working curved chair surfaces

[Mike Holbrook]

I recently took a class, Making a Continuous Arm Windsor Chair. I was very impressed with the level of detail a few relatively simple hand tools accomplished in experienced hands.

The tricky work always seems to be in those curved surfaces where grain direction changes or falls off. The instructors could work in very tight, curved, tricky grains with a large drawknife without causing tear out, often achieving exceptionally smooth curved surfaces with a single impressively large cut. I admit I am still struggling to master some of these techniques with my personal collection of drawknives and spokeshaves.

Although experience/skill level is obviously a major factor in ones ability to produce the curved surfaces on a Windsor Chair two other factors are also very important, tool design and how the tools surface is beveled and sharpened. Sometimes, as is the case with drawknives, subtle tool design differences and sharpening technique changes can make a major difference in how the tool functions.

A frequent topic of discussion on these pages is how to effectively design the intersection of the two surfaces of an edged tool to make it a more useful cutting devise. This topic reaches a whole new level of intrigue when attempting to make bevels and cutting surfaces that can reach into a tight curve with complicated grain and remove a chunk of wood, leaving a smooth surface behind.

For instance, some experienced chair makers place a small bevel on the backside of their drawknife, which others may prefer dead flat. In my limited experience, a small bevel on the backside of a drawknife can make a dramatic effect in it's ability to "scoop" out wood in tight curves with complicated grain. Similarly, small changes in the relative curvature and angle of the sole of a spokeshave can also make an impressive change in how it can work a curved surface. The instructions that come with both the Lie-Nielsen Boggs and Small Bronze spokeshaves with curved soles explains that if the owner can not see the curve in the sole, placing a straight edge against the surface will reveal that the soles are curved. The instructions also suggest that the owner can adjust how wide or tight a radius a specific spokeshave can cut by adjusting the curvature and angle of the sole. I am interested to find that all the drawknives and spokeshaves I have seem to work differently, even the ones that might appear quite similar.

I am also learning that the relative hardness of the metal on the edge of each tool can also be significant. The prying action against the edge of a drawknife being used in tight turns with difficult grain can be tough on hard/brittle steal. I find that a tougher steel may be less prone to chipping off pieces of an acute edge. I also find that an edge used for this purpose needs to be a little less acute.

[Steve Voigt]

Hey Mike,
Who taught the class? Any pics of your chair?

[Jim Koepke]

My use of a drawknife is a bit limited. My use of spokeshaves is growing.

One thing discovered with both of them is how skewing the cut can be a great helper in making smooth surface. Especially with a drawknife skewing the cut while sliding the blade to slice the wood instead of splitting the wood can make a big difference. The experience comes into play from understanding the wood and knowing how it will react to the tool as it is being used.

Chisels, gouges, rasps and other tools all have there little use enhancements for us to learn.

jtk

[Mike Holbrook]

Steve, Peter Galbert and his buddy Seth taught the class, 10 people strong at Highland Woodworking. When I finally get the chair finished I will post pictures. It is a long story and maybe not appropriate to discuss here.

Jim, yes, I developed a decent feel for skewing the drawknife blade and drawing it through the wood as well. Those techniques certainly contribute to obtaining a smooth surface particularly in testy grain. The technique I am still working on is removing specific smaller pieces, particularly where the grain is tricky. The trick is getting the knife down into and out of the wood without splintering or breaking off pieces. This is where small changes in the bevel/edge on either side of the drawknife seems to make a large difference. Peter took one of my drawknives and made a few small changes while sharpening it for me. I was amazed at how much difference the small changes made in how well the drawknife worked at entering and exiting cuts. One of my drawknives, a Barr 6" Carver's Drawknife, has gently radiused edges and small bevels, on both sides of the blade. Drawknives designed or sharpened like the Barr Carvers blade work much better at making the more delicate, quick in and out cuts. Drawknives with flat backs and sharper edge angles, seem to me, to work better at slicing off long, full length, pieces. This style edge seems to work more like a wedge/froe splitting the wood along grain lines. I was amazed to see how much wood can be accurately and quickly removed from large work pieces with a drawknife. Peter and Seth seemed to favor drawknives with slightly steeper front bevels and small bevels on the back/flat side as those edges/bevels are very versatile.

Spokeshaves seem to me to be potentially more complicated to tune than drawknives, maybe because there is a sole to deal with in addition to the actual cutting edge. Talking to Glenn at Woodjoy about his #85 spokeshave, I was surprised to find that the "flat" style sole was not actually flat but, as I recall, 3-4 degrees from flat by design. Some of the Compass style spokeshaves do not seem to have much variation from flat either. It seems odd to me that most spokeshave soles either have small deviations from flat or have edges that are close to semi-circular. Then there is the option of actually skewing the edge of the blade in relationship to the sole. A skewed blade offering a deeper cut on one side and a more delicate cut on the other.

[Jim Matthews]

The advantage built into the spokeshave is the depth of cut limitation.

The advantage built into a drawknife is that you can cut quite deep.
I would guess that the projects progress from what you can make
with a flat backed drawknife (like mine, which I use on things too narrow to saw)
to the advanced sharpening profiles described.

The more I do, the more I lean on a flat edge meeting a convex bevel - because I can get repeated results.

I saw Brian Boggs freehand sharpen a drawknife in a spindle making demonstration.
He continued working the crowd while touching it up and promptly went back to work.

Three garbage cans of shavings a day, that weekend.

[Steve Voigt]

Steve, Peter Galbert and his buddy Seth taught the class...

That sounds like a blast, Mike. Peter's blog and videos are a great source of info.
Question: when you drill the seat for the leg mortises, prior to reaming, what size drill do you use? Drew Langsner's book sez 11/16", but that seems small to me, so I was curious what Peter uses. Also, what's the finish size on the leg tenons (at the smallest point)?
I spent most of the weekend working on the chairs I started last summer…you better post yours before I finish mine! :)

- Steve

[Mike Holbrook]

Steve,
Sorry to take such a long time to respond. I misplaced the notes Peter gave us at the class and just found them. During the drilling of seat and stretcher holes during the class I just picked up a bit Peter designated as correct for the job not necessarily knowing what size it was. Peter modifies bits, on a grinder, specifically for the job. I think it is important to know that each tapered hole we made was customized using specific wood chair reamers made by Tim Manney in collaboration with Peter. Thus I have no idea exactly what size the holes in my seat and stretcher are, which is why I have been procrastinating in answering your questions.

Checking the notes Peter gave us there is information on drilling seats and stretchers. However, there is no mention of specific bit sizes. Had I known how much specific info. was missing from Peter's notes I would have taken more notes from the examples Peter drew and labeled during class. Peter was very quick in class to refer people to specific information in his Blog. Unfortunately finding specific info. in that large library of information can be a challenge. During the mad rush to get specific work done in the short allotted time I am afraid I did not take the time to copy the diagrams Peter made during class to illustrate the work. I was hoping the notes in the hand out would contain specific numbers...

I got sick during the class and I still have not totally rid myself of the chest congestion, which has me behind in everything! Now my green wood is dry and I am working out how to finish my chair. Just about everything I was taught technique wise in class assumed the wood being worked would be green.

[Steve Voigt]

Steve,
Sorry to take such a long time to respond. I misplaced the notes Peter gave us at the class and just found them. During the drilling of seat and stretcher holes during the class I just picked up a bit Peter designated as correct for the job not necessarily knowing what size it was. Peter modifies bits, on a grinder, specifically for the job. I think it is important to know that each tapered hole we made was customized using specific wood chair reamers made by Tim Manney in collaboration with Peter. Thus I have no idea exactly what size the holes in my seat and stretcher are, which is why I have been procrastinating in answering your questions.


Hey Mike, no worries. A guy who was probably in your class posted some pics on woodnet…he said Peter uses 11/16", which is what Drew Langsner also uses, so I'll definitely go with that.



I got sick during the class and I still have not totally rid myself of the chest congestion, which has me behind in everything! Now my green wood is dry and I am working out how to finish my chair. Just about everything I was taught technique wise in class assumed the wood being worked would be green.

I wouldn't worry too much. I split and rived a bunch of white oak a year ago, roughed out all the parts, and then let it sit until now. Last week, I drawknifed a couple of the crest rail blanks and bent one; it seemed to work just fine.

[Mike Holbrook]

Apparently someone at that class took better notes than I did, or simply has a better memory.

Fortunately the major wood I need to remove is on my seat, which is pine. I also need to come up with some small wedges for my spindles. A few of my spindles developed some serious curve in them which I have been trying to flex out. I bought a steamer to make a steam box with but have not gotten around to it yet. Not sure whether or not I should re-bend a few spindles or not. According to Peter bending wood that has dried can work as well as or better than bending it when it is green.