A question on Plane blades

[Arlin Eastman]

I was reading the post about BU blades and got me to thinking.

Since I know nothing about angle or BU or BD I try to keep the blade sharp and adjust the mouth if something is going wrong.

Almost all the time I have the plane skewed and find it cuts shaving much better and easier then having the plane go straight on the cut.

To me I want to think on a single think and not worry about the bed of the blade or the angle or anything else like that.  I also know there was a big talk of BU or BD awhile ago and some like it one way and others like it the other way.

When Rob Lee sent me the block planes he sent me two spare blades and said to go BU for best cuts.  So just to be clear really what is Bevel Up mean to you?

It is where the point of the blade is on top of the bed or bottom of the bed?

Thanks for all the help and advise

[barryvabeach]

Arlin, in general, plane blades are sharpened on only one side, the other side is kept flat.  The side that is sharpened is called the bevel side, and if that faces up in the plane, it is called bevel up.  In the standard Stanley bench planes -  like a Number 4, the blade is inserted so that the sharpened or beveled side is down.  Since the frog in that plane is normally 45 degrees, whether you sharpened the blade to 20 degrees, 25 degrees , or 30 degrees,  the cutting angle of the blade in the plane will be 45 degrees, since the shaving runs along the top of the blade.  If you have a bevel up plane, like many block planes, the sharpened side of the blade faces up.  So if you sharpened the blade to 20 degrees-  the cutting angle of the plane in the blade would be the bedding angle ( if a Low Angle plane - say 12 degrees  bed angle ) plus the bevel angle of 20 for a total cutting angle of 32  ( which you would like, since skewing the plane is similar to a lower cutting angle ) .  If you resharpened the blade to a 30 degree angle, the cutting angle of the blade in the plane would be 42.http://www.leevalley.com/us/shopping/Instructions.aspx?p=33287

[hbmcc]

Almost all the time I have the plane skewed and find it cuts shaving much better and easier then having the plane go straight on the cut.

As Barry noted, skewing a plane in reality lowers the cutting angle--bevel--which has the effect of making the cut easier. In the extreme, compare the angle of a knife slicing wood at 25 degrees, or so, and an ax driving into wood at roughly 80 degrees. The ax requires more work.

[AHill]

Here's the terminology and the orientation of the blade.  The blade really doesn't change much between bevel up or bevel down.  It's how it's installed in the plane.  Planes are made to be used exclusively one way or the other.  In a BU plane, the cutting angle is the angle of the bed + the angle of the bevel on the blade.  In a BD plane, the cutting angle is the angle of the frog.  I won't confuse you with back bevels for BD planes.  In the picture below, the left one is a bevel up plane and the right is bevel down.

[Arlin Eastman]

So in the first picture it is bevel up correct?

Also the way it figures the angle is the frog bed = 45* and add the degree of the blade = 20* = 65* correct?

So why would someone use bevel down?  Thinking about it would seem it would break the edge off easier.

[Aram]

So in the first picture it is bevel up correct?

Also the way it figures the angle is the frog bed = 45* and add the degree of the blade = 20* = 65* correct?

So why would someone use bevel down?  Thinking about it would seem it would break the edge off easier.

One reason: if you want or need a chipbreaker, a bevel down configuration gives it a flat surface to rest on very close to the edge. It's hard to see how you would get a chipbreaker fitted to a bevel up blade. Though things being what they are, I'm sure some fanatic has done it somewhere, somehow, just because he could!

[DaveParkis]

The first picture is bevel up, but the bedding angle is only 20 degrees. If you combine that with the 25 degrees on the bevel, you get 45 degrees. With bevel down planes, the bevel angle is irrelevant because the bevel side isn't hitting the wood.

[Bibliophile 13]

It's a complicated issue, but there are definite answers. 

Bevel-up and bevel-down are two ways of accomplishing the same task.  Both can present the cutting edge to the wood at a number of different angles, the most common being about 45*.  But there are some mechanical differences to be aware of.

One thing to know first: all other things being equal, a HIGH cutting angle tends to reduce tear-out but make the plane harder to push; a LOW cutting angle makes the plane easier to push but tends to allow more tear-out.  But a LOW cutting angle is easier to use on end-grain.  So historically, most planes have split the difference at 45*.  

Bevel-DOWN blades, as used in most Bailey-pattern (e.g. Stanley) hand planes, have a fixed cutting angle of 45*.  (You can get some, such as LN handplanes, with special frogs for raising the cutting angle to 50 or even 55 degrees.)  Whatever angle you hone on the blade, usually between 25* and 35*, the effective cutting angle stays the same as long as you plane straight forward.  But when you skew the plane, it lowers the effective cutting angle, which is why the plane becomes easier to push when you skew it.  However, with that lowered cutting angle also comes some potential problems, mainly tear-out.  Most woods tear out less with higher cutting angles than with lower ones. 

However, if you set the chipbreaker extremely close to the edge of a Bevel-Down plane blade, you effectively raise the cutting angle (a lot) and reduce or eliminate tear-out.  If you want to make the plane easier to push and can risk a bit of tear-out (or are planing stock that is in no danger of tear-out), then you can just back the chipbreaker off a little bit.  (Chipbreakers are only available on Bevel-Down planes as far as I know.)  But other than skewing the cut, there is no way to lower the cutting angle on a Bevel-DOWN plane, which is one drawback of the design.

Bevel-UP blades give you the option of changing the cutting angle by establishing a different bevel angle on the blade.  That's why Veritas sells blades with different primary bevels: so you can swap out blades if you want a higher or lower cutting angle.  But because Bevel-UP blades have no option for a chipbreaker, the only way to really control tear-out is a high cutting angle PLUS a very tight mouth.  The tight mouth has the disadvantage of being prone to choking, if you don't set it just right.  On a block plane, which is designed for trimming jobs where minor tear-out is okay, the Bevel-UP configuration gives you a lower center of gravity, makes the plane easier to push, and allows you to use the tool one-handed.  Bevel-UP bench planes take that basic design and apply it on a larger scale, with similar results.  With a high cutting angle and a tight mouth, you can avoid tear-out quite well, but the plane will be harder to push.  But Bevel-UP planes really excel at planing end-grain, and are especially good as shooting-board planes.  As with bevel-down planes, you can lower the effective cutting angle by skewing the cut.  The disadvantage is that, in order to raise the effective cutting angle to reduce tear-out, you have to switch blades or re-grind the bevel. 

So, like I said, two different ways of accomplishing the same task.  The traditional Bevel-DOWN planes allow you to raise the effective cutting angle by setting the chipbreaker close, but you can't lower the cutting angle except by skewing the cut--which is not always possible (say, when jointing).  The newer Bevel-UP planes allow you to raise or lower the effective cutting angle by switching to a different blade, which means keeping two or more different blades on hand.

Hope that makes sense.

[Arlin Eastman]

Now that is a lot of info and I will have to copy and paste that on a word doc and read it to get what you are saying and then take it out to the shop and so what you are saying.

Some of it is above my head.

[bandit571]

Hmmm...ever wonder, when you pick up an old wooden plane, and notice how it is worn?    Could be because the original owner used that plane at a skew..even when jointing?

The ONLY planes I have in the shop, that I use...are the bevel down style.    Unless you count the block planes...which is the only place I have bevel up irons....and, no, I don't change those block plane irons.....I just change block planes..
...from two kinds of low level  and then the "standard angle" block planes.  

One little tip, for pushing a plane.....rub a plain old candle across the sole of the plane...just a few squiggly lines will do....and HANG ON!.....be surprised how easy that plane is to push...