a little table talk

[crannygoat]

Hats off Chris, I don't know how you get the work done, record it, and blog about it. Same goes for all of the frequent posters here. Is there a time stretcher I'm not aware of? I could probably use a board stretcher too.


Something I'm working on for a client.

I hope I have resized these correctly.

[Paul Atzenweiler]

is that a backpacking table?

[Brian]

Cool stuff Cranny, did you dovetail in the battens?

I always have a hellish time cutting successful sliding dovetails with a router, wondering if you have any suggestions on how to do them successfully. I manage full length DT's by hand well, but when I want them to be stopped I'm left to the router.

I have an OF1400 and rail.

[Chris Pyle]

I'd be interested in seeing more as well. And any explanations on set-up for sliding dovetails would be great!

[crannygoat]

Paul, yes it is a backpacking table. Very transportable at 20 feet long.
Chris and Brian I did dovetail the battens. I used the track and router with careful knifed in layout for the female dovetails. The micro adjust on the router's track jiggy thing was very useful, more articulate than "router's track jiggy thing".
I roughed out the male shoulders on the table saw and finished on the router table, test piece first! Each one was fitted individually.
They came out pretty well, but please learn from my mistake. Some other projects took priority for about two weeks (time lapsed between cutting the females and then the males). The table top boards have cupped slightly, making the right fit impossible over the width of the boards. I tried water in the cup to no avail. I tried clamping the boards flat to partial avail. So now I'm using my jointer plane to deck part of the female shoulders. I'm looking for about 75% freehand engagement. Still I think I'm running the risk of a loose joint during part of the year.
The table top is 2 1/2" thick bay laurel, book matched as per clients desire. One smiling, one frowning. Curiously, both boards cupped up, which suggests I would have been wise to flip the boards daily during their waiting period. It seems that the upper surface dries more than the under surface, to the point that smile/frown is a moot point. If I had two weeks to spare on the deadline, I would flip them see if they flattened out. The boards are at a nice air dried 12% MC, and my shop maintains a pretty steady 50-60% RH. Must be slightly drier than their former former home at the mill. No surprise there really. Some pics will probably clarify the situation. Hopefully you can make out the smile/frown on the end grain.

[Brian]

I very much understand your frustrations, I can echo them on my current project. I'm building the web framing of a cabinet with a lot of drawers, since the case is thin material (5/8) I decided to install the web frames with blind sliding dovetails.....sigh. I let the material sit for about a bit (couple weeks) and when I returned to dovetailing it was in need of heavy clamping to get it to sit flush against my bench.

Thank you for the tip on knifing in the marks, I never think to do that when cutting dovetails with a router, but it makes good sense.

I received advice previously to build tapered sliding dovetails when building cabinets, I have failed to heed the advice thus far but will likely change my approach for the next casework project.

[crannygoat]

Moving along. I seem to recall a detailed discussion of wedging tenons here or on CW but I can't seem to find it. Anyone have a clue where that is? Wedge against end grain, size wedges to mortise tapers. One thing that's never made much sense to me is angling the saw kerfs in towards the middle of the tenon. What is gained by this? Seems to me a straight kerf means less short grain, therefore stronger. If there's an error in my thought, enlighten me please.
I haven't settled on an approach to wedging the long and short apron tenons. They both have a meaty haunch, and then they lap each other. I could do short wedges, (they cross at 3/4" form the outside face of the leg). Or a longer wedge and trench the tenons. Anyone care to weigh in?

Brian, I'm not sure what the advantage of tapering sliding dovetails in a cabinet would be. They never seem to land quite where I want them to, and may shift unpredictably with expansion and contraction. I think a straight sliding dovetail that is fit well and pinned near the center of movement would be a fine option. It is harder to nail the fit, a tapered joint will eventually get tight, but maybe two inches beyond the mark. I've done that.

[Brian]

Cranny,

Looking good! That table is a beast, what is the overall length going to be?

Here is a quick write up I did for a friend on wedge tenons;

Start by making a plain through mortise and tenon. Wedge tenons do not need a really thick wedge to keep them together, so I will determine how much wedge by how deep the tenon is. For my bench the tenon was about 2-1/8" tall, so I figured about 3/32 of wedge would do it. So I move my marks on the mortise on the outside by 1/8" (3/32 - saw kerf and some compression).

This is where there is a bit of finesse, I will approximate the angle at the mortise ends and chop almost to the bottom of the mortise, then flatten the cut with a paring chisel. It's best to creep up on it, rather than overshoot and wind up making your mortise too tall on the inside.

I usually keep the wedges about 1/4" from the edge of the tenon, MAX about 3/8 on a big tenon. Mark the tenon for the wedge cut, Drill a hole as a stress relief through the tenon at the base of that line, just above the shoulder.

Cut wedges, the gap you need to fill is the 3/32 for the offset (for this example) plus the kerf, then add a slight bit (another 1/32~) cut the wedge on a taper from stock that is the same thickness as your tenon. Taper the wedge down to zero along it's length and make the length just shy the length from the top of the tenon to the bottom of the stress relief hole.

Knock everything together like a typical through tenon, then I clamp everything while I set the wedges so that it doesn't back apart.


I cut the kerfs straight on, I would expect that angling them in has a benefit in certain applications, but for heavy tenons I want to make sure that they're going to bend.

[crannygoat]

Here is a quick write up I did for a friend on wedge tenons

Thanks for that Brian, much appreciated. The corner tenons have a pretty meaty haunch. I'm thinking it's best to stop the wedges before that.

It'll finish out at 20'.

With all the joinery dry fit, I brought some help in to flip it on it's feet. I wanted to check the behavior under it's own load. It's a pretty heavy top, and I was worried about racking without a triangle in sight. To my relief it sat stout and firm (I was kind of getting excited about the prospect of needing to make giant's arm braces though). With wedges and glue, I feel no concern for the structural integrity.

That done, I pulled it all apart, and it's time for chamfering, sanding etc. I attempted to hand plane the bay laurel, hoping to finish it in that manner. I can handle curly and roady sapele with no problem, but this tears out like crazy at every grain reversal. 45 degree bed angle. Any thoughts on a better approach, as it were? Some of you may know it as Myrtle wood. It seems to be a very resilient wood, which makes me think it has a high lignin content with tough fibers. I'm no wood scientist, that's just my impression. Anyway, on it's feet:

[Brian]

Anytime!

Do you have a chip breaker? If so, what is your current setting?