How Square Do Chisels/Plane Irons Need To Be?

[Derek Arita]

I keep hearing and reading with regards to forming a new, primary bevel, don't worry so much about the edge being dead square. It doesn't need to be. Is that true? I've always been very concerned with getting the edge square on both, but now I'm thinking maybe I should relax a little...a little!

[Al Launier]

In my opinion chiseling square corners would be easier with a square chisel; for a plane perhaps not so much.

[Derek Arita]

Seems to me as well, that chisels should be as close to dead square as possible, however with plane irons, I'm not sure.

[brian zawatsky]

I will take extra time to make my chisels square if necessary. Maybe not so important for paring chisels, but anything that I use for chopping has got to be square. If you start your chisel on or parallel to a knife line you want to be able to register the chisel by setting the entire cutting edge on the work, otherwise you're guessing as to whether you're actually on the line. If the edge is not square then the chisel is not perpendicular to the work, and when you strike it will not cut straight in but at an angle. Square edges make it easier to chop accurately, IMO.

I think this is less crucial for plane irons, as long as your plane has a lateral adjuster. I try to get them square but don't spend as much time fretting it as I do chisels.

[James Waldron]

One point to consider with plane blades is that many (most?) are cambered, so that "square" is a relative term.

For chisels, I'm with Brian. As an additional thought, I've found that an "unsquare" edge will be inclined to twist as it cuts. Hard to keep the result clean. (It's possible that what I've seen as twist is actually a result of inability to properly register the edge on the work before starting the cut.)

[lowell holmes]

Why don't you fix two chisels, one square and one rounded. Then you can experiment with them and make up your mind.
Just thought. . . . . .

[Prashun Patel]

Most honing guides work best if the tip is square.

If the tip is skewed it will be easier to pare into half of all corners and harder to pare into the other half of all corners.

[Jeff Heath]

Most honing guides work best if the tip is square.

If the tip is skewed it will be easier to pare into half of all corners and harder to pare into the other half of all corners.

Yes, and then you would need two equally opposite out-of-square chisels.

It's not that difficult to get things square with a little diligence. In a plane iron, if it's a little bit out, it's easily adjustable. With chisels, I pay extra attention to keeping them ground square.

[Derek Arita]

So, I'm assuming you all are saying that chisels should be "no lite shining thru", square? Do you actually check for that after honing?

[Andrew Hughes]

I know good way to check the shape of your chisels or plane blades. Look at the back holding up in the light you can quickly see what side needs more work. It’s surprising how precision our eyes are.
Its very much how our fingers can feel the length of two short pieces from the shooting board.
Try it then report back.

[Robert Hazelwood]

Chisels should be pretty square, but I don't take a square up to them, I just look at them closely when sharpening. If it looks square that's good enough.

For bench planes the irons should match the chipbreaker, meaning you can set the chipbreaker close to the edge, evenly across, without rotating the chipbreaker relative to the plane iron. On a Bailey design it's not a big deal if you have to rotate the chipbreaker, but on a wooden plane the effective width of the iron+chipbreaker package is increased and there is not much side-to-side room in the mortise, so it may not fit at all, and if it does fit you will not have much room for lateral adjustment.

Shoulder planes require the most precision in squareness IMO.

[Richard Jones]

So, I'm assuming you all are saying that chisels should be "no lite shining thru", square? Do you actually check for that after honing?

I do that after grinding the 25° bevel, but not after I hone at 30°.

Yes, most chisels gotta be square,,,,,

[Derek Arita]

I just tend go overboard of things and strive for perfection. It drives me crazy when things are not, so I want to make my obsession well placed. Seems it is on chisels, however on plane irons, not so much.

[Jim Koepke]

I just tend go overboard of things and strive for perfection. It drives me crazy when things are not, so I want to make my obsession well placed. Seems it is on chisels, however on plane irons, not so much.

If one of my chisels is out of square, it is worked out during the next few sharpening sessions. It is helpful to have them perfectly square. It is only worth fixing to the degree it prevents the user from doing a task.

At times it is helpful to have purposely skewed edges on a chisel for getting into corners and tight spots. With a shallow bevel a slightly skewed edge can get in to both corners of a blind socket.

jtk

[John Schtrumpf]

... With a shallow bevel a slightly skewed edge can get in to both corners of a blind socket.

jtk
It took me a while before I realized I only needed one skew chisel to do both corners (ride the bevel on one corner, ride the back on the other).

[Andrew Seemann]

I like chisels and plane blades to be square, chisels more so than plane blades. But, I square them by eye on the Tormek jig & stone. I usually don't mess around with a square unless I am having a really bad sharpening day. I figure if I can't see it as out of square, it is close enough. As long as the tool works as well as it needs to, that is all that matters.

I'm not sure if there is an actual benefit to a chisel edge being square. It probably helps when registering the blade against the wood to have the chisel be perpendicular. I know it would drive me nuts if the chisel leaned to one side when I did that, and maybe it would drift when being used.

[Mark Maleski]

I'm not sure if there is an actual benefit to a chisel edge being square.

Absolutely there is! Imagine cleaning out the bottom of a dado with a skewed chisel. Or chopping dovetails. Or squaring off mortise walls. Or...

[Andrew Seemann]

Absolutely there is! Imagine cleaning out the bottom of a dado with a skewed chisel. Or chopping dovetails. Or squaring off mortise walls. Or...

Yep, that is probably why out of square chisels drive me nuts;)

[Prashun Patel]

I don't check for square after honing - only while establishing the bevel.

[Jim Koepke]

[edited]

I'm not sure if there is an actual benefit to a chisel edge being square.


Absolutely there is! Imagine cleaning out the bottom of a dado with a skewed chisel. Or chopping dovetails. Or squaring off mortise walls. Or...

Except for chopping, my skew chisels do come into play when cleaning out the bottom of a dado, cleaning mortise walls and removing waste in dovetails, especially half blind dovetails.

jtk

[Derek Arita]

I don't check for square after honing - only while establishing the bevel.

+1. That's when I check as well.

[lowell holmes]

You might consider easing the bevels at the outside of the edge to eliminate tracks. I do this on plane irons.