Iron Camber

[outofstepper]

Aren't I just full of questions today?

Related to my "frankenplane" post, I'll be grinding a cambered iron soon.

However, a little point that confuses me: I often hear things like

"use only a small camber.. like 3" and then "XYZ uses a much larger camber,

like 6 or 8" for aggressive cutting".. basically "slight cambers" seem

to be quoted as smaller radius.

But wouldn't a smaller radius give you the most aggressive cut? And a large

radius be "less" of a camber? I'll attach a sketch.. maybe my terminology is

wrong? or I haven't gotten it yet.. is my sketch correct? wouldn't a 3" camber

make a much more aggressive (deep) cut?

[mlehikoinen]

You are correct. It really comes down to personal preference. I use a 4" radius, but that's because of all the different opinions, it was Oprah, er I mean Chris Schwarz that told me

[PaulMarcel]

I've never understood much of the techie-talk about cambers, either, for the reasons you state. Their terminology is contradictory. Usually the goal is to eliminate the plane tracks so you really only need the outside corners softened. Putting a radius on a blade like that would seem to give scallops, albiet very soft ones.

[Roger T]

I've never understood much of the techie-talk about cambers, either, for the reasons you state. Their terminology is contradictory. Usually the goal is to eliminate the plane tracks so you really only need the outside corners softened. Putting a radius on a blade like that would seem to give scallops, albiet very soft ones.

Paul,

Think of it this way, heavy-heavy stock removal (cambered blade ie 6" or 8" radius in a #5 or Stanley Scrub plane) big honking thick chips. Then a less cambered blade to start knocking down all the ridges left from the heavy removal, then like a #6 Fore plane to start getting things whipped into shape, then the #7 or 8 for getting everything flat and true, then the smoother for the final finish.

Or kind of like skip planing or hit/miss planing on the Elec Planer. Then taking progressively lighter cuts on the way to having the final surface.

Roger

[baok]

I recently put a camber on my smoother's iron but I don't know the radius. I just held it up to a square and when I could see light under the edges I stopped. I really got rid of the plane tracks when putting that final surface on a pure if wood.

I got on YouTube and looked up 'lie Nielsen'. They have lots of videos on how to used their planes and there was one on the scrub plane. It has a super Cambered iron and it really leaves deep scallops. Of course you expect that with a scrub.

[jhl.verona]

It's one of those "more is less" things, isn't it? If you want more camber, you need less radius, and vice versa. Easy to get wrong, but outofstepper has it right, as his excellent diagram demonstrates.

There are lots of reasons to camber a plane iron, including reducing plane tracks as Paul-Marcel noted. But to do that requires only the slightest of cambers, usually created by applying more pressure on the extreme edges of the blade during honing - a very slight camber or very large radius, as you prefer.

The radii outofstepper is discussing is in relation to scrub planes (his other question about the frankenplane). They have much bigger radii which have to be ground, rather than honed. There you go, now I'm getting it wrong, bigger camber, smaller radii. That could have got me on the Onion...

Why the heavy camber for a scrub plane? I don't really know, but the scrub has to get rid of the rough surface quickly, and leave something flatter and somewhat smoother for the jointer plane. So wtthout being a professional body builder, the camber makes sense,and the jointer will remove the high points between the scallops first due to it's length. Probably why the scrub is used at 45° or even 90° to the grain. A straight blade would either have to be narrower, or require tremendous force, and could leave deep gouges at the edges of the blade,which the jointer would have to clean up afterwards.

John

[jimmykx250]

Repeatability from a sharpening aspect seems quite difficult when it comes to a cambered blade. I know i need to do this to my millers falls #9. I am currently working on a table and i wanted to smooth out some of the joints on the top and ended up with tracks. I may end up just rolling the corners.

[Vic]

A Trick of the Trade from PWW and our own beautiful and talented Ms. Kari Hultman. http://www.popularwoodworking.com/article/video_tricks_in_action_plane_blade_cambering_jig/

[outofstepper]

Thanks everyone for the insight.

In thinking about this a little more yesterday, I realized that (in theory), your

depth of cut will probably always be the same no matter what camber is on the iron.

That is, if your iron has a tight camber (say, 3"), you're not going to stick it out

twice as far as a 6" cambered iron.

That said, (with the same depth of cut) a "more aggressive" / tight / 3" camber will

actually cut less wood than a larger one.

Think of a beading tool that makes a small 1/4" round -- thats alot of camber! but its

certainly cuts less wood than a 3" cambered iron in a scrub.

-Tony

[Bob Rozaieski]

Thanks everyone for the insight.

In thinking about this a little more yesterday, I realized that (in theory), your

depth of cut will probably always be the same no matter what camber is on the iron.

Not at all. The point of cambering more is so you can increase the depth of cut and still not have the corners of the iron digging in. In my opinion, you should forget all the talk of radius. The radius is irrelevant as soon as you are talking about a plane that is different in any way from the one that the person talking about the radius is using.

If you put an 8" radius on a scrub with a 1-1/4" wide iron, the depth of cut possible with that plane will be drastically different than a #8 plane with a 2-5/8" wide iron with the same radius camber. In this case, the #8 will be capable of taking a much deeper cut without leaving plane tracks, though you probably wouldn't want to as it would be like planing iron wood.

At the same time, two planes set up for a 1/16" depth of cut can have very different cambers. If you are using a scrub with a narrow iron and I am using a #6 with a wide iron, my plane will have a larger radius of camber than your scrub. However, both will be taking 1/16" thick cuts.

To add one more complexity, a bevel down plane with a 2" wide iron and an 8" raduis camber and a bevel up plane with a 2" wide iron and an 8" radius camber will take completely different depths of cut, with the bevel up plane's cut being much shallower. For the bevel up plane to cut as deep, it will need a much smaller radius (i.e. a much tighter curve).

So there's a lot more to it than just the radius. The witdth of the iron and it's bed angle also have to be considered. This really makes radius a poor way of communicating amount of camber because most of us don't all use exactly the same planes.

Instead of thinking about radius, think depth of cut. As an example, I'll use my fore plane (also called a jack plane). I use it for initial planing of rough sawn boards and rapid stock removal. I'm not really sure how wide the iron is, but it doesn't matter. What I do know is that I want it so I can cut deep and still have the corners of the iron out of the cut. I like it set up so I can hog up to 1/16" deep per pass on softer woods like pine and poplar. So to set up such a camber, I wedge the iron in the plane, expose enough iron from the bottom of the plane that the cut is 1/16" deep from the sole, then mark the iron at the sides where it meets the mouth of the plane with a fine point Sharpie. Remove the iron and draw a smooth curve starting top center and ending at the sides where I marked the edges. Grind the iron blunt until the edge follows said curve, then grind and hone the bevel.

When I do my try/jointer plane, I do the same thing, however, I decrease the depth of cut. This results in a flatter curve that will take a thinner shaving and therefore refine the surface left by the fore plane. When I do the smoother, I simply grind the edge square and straight, then add a very slight amount of relief to the corners by honing a little more on the corners with my stones than I do in the center.

So really, the amount of camber to use is determined by the depth of cut, not the other way around. So if you ask me how much camber I use on my jointer plane and I tell you that the plane is set up to cut about 1/64" deep at maximum projection, then it is easy for you to set up one of your planes similar to mine regardless of whether or not you are using the same plane as I am. However, if I tell you it's a 20" radius, then you and I could have very different setups if we are using different planes. Depth of cut is a much better way to think about camber in my opinion. It saves a lot of confusion and miscommunication.