Building a Thos. Moser Design New Gloucester Rocking Chair #9: Producing Wedges and Sawing Kerfs

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Blog entry by DustyMark posted 12-26-2012 05:56 PM 6273 reads 0 times favorited 5 comments Add to Favorites Watch
« Part 8: Fitting a Laminated Leg Brace Part 9 of Building a Thos. Moser Design New Gloucester Rocking Chair series Part 10: Designing and Cutting the Rocker »

Wedges provide a bit of extra security in a leg joint. If the glue ever fails, the mechanical power of the wedge will hold the chair together longer.

Producing Wedges

I prefer a wedge with 4 degrees of taper. This shallow taper has a lot of power. However, you must get the thickness at the entry of the wedge close to the right thickness. If it is too thin, the wedge will bottom out in the joint before reaching its proper tightness.

Begin the process by surfacing wood to the thickness of the width of the tenon. A 1” tenon rquires 1” thick stock. Wedges need to be cut with the grain to remain strong. Crosscut a piece of wood to the final length of the wedge. This wood is then ripped on the tablesaw using the miter guage with an auxiliary fence.

Set the miter guage to 2 degrees. Make the first cut and throw the wedge away.

Flip the wood over.

Make another cut. Make a mark on the auxiliary fence to reproduce wedges with the same thickness.

Here’s what the wedge looks like right off the saw.

This stack of wedges will hold the the seat tenons in place on two rocking chairs.

Marking Kerfs

The wedges need to run perpendicular to the grain. If they run parallel to the grain, they will likely split the seat or the rocker.

Marking out the seat tenon.

Marking out the rocker tenon.

Sawing Kerfs

I have cut the kerfs by hand on some previous projects. However, I like to cut them on the bandsaw with a V-block now.

Here’s a view of the technique in action. The roller stand keeps the V-block steady. The v-block keeps the leg from rolling.

Sight the blade with your mark to ensure correct orientation.

Close-up of a cut. I make a slight wedge-shaped cut for the seat tenons and a simple kerf for rocker and spindle tenons.

A chair’s-worth of legs kerfed and ready for assembly.

I need to complete the rockers next…

-- Mark, Minnesota

5 comments so far

View lysdexic's profile


5254 posts in 2619 days

#1 posted 12-27-2012 03:57 PM


I am just getting caught up. Wonderful blog and thanks for taking the time.

-- "It's only wood. Use it." - Smitty || Instagram - out_of_focus1.618

View DustyMark's profile


346 posts in 2066 days

#2 posted 12-28-2012 05:11 AM


Thanks, it’s fun documenting a challenging project like this rocking chair. I’m designing at the bench since I don’t have a plan and I’ll likely be making some changes in the next batch. I’ve got a few weeks off from my part-time job and I’m taking full advantage of it by spending quite a bit of time working on these rocking chairs. I’m ready to assemble the bottom half on Friday.

-- Mark, Minnesota

View stefang's profile


15881 posts in 3330 days

#3 posted 12-31-2012 03:48 PM

One question Mark. Why did you choose straight tenons over tapered tenons? My reason for asking is that it seems to me that as tapered tenons dried out, that the weight from sitting on the chair would tend to tight the joints whereas the straight tenons would get no benefit from constantly sitting on the chair. Please don’t take this as a criticism as I am not a chair builder, and I know from experience that what works is good. I just thought that I might gain some insight from someone with your experience. I do have a production pine rocking chair that was purchased about 25 years ago with straight tenons and it has held together tight as a drum.

-- Mike, an American living in Norway.

View DustyMark's profile


346 posts in 2066 days

#4 posted 12-31-2012 05:01 PM


I have a tapered tenon bit for my bit brace. I bought that and a set of spoon bits when I thought I was going to build a Windsor chair with green wood. You’re right about the advantages of a tapered tenon for a seat tenon. To me, it’s simpler to turn out a straight tenon and further secure it with the wedge and braces. Most of my bowback chairs will hit 20 years in 2013 and none of the joints have loosened. That gives me confidence in wedged straight tenons.

-- Mark, Minnesota

View a1Jim's profile


117090 posts in 3573 days

#5 posted 12-31-2012 05:23 PM

Just catching up on your blog ,I’m thoroughly enjoying each installment.

-- wood crafting & woodworking classes

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