Why No Low Angle Wooden Jack Planes?

[Sam Takeuchi]

You'll need something under the blade to support it, otherwise it'll flex and chatter. Without it, if you run it over a knot or unusual grain, the blade edge get snugged and probably dig in while blade is slightly bent. You can adapt Bob's design and put cap iron underneath, which will add quite a bit of resistance to flexing.

Another thing is the gap under the blade. On a flat surface, it should plane ok, but at the end of the board, when you reach the very end of the board, the blade will slightly dig in once front part of the sole leaves the board. It'll be like slightly chamfered edge. More you plane over that part, bigger this gets. It happens because you plane past the front part of the sole, the only points supporting the plane is the blade edge and the heel. Blade naturally tries to cut downward once there is no sole to keep it steady. To over come that, you need more sole on the back part of the sole where you can exert enough pressure to keep plane level without the front part of the sole, so that the blade leaves the end of the board straight.

[Robby Tacheny]

Bob Strawn said
If you put sides on it like a Krenov, then you might still have full stability.

I think that's a good idea. It would add a lot of rigidity. How would you adjust laterally though? Maybe two smallish holes toward the very back of the iron on the sides?

Sam Takeuchi said
You'll need something under the blade to support it, otherwise it'll flex and chatter

I tried to illustrate that under the blade. I am thinking something like a table saw arbor nut. It is round and slightly convex with a hollow center and snugs the outside portion as you tighten the center. I am also considering trying design this with only a 2" blade so it would be less likely to flex. I think as mentioned above, adding sides could really strengthen this design.

[Aaron Kline]

Larry, could you post a drawing showing in detail whats happening with a low angle versus a standard angle plane? I don't quite understand the clearance angle issue. Do you mean the fibers of the board spring up directly behind the cutting edge and with a bevel down plane the small open area at the bevel is the clearance angle compared to a bevel up plane which has no area for the fibers to do so since the cutting edge is bedded flat?

[Larry Williams]

Larry, could you post a drawing showing in detail whats happening with a low angle versus a standard angle plane? I don't quite understand the clearance angle issue. Do you mean the fibers of the board spring up directly behind the cutting edge and with a bevel down plane the small open area at the bevel is the clearance angle compared to a bevel up plane which has no area for the fibers to do so since the cutting edge is bedded flat?

I've been trying to think of a way to draw this but I'd need a lot of images to show what's happening. If you think of slicing bread, you can probably remember seeing this. The fibers in the bread resist being cut and deflect ahead of the edge but, after they're severed, they spring back. Wood and other materials, even metals, do the same thing. When the fibers are displaced, the area actually cut is at a slightly higher level than the cutting edge. Wood fibers return with more force than bread and need to have space for their return.

There are a lot of variables involved--effective cutting angle, how acute the cutting edge is, the depth of cut, the species of wood being cut, how sharp the edge is and others. A 12º bedded block plane has barely enough room for the spring-back if the iron is sharpened at 25º, very sharp and the cut is light. My middle pitch (55º) smooth plane cause, sharpened at 30º has 25º of clearance which is barely enough. I free hand sharpen and, when I get in a hurry sometimes I hone when I should regrind. I just pick the iron up a little more to avoid a lot of honing. When I get the angle more than a couple degrees above 30º, my plane doesn't work well. It balks, acts dull, is prone to chatter and worst of all leaves behind a burnished surface. Burnishing inhibits good penetration of adhesives, stains and finishes. I've never measured the exact angle where this happens but I sure know it when I get to that point.

I think clearance angle may be one of the most important factors in plane performance and it's almost always ignored. The necessity of adequate clearance and the ramifications of not enough is hard to describe and there are so many variables.

[Wilbur Pan]

Hi Larry,

Do you think that the "best" clearance angle depends on the angle that the wood fibers are at relative to the edge of the blade when they are being cut? That is, the ideal clearance angle when you are trying to plane end grain with a low angle block plane might not be the same as if you use the same block plane to work on an area of face grain. That makes some sense to me -- it seems that the amount of spring back would be different if the fibers are more perpendicular or more in line with the surface of the board.

That might also be another factor why curly woods are so hard to deal with -- those fibers are at constantly changing angles relative to the plane blade, which would make the ideal clearance angle constantly changing as well.

[Robby Tacheny]

Larry thanks for that excellent explanation. The bread slicing analogy is really vivid in explaining, at least for me.

So in your explanation, you'd say that the low angle may increase tear out since we'd essentially be ripping the wood or would you say that its not going to get a good cut because there is a lack of springing back? Also, do think this could be corrected by adjusting the mouth opening or maybe by just slowing down the stroke?

-R

[Larry Williams]

Wilbur,

Grain orientation certainly plays a roll in how much spring-back happens when the fibers are severed. It's just one of a number of variables. I don't know of any real scientific data on this. The study and examples from the study quoted in Leonard Lee's sharpening book basically ignores viscoelastic deflection, clearance angles and spring-back. I'm not a physicist and don't have the means to do any actual scientific testing, I only know about what I experience and see.

I do have a question for you. Wiley tells me those who use Japanese planes are, by necessity, versed in clearance angles. I've wondered if Japanese planes aren't intentionally set up to burnish the wood as they cut? With the low bed angles and critical attention to iron bevel angles, this may be possible.

I have serious reservations about the practice if that's the case but I can see where some might consider burnished surfaces better. It took me a while to figure out the planed surface I want is a uniform dull surface with all the pores of the wood standing open and as little damage to the walls of the pores as possible. Early on I thought the shiny burnished surface was what I wanted. On the Internet, I often read descriptions of planed surfaces and it sounds as if some people think like I did before I realized all the problems a burnished surface will create in finishing and joint strength.

[Larry Williams]

Robby,

A tight mouth can help reduce tear out but tear out isn't necessarily related to spring back.

I think tear out happens when the resistance to the cut is greater than the strength of the fibers or when the lifting action of the cutting geometry is greater than the strength of the fibers. I still have a lot to learn. One thing I have learned is that planes, especially 18th Century British wooden planes, are highly evolved and incredibly sophisticated. The tools have to be as sophisticated as the products they produce; Chippendale, Sheraton and others didn't make the masterpieces they did with stone axes.

Another important thing I've learned is not to try to redesign or change the traditional designs with out really studying purpose of the features I'm attempting to improve and the ramifications. Leonard Bailey, Justus Traut and the other 19th Century design contractors for Stanley were pretty bright and talented guys. Still, when they translated wooden plane designs to metal they missed a lot. They had a lot of years and money to improve and refine those iron planes but in so many cases they never got it right. I think a lot was lost in the translation.

I know I'm not nearly as smart as collective knowledge of all those that worked before me. I'm still trying to figure out what all they knew. The idea that I might make some big improvement has vanished. At this point, I think it would be arrogant to think I'll improve anything. I just want to figure out all I can from the evidence the early plane makers left behind.

[David Keller NC]

"I do have a question for you. Wiley tells me those who use Japanese planes are, by necessity, versed in clearance angles. I've wondered if Japanese planes aren't intentionally set up to burnish the wood as they cut?"

Larry - that may well be the case. From the little I know of Japanese woodworking, much of it is soft-wood coniferous species, and are left as bare wood (i.e., no finish), so a burnished finish might be highly desirable - such a surface would probably stay a lot cleaner on a door, for example, and japanese culture is obsessed with cleanliness. The examples in cabinetry books that I have on antique Japanese work seems to fall into two classes - either left au naturale or finished with about 30 to 40 coats of urushi laquer, usually tinted.

[Sam Takeuchi]

I know it's little off topic here, but let me share a commonly quoted wisdom among the miyadaiku - carpenters who specialize in temple and shrine building and restoration, that the ancient wooden temples and shrines are build with wood surface so polished that they resist moisture and exposure. I don't have any scientific evidence to back that up, but seeing original structural parts of 1000+ year old building still stubbornly resisting rain, sun and snow to keep supporting those structure, maybe there is some truth to that. I live in Yokohama and Kamakura (ancient capital of Japan, like 800 or some years ago) is right next door. They got temples and shrines left and right between the age of 400 and 1000 years old. Of course they do go through occasional touch up every couple of hundred years (no I wasn't around when they did it the last time), but if they take them apart, they build it back with the original parts unless original parts need to be replaced.

That's been one of major interests for me. What is it about them that's so different. But then I prefer to spend time working on wood than coming up with hypothesis and experiments. I shall wait until someone figure it out.

[Wilbur Pan]

I do have a question for you. Wiley tells me those who use Japanese planes are, by necessity, versed in clearance angles. I've wondered if Japanese planes aren't intentionally set up to burnish the wood as they cut? With the low bed angles and critical attention to iron bevel angles, this may be possible.

Hi Larry,

Well, I must be the exception that proves the rule because out of all the things there is to know about planes, Japanese or otherwise, I can easily say that clearance angle is the thing that I know the least about.

As far as the burnishing thing goes, I'm going to stay away from the word "burnishing", and just go through what happens with a Japanese plane in use compared to a western plane. There is a key difference here, and whether you think the final surface is burnished kind of depends on what you think burnished means.

Here's a schematic diagram of the sole of a Japanese plane, greatly exaggerated, compared to the sole of a western style wooden plane:



The key here is that the Japanese plane has a relief along the entire sole of the plane in back of the blade. There's also a relief between a small area at the very front of the plane, and a small area immediately in front of the blade. On a western plane, in contrast, the entire sole is flat.

There are two things that I can think of that could make the planed surface be different with Japanese planes. First, with a Japanese plane, because of the relief on the back part of the sole of the plane, the last thing to touch the wood is the blade. What you are left with is a surface fresh off the blade, and the blade only. With a western plane, the sole of the back of the plane does rub over the planed surface after the blade cuts the wood. So you could say that a western plane "burnishes" the surface of the wood more than a Japanese plane does.

On the other hand, the sole of a Japanese plane only touches the surface of the wood in two spots: the very front of the plane, and the area just in front of the blade. Compare this to a western plane, where more of the sole is in contact with the board. Because of this, it may be that the two touch points on a Japanese plane puts more pressure on the board because of the reduced area of contact, causing more compression of the wood fibers just prior to being cut by the blade. In this sense, you could say that the Japanese plane does more "burnishing" than a western plane.

I'll add in a third factor just to confuse things. Although this is definitely not going to be a universally true statement, it seems to me that for the final planed surface, typical Japanese woodworkers may get their plane irons sharper and take a finer final shaving than a typical woodworker using a western plane. This difference may also account for the "burnished" appearance of woods planed with Japanese planes.

Hopefully you can see why I wanted to avoid the word "burnished", since the appearance of a planed surface done with a Japanese plane, with its slightly shiny appearance, may not be due to burnishing at all. I can see why it might appear to be that way based on what boards look like after being planed with a Japanese plane, at least in my hands.

Also, I don't think that this is a softwood vs. hardwood issue. I see similar things when I've planed hardwoods, including cherry, white oak, walnut, and a few South American species, with Japanese planes.

[Robby Tacheny]

Briefly back to the original topic,

I tried the design I posted. It did exactly as people mentioned; Chatter and digging in at the ends. Two good things happened though:

1. The design of having the bolt go through the block and going to a nut held the blade very firmly. I couldn't even do fine adjustments, which kind of stunk, but the blade barely moved even when struck with "objects".

2. I found out that the blade bedded at 12* took very smooth cuts, even though that design never produced thin shavings.

Even though that design ultimately stunk, I had fun and was surprised how just cutting the scale drawing out (paper pasted directly on the board) on the bandsaw yielded a plane in about 5 minutes.

I definitely need to try making another plane soon. Maybe I'll take a shot at that 30* bevel down plane.

Can anyone give me a formula for calculating the actual cutting angle from the blade's bevel and the angle that the blade is bedded?

P.S. I didn't realize Larry Williams actually has a company making wooden planes! No wonder he is a wealth of information on this stuff. He is a pro! Larry, do you teach and if so are you teaching any classes near Maryland this year?

Now hopefully back to some really interesting and informative hand plane design theory. Thanks again everyone for the great advice.

-R

[Sam Takeuchi]

30 degree bevel down plane may have some problems as well. For the sake of discussion, ignoring the plane's body rigidity, 30 degree bevel down blade with 25 degree bevel will have only 5 degree clearance, which is quite insufficient for practical purposes. If you decrease the bevel angle to less, blade edge will be very very weak.

For bevel down planes, cutting angle is the blade's bedding angle, if the blade is flat and not tapered type (wedge shaped), and there is no back bevel.

In practical sense, 30 degree bevel down plane has many problems. First, like it was discussed earlier, a lot of 'meat' from the plane's body have to be removed to accommodate the blade, and weakens the body. Worse, a tapping a wedge in is enough to deform the body, worst, split the body. Second, a 30 degree cutting angle doesn't yield any special result a plane with cutting angle between 35 and 40 degree won't do. Third, bevel and clearance angle issue. You can grind the bevel to 20 degrees to make room for clearance, and add 5 degree back bevel, but then that would make your plane 35 degree cutting angle with a 25 degree bevel, totally making a 30 degree angle plane pointless.

Basically it comes down to all the things that have been discussed thus far. Back to the very first question as to why no low angle wooden planes sort of came to the answer by itself, didn't it? Plane is a very simple tool with long history (a couple thousand years at least), I'm quite certain what can be done with a wooden plane has been all tried regards to cutting angle and bevel up or down, what we see is the designs that didn't fail at some point in the history.

[Bob Strawn]

Another brave soul who learns by making failed tools! The knowledge that you glean is all the better understood for the failures!


Bob

[Bob Strawn]

Robby,

A tight mouth can help reduce tear out but tear out isn't necessarily related to spring back.

I think tear out happens when the resistance to the cut is greater than the strength of the fibers or when the lifting action of the cutting geometry is greater than the strength of the fibers. I still have a lot to learn. One thing I have learned is that planes, especially 18th Century British wooden planes, are highly evolved and incredibly sophisticated. The tools have to be as sophisticated as the products they produce; Chippendale, Sheraton and others didn't make the masterpieces they did with stone axes.

Another important thing I've learned is not to try to redesign or change the traditional designs with out really studying purpose of the features I'm attempting to improve and the ramifications. Leonard Bailey, Justus Traut and the other 19th Century design contractors for Stanley were pretty bright and talented guys. Still, when they translated wooden plane designs to metal they missed a lot. They had a lot of years and money to improve and refine those iron planes but in so many cases they never got it right. I think a lot was lost in the translation.

I know I'm not nearly as smart as collective knowledge of all those that worked before me. I'm still trying to figure out what all they knew. The idea that I might make some big improvement has vanished. At this point, I think it would be arrogant to think I'll improve anything. I just want to figure out all I can from the evidence the early plane makers left behind.

I think one can improve within the bounds of ancient collective knowledge. Every now and then someone rediscovers a method that was mostly lost or passed over. Every now and then someone combines elements from separate traditions and makes something extraordinary. For example, the low angle bed, high angle plane works brilliantly with really hard wood and difficult grain, but seems to be fairly recent. That said, without examining and returning to the body of work that has been evolved, innovated and even revolutionized by great craftsmen and thinkers who worked with and maintained these tools on a daily basis, reinventing the wheel is inevitable.

I have found in my experimentation, that often I have to reinvent the wheel, to even know why the wheel is there. The chip breaker was an innovation that spread quickly and almost universally. Yet many modern woodworkers see little value in it except as a cap iron. I personally set out to prove to myself it was a waste of time, and in doing so discovered how marvelous an innovation it is. With a sharp chip breaker just a couple of thousandths of an inch behind the blade, some of the most uncooperative wood starts to become a pleasure to work.

Planes are I think a good place to learn and innovate. You can make one in a day or less, and they don't cost that much to make. I can make a superb wooden plane faster and cheaper than I can tune up an old Stanley. The old Stanley may have the advantage in stability, but it will never communicate back to my hands the grain and cut information that a good wooden plane does. I will never be able to adjust the Stanley to the precision that I can adjust a wooden plane.

What I am aiming for, is the plane equivalent of perfect woodturning. Sometimes, when woodturning, everything comes together, Rake angle, clearance angle and blade angle line up and my approach to the wood is perfect. Then the blade feels like it is being pulled into the work and a perfect surface, not crushed, barely burnished, is left behind. The blade does not dull and long clean shavings fly.

When the angles are perfect, the cutting edge only touches wood at the start of the cut. So the blade really does not dull at all. My goal is to achieve that in the flat with a plane. It seems like it would be easy, since when turning you usually face grain wrong twice per rotation.

In chaper 4 of Mike Darlow's Fundamentals of Woodturning, is one of the best discussions of clearance and rake angles that I have found. His ideal clearance angle is somewhere between 5 and 1 degree depending on how much wood you want to remove, and how smooth a cut you want.

To achive these low angles a bevel down blade seems to be the choice however, so low angle beds, despite the stability that they impart are going to cause more instablility at these angles.

The thought of a flush cut plane with a concave relief near the blade seems tempting, but it would not survive many sharpenings before it needed to be seriously reground. I think that a spear plane or even the right slick, would give much the same result and more stability.

I think it is worthwhile to try and innovate, even if it only helps you to appreciate the already existing body of work. My failures have taught me to be able to see many of the details on older planes that I would have otherwise ignored.

Bob