Plane blade design and sharpening/flattening

[Mike Holbrook]

I just received a dozen plane blades with some plane kits I ordered. The plane irons are 2" wide, 1/4" thick, straight sides, concave backs, different lengths. The bevels/edges were very rough. Not sure what the steel is yet. They are Steve Knights remaining stock from his plane kits.

I jumped at the opportunity to work on my skills with my Tormek grinder. I have had trouble using the Tormek with the attachments and wanted to try doing the work by hand as one poster here suggested. I guess I am a hand work kind of sharpener because I immediately found the work easier when I did not have an attachment restraining the motion of the plane blade on the wheel.

A few questions have come up for me:
I believe many traditional Japanese plane blades have concave backs as part of their design. I only "flattened" the backs of the plane irons enough to level them to my new edge and remove the rolled over steel as I worked. I left the concave shape. I am not sure how or if the design of the plane backs "should" effect my work on my plane bodies? and wedges.

I am also a little unclear whether to obsess on certain aspects of grinding and sharpening the blades. Does the cutting edge of the blade need to be a perfect 90 to each side of the blade? I end up with a slightly convex bevel working by hand, as opposed to the concave bevel I get with Tormek jigs or the flat bevel I get using a Veritas jig on stones. Does a convex bevel preclude or reduce the rationale for a micro bevel? Some plane blades, particularly Japanese blades, taper toward the top, along part or all of the sides. I can see that this might reduce weight but I am not sure if there are other advantages? How important is an exact bevel angle? Obviously different bevels work better on different types of wood but does a couple of degrees on either side of standard make a significant difference?

[David Weaver]

I just received a dozen plane blades with some plane kits I ordered. The plane irons are 2" wide, 1/4" thick, straight sides, concave backs, different lengths. The bevels/edges were very rough. Not sure what the steel is yet. They are Steve Knights remaining stock from his plane kits.

I jumped at the opportunity to work on my skills with my Tormek grinder. I have had trouble using the Tormek with the attachments and wanted to try doing the work by hand as one poster here suggested. I guess I am a hand work kind of sharpener because I immediately found the work easier when I did not have an attachment restraining the motion of the plane blade on the wheel.

The benefit of the tormek with the jig is that it will put on a very tidy hollow grind that takes little work to sharpen. Because it's low speed, you won't be able to do as tidy of a job by hand. Don't give up on their jig yet for grinding the primary bevel.



I left the concave shape. I am not sure how or if the design of the plane backs "should" effect my work on my plane bodies? and wedges. unless the back (the part on the bevel side) of the iron is against the bed of the plane and VERY convex, it should have no effect at all. Fit the iron to the bed of the plane and the wedge to the iron so that everything is tight. The iron doesn't have to be perfect, the wedge is fit to it however it is. Don't lap out the concave part for no reason, unless you have a bit of unluck with its shape, it'll likely save you work.


I am also a little unclear whether to obsess on certain aspects of grinding and sharpening the blades. Does the cutting edge of the blade need to be a perfect 90 to each side of the blade?

no, it needs to be close enough that you can adjust it to be straight in the plane. If it is too far out of square for that, you'll find out with experience. Steve's planes have a LOT of room on each side of the iron so you'll never have a problem like that unless you have it ground like a skew chisel. Just develop skill to be able to tell that the iron is square by eye. I never check mine for squareness any longer, the plane will tell you when the squareness is becoming a problem.



I end up with a slightly convex bevel working by hand, as opposed to the concave bevel I get with Tormek jigs or the flat bevel I get using a Veritas jig on stones. Does a convex bevel preclude or reduce the rationale for a micro bevel?

Makes no difference with micro bevels.


Some plane blades, particularly Japanese blades, taper toward the top, along part or all of the sides. I can see that this might reduce weight but I am not sure if there are other advantages? How important is an exact bevel angle? Obviously different bevels work better on different types of wood but does a couple of degrees on either side of standard make a significant difference?

The taper along the length of the irons is so that the iron wedges into the plane body. The trimmed corners at the cutting edge are for the purpose of keeping the plane feeding well. If the iron is allowed to go all the way to the corner of the mouth, the cutting edge is tight against the abutment which goes all the way down. That's bad. You won't have that in steves design.

[Bill Haumann]

How much of a radius edge you want on an iron depends on the intended use - fore, try, jointer, smoother, etc.
The iron should not fit so tight that you can't make some lateral adjustment to get the edge parallel to the sole (some wooden plane irons taper in width so those are not truly square to the edge.
If you intend to fit the iron without a wedge, that is when the Japanese tapering toward the edge geometry would be needed.
A concave bevel will probably make it harder to freehand hone, but a micro bevel should still work.
I have some of Steve's 1/4 inch irons, and they are quite easy to freehand with a convex bevel.

- Bill

[Mike Holbrook]

Thanks for the replies guys. What I bought from Steve is probably atypical. I had talked to him just before he decided to shut down his plane kit business. I think I ended up with some of his left over stock as part of the deal, 12 irons, 13 wedges, a whole board of adjustable mouths...Although Steve's old site is gone there is a single page there now which indicates he may revive his plane business through another individual/company. I have no idea what the new business may offer.

The directions concerning plane construction, I rescued them before the site closed, caution the plane builder to be precise on some of the aspects of cutting and refining the bed for the plane iron and wedge. I am hoping that most of the work done by Steve's CNC router will not require alteration though.

[David Weaver]

I had one of steves very early kits. Bought it from someone else. It didn't line up and would've required a good bit of work to get the halves to align given where the alignment holes were, but when you first start doing custom one-offs, there will always be issues.

I would imagine as he started making lots of those, the templates (or maybe the CNC programs) were tightened up and things line up closer, but doing a good job of fitting a wedge and bedding an iron is such a precise (but not difficult) operation that it's unlikely that you would ever not have to do a little something of some sort.

Just try to make sure the iron beds on the plane bed near the mouth and reasonably far up toward the other end (the middle of the bed doesn't matter too much as long as it doesn't high-center the iron), and try to get the pressure on the iron fairly even laterally so it doesn't have a tendency to work itself out of lateral adjustment in the cut.

it's all really easier than it sounds.

[Mike Holbrook]

Fortunately, my engineer's square suggests the alignment holes on my kits are spot on. Sounds like the adjustments you suggest need to be made after the halves are glued up and the irons can be placed in their beds? Since the plane beds were cut with the CNC router I am wondering if the plane irons may be more the problem? I think the concave nature of the rear side of the blades occurs naturally from the irons construction/tempering and may not be consistent in all blades although the ones I have worked with so far seem to be. I would imagine the solution requires that the plane bed and plane iron are both worked into a snug fit? I'm certainly not short on plane irons and I guess they will all be a little different, even/especially after I regrind the bevels and backs. I plan to do the final iron fitting/flattening with the Sigma Power & Select II stones I got recently from Stu.

I also picked up a couple Iwasaki plane/carving files. I just got the flat ones but will probably invest in a couple rounded ones too. They are much kinder to my wallet than the Auriou rasps or even Lee Nielsen's plane/joinery floats. The very reasonable set of small Nicholson files has also proven helpful. I think my favorite tool for this work thus far is a couple Microplanes I have. They cut much like floats but have very sharp replaceable blades. Highland Woodworking is carrying one now that has a set of Snap In Rasp Blades in coarse & fine, flat, angle, round. The blades are $9.99 and the Microplane is only $12.99. The 8" blades will be a little large for some work though. The Iwasaki's are much smaller and should work in smaller recesses. I have my Ashley Isles chisels and block planes all sharpened up too.

PS
Just found out on the Microplane home page for woodworking tools that they are making a rasp/plane that uses 3" Snap In Blades too.

[john brenton]

"I am also a little unclear whether to obsess on certain aspects of grinding and sharpening the blades. Does the cutting edge of the blade need to be a perfect 90 to each side of the blade?"

It's fairly critical on rabbit planes and other joinery planes, but not really for other wooden bench planes. I know I have one or two woodies where the back of the iron is sticking out all skewed to the side, but I haven't checked to see if the culprit is the squareness of the edge or the sole of the plane itself.

[David Weaver]

I have the microplane rasp. I don't like it, it's not close to rigid enough. I cleaned mine off and put it in the kitchen for zesting.

That's about all I can say about those.

As far as the reason for bedding and whether it's the iron or the plane, if the plane is cut into halves, you'll still have some variation, but it's no matter where the error is coming from, the exercise of tuning the bed ,and especially the wedge fit, is a good skill and something that should be done. It's just made a lot easier if everything is close to start.

[Tom Vanzant]

Mike H.: Unless Steve changed at some point, the Knight irons are O1 steel. Flattened and honed, there are great!

David W.: My microplane is also in the kitchen. Zesting has never been easier.

[Mike Holbrook]

Again, to each his own. I like the Microplanes better than the similar rasps or files I have tried thus far. I will take a Shinto saw rasp for heavy, rough stock removal. I like the smother surface and lack of tear out, more like a scraper, that I get with the Microplanes.