Camber for plane blades, how much is enough/too much

[Mike Holbrook]

I spent a large part of my day yesterday sharpening and cambering plane blades for my family of Stanley planes. I use a mix of premium, wood, & restored planes. I typically use my restored planes more for rougher work reserving the premium planes for fine work. One reason for this strategy is my three Lee Valley BU planes have blades that can be a challenge to camber. I am aware that this can be done, and have read Derek Cohen's methods for doing this on his Blog. Still it makes more sense to me to set the premium planes up with smaller cambers for finer work. Obviously the thinner, often softer metal in older planes can be easier to grind camber into.

I probably should add that I have a grinder and CNC wheels. I realize that some may find these devises unnecessary but I am a tremendous fan. The speed and precision with which I was making cambered edges yesterday is something I have struggled with for years. Just being able to get immediate feed back, due to the faster cutting wheels, has dramatically improved my ability to make better/sharper tool edges.

I spent a while on Derek's site yesterday rereading various articles he has written on sharpening, especially since he started using CNC wheels. Like Derek I am largely a hand sharpener who likes to get done with the sharpening and back to cutting the wood. I was interested to read how Derek had evolved in his thinking about how much camber to put in a blade. From what I read I believe Derek himself is still working out precise cambers for specific planes and the blades they use.

The question that seems to rise is matching the camber to the width of a particular blade. Too much camber and the plane either does not take a full width shaving or the amount of wood, the shaving, the plane tries to take is more than can comfortably be managed. The issue for me is my desire to have planes that can remove larger amounts of wood. I was tuning up Stanley #5 1/4, 4 1/2, 5 1/2 & 6 planes yesterday experimenting with whether the thinner blade on the 5 1/4 made taking a larger shaving easier than attempting something similar with a #6 with 2 3/8" blade or a # 5 1/2 with a 2 1/4" blade. My base for testing being a Stanely #5 with a hand ground/sharpened blade that has been my go to for stock removal.

Thus far my results have not been conclusive. My 5 1/4 has major camber at this point, so I am not getting a full width shaving, even with the 1 3/4" blade. The 5 1/2 has much less camber and takes a full width shaving, but so far not too thick. I am having a problem with Stanley's fairly small mouths. Blades with large amounts of camber tend to clog the mouth due to lack of room for a large shaving to pass. I am thinking about opening up the mouth of one of my Stanley's, once I figure out which one might be best at taking larger shavings.

[Garrett Ellis]

you will never get a full width shaving with camber. that's the point of it.

the rougher the operation, the more camber you want. you just want to hog off material. for a scrub/jack/fore plane, somewhere around 8 inch radius is what i usually read. that's what my jack plane has.

for smoothing planes, less camber. just enough to avoid plane tracks.

if you have enough planes, its nice to keep 1 jointer with a square blade for jointing edges, but that's just a preference thing.

[ian maybury]

It's been said before, and i'd leave it to others more experienced to make recommendations on specific camber amounts Mike (but broadly it's got to correlate with the required maximum depth of cut expected of the plane) - but i think a huge factor in the call is your style of working. As ever in these matters it comes down to setting the tool up to do the specifc job that needs doing.

Many of us these days mix hand tool and machine working - and if that's the case then camber is perhaps more about avoiding corner marks while removing small amounts of material or smoothing - or maybe squaring up an edge.

If on the other hand it's about committed hand tool do everything working then as well as the above the requirement to hog off large amounts of material will arise. This is where heavy camber seems to become very useful - or when the requirement is to create surface texture. I set up my first scrub plane last year (the Veritas one - i just honed up the iron with the stock camber on) and was blown away by how it effortlessly peeled off cuts so thick partially cross grain as to be unimaginable.

It's possible to set up bench planes with heavy cambers to function as quasi scrub planes/to remove more wood, but there seem to be definite limits with these where either a restricted mouth opening or use of a chip breaker (which latter will more or less 'stop' the plane if the chip gets too thick) decides the maximum depth of cut that's realistically possible….

[Mike Holbrook]

Garret, I understand your reasoning and the convention of a 6-8" radius for hogging and a "slight" camber for smoothing, flat for jointing. I have traced these radiuses onto a plane blade and then tried to grind them in. I can come fairly close. The question even within your parameters becomes the same, exactly what size radius do I use for X width blade. Do I take the weight/width of the plane into consideration. I am not a fan of "scrub" planes as I find the plane designs very light for trying to remove larger amounts of wood. I like a plane with some weight if I am going to be trying to push through tough grain or remove a thick shaving.

It seems to me that the "average" woodworker may not need to remove large shavings to simply level a few boards so the issue may not come up. Lunch box planers are relatively cheap these days. However, over the years I have read many a horror story of how much time it took some fellow woodworker to flatten a bench/table top with hand planes that I am betting were not set up for removing large amounts of wood.

I just took a new experimental class with Chris Schwarz on making sawbenches. The point of the class was not so much to make a sawbench as to learn a woodworking technique for adding legs to all sorts of furniture. We started with 2/2" inch oak boards. We were to plane these into tapered octagons, try it sometime. Suffice it to say, even in a two day course, no one got two sawbenches done, even though making the legs was just about all there was to making the sawbenches. Chris had just one #5 set up to take a large amount of wood. A few months later I made similar legs for a "Welsh Windsor/Stick chair at Country Workshops. I was much better prepared, having set up my #5 Stanley like Garrett mentions. Still there was plenty of room for improvement. There is a reason most chair makers turn the legs & rungs for the chairs they make. I would like to be able to do the job the old way, by hand. I am working on a bench design....Somehow this work was done in the past without all the machines. Drawknives probably did a good deal of the work, but drawknives are mostly for green wood, try taking large shavings from dried wood with a drawknife.

[Mike Holbrook]

Thanks for your thoughts too Ian. I think I unwittingly responded in my post answering Garrett.

Here is the other issue I have found. I traced some radius on my #5 when I ground it. I can't remember now what that radius was. I know I changed it a little while making it and adjusted it a few times later. I guess I could trace the pattern on another plane blade, but chances are good that blade will be a different width. Derek has apparently tried to resolve this issue by making wood templets to trace onto his blades. Still different blades are different widths, thicknesses.....Even in Derek's more technical approach, he mentions that there is still room for thought in figuring out optimal cambers. My guess is in the past people learned to eyeball functional patterns from other successful patterns, few/none of which exist today. As others have mentioned, the final answer probably will not be a specific radius for the entire width of the blade. I am thinking something with more rounded corners and less radius in the middle. I have a couple planes made years ago by Steve Knight. Steve cut the corners off those plane blades, unless Tom Vanzant, the original owner, did it.

It seems to me that the optimal "pattern" for any plane blade isn't something that can be created with any kind of jig or tool rest out there. I think we are talking hand/eye work. Derek tries to explain his methods for less dramatic patterns in terms of strokes on a specific stone, readily admitting the lack of precision. This is why I think this is a hard topic to discuss but one deserving the time and thought to resolve/improve our methods.

[Tom M King]

Mine vary from half a thousandth on a 4-1/2 to maybe an inch and a half radius on a Scrub plane. My 8 is straight, 7 maybe one thou. 5 about 10 inch, and a couple of 6's between 4 and 8 thou. Deepest smoother is one of the 3's at 9 thou, to match some old smoother texture. several smoothers between that 3 and the 4-1/2. All of these are either Records or Stanleys. Most of the Records I bought new. I look at the iron protrusion sighting down the sole, and measure shavings. None of this was done all at one time, but on various rainy days over the years. When I use a jig on a cambered iron, it's an old Record with about a half inch ball for a roller.

[Daniel Rode]

Is your concern to convert a particular camber between blade widths?

I don't think of the iron camber as a particular radius but a particular shape to perform a specific function. This includes the width, the projection and the shape of the edge (flat, cambered, flat with feathered edged, etc). So I first think about what I want to accomplish and then what plane with what type of iron shape will do this for me. I couldn't tell you what the radius is on anything. I mostly start with an idea of what I think will work and adjust from there. Sometimes that adjustment is a little tweak when honing, sometimes it's been regrinding. When I first setup my #5 hogging/scrub plane, I used a camber that was too aggressive and had to regrind flatter.

I'm darn sure no expert, I'm just learning myself, so I might have the whole thing wrong. I seem to have better results when I work by feel than by ruler.

[ian maybury]

I suspect it again comes down to what the iron is intended for Mike. If the camber is used to square joint the edge of a board then it's got to pay to use a profile that deliveres a predictable response in terms of change of slope/angle/inclination to moving the plane over towards one or other side of the blade. Rounded corners will obviously not be very useful for that, but they do seem to be a very valid option for smoothing.

There may be subtler considerations, but with a scrub plane it's maybe about coming up with the profile that removes the greatest volume of wood for the least effort - while leaving a surface that's a decent starting point for flattening and smoothing afterwards. e.g. no deep or inconsistent gouging or splintering.

I guess there's a lot to be said for a profile using a standard radius that can be applied using a simple holding device that rotates about a point. A CBN wheel though given that it cuts so fast should as you say though make it very feasible to using a honing guide or something to maintain the bevel angle grind back to a marked line to create a custom profile if needed - maybe even (if we're to speak very hypothetically/experimentally) with enough creativity in the set up one that includes concave sections ground off a corner of the wheel.

I've no idea though how unusual profiles like this might perform though...

[Mike Holbrook]

Good info. Tom. You have some major cambers 1 1/2-4 "is steep. You must work from wood that is not squared or dimensioned? You must grind these by hand & eye?

I have a Record #7 and a 4 1/2 I bought "new" too, which was about all there was at that time, at least within my budget at that age.

[Tom M King]

scrubplane2.jpgHere's a picture of the Scrub plane. It's actually used as a SCrubber of dirty beams before I put a good iron in the wood. I'm just guessing the actual radius on that one. Just by hand on stones, for all but the 5, and the old red Record honing guide to start with. I don't have a picture of that guide on here yet. I work with old stuff, on old houses. An example of using several of these planes can be found in the picture linked below. The original panel had rotted away from windows being knocked out of the house for 40 yeARS. I found this board in the attic behind a knee wall. It's hard to find 17" wide Heart Pine boards, so I felt lucky to find this one. It was used as a floor board, and probably stuck behind the knee wall since it was split all the way down the middle. I fixed the split so it could only be seen if I tell you where to look, but only by leaving a hump going all the way along the length of the board. Others have humps too, so that was okay. It had to be straight on the ends to allow for the tongue into the stiles, and to allow the little molding to fit (not yet installed in this picture). If I cut all the hump down, it would have exposed some of the West epoxy in the middle of the panel. Both ends glued together close enough that I could flatten them on down to straight. I used a number of planes on that one panel, but don't remember exactly which ones. Surface texture is from one of the smoothers that matches the adjoining wainscot panels on that one 20 foot long wall.

It's the panel above the electric box: http://historic-house-restoration.co...._2012_052.JPG

The texture on these steps is from the deep cutting 3, and matches other such smoother texture found on some original boards in that 1828 house: http://historic-house-restoration.co...nghead_001.JPG

I hone under running water in a sink on waterstones-currently Sigmas. I judge where I'm cutting by the dark swarf tracks on the stone. The water doesn't wash them off, and when there are is so much marking left on the stone, it goes in the adjoining sink to be quickly flattened back to a clean face.

[Jim Belair]

My opinion is for stock removal anyway (as opposed to jointing) the ideal camber does result in a full width shaving. If smoothing and taking a one thou shaving, that shaving tapers to zero right at the edges of the blade. And if its a scrub and you're taking off 0.1" per pass, again the shaving tapers to zero at the edges of the blade. A jack plane for moderate removal would be somewhere in the middle, but again, the shaving tapers to zero at the edges. Pick the plane/blade/camber combination for the task at hand.

[Tom M King]

absolutely. With a heavily cambered iron though, you don't always push the planes sole all the way to the wood surface, depending on how hard the wood is, and the cut you need on any given stroke. It's easy to see how the camber goes all the way across by sighting along the plane's sole with the corners of the cutting edge flush with the plane bottom. I was....can't think of the word....when I saw some video of someone just rounding off the corners. Why use a 2" wide iron if you aren't going to use the whole width?

[Doug Trembath]

I follow these threads closely, as I do a significant amount of flattening rough sawn slabs for furniture, and rough sawn boards too wide for my jointer and planer. I have tried a few setups with cambered irons. I think that Mike is trying to relate a camber size, based upon a part of a circle, consistently among the different sizes of blades, ie. 3" radius, 4", etc. for all blades. His question, as I read and reread it is "how much camber is right?"

I seldom use it other than finish smoothing, and that's a thou or three. I don't measure stuff like that, it's my best guess.

Obviously a stock Stanley #40 has a radical camber, at least mine does, and will take a heck of a bite at one time. It's great if you need to take severe wind out of a board. It will quickly reduce the high corner, but leave a troubled surface. Using a #6 with a little camber ( just enough to reduce the blade's effective width), leaves a much nicer surface but will still take a significant shaving, and still remove a lot of wood without making it a dedicated scrub plane. One reason I don't really buy in to the heavy camber argument is that I don't really need it, even with distorted timber. I can use a flat blade on rough timber and still take a significant shaving and quickly rough a surface down for a try plane. At that point, who cares about plane tracks?

Another reason is that although I have acquired more than 40 vintage handplanes, I have never found one on the market with any camber applied with the exception of smoothers. I did get one from the estate of a friend of a friend after he passed, a broken 605 that had significant camber, but that is the only one I have personally acquired with any camber at all. It worked great, but not really a whole lot better than a straight blade, hence my questioning the necessity for camber on all planes. I'd be interested to hear your thoughts.

Doug Trembath

[Andrew Hughes]

I'm pretty sure all my blades have a camber, it's better than a blade with a concave edge.If I really want a straight edeg I pay attention to want I'm doing on the stones.Same with a heavy cambered edge.Just got to pay more attention.

[Mike Holbrook]

Most of what I have read on SMC relates cambers to radiuses (usually drawn with a pencil/pen compass) as Doug gleaned from my posts. It took me a while to figure out what people meant when they referred to 6-8" cambers so I understand how this might not be crystal for others. The radiuses term at least gives us something to gage what we are talking about doing differently, compared to a straight plane edge.

As I read Derek's post on his Blog., he seemed to be attempting to make a camber that could take a full width shaving. If the entire curve of a given radius is not beyond the planes mouth then it isn't going to take a full width shaving. In the case of major radiuses the distance the blade needs to protrude for the entire camber to be exposed can be large. On my Stanley planes the relatively small mouth openings cause larger cambers to start jamming shavings before the entire camber is exposed, if I can even get the entire camber out of the mouth without it contacting the plane body. I seem to eventually end up with the center of my cambers becoming flattened instead of an exact radius. In the case of smoothing plane blades the curve of the radius can become so small it may not even be visible, or the corners of the blade may simply be relieved. As some one mentions above, if there is no camber at all in the center of the blade we may end up with a concave edge which does not reach the wood.