Hand plane question

[Cameron Wood]

This is something that I've wondered about.

I generally have set up planes so that the frog in the same plane as the back of the mouth, so that the iron is supported there,

but to get a close mouth opening, the iron is supported only by the frog, about 5/16" back from the cutting edge in this example, and the chipbreaker/cap iron are in effect flexing the iron down.

What's the deal?

IMG_4858.jpegIMG_4860.jpeg

[Eric Brown]

The flex is usually minimal with thicker blades. So usually on better quality planes this is not an issue. Also consider that with a thinner shaving less force is required. If you experience chattering, then either take a thinner shaving or sharpen the blade some more. That should take care of most issues. If working with difficult changing grain, try approaching from different directions.

[Jim Koepke]

The deal is that the mouth opening isn't as effective as a proper setting of the chip breaker at preventing tear out.

Another thought, some may say is just my opinion, is if the chip breaker is flexing the iron, it may be exerting too much pressure on the blade.

IMO, the unsupported area of the blade may be subject to resonate vibrations. (aka chatter)

jtk

[Jim Koepke]

Cameron, here is a picture of one of my planes applying a bit too much pressure from the chip breaker:

Plane View.jpg

The breaker was pulling the blade up off of the frog.

A little adjustment of the chip breaker cured this problem.

jtk

[Rafael Herrera]

Not all panes have the back of the mouth machined at 45 degrees to match the frog angle, so one has to find the best setting to take that into account.

What is important is to have the area behind the heel of the iron bevel rest flat all the way to the tip of the frog. That coupled with the frog feet making solid contact with the plane body, provides as much support as you can get with the Bailey plane design.

If you look at your closed mouth picture, provided the iron is firmly resting on the frog toe, it seems like there's only about 1/4" of unsupported iron. Given that this is hardened steel, I would venture say that small bit of steel is not going to vibrate. However, if the iron is not resting on the frog and kind of floating, or the frog feet are floating, then the iron is likely to flex and chatter.

By the way, the whole idea of closing the mouth is bogus. The narrower you set the mouth, the more you have to move the chipbreaker up in order to allow the shavings to pass, otherwise the shavings choke at the mouth. A closed set mouth also forces you to take thin shavings, slowing you down. If the rationale for doing this is to mitigate tear out, setting the chipbreaker close to the edge the appropriate degree is all you need to do. Having the frog set up as in your first picture is the optimal setup, if it can be achieved and works with the plane at hand.

P.S. This opinion is within the context of Bailey planes and in general, double iron planes. There are planes specifically designed with very tight mouths, like bevel up planes. Double iron planes don't need a tight mouth.

[Rafael Herrera]

I did a test in response to a question about tear out the other day. The OP got the usual answers about closing the mouth and higher angle frogs.

Here's a piece of smooth oak and a smoother with the cb set high, that is, not set to mitigate tear out. Planing agains the grain, on purpose, for a few passes created tear out.

20240310_183019.jpg20240310_184208.jpg

This picture shows a second smoother with its cb set close and after a few passes the tear out is gone. For emphasis, to demonstrate what an advantage the cb is, I planed the damaged piece of oak agains the grain. Of course, I could have planed with the grain, but the point is that in the cases where there is no other option but to plane against the grain, a cb will suceed. There will be no need for more surface repair like sanding or scraping.

20240310_185708.jpg20240310_184819.jpg

[Rafael Herrera]

Since we're talking about aligning the frog with the mouth, here's a Sargent 409 smoother I found yesterday. I'm looking at the mouth bevel and it doesn't look like 45 degrees. I measured the angle, it's 35 degrees. That's kind of interesting.

I took out a couple of Stanley Baileys and checked their mouths, I measured one, it's 45 degrees.

There seems to be some variability out there, so I won't make some sweeping statement as to what to do exactly. There's a lot of leeweay on setting these planes up. In fact, one of my Stanleys was setup with the frog set a bit back, not coplanar with the mouth bevel. It works fine.

20240317_174741.jpg20240317_182402.jpg

One of my smoothers, frog set a bit back. The plane works great.
20240317_181140.jpg

I think the bottom line is that these planes will need a bit of fiddling to get to work. Traying to aim for a very prescriptive configuration, like a very closed mouth, etc. is a distraction. These planes will work under a wide range of configurations, being aware of how the plane will behave will result in a plane suited to what you need it to do. Once you have the plane working, there's usually no need to screw with them again.

(I'm not done refurbishing the Sargent plane, so I don't know if it will suck or plane marvelously. It looks like all is there to make this a good plane. though.)

[Jim Koepke]

Given that this is hardened steel, I would venture say that small bit of steel is not going to vibrate. However, if the iron is not resting on the frog and kind of floating, or the frog feet are floating, then the iron is likely to flex and chatter.

Hardening steel will make it stiffer, but it will not prevent it from vibrating. Part of the reasoning behind the design of the Bailey chip breaker was to prevent flexing of the iron. This allowed the use of thinner irons.

Hang a box wrench by a string and tap it with a piece of wood or a hammer. That ringing sound is the vibration frequency of a hardened piece of steel.

jtk

[Rafael Herrera]

But the iron is not free to vibrate its full length, only the short 5/16" length or so, as in the op first picture. The cap iron pressing down the iron to the frog at its feet stops vibration to travel up the iron's length.

That short length might be too short to vibrate enough to create the flex to cause chatter. Assuming the assembly is not loose, which is not difficult to ensure it's not.

Hmmmm, is it because the cb is close to the edge that the assembly is less likely to chatter? If one were to set the cb, say 1/16 or 1/8, behind the edge, would the plane be prone to chatter? Just a thought.

[Warren Mickley]

Hardening steel will make it stiffer, but it will not prevent it from vibrating. Part of the reasoning behind the design of the Bailey chip breaker was to prevent flexing of the iron. This allowed the use of thinner irons.



jtk

Plane irons were thin in the 18th century, both double irons and single irons. The 18th century single iron I have is under 1/8 inch thick.

[Jimmy Harris]

This is something that I've wondered about.

I generally have set up planes so that the frog in the same plane as the back of the mouth, so that the iron is supported there,

but to get a close mouth opening, the iron is supported only by the frog, about 5/16" back from the cutting edge in this example, and the chipbreaker/cap iron are in effect flexing the iron down.

What's the deal?

IMG_4858.jpegIMG_4860.jpeg

This is by design. The frog being inline with the back of the mouth is as far back as you can move the frog without flexing the iron up, which will create problems. So that's the largest opening you want to make with the plane's mouth. And that's great for taking thick shavings, as you'll also have maximum support for your iron at that point. As you move the frog forward, you'll lose some support and close off the mouth, which means you'll have to take thinner shavings to prevent it from clogging. So you'll generally need less support under your iron with the thinner shavings, because the iron won't be digging as deeply into the wood.

As for the iron flexing down, that shouldn't matter in practice. Though if it bends too much, I guess it could be an issue, so you might want to adjust your chip breaker if you run into problems. But in theory, the iron flexing down should make it more rigid and less prone to vibration, by putting a constant stress into the steel. Kind of like flexing a card scraper. This is actually how a chip breaker is supposed to work. So it shouldn't work against you if the iron is flexed downward slightly.

[Rafael Herrera]

By the time the Bailey patents were filed, the chipbreaker had been in use for over a century. I've scanned the patents and there's no mention of the cb's used for reinforcement. Probably not a patentable claim. I don't see a rationale for the thinner irons either, but that would not have been mentioned in the patents either. If there were irons as thin as 1/8" in the 18th century, irons at 0.8" thick in the 19th century would not have been a patentable claim either.

https://www.datamp.org/patents/searc...art=0&id=11766

(of course, I've not read every single word in the documents, so if someone spots a good piece of information in the patents, please post it here.)

[Cameron Wood]

Thanks for the thoughts, and especially for the report of an actual test!

It's mainly an academic question for me as I use mostly Japanese planes these days, but something that I've long thought about.

Japanese planes figure a close mouth opening as one of the factors to get a good result for the finished surface. Their thick irons reduce vibration or flex.

I do use block planes, which absolutely benefit from a tight mouth opening. I wonder if a low angle plane with a chipbreaker landing on the bevel would work.

[Christopher Wellington]

Hardening steel will make it stiffer, but it will not prevent it from vibrating. Part of the reasoning behind the design of the Bailey chip breaker was to prevent flexing of the iron. This allowed the use of thinner irons.

Hang a box wrench by a string and tap it with a piece of wood or a hammer. That ringing sound is the vibration frequency of a hardened piece of steel.

jtk

Heat treatment generally doesn't change the stiffness of steel, it changes the strength. These are two different material properties.

The natural frequency is related to the stiffness of the material (and the size/shape) and not the strength, so heat treatment will not generally affect how a part resonates either.

For a blade hanging down into the mouth of a plane, the natural frequency will be inversely related to the amount of overhang. More overhang = lower natural frequency = more chance of chatter. Increase the natural frequency by reducing the overhang or increasing the thickness of the blade.

[Jim Koepke]

But the iron is not free to vibrate its full length, only the short 5/16" length or so, as in the op first picture. The cap iron pressing down the iron to the frog at its feet stops vibration to travel up the iron's length.

If the iron is not well seated on the frog's bed, flexing could occur beyond the point where the iron is in contact with the frog.

I've scanned the patents and there's no mention of the cb's used for reinforcement. Probably not a patentable claim. I don't see a rationale for the thinner irons either, but that would not have been mentioned in the patents either.

Bailey's patent of December 24, 1867 states:

My object is to use Very thin steel plane-irons, and in so doing I nd that they are liable to buckle under the pressure of the cap, which causes them to chatter, and makes them otherwise imperfect; and my invention consists in the providing of an auxiliary point of contact between the cap and plane-iron, and at the point where the plane-iron tends to buckle or rise from its bed or base, and thus have a pressure at that point in addition to that at the cutting-edge, which firmly holds this thin plane-iron to its bed.
The cap-iron, as commonly constructed, that is, as shown at D, in fig. 3, when applied to the plane-iron E, will rest thereon only at the extreme lower end of the cap-iron, and also at or very near its upper end. There will be a long angular space, between the two irons, when they are clamped together by the holding-devices which are represented in figs. 2 and 3, at A, B, and C, and consist of a screw, A, a bearing, B, and ay cam-lever, C, arranged in a manner well known.
The difficulty experienced from the construction of the cap iron with the single bend a, is, that it allows of vibration of the cap-iron and the plane-iron while in use, such vibration being productive of what joincrs term chattering, and consequent defective operation of the plane.

The cap iron patent claims an improvement from previous cap irons.

Thinner irons using less steel, could create more profit or claim to be easier to hone as an advantage.

jtk