Sliding dovetails. A botched job.

[Kees Heiden]

Of course I should have used buttons and screws or something simple like that, but I decided that it would be nice to attach the top to my cabinet with sliding dovetails. This would be the goal of this operation (but in this picture the top is lying loose).

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So I made the first dovetail socket. Cut with a handsaw along a beveled batten.

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Then chop out the waste in between. You can see a third sawcut in the middle, very usefull to get the chips out of the groove!

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Plowplaning to final depth (plus a little extra so the dovetail doesn't bind on the bottom of the groove).

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Then I used my dovetail plane to adjust the width of the tail until it fitted into this groove precisely.

Next issue was determining the exact postion of the second groove at the other end of the cabinet. This should be positioned very precisely. After much turning around in bed at night I came up with this system to mark the exact position of the second dovetail.
A story stick is clamped to the cabinet and I mark the exact position of the bottom of the dovetail with the help of this ruler. I do this on both ends of the dovetail. Then the story stick was used to mark the top.

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So, full of pride and fully confident I proceeded to slide the top in place. But low and behold, it doesn't fit at all! :eek:

After much head scratching I found that the front of the cabinet is about 2mm wider then the back. No idea how that happend, I thought I had marked the shoulders of all 4 rails at the same time. But this is now what I am looking at. Wise lesson: When you want to slide a top on two sliding dovetails, then those two should run parallel. They shouldn't diverge, not even by these two miserable milimeters.

It's easy to adjust the width of the front of the cabinet. Just resaw the tenon shoulders. Not so easy though to decide what to do with the diverging grooves in my top. Starting all over with new wood is NOT an option (the damned thing was expensive enough). I think I am going to glue in a filler piece in the crooked groove (taking care of the correct grain direction) and resaw and chisel the groove. Luckilly it will be the underside so my botch job isn't going to be very visible.

[Archie England]

Good looking Table!

By sharing your "design opportunity," you've encouraged me to plunge ahead in various projects. Human error is inevitable, and learning from it, diagnosing resolution, and implementing corrections is a far better path than immobilization induced by fear of failure.

Look forward to hearing how your resolution works out.

[Derek Cohen]

I think I am going to glue in a filler piece in the crooked groove (taking care of the correct grain direction) and resaw and chisel the groove

Yes.

Kees, I always make the male section first, and then mark the socket from this. That is the same as "tails first".

Anything 2" and shorter I leave the sides parallel. Longer than this and I create a tapered sliding dovetail.

It also pays to measure the base of the male section with dividers to ensure that you get the dimensions correct.

http://i13.photobucket.com/albums/a262/Derek50/Furniture/Sofa%20Table%202/Rails/6a_zpsznxrexft.jpg

http://i13.photobucket.com/albums/a262/Derek50/Furniture/Sofa%20Table%202/Rails/10a_zpso6xtc74z.jpg

http://i13.photobucket.com/albums/a262/Derek50/Furniture/Sofa%20Table%202/Rails/SD1_zpspdk97ktx.jpg

The base points are plotted on the surface of the wood. The angled wall is created from that (i.e. inside the "dado").

http://i13.photobucket.com/albums/a262/Derek50/Furniture/Sofa%20Table%202/Rails/11a_zpssdtmeonm.jpg

Regards from Perth

Derek

[Kees Heiden]

Yes Derek, I did that too. And that works perfectly. The exact position of the second groove makes things harder, but I managed that one too. But getting the two grooves parallel, that's where things went wrong.

And yes my sliding dovetails are tapered too. There are two tapered sliding dovetails that need to run parallel.

Our antique coffeetable has a system of two parallel grooves for sliding dovetails. I am now in awe how they pulled that of, it's not as easy as it looks.

[Nicholas Lawrence]

I think I see the problem. You were using the story stick instead of all of the tools you listed in your "Essential Tools" thread. If only that story stick were ANSI something or other compliant. Oh well, nothing a large credit card can't fix I am sure.

Seriously though, errors of this sort have certainly happened to me. When I get time to resume work on my office table, item of business No. 1 will be to shorten one of the rails because it "somehow" ended up longer than the other, and I did not notice it until I put all of the parts to the base together for a dry fit.

The only real advice I can offer is not to make the fix in haste: I have done a couple of fixes when I was angry at myself over the original error, and ended up compounding the error, or creating a new problem somewhere else.

And I agree when it is done it will look very nice.

[Derek Cohen]

Ahha!

Yes, that is harder. And these were the first you made! :eek:

Regards from Perth

Derek

[Kees Heiden]

I made some small sliding dovetails before for drawer dividers.

No worry, I am not angry (anymore). I don't think I'll get much work done the next few days and in the weekend I will be in Belgium. So, no hurry.

[Kees Heiden]

Funny thing is, i made a critical mistake waaaay earlier. The two long rails you can see in the top picture are just a bit longer then the equivalent rails in the back. Those should have been the same length. Something which is easilly accomplished when marking all 4 together with a large square. I don't remember what I was smoking back then.

[Brian Holcombe]

Kees, in future situations like this you might consider single sided sliding dovetails. This will allow you to knife the outside edge of each DT.

Mind you, dovetails holding a top down need to be exceptionally tight. So normally the type of thing where you would fit the batten first, then attach the batten to the cabinet. Knocking together two large sliding dovetails which fit tightly into a top in the way you have arranged to do so requires one of those timber framing mallets and likely will not go well.

[Kees Heiden]

Hmmm, you give me another nightmare Brian.

At the other hand, it might be a solution too. Rip the dovetail from the top. Fit the now loose dovetail tightly to the groove. Then somehow reattach it in the right spot. Hmmm, need to think this over further.

Thanks anyways.

[Pat Barry]

It's easy to adjust the width of the front of the cabinet. Just resaw the tenon shoulders. Not so easy though to decide what to do with the diverging grooves in my top. Starting all over with new wood is NOT an option (the damned thing was expensive enough). I think I am going to glue in a filler piece in the crooked groove (taking care of the correct grain direction) and resaw and chisel the groove. Luckilly it will be the underside so my botch job isn't going to be very visible.
This should be a fine enough fix for this problem. Verify front and back spacings to the cabinet dovetails are the same AND that the sides are perpendicular to the front as well (at least close enough so that the tabletop overhang is enough to hide any lack of squareness.

[Brian Holcombe]

There is a steep learning curve with sliding dovetails. When I was starting out I had one set which quickly turned to a dado, haha.

Make two (per side) tenons with dovetails on their ends, fit them in the grooves then mortise them into the batten. Pin them into place. Likely you won't be able to draw bore them, so just clamp and pin.

[Brian Holcombe]

This should be a fine enough fix for this problem. Verify front and back spacings to the cabinet dovetails are the same AND that the sides are perpendicular to the front as well (at least close enough so that the tabletop overhang is enough to hide any lack of squareness.

The patch is fine, but you can't cut back into it since you would be creating a short grain situation.

[Kees Heiden]

Many thanbks for the ideas. I was also thinking about squaring the existing groove (making it into a wide dado. Glue in a patch. Then moving my attention slighty inwards (towards the inside of the cabinet). Cut a new dovetail groove there, single sided this time. Then I can make a loose dovetail and somhow attach that to the inside of the top rail.

But your solution brian has the advantage of making use of the existing groove and it will be totally invisible, apart from the pins.

[Prashun Patel]

"two miserable millimeters."

I feel your pain.

Please post the fix. I find this valuable.

Beautiful cabinet.

[Pat Barry]

The patch is fine, but you can't cut back into it since you would be creating a short grain situation.
Kees had noted that he was planning to "taking care of the correct grain direction", therefore I figured there wouldn't be the same cross-grain situation you are noting.

[Brian Holcombe]

Kees had noted that he was planning to "taking care of the correct grain direction", therefore I figured there wouldn't be the same cross-grain situation you are noting.

Im aware that was stated which is why I pointed out 'short' grain. The patch would be anchored onto end grain and likely fail once cut into.

[Kees Heiden]

Yes it needs to be wider indeed so it has sufficient long grain gluesurface. But that would rule out a new groove at almost the same spot.

[Pat Barry]

Im aware that was stated which is why I pointed out 'short' grain. The patch would be anchored onto end grain and likely fail once cut into.
Oh, on the sides... That makes sense - thanks for clarifying

[Patrick Chase]

Yes.

Kees, I always make the male section first, and then mark the socket from this. That is the same as "tails first".

I see what you did.

I agree. As we all know, tails first is the one and only true way to cut DTs (and it wouldn't be an SMC thread without a tangential flamewar now would it?)

[Patrick Chase]

Hmmm, you give me another nightmare Brian.

At the other hand, it might be a solution too. Rip the dovetail from the top. Fit the now loose dovetail tightly to the groove. Then somehow reattach it in the right spot. Hmmm, need to think this over further.

Thanks anyways.

Yeah, that was my first instinct as well.

[Patrick Chase]

I think I see the problem. You were using the story stick instead of all of the tools you listed in your "Essential Tools" thread. If only that story stick were ANSI something or other compliant. Oh well, nothing a large credit card can't fix I am sure.

Yep, I think this would just about do the trick: http://www.starrett.com/metrology/product-detail/Solid-Squares/Squares/Precision-Hand-Tools/Precision-Measuring-Tools/20-36

The 24" version would probably be marginally acceptable for woodworking, and only costs $1681.

[Alan Schwabacher]

One edge of the dovetail socket needs to be cut more (straightforward) and the other less. What if you convert to a half-dovetail by filling the part that needs to be cut less, leaving the edge square? Even if undercut it would not hold well because of short grain, but cut square it would be held tightly in place by the dovetail. You could orient the grain of the filler pieces crosswise, and just leave it several pieces to take care of crossgrain expansion. They would not even need to be glued to be strong.

[Graham Haydon]

That's a bold solution to affix a top! I think my proposal is similar to Brian's, but I can see things better than I can read them.

I would carefully rip the sliding dovetail part from the rails with a view to reuse them. The ripping will create a joint that is too tight as the dovetail will move lower within its housing. I would then screw the ripped dovetail pieces into the correct position. That might mean a few attempts at getting them screwed in the right spot and planing an edge of the dovetail as required. Once happy with the fit I'd then glue and screw the dovetails back onto the rails. Then fix the top on. Nobody would ever know!

Good luck! Hope my ramble made sense and sorry if it's just a copy of others tips.

[Kees Heiden]

For everyone who has not the slightes idea what we're talking about, here is a sketch, heavilly exagerated of course!.

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Explanation: As you can see there is an error in the parallelity of the grooves and the sliding dovetails. If I could drop the top down onto the cabinet, then the fit would be fine. But because these are dovetail shapes, I have to slide it in from the front. Of course that is impossible in this configuration.

Last night while hanging around at the climbing gym, I thought about a possible solution.

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I cut up the crooked dovetail. The part above, near the letter B can remain in place. The error at this end is too small to worry about. The end below needs to be loose and it must be able to slide from side to side. So I can engage it when I start to slide the top onto the cabinet, and when I advance, it can slide back to its permanent location.

How I am going to fix it in place afterwards is another thing of course, and I still have to weigh up the various possibilities. It depends on how much meat I have in the top rail at this point.

[Noah Magnuson]

How about rather than patching the groove, you laminate onto one or both sides of the tail as necessary (you could even square it up first to ease lamination/clamping). Then widen the groove the necessary amount to make it parallel to the other groove, and finally recut the tail accordingly.

[Pat Barry]

I think at this point you should cut your losses and switch to metal tabletop fasteners and screw them in from underside and take this as a learning experience.

[Malcolm McLeod]

I'm not following some of the proposed solutions, so pardon me if I'm aping someone else's idea:

Could you cut one of the existing 'grooves' out to be rectangular cross section - keeping same depth, but say 75mm wide. Leave the dovetail of the carcass alone.

With the top upside down, invert the carcass and slide one dovetail into it's mating groove. The other dovetail will sit loosely and approximately centered in the new rectangular groove.

Now make several gibs (~25mm W. x ~100mm L.) with one edge matching the angle of the loose dovetail. Drop a gib into the open groove, engage the 'loose' dovetail, and screw it to the top. Repeat for the opposite side of the dovetail. Alternate installing gibs back and forth along the loose dovetail's sides - leaving enough gap between the gibs to allow seasonal expansion of the top ...???
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******************************
Edit: You could even do this to one side of the groove (just be sure to pick the correct side):
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[Kees Heiden]

You all have great ideas. Now I have sleepless nights about which one to choose. :)

[Kees Heiden]

I managed to find some time to work on a solution. The problem is that the two grooves and the matching dovetails don't run parallel. That makes it impossible to slide the top in place. Some of the solutions have the same problem, it would fit nicely when done, but it would have an assembly problem.

So, I decided to cut of most of the dovetail. Only the last 10 cm was left in place. At that end the error is so small, that it doesn't really matter. Next I made two loose dovetails with tenons. These can be inserted in mortices cut into the top of the rail. But to be able to assemble the top I made these morices very sloppy, so the dovetail key can slide a bit from side to side. This makes it possible to slide the top in place.

Of course, now those two dovetail keys are pretty loose in their mortices and won't hold the top down. to fix that I will drawbore them. This also has the tendency of pulling the dovetail down and thus locking down hard. Of course now there will be two draw bore pins visible on the outside, but that is not a problem. I think that only adds to the magic of the piece :p

Here are the two loose dovetails and the piece that is still fixed. I have pulled the middle one out of its mortise, so you can admire my spotless joinery technique :D

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And this is how it would look in the finished piece. Of course those two holes will be filled with a wooden pin.

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[Noah Magnuson]

Looks great, too bad the rail wasn't a tad thicker; you could have draw-bored from the inside just shy of the outer surface. Oh well, you made the best of the situation, me thinks.

[Kees Heiden]

Luckily I won't loose even a second sleep over this. It's going to be a piece, based on 17th century stuff and antiques like this are often full off weird patches, strange solutions or unexplained items. More important to me is that it really looks like a 17th century botch, so no steel hardware.

[Nicholas Lawrence]

It looks good Kees.

[Brian Holcombe]

Cool, I think it will work nicely.

[Malcolm McLeod]

Certainly a more elegant, traditional solution than my bombarding it with screws!:cool:

[george wilson]

Can you adjust the female dovetails by gluing veneer or thin tapered strips on one side, and widening the other side of the SAME dovetail ? Do the same shiming and recutting on both sides of the top's dovetails till it will fit?

I know you won't like it, but this will not show on the finished piece after it is assembled. I know you don't want to do this sort of thing, but if it doesn't show,and works, why not. You didn't make this for the Queen of England (like I have!), did you?

I have an inlaid,marquetry faced tall chest of drawers in my bedroom that I bought in the 60's at an auction. Its legs were shortened at some point,and THE TOP IS JUST GLUED ON WITH SHORT DOWELS. And,the darn thing can be pulled OFF,too!! Yours will still be stronger than this once expensive piece. I enjoy the marquetry though. And leave the top alone!!! It isn't the end of the World.

I worked for many years very frequently for the most particular lady in this country. She has micrometer eyes,and at the smallest mistake,I've had to totally REMAKE a $2,000.00 part! And no charge except the original one. No one else in Williamsburg would do this kind of work for the lady.(Nor could they). I was quite happy to,and did not fuss or cast a fit if I had to de make a complicated part that WAS,as she said,a bit off. It made me a better craftsman. Such things happen even to seasoned craftsmen. Get used to it. I guarantee it WILL happen again. And you'll get tough and hard headed enough to fix it or start over.

P.S.: What happened to me was I got very proud when she would take both the original part(if the device had multiple same parts),and ask "Which one is the old one?" That happened with the spinning wheel arbor and ivory and boxwood bobbin I have posted pictures of here before. She collected those mahogany,ivory,and inlaid spinning wheels that only the wealthy ladies had in the 18th. C. Spinning was a traditional part of a ladie's edcation back then. Only if it was just "ceremonial. Even Queen Elizabeth the First learned to spin. Curiously,all the weavers were MEN! (maybe sometimes they would have to knock apart a heavy loom and re configure it. They do that to spin extra large,special order rugs even today). Ladies would spin enough thread to weave into cloth. Then,the weaver took it and made cloth from it. Textiles were VERY valuable back then. I recall hearing how Bacon's Castle,near here,was threatened by British forces during a pre revolutionary spat. It was mentioned that the residents took the drapes,bedspread,etc,off their 4 poster bed when they fled. They had servants,but did not have them knock the bed down and carry the parts.

[Archie England]

Kees,

That's a practical, innovative solution--even if you might have sacrificed some holding confidence on the re-cut side. Nonetheless, as one of those who struggled to comprehend the conversation, I think your solution is an excellent one. Thanks for sharing the thought process for dealing with mistakes. I appreciate your attitude in handling this.

Archie

[Kees Heiden]

Sure, it's not for the queen of England, it's only for my bathroom! I do all this in the first place for fun. Working out a solution was fun. Running back to the lumberyard and getting a new 180 euro piece of wood might make me a better craftsman, but certainly wouldn't be fun!

Anyway, on to the rest of the piece. I am going to botch up the interior parts now.

(And I like your story George, thanks for sharing, I might learn something from it in the end anyway).

[Jim Koepke]

Great save Kees.

jtk

[John Kananis]

Kees, I really like your solution and the piece looks really good.

[Patrick Chase]

You didn't make this for the Queen of England (like I have!), did you?

Now THAT is a gloat (and a well-earned one at that).