constant thickness curved back slats
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Folks,
What do the volume production people do to make curved back slats for chairs? Everything I have seen says band saw to rough shape from a blank and then use hand planing or belt/drum sand to final shape. I have not considered steam bending as that is a skill I have not tried, plus the tenons on the end are difficult. In the end I still end up with uneven thickness across the width of the slat – not bad but not the same accuracy as my joinery and the rest of my work.
I have considered template routing but the parts are pretty thin and getting template on and fixed properly is difficult. Thought about using a fixed pin 1/2″ away from a fluted router bit and running the slat through that somewhat along the lines of ‘curved planer’ concept.
Thoughts and ideas are welcome.
Dan
Replies
Steam bending for thin slats. Bandsawn slats, like the splats on Chippendale chairs have to be beefier if the curves are more than trivial because of the short grain issues created by the curves. But, another alternative is to laminate the slats. That gives you quite a bit of design flexibility.
Bacl splats
Dan,
I have always laminated mine. My most recent chair has splats that are 3/8" x 3/4". I cut 1/8", possibly a little thinner, strips and clamped them up with regular PVA glue against a form I had shaped. (I've done it many times on a variety of components.)
To get an even curve, mine is slightly "S" shaped, it is necessary to provide a 'caul' of something like masonite or a thicker piece of the splat material. Wax everything, or use Saran wrap or whatever, so you don't glue the whole contraption together. When the glue is set, I joint one edge, then gang-thickness plane them to obtain a uniform width. Finally I shaped them with a bearing equipped, roundover bit on the router table.
Frosty
My guess is that steam bending will best meet your needs. You can plane all the slats to uniform thickness and form tenons while the slats are flat. If tenons bent to same radius as the rest of the slats, you'll have to angle the mortise slightly, but once the drilling jig is worked out all would be the same. Resawing would allow glued laminations, but would have to mill tenons after laminations glued. And laminated slats wouldn't all be the same thickness unless care taken in resawing and smoothing the strips of wood.
Back splats
"laminated slats wouldn't all be the same thickness"
I've had no trouble glueing up laminations - with virtually invisible seams - straight from the bandsaw. My tenons (3/8" thick) are the same thickness as the back splats so nothing to be carved except width.
Frost
Wish I had as much luck with bandsaw resawing. . .
Laminations
Don,
About 18 months ago I gave my smaller Laguna saw to my son. (I rationalize a great deal, convincing myself that he needs something so I can upgrade.) In replacement I bought a 16" Laguna and popped for the Driftmaster fence.
I didn't care about the supoosed 'ease of correcting for drift', but I was interested in the fact that it was equipped with what I call a "lead screw". One rotation of a handle advances the fence 1/16th". The laminations fall off the outside of the blade so I can get consistent thickness without trapping the lam between the blade and the fence. . I also purchased their 1" resaw blade.
You will notice that I only mentioned machinery features - never did I venture into the depths of "operator skills" or luck.
Frosty
handing down
Handing down in advance could be considered as a new form of "paying forward" - an admirable approach, considering you were "forced" to upgrade, Frosty. ;-)
I'd offer myself up for adoption, so you could upgrade even further, but the age similarity might be an issue. ;-)
Adoption?
Take a number, Ralph. I am much in demand and can only process a few requests each year.
Are you clean? Well mannered? Polite to your elders? Do you have good table manners?
These are all important attributes for those seeking membership in Frosty's hand-me-down club.
Uncle Frosty - whose adoption standards are very high.
the line
Chuckle. I thought there might be a line, Frosty.
FWIW, my beard is white, which I consider to be an indicator of cleanliness. I open doors for women and the elderly, even when it is likely they are younger than I. I also remove my hat at the dinner table, and keep my elbows off the table. I will admit, however, to becoming confused if there are too many forks in the place setting. ;-)
Is this what you mean?
I am about to start working on a chair (Stokke replica). The back slat profile is shown below. It's about 3 inches wide, and I plan to create a mortise and tenon joint into the side posts.
Would you laminate 1/8' sheets for that? I reckon I'll make them 5/8" or 3/4"
Back splat
I know this was not addressed to me but I will respond.
Yes - I would, you can, laminate this piece. I'm not sure how thick a solid wood piece would have to be for you to bandsaw this shape, but picture the grain patterns that process would expose. If it is laminated, you will have a continuous grain pattern across the face.
Because the two reverse curve ends are so short, I would bend a section that is at least 8"-12" longer than necessary - at EACH END - so you have enough purchase for adequate clamps. After you have cut your form of stacked 3/4" plywood or MDF, you are good to go.
Good luck,
Frosty
Thank you
Thanks for the tips. I am sure I would have messed that up. I do think I'll make a straight mortise and tenon for the splats (though as you correctly pointed out, they are not parallel with the sides). The side to bottom leg joint will be an angled mortise and tenon. Not yet sure which way to go, but will probably angle
The mortise to maximize my tenon size as there are no back legs. Lobe the tips, keep em coming anytime. Sorry to OP, didn't intend to hijack your thread. I'll let you know how my lamination goes. Can I just use regular wood glue, like titebond or do I have to use something different?
Back splats
My first lamination job turned into a 'Chinese fire drill'. I was afraid of creep so I used Gorilla glue. Do NOT repeat my mistake. No - it didn't creep but everything within 15' feet of the work area became covered with a sticky, foaming mess. Yours truly included.
Ever since I have use regular PVA without any evidence of creep. The critical requirement is to use as many laminations as possible. In one instance, either the bend was too tight or my lams too thick, I forget which, and I had to start with 3 lams instead of the desired 5. When I removed the clamps I had significant spring-back. (Ooops! I'll have to modify my design.) But - when I added the last 2 lams, the bend was solid as a rock with NO spring-back.
Good luck.
Frosty
spring back
Glad to hear you finally achieved the silence of the lams, Frosty. ;-)
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