Tapered sliding dovetail battens

[Brian Holcombe]

Gentlemen!

Hoping I can acquire some insight. I'm building a tabletop and debating wether to make the crossgrain battens with a tapered dovetail rather than a plain sliding dovetail. The plain dovetail works fine for this, but to get a very tight fit I would like to make a minor taper.

When introducing a taper to this, does that change make the joint something that will bind when the RH drops assuming also that the tapered dovetail is pinned in the center?

The taper will be quite minor, something like 1/16" over the 30" width, so I'm wondering if the bind will be muted by compressing grain.

Thank you for any insights.

[Kent A Bathurst]

Brian -

I got nuttin.

Except - a plea for a bit of photo/tutorial on how you do it - tapered or not.

[Brian Holcombe]

Hah, no worries I will post up some photos of this table once I get through the stock prep into the interesting stuff.

BTW, the bed is finished, so I will be posting that up once it's installed into the room. :cool: Waiting for the waterlox to completely out gas....that stuff can linger.

[Pedro Reyes]

Gentlemen!

Hoping I can acquire some insight. I'm building a tabletop and debating wether to make the crossgrain battens with a tapered dovetail rather than a plain sliding dovetail. The plain dovetail works fine for this, but to get a very tight fit I would like to make a minor taper.

When introducing a taper to this, does that change make the joint something that will bind when the RH drops assuming also that the tapered dovetail is pinned in the center?

The taper will be quite minor, something like 1/16" over the 30" width, so I'm wondering if the bind will be muted by compressing grain.

Thank you for any insights.

Not having done one, I will offer what my mind thought. All this is in theoretical form and in real life it may not matter at all with such a gentle taper (I suspect).

Once assembled, if everything was perfect, the sliding dovetail is tight along its full length. if you tried to slide your table top, you could always slide it towards the thin end, and never towards the thick end (of your tapered batten). If you pin in the center, half moves towards the thin end, half towards the thick end. If you pin at the thick end, all shrinks towards it (bad). So in theory you would pin on the thin end of the batten and the table top moves towards it, which is equivalent to pulling the batten out.

In real life, I don't think it will be that critical.

Pedro

[Warren Mickley]

I think it is a lot easier to make a tapered fit. You slide it in, see where it binds, near end or far end, remove a few shavings until it fits. You can slide it in easily to within an inch of the end then hit it tight. Otherwise you are fighting the whole way to thread the batten in or to remove it if too tight.

I would not fasten it at all; just let nature take its course. I think I would make it a few inches shorter than full width. That way it does not interfere with those seated at the table. Sometimes a small filler piece (flush with table bottom) is put in behind the batten.

[David Wong]

I used 14 inch tapered sliding dovetails for support battens on a floor workbench. I found a 1/16" taper did not make for easy insertion of the batten. Everything was done with saw and chisel, so I probably lacked precision in my joint, particularly the male dovetail. I wanted the joint to seat hand tight 2 inches from the end. I used a bar clamp to help me close the joint the rest of the way. I did not use any glue since the joint was very tight. If I were applying glue, I would dab some on the female portion of the narrow end, so the top could move towards the wide end. I completed the workbench in March, and have not noticed any joint movement (but I am in a temperate climate).

A few pictures...
https://lh3.googleusercontent.com/P3CMbfNDhgSCm7AJp7_UbJEtWKAR7T2L22C21G2goo0=w720-h600-no

https://lh3.googleusercontent.com/nZAaHmwcOJ4vibxowuBDO8R355_H5wloTa3HIjCmSxg=w720-h600-no

https://lh3.googleusercontent.com/cSrork45G9GxfmjarTL7q7X_QDr57ta8EnTOfPiTfjI=w720-h600-no

[Brian Holcombe]

Thanks fellas, this info is very much appreciated.

I think I may be able to alter the joinery so that the batten is floating through the remainder of the joinery and not fixed. That way I will be able to leave it unpinned.

Warren, I will heed your advice to keep it shy of the full width.

David, Thank you and especially for posting the photos. Gorgeous work and I appreciate the perspective.

[Mike Allen1010]

Brian, going w/ Warren's advice is always a good call. I'm really looking forward to your posts of the finished bed and your new project!

David, very nice work! Dude, don't hold out on us - personally I would love to see more of your work - hand cut sliding DT's - very nice!

Cheers, Mike

[Derek Cohen]

Hi Brian

I think that I could rename the Lingerie Chest and call it the Sliding Dovetail Chest as there are so many :) The only difference with what you have planned is that the housings are short, and some are "gang" shaped, which means that keeping them parallel was indicated.

What I wanted to bring your attention to is the little dovetail plane I used, the one based on a Stanley #79.

http://www.inthewoodshop.com/Furniture/SlidingDovetails-LC_html_680e7f25.jpg

This really would be worth your while to make. It enable really easy and accurate tuning of both the male and female sections.

More info here: http://www.inthewoodshop.com/Furniture/SlidingDovetails-LC.html

Regards from Perth

Derek

[Brian Holcombe]

Thanks Derek.

I use the HNT gordon DT plane currently, it works well. IIRC you have both, do you prefer the stanley?

The mechanics of building them are not all that concerning, what has been a concern is wether the taper will cause a bind and possibly a split in use. So I've altered my plan a bit to accommodate some shifting in the battens over the course of the seasons.

It's concerning because I expect this tabletop to shrink/swell about 1/4"~ over the seasons. This particular house gets pretty dry in the winter, I built a table for them a few years back in rosewood that shrank 1/4" in the winter over about 24" of table width.

[Prashun Patel]

"...assuming also that the tapered dovetail is pinned in the center"

(dumb question alert): If your tapered dovetail is designed to fit tightly, would you need to pin it?

[Brian Holcombe]

I have joinery planned for the center of the table that will lock into the tabletop and possibly pin the DT in the center in the process of doing so. So I'm not pinning it with a dowel, but the joinery will possibly lock it in the center....I'm working on a way to make it float and still have all the joinery remain functional.

[Pat Barry]

It seems to me that you want the batten to be a slip fit in the underside of the table top, and it seems to me, ideally pinned in the center to let the top expand and contract naturally. I think the whole concept of a tapered sliding dovetail batten assembly is not what you really want. That will be too tight IMO. Now maybe you have some tricks up your sleeve to overcome the fundamental problems but, even if you do, the fancy tapered sliding dovetail is then not needed. Why not just use a plain old sliding dovetail and pin it in the center?

[Brian Holcombe]

It's problematic to fit a 28" long sliding dovetail without some taper. I did them on the cabinet I'm building and that was only 15".....they were a bear to fit.

I don't plan to make a heavy taper and compound the issue, but doing this without a taper at all and I might as well just use screws with elongated holes....I've used that in the past but I'm looking for a more complicated solution to a simple problem today :)

[Pat Barry]

I agree they would be difficult to fit across a tabletop that is maybe 36 wide so I feel your pain. I recall a long time ago using a router setup to do sliding dovetail fronts for some drawers - ie: the drawer sides slid into the drawer front from underneath. I wanted a snug fit and it took quite a while to get them to fit right and they were only 4 inches long. I think for your situation you want a slip fit but you want the batten to hold the top flat, right? What are your thoughts on the geometry of things? How tall is the batten, how thick is the table top, what angles will be on the dovetails, how deep will the dovetail slot be, etc? Have you drawn this up to scale?

[Brian Holcombe]

They're complete now, once I have some good progress on the overall build I will post it up.

These do not need to be especially heavy, in my opinion, because they will be used in conjunction with breadboard ends.

After building these I came to conclusion that I was over thinking this, the fact is I can knock them with a hammer and further compress them more than season movement would be able to. The major plus is that these were significantly easier to execute than straight sliding dovetails.

[Dennis Aspö]

The tapered sliding dovetail batten is a traditional method used in Finland that dates back to the 1700s. I just found out what it was called in english so I noticed this thread.

The taper was then to make them fit snugly and keep the table top or whatever they where attached to, straight. But this is not new info to you. I just found it interesting I stumbled upon this just as I had learned what it was called.

[Stanley Covington]

Tapered sliding dovetails are excellent. Far superior to plain sliding dovetails. David Wong's post and pictures showing how to cut them are excellent. The same jig can be combined with a well-fettled dovetail plane for increased speed, if the dovetail groove is of sufficient width. But a sharp azebiki, as shown by David, works just as well.

The tapered dovetail does have one potential drawback: With wide swings in humidity, battens attached using tapered sliding dovetails to surfaces subject to vibration (like a tabletop) will sometimes wiggle loose. But with a slight modification, this can be overcome.

I call it a dual-taper sliding dovetail. It is identical to the one David illustrated so well, but the depth of the dovetail groove in the wide surface is sloped along its full length, with the batten slopped to match. It is easy to slope the groove with a rabbet plane, or even a router plane, and a kote nomi. Work from both ends to the middle, checking frequently with a straightedge. The area in the groove underneath the sloped sides is easiest to clean up with a kote-nomi or cranked chisel, in the case of wider boards.

http://blogs.c.yimg.jp/res/blog-e1-59/tukiichihiro/folder/1108171/82/29301382/img_1?1346080193http://blogs.c.yimg.jp/res/blog-e1-59/tukiichihiro/folder/1108171/42/29321142/img_3?1250603420http://www.qy1.de/img/n315070.jpg

The weight of the tabletop, and anything resting on the tabletop too, for that matter, tends to keep the dovetail locked tight despite vibration or changes in humidity. It also has the advantage of being easily disassembled, and so is especially useful for knock-down furniture, and for some wooden handplanes, which is where I first learned of this very useful and elegant but understated joint.

The one potential drawback of this joint is that, if you fit it poorly, or drive batten and board together with a hammer with too much force, the dovetail groove may split out. Easily prevented with a little common sense.

This is a joint for the advanced woodworker, but once you learn how to do it, you will find yourself using it routinely. Also, it is difficult to imitate with a router, a feature that makes it especially attractive to me. And good kote nomi are just a joy to use.

The first two pics above are of Kiyotada chisels, similar to ones I own. These are based on an especially beautiful design by Chiyozuru Korehide. The last pic is from Dieter Schmid's website. I don't know how well they are made, and am not endorsing them. I was just surprised to find such an attractive set of skewed kote nomi still available, and in Germany no less! Hard to find decent ones here in Japan anymore.

The same job could be readily accomplished with Western cranked chisels too.

Stan

[Brian Holcombe]

Stan, Those are gorgeous! Thank you for the insight and suggestion, since this is already complete I will keep it in mind for future projects.