I’m just full of ??? today. Here’s a photo of a full size chair model that I designed. I’m afraid that I overdid it, designing something that cannot be economically produced — not for sale but personal. Maybe somebody can help because I’m about to scrap it and try something else. I’d llike to salvage the design if possible.
The problem is simply too many angles. The back tapirs toward the top as well as being angled back 10 degrees and the 8 slats are mortised in an arc at the bottom but in a straight line at the top rail. This causes them all to angle inward toward the center. The slats are 3/8 x 7/8″. I had no problem with teh mortices, but those tiny tennons turned into a nightmare. I’ll need to make 96 of those tennons for 6 chairs. The tennons are 3/8 square.
Does anyone know of a technique for production machining small tennons on an arcing angle like this? In the model I did them by hand, but it took WAY too long. Perhaps it could be done with a router jig?
Replies
The JDS Multi-router would produce that design. If you changed the tenons to round tenons you could do it with tenon cutting tooling from WL Fuller or Veritas which would be a faster way to go.
Boatman,
Am I correct in assuming you have a double slope on the shoulders of the slats....and therefore require a double pitch to the tennon? My only guess wiuld be a tennon jig on the TS with some wood templates for the pitch back and tilt the blade for the pitch to the center?
Right, I got no problem with the mortises, those were easy. It's the #$%^@ tennons. What's worse is that every slat is a different length. Maybe I should forget tennons and mortise for the whole slat dimension. Just stick it in the hole like a dowel.
Tennons are too small to do on TS accurately. Tried that.
Edited 8/7/2003 2:36:47 PM ET by boatman
Had the same problem recently, but on a design that is way simpler than yours (copy of an existing chair). Curved bottom and crest rails, with 3/8 by 7/8 slats that flared from top to bottom, six chairs to do. Routed mortises exact same size as slats with VERY tight fit about 10 degrees angle to rear on bottom rail and I believe straight on crest rail. Assembled slats with no glue. Very forgiving, no messing with compound angles or curved shoulders. No slop, rattle or misfits. Put all the time into a router jig for precise, repeatable mortises.
Bruce
Nice chair!! I think I just got too fancy and should have kept it simpler, but I love the tapering slats. I can forgo the curved shoulder or top rail, tho that clearly alters the design. But maybe I could figure out a router jig that would cut all 8 slats together. Wife sez there's smoke coming out my ears!
I agree with Rick, round tenons would be more production friendly. If you are worried about the slats twisting, you could always pin them with a small,3/16" dowel. Inserted from the back, they would be out of sight, or in through the front and be a decoration of sorts.
After about ten hours of thinking on this I discovered that my problem was not the design but my choice of joint. Switching from M&T to a half-blind dovetail joint, it all becomes easy. It only required a simple angle indexing jig for the router table. The entry point for the router bit in workpiece is then covered over with a veneer after the slats are glued in place so that no joint is visible at all.
The slats are on a compound angle but I ignored this, cutting the dove tails slightly oversize, allowing the slats to twist. The glue up is then done with epoxy with each slat being manually alligned, but no slop in the joint is visible. They're hidden by the seat cushion anyway.
I'll post a pix of this a little later.
i'm not really sure by your description, but if i'm reading it correctly, the slats ending in exposed (as opposed to veneered over) dovetail tails might look pretty slick across the back of the chair seat. (in case this makes no sense, maybe i should mention that i'm sleep deprived and am surfing in an attempt to to stay up long enough to sleep thru the night for a change)
m
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