bench vs block plane irons

[bill littleton]

hi all, a few questions for you all. does anyone know why block planes dont need a chipbreaker and why the iron is flipped the other way in a block plane than in a bench plane. my wife asked me and i couldnt answer her:eek:

bill

[Matt Wilson]

hi all, a few questions for you all. does anyone know why block planes dont need a chipbreaker and why the iron is flipped the other way in a block plane than in a bench plane. my wife asked me and i couldnt answer her:eek:

bill

I would expect that if a block plane where to be bevel down it would require some serious redesigning. As it is now a block plane uses the bevel of the iron to increase the over all angle of attack. To me this makes it much easier to hold a plane designed like this in one hand. If we where to rely on a frog to do this it would be a fair bit more awkward.

just a theory..
Cheers
Matt

[Prashun Patel]

Placing the bevel up allows you to alter the effective cutting angle into the wood by just changing the bevel angle on the blade.

The bevel itself acts as a chip breaker in a bevel-up plane.

[Robert Rozaieski]

Neither require a chip breaker. Historically (like in the 18th and early 19th centuries), bench planes were single iron as well (i.e. no chip breaker). Clark & Williams still makes their bench planes this way. Additionally, no other wooden plane (dado, rabbet, fillester, molding, etc.) uses a chip breaker and they are all bevel down with high bedding angles (45° and higher). In a well designed and well bedded plane, a chip breaker isn't needed regardless of bevel orientation, and in my opinion, is a drawback. When a plane (especially a wooden plane) has a tight mouth, the chipbreaker needs to be moved so far back from the edge to prevent the throat from clogging that it serves little, if any real purpose. There was a Japanese professor that did a study some time ago that showed that chipbreakers had little real effect "breaking chips" unless they were placed extremely close to the cutting edge, which in most cases, is impractical and would cause the mouth/throat to jam with shavings unless it was really wide open.

Today, I think the real necessity for the chip breaker in the bevel down design is to provide the yoke of the frog a way to engage the irons in order to be able to adjust the depth of cut. If the frog and iron of bevel down metal bench planes were redesigned (similar to the bevel up design), and the iron was well bedded to the frog, the chip breaker could definitely be eliminated.

Orientation of the iron (i.e. bevel up vs. bevel down) wasn't a real concern until miter planes were intorduced in the late 18th/early 19th century. Planes were better off bedded bevel down because in a bevel down configuration, the grind angle of the bevel has no impact on the actual cutting angle of the plane. Instead, the cutting angle is determined by the bed angle. However, a bevel down plane can only be bedded so low before clearance behind the cutting edge becomes an issue. For example, with an iron ground with a 25 degree bevel, the bed angle of the plane can't really be any lower than about 30-35 degrees or the heel of the bevel will ride the wood and the plane will not cut.

Flipping the iron to a bevel up orientation allows for a lower bedding angle without the clearance issue, which can improve the plane's performance on end grain. However, there is no real benefit on long grain as long grain benefits more from higher cutting angles, not lower. Additionally, the bevel angle of the iron becomes very important in a bevel up orientation as the cutting angle of the plane is determined by the sum of the bed angle and bevel angle. So in a bevel up design, a plane's performance characteristics can be changed (purposely or inadvertantly) with just a small change in the bevel angle.

There is no historical evidence that the perceived versatility of the bevel up planes that is often talked about today was a consideration when the bevel up design was originally introduced. At that time, joiners and cabinetmakers were not interested in versatility. They embraced specialized tools designed to excel at a specific task because time was money. Bevel up miter planes were designed soley for shooting miters and end grain. There were plenty of other planes available that were much better suited to long grain work. The bevel up plane was a specialty plane similar to a dado or rabbet plane. It was designed for a specific task (shooting end grain), at which it excelled (and continues to do so).

Probably a longer explanation that you were looking for :o. Sorry for the long winded reply :D.

[Sam Takeuchi]

The function of cap iron (or chip breaker if you wanna call that) is to provide stiffness to the thin plane iron. Original patent of this design (someone posted that a couple months back) also cite this as a function of the cap iron. Breaking chip or shavings is perhaps a welcome side effect, but chip breaking effect came afterward I believe.

On bevel down plane, the force that tries to pull blade backward is great due to the design of the plane. Because the angle blade is placed, the force, or drag, concentrates on the tip of the blade. If blade isn't stiff to withstand that, it'll flop much like a flag would in the wind (not that extreme, however). Cap iron serves to channel that vibration to higher area of the blade so that the force is spread out and frog can also help to absorb that vibration. Stiffer the blade and cap iron, better transfer of the vibration. Take a wooden and iron rod, tap them with a hammer. Iron rod has better sound (vibration) transfer for it being stiffer. Wood is a lot softer and the sound comes out is muffed, it is because it absorbs it. For a bevel down plane, it needs a material that can spread the vibration, hence, soft stuff like wood wouldn't work so well. I guess if you want to get nitty gritty with it, it's a lot deeper, probably stuff about quality of material and some stuff about frequencies and such, but I don't know the details and I don't care.

On bevel up plane, angle of the blade is much shallower, and the force is naturally directed from the edge to blade. There is still a force that tries to bend the edge backward (push), but instead of blade edge sticking out without much support, but the edge has a whole blade to absorb that force, and transfer the vibration to the body. So in this case, cap iron isn't necessary to stiffen the blade, because blade itself does the job.

[Sam Takeuchi]

One thing to consider is that pre-modern planes had a lot thicker blade. I think it was Bailey patent on cap iron/blade assembly that said the feature was that the assembly allows use of thin blade. If you take a look at Stanley blade, they are pathetically thin compare to blades that came with old planes. I wouldn't doubt that flimsy Stanley blade would chatter like a machine gun without some sort of reinforcement of some kind in bevel down plane. It just doesn't have the stiffness or meat to really withstand much force, especially when that force is concentrated on the blade edge. AND there is no mechanism to firmly press the blade against the frog closer to the edge.

I think versatility sought today is mostly due to varied tasks woodworkers of modern times perform. Instead of specializing, people do various things, much wider tasks than artisans and craftsman who specialized in their trades. And I think it's good that the more versatile tools are popping up. Even though hand tools may not be the leading gadgets of modern manufacturing, it has to evolve, even so slowly. Whether bevel up planes were historically designed for such and such task, I have no doubt about it, but also I believe it is more versatile and useful than in the past due to materials and technology available to produce these planes. I use them on soft and hard wood, history and theory aside, it produces wonderful planed surface on most of wood I deal with. I'm more than sure that the wooden plane following the 18th century design would certainly be able to perform similar task satisfactorily with appropriately designed bedding angle and such, but like I said, personally I prefer the versatility of modern bevel up planes than have an army of planes to do specialized tasks.

P.S. I do use a home made high angle woodie and standard angle smoother and I love them. But I simply can't keep building planes for each task and material. I build musical instruments and my priority is there.

[bill littleton]

thanks for the replies. so if i understand right any plane could have bevel up orientation? so for my wooden planes i just built hocks irons with chip brakers are unnessesary? i could just have a blade bevel up in all my wooden planes? my wooden planes have a 45 degree bed

thanks

[Sam Takeuchi]

No. Wood isn't strong enough to provide structural rigidity to hold the blade and withstand the force of edge. Plus, unlike metal plane, in wooden plane, there is no mechanism to lock the blade. In metal planes, blade is locked in the position by depth adjuster, either through a pin or little ridge that engages the slot or hole on a blade. For a bevel up plane to have standard cutting angle of 45 degrees, you'll need to make 20 degree bed (assuming bevel angle is 25 degrees). You can imagine how shallow and thin wooden bed has to be to accommodate that kind of angle. You can make it of course, but there's a good chance sole popping out when you drive wedge in or at least deform over time. If you manage to use it, probably blade will slip out, because the force that pushes the blade backward is directly aimed at the blade. Wedge has to be driven really tight to hold the blade...and risk getting sole popped out like I said.

Edit: Oh you already have a plane with 45 degree bedding angle? Unless you want really high angle plane, near scraper, no. Just build a normal bevel down plane. Whether you like cap iron or not, it's not worth making a scraper just to skip cap iron when you want a regular plane.

[Robert Rozaieski]

thanks for the replies. so if i understand right any plane could have bevel up orientation? so for my wooden planes i just built hocks irons with chip brakers are unnessesary? i could just have a blade bevel up in all my wooden planes? my wooden planes have a 45 degree bed

thanks

If you put the blade bevel up with a 45 degree bed, you will basically have a scraper plane (i.e. 45 degree bed angle plus 30 degree bevel angle is a 75 degree cutting angle). You can do it, but it will only be useful for very light scraping cuts and the iron will dull very quickly. There's really no need to put the blade bevel up in a plane with a high bed angle. The bevel up configuration began in order to allow low bedding angles, lower than a bevel down configuration would allow.

However, you could certainly use your 45 degree plane with the iron bevel down without the chip breaker. As long as the iron is bedded well and the mouth is tight enough, bevel down without the chip breaker will work fine. The problem you will have if you already built the plane is that the wedge angle is dependant upon the iron/chip breaker combo. So if you remove the chip breaker, you change the angle of the wedge. Of course you could just make a new wedge to be able to use the plane iron without the chip breaker.


No. Wood isn't strong enough to provide structural rigidity to hold the blade and withstand the force of edge. Plus, unlike metal plane, in wooden plane, there is no mechanism to lock the blade. In metal planes, blade is locked in the position by depth adjuster, either through a pin or little ridge that engages the slot or hole on a blade. For a bevel up plane to have standard cutting angle of 45 degrees, you'll need to make 20 degree bed (assuming bevel angle is 25 degrees). You can imagine how shallow and thin wooden bed has to be to accommodate that kind of angle. You can make it of course, but there's a good chance sole popping out when you drive wedge in or at least deform over time. If you manage to use it, probably blade will slip out, because the force that pushes the blade backward is directly aimed at the blade. Wedge has to be driven really tight to hold the blade...and risk getting sole popped out like I said.

I think what Sam is talking about here is regarding a low bedding angle in a bevel up wooden plane. While there are some rare English examples of this, it's not a common plane for the reasons that Sam states. Very low bedding angles in a wooden plane put too much stress across the grain due to the wedging action in how the iron is secured. This can lead to splitting of the plane if the wedge is over tightened and slippage of the iron if it is not tight enough. However, there are steel/iron wedged low angle bevel up planes that perform just fine. http://www.toolsforworkingwood.com/Merchant/merchant.mvc?Screen=NEXT&StoreCode=toolstore&nextpage=/extra/blogpage.html&BlogID=141
(not sure if the plane pictured in Joel's blog, linked above is bevel up or down but they were made both ways).

[bill littleton]

ok so wooden plane 45 degree bed.....bevel down iron with chip breaker.
think i got it.
thanks guys

[Sam Takeuchi]

Ah he mentions it a bevel up plane. If you see the picture of the mouth, you can see that the blade is riding on the back of the mouth as well. That's one tight mouth.

[Mike Henderson]

Sam and Robert - very good discussion. Thanks for the postings.

Mike

[bill littleton]

here the to planes im working on

[Sam Takeuchi]

How thick/thin is the sides of smaller one? From the picture, they look a bit fragile.

[Eric Brown]

Joels blog has info on bevel up wood planes. Might find of interest.

http://www.toolsforworkingwood.com/Merchant/merchant.mvc?Screen=NEXT&StoreCode=toolstore&nextpage=/extra/blogpage.html&BlogID=145

Eric

[bill littleton]

the sides are just over 1/8 with a slight taper at the top