simply the cutting angle, but this in association with the high centre of effort. Before I moved to using the chipbreaker, I had 55-degree frogs in LN #3 and #4 1/2 planes ... and they were not used as they were just so resistant to being pushed.

Regards from Perth

Derek

Both mine & Derek's responses have concentrated on planing side grain, where BU planes just don't shine, for the reasons mentioned, but there is one thing a low bed-angle, BU plane usually does better than anything else, & that's slicing end-grain. This is a situation where cutting angle matters a lot, but I think it also helps that the forces are being transmitted from cutting tip to the plane body more in line with the centre of the blade's mass, & the tendency for the cutting tip to deflect is lessened. Other factors such as the mass of the plane & the blade retaining mechanism all contribute - too many variables for easy analysis, so I won't go there. Suffice to say that empirical evidence is it works, & works very well.

If trimming large 45 degree mitres is your thing, or if you use a shooting-board other than very occasaionally, I think it's handy to have at least one decent-sized, BU, low-angle plane in your kit. The earliest metal planes of the modern industrial era (there were cast-iron planes in Roman times, but they seem to have disappeared from the scene for more than a thousand years) were those strange-looking British mitre planes with low-angle, BU blades. They are hefty & cumbersome-looking things, that can't be much fun to use, though I've not tried one, so maybe I'm wrong on that. They were made in large numbers over a long period, so they obviously did what their owners wanted well enough. The only illustration I've seen of one in use showed it being used to trim a large mitre, on a "donkey ear" shooting vise, & my thought was, a 62 with a similar blade geometry, but blessed with handles, would surely be easier to manage in that situation!

Cheers,

http://www.veritastools.com/Content/Assets/ProductInfo/EN/05P2301AI.pdf

In a bench plane, the blade is used bevel down, so the bevel angle has no bearing on the cutting angle. This is determined by the angle of the bed which, in this case, is 45°. In the past when steeper cutting angles were desired, particularly for smoothing, special planes were produced with bed angles of 50° or 55°. However, the same net effect of altering the cutting angle can be achieved by introducing a back bevel on the face of the blade. In this way, a 5° back bevel will yield an effective cutting angle of 50° (commonly known as a York pitch). A back bevel of 15° will yield a cutting angle of 60° (see Figure 5); this will result in an entirely different cutting action from the standard 45°, producing what is known as a Type II chip (or shaving) as opposed to a Type I (reference: The Complete Guide to Sharpening). With this type of chip the wood shaving fails right at the cutting edge, eliminating tear-out and enabling the working of difficult grain patterns. This type of cutting action is similar to that produced by a scraper. The higher cutting angle increases the force necessary to propel the plane and is not required when working with the grain. However, when you have to work wood with widely varying grain (e.g., bird’s-eye maple) it’s handy to have a back beveled blade at hand. Changing blades has the same effect as using a high-pitch plane.We recommend a back bevel of 15° to 20° for most difficult planing situations, which yields a cutting angle from 60° to 65°. Note that even within this range, there is a significant difference in how the plane performs. At 60°, the plane will cut well against the grain, except around knots and the more dramatic grain swirls. Increasing the angle to 65° will all but eliminate tear-out, even around knots and rippled grain such as found in bird’s-eye or curly maple. The 5° increase will, however, make the plane noticeably more difficult to push. We therefore recommend beginning with a 15° back bevel to produce a 60° cutting angle, and only increase it by another 5° to 65° if you still experience tear-out. It is also important not to skew the plane in use when a back bevel is employed as described here as this has the effect of reducing the included angle.

Originally Posted by planemaker

http://www.veritastools.com/Content/Assets/ProductInfo/EN/05P2301AI.pdf

While technically correct, this quotation from Veritas misses the point, and it does not answer the question raised at the start, "what is the difference "(in planes with the same high cutting angle). The point is that there are subjective differences, primarily in ease of use and control, in how a plane is set up to carry a high cutting angle. I have outlined these above. In short, high cutting angles are not the same. Ergonomics and dynamics linked to force vectors are different.

Here is one article: Centre of Effort in a HandPlane

Regards from Perth

Derek