Jensen-style Z-Chair

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Blog series by Ross Leidy updated 08-09-2019 12:45 AM 29 parts 32209 reads 105 comments total

Part 1: Introduction

05-17-2019 08:07 PM by Ross Leidy | 13 comments »

Like a handful of other folks here, I’ve been bitten by the bug to build a chair modeled after the Selig Z-chair designed by Poul Jensen back in the 1950’s. I’m a fan of Danish design in general, and for some time this chair in particular has been stuck in my head. The Z-chair projects shared here were definitely an inspiration, and they provided the nudge I needed to make that crucial first step – deciding to get started. Most notably, I’d like to thank Jam...

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Part 2: Planning and Prototyping

05-18-2019 02:41 AM by Ross Leidy | 3 comments »

My first thought was that I would try to find some plans for this chair on the internet. Nope. All I found were some plans for a really atrocious mockery of the design. Not even close to the proportions and style of the original. So, armed with some basic dimensions that I found here and there, a decent side-view photo that I could scale and trace to get the angles right (or close), and hours of google searches studying images of this chair for telling details, I set to work. I have a ...

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Part 3: A Jig Interlude

05-18-2019 03:16 PM by Ross Leidy | 4 comments »

Since I was switching gears to use butt joints with floating tenons instead of the puzzle joints, I started looking at various router jigs for cutting the mortises. I found a lot of helpful videos on homemade jigs, and eventually I modeled mine largely on the Morely Mortising Jig However, for mine I wanted to use interchangeable templates for repeatability and ease-of-use, rather than use the siding side stops that Morely uses. Other than that, the structure of mine is like the Morely jig....

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Part 4: Slats

05-18-2019 07:04 PM by Ross Leidy | 11 comments »

With the mortising jig ready, I could get back to the chair project. I had some rough-sawn cherry that was gifted to me by my brother-in-law years back, and I thought I’d use it for this project. It’s not particularly nice looking wood – kind of mottled – but it was free, so perfect. For the slats, I re-sawed and drum sanded some pieces to 3/4” thick. The slats were to be 3/4” deep at each end, 1-1/2” deep at the peak, and 17” long. Cutti...

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Part 5: Seat frame - strap recesses

05-19-2019 03:47 PM by Ross Leidy | 6 comments »

Since I was already working with 3/4” material on the slats, I opted to start on the seat frame next. I estimated a width of 2-1/2” for the seat frame, which now I think was a little wider than the original. I’m guessing it was more like 2-1/8” to 2-1/4”. The images I found don’t seem to be entirely consistent, so the manufacturer may have used different widths. I’m not sweating it though since the width of the frame won’t be visible once a ...

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Part 6: Seat frame - shaping and joinery

05-19-2019 07:38 PM by Ross Leidy | 4 comments »

I’ve been captivated by one detail of the original design that’s easy to overlook. But as small as it is, I think it contributes to the overall lightness of the form. It’s that the side pieces of the seat frame are slightly thinner than the front and rear pieces, and that the side pieces are inset slightly so that there’s a slight reveal at the joint with the front and rear pieces. I tried to find a good photo to show a blowup of the area – this one is okay, b...

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Part 7: Rails

05-20-2019 04:36 PM by Ross Leidy | 9 comments »

Feel free to correct my terminology, which could be wrong since I’m not chair anatomy savvy. I did research a bit, but there didn’t seem to be consistency in the terms. For this build, I’ll refer to upper/top rail as the one at the top of the back, rear rail as the one at the back of the seat, and front rail as the one at the front of the seat. All rails are 22” long. The front rail is 3” x 3/4”. I played around with the shape for the arc cutout, s...

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Part 8: Side structure - Getting started

05-24-2019 04:30 PM by Ross Leidy | 1 comment »

Once I tweak the design for future chairs, I’ll cut templates on the CNC for the the legs and back stile and use a pattern bit on the the router table to cut them out. For this initial chair, I cut out the pieces directly on the CNC. The one benefit of this is that I can have the CNC cut the mortises as well. But mortising slots could be worked into the templates as well. Since there’s a lot more waste and setup time on the CNC, I wouldn’t want to do this every time. ...

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Part 9: Dry fit pieces to date

05-24-2019 04:47 PM by Ross Leidy | 3 comments »

In the interest of procrastinating work on the arms, which I think will be the more challenging part, I took some time to dry-fit the pieces I had so far. It’s starting to look chair-like now. I discovered a slight issue with the seat frame that I need to remedy. Because of the rounded edge, the back part of the frame sits out pretty far on the little ledge on the rear rail. I will likely just cut a bevel on the rear piece of the seat frame so that it snugs-up to the rear ...

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Part 10: Starting the arms

05-26-2019 07:59 PM by Ross Leidy | 5 comments »

I’ve been saving this part for last because to me it seems like the most difficult piece to shape. I have a approach in mind, but I’ve been letting the idea rattle around for awhile to see if any refinements occur to me. I’ve cogitated long enough. Time to start cutting wood. I went old-school with the template, opting to print out the arm outline on multiple sheets, tape them together, glue the paper template to MDF, rough cut it, then sand down the the line. I think...

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Part 11: Sanity check

05-28-2019 10:24 PM by Ross Leidy | 1 comment »

I used a piece of scrap to confirm the bevel angles where the arm will join the rest of the side structure. There’s the computer model and then there’s reality, and sometimes they don’t align. Fortunately, this time they did. For the long bevel in front, I rough-cut it on the bandsaw and use the disc sander to sneak up on the line. I won’t cut the bevels on the arm pieces yet. I’ll do that after I get the top shaped. I did want to get the 1/2”...

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Part 12: Seat frame - slight adjustment

06-08-2019 10:16 PM by Ross Leidy | 0 comments »

I beveled the rear piece of the seat frame so that the edge will sit flat against the rear lower rail. This will keep the weight as close as possible to the glue line of the lip that’s on the lower edge of the rail. That’s better.

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Part 13: Rear upper rail mortises

06-08-2019 10:25 PM by Ross Leidy | 0 comments »

I waited until the back was dry assembled before marking the locations for the upper rail mortises. They needed to be located based on the already-cut mortises on the back stiles that were done on the CNC machine.

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Part 14: Back stile dowel holes

06-08-2019 10:36 PM by Ross Leidy | 5 comments »

The 1/2” dowel holes in the back stiles where the arms attach are not at right angles to the joint. I transferred a line to the side of the stile that was parallel to the dowel, and then clamped some blocks to either side of the stile to elevate one end so that the line was at right angles to the work surface. Then drilled the dowel holes on the drill press.

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Part 15: Arm rough shaping and fitting

06-09-2019 07:52 PM by Ross Leidy | 4 comments »

The arms on the original chair have a little raised lip along the outside edge that tapers-off to nothing at the front tip of the arms. I’ll try to do something similar. I used the CNC to sculpt the long, shallow concave section on the top of the arm using a 2” diameter cove bit. With the rough shaping done on the top, I moved on to beveling the two ends of the arms where they join the back and arm support. I cut shy of the sketched c...

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Part 16: Arm mortises

06-11-2019 04:46 PM by Ross Leidy | 3 comments »

Here the underside of the arms has been trimmed away to leave about a 5/8” thickness along the inside edge. Mortising the underside of the arm: Mortising the arm support/rear leg: And that’s the last of the mortises for the chair.

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Part 17: Arm shaping

06-14-2019 01:25 AM by Ross Leidy | 2 comments »

This feels more like woodworking. I started with some layout lines for a chamfer along the lower/outer edge of the arms. I was conservative with their placement so that I wouldn’t remove too much wood initially. Ultimately, this will all be rounded-over.The extra length at the tip I allowed for slop, and it will remain for clamping and then trimmed. Proof that I do sometimes use hand tools. A freshly-sharpened plane iron is a wonderful thing. There’s room for a b...

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Part 18: Dry fit with arms

06-15-2019 06:04 PM by Ross Leidy | 5 comments »

Time for another dry fit to see how the arms are looking. It’s looking more and more like a chair. I’ll need to do some adjustment on the back stiles at the arm joint. Due to my 1” stock, the joint height needs to be reduced from the design height. I did a sit test, too, because I was/am worried about the long arm-support-rear-leg piece being compromised with the two close mortises where the lower rear rail and back stiles attach. There was creaking due to n...

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Part 19: Seat frame - mounting holes

06-21-2019 02:47 AM by Ross Leidy | 6 comments »

The sides of the seat frame will become structural members for the side assemblies, keeping the legs from splaying away from each other when there’s weight on the chair. So, it’s important that the seat frame is mounted securely. In Tango’s disassembly photos of an original chair here, there are a couple of dowel pins on the top edge of either side of the front rail that index into holes in the bottom of the seat frame. There are then screws that hold the frame in place, ...

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Part 20: Back stile tapers

06-23-2019 02:10 AM by Ross Leidy | 0 comments »

As best as I can determine from photos, the back stiles taper inward a little from above the joint with the arm to the top end. I didn’t notice this until long after I had cut the mortise for the upper back rail. That mortise is 0.8” deep in the 1” thick stock, so it had to be a gentle taper so that I wouldn’t expose the bottom of the mortise on the outside of the stile. I marked out a layout line about 1/8”+ at the top end of the stiles tapering to nothing ...

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Part 21: Side structure - Edge round-overs

06-23-2019 09:54 PM by Ross Leidy | 2 comments »

If you happen to look obsessively at photos of the Z-chair, you’ll notice that outward-facing edges of the side structures are rounded more heavily than the inward-facing edges. This reduced round-over makes practical sense at the top of the back stiles, where too much rounding would eliminate the flat surface where the rail attaches. To a lesser extent, the same applies to the front seat rail. To replicate this (or approximate it), I’ll use a 1/2” radius bit at full...

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Part 22: Side structure - Glue-up

06-25-2019 01:28 AM by Ross Leidy | 0 comments »

I’m going to savor this part of the process, so progress photos will be a little slow in coming. I started by gluing the back stile to the long arm support/rear leg. I made some clamping blocks to provide some parallel clamping surfaces. For the long arm support, I made a wedge of soft paulownia and put a concave edge on it to approximately match the edge profile of the long arm support. For the rounded tip of the back stile, I used a scrap of BB ply with a similar rounded curve...

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Part 23: Seat frame - maker's mark

06-29-2019 09:05 PM by Ross Leidy | 1 comment »

During the entire project to date, I didn’t really have a firm idea on what to do for a maker’s mark. I deferred until yesterday when I just couldn’t put it off any longer. Here’s what I came up with. I wanted to pay homage to the Selig badge and the chair’s Danish heritage. I started with a scrap of dyed-red maple burl, about 1.25” square and about 0.25” thick and glued it to a sacrificial substrate that would securely mounted to the CNC bed...

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Part 24: Side structure - Final shaping and sanding

07-03-2019 09:48 PM by Ross Leidy | 1 comment »

With the side pieces all glued-up, it was time for final shaping of the tips of the arms (I had left them long so I could clamp directly against the end), some blending of the underside of the front arm joint, and then sanding the side structures entirely. I kind of enjoyed the sanding for a while, but by the time I got down to 400 grit, I was ready for it to be over.

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Part 25: Seat frame - glue-up

07-03-2019 09:56 PM by Ross Leidy | 0 comments »

Not much to see here. I did have to make a couple clamping blocks to account for the bevel on the rear edge of the frame.

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Part 26: Pre-assembly finishing

07-04-2019 06:59 PM by Ross Leidy | 3 comments »

I’m at a point in the project where it makes sense to pause and apply some finish before completing the final assembly. It’s going to be easier to do it now than to try to work in tight quarters after the chair is assembled. I started with the back slats. I used a piece of plywood with dowels to support the slats as they dried. I’m trying Odie’s Oil for the first time. It’s got the consistency of slightly grainy honey. The product is appli...

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Part 27: Back glue-up

07-05-2019 09:56 PM by Ross Leidy | 1 comment »

Because the curve on the underside of the lower rear rail was off-center from the slats, clamping directly against that curve would put uneven pressure on the end of the slats as it tended to twist the rail. To restore a right-angle clamping surface, I made a couple of these clamping blocks for each end of the bottom rail. I pre-glued the dowels into the ends of the slats, then began gluing them into the bottom rail. The CNC-cut jig in the foreground was to ensure that the peak on th...

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Part 28: Final glue-up

07-06-2019 03:28 PM by Ross Leidy | 4 comments »

After all the lead-up to this step, it was over in 30 minutes. I finally have a chair. I still need to make the webbing straps and decide on the box cushions, but the woodworking part of the project is suddenly over. I lined the jaws of the pipe clamps with cork to minimize any marring, but I’ll probably apply another coat of the Odie’s Oil after the glue-up. Just to stretch-out the project a little longer. :)

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Part 29: Finished!

08-09-2019 12:45 AM by Ross Leidy | 7 comments »

My wife made the box cushions for the chair and matching ottoman (blogged here). I plan to tap her upholstering skills again for future projects. I’ll post some more finished photos as a project entry once I take some better photos, but here is one pic to cap-off the project blog.

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