I have a 34" wide tabletop and 24" cleats which I want to attach to the underside of the tabletop using a long tapered sliding dovetail.
Is there any "rule of thumb" as to how much wider the entry side should be so that the dovetail can be driven home without too much slop at the entry end?
(12-27-2017, 10:59 AM)mound Wrote: [ -> ]I have a 34" wide tabletop and 24" cleats which I want to attach to the underside of the tabletop using a long tapered sliding dovetail.
Is there any "rule of thumb" as to how much wider the entry side should be so that the dovetail can be driven home without too much slop at the entry end?
Aren't both the male and female portions tapered? I've never done what you propose, but it seems to me they are IIRC correctly what Roy Underhill was showing on one of his projects.
John
Good question. I didn't think so but now I'm not sure. Surely that would complicate things!
(12-27-2017, 06:44 PM)mound Wrote: [ -> ]Good question. I didn't think so but now I'm not sure. Surely that would complicate things!
Use a tapering jig to cut the cleat to match the taper you mill in the underside of the table top. That's the only extra step.
The benefit is that when you install the cleat it will be tight in the slot and end up exactly where you want it to be in relation to the top. A straight cleat will only be tight at the closed end and the slop will increase more and more as you get to the open end. It can't hold the tabletop flat with that configuration.
This is no different than how a wedge is fit into the end of a stretcher in a trestle table. Both the wedge and stretcher mortise are tapered.
John
(12-27-2017, 07:08 PM)jteneyck Wrote: [ -> ]Use a tapering jig to cut the cleat to match the taper you mill in the underside of the table top. That's the only extra step.
The benefit is that when you install the cleat it will be tight in the slot and end up exactly where you want it to be in relation to the top. A straight cleat will only be tight at the closed end and the slop will increase more and more as you get to the open end. It can't hold the tabletop flat with that configuration.
This is no different than how a wedge is fit into the end of a stretcher in a trestle table. Both the wedge and stretcher mortise are tapered.
John
Thanks John. I'm having trouble visualizing what the tapering jig would look like to cut a matching taper on the edge of the cleat. For the underside of the tabletop it's just a matter of having two almost parallel fences for the router to ride between..
Mound,
In Fine Woodworking (#187–Nov/Dec 2006) Garrett Hack wrote an article about building a hunt board. This may have been a two-part article (published in two issues) I don't recall now if it was. In any event, the interior case dividers are attached to the bottom of the case with sliding dovetails. Hack explains how to cut the sliding dovetail joint with a router. I took his explanation and built a simple jig that works very well. Unfortunately, that was five or six years ago and I have misplaced it. I will try to explain it, but my explanation won't make much sense if you have't read Hack's article.
The jig is a fence to guide the router to cut the female socket of the sliding dovetail joint. The male member is cut on the router table. The jig has a 90degree bracket that aligns it to the workpiece. The fence is split into two parallel pieces, only one of which is attached to the 90 degree bracket. The other piece is attached to the first piece at the front, nearest the operator with a flexible hinge (I used a thin piece of maple and screwed it to the ends of both fence members). The hinge allows the two pieces to separate like a pair of scissors. The far end of the second piece of the fence floats. Look at the tapering jig John linked below for the general idea. Note, however, that in use, the operator stands at the hinged end of the jig rather than at the far end as pictured in the Woodcraft photo John linked. It works as follows:
To cut the female socket:
1. Align the jig and clamp it to the workpiece. There two fence pieces are clamped together so they are parallel with no gaps between them, I.E., a straight router guide fence.
2. Make the first cut with the router and dovetail bit. Actually, if I recall correctly, I made the first cut with a straight bit to waste out the socket and followed with the dovetail bit.
3. With the jig still clamped to the workpiece, separate the two halves of the fence and insert a thin piece of material (I used thin piece of maple about 3/32" thick) between the two fence pieces as a spacer so the fence members are no longer parallel. Measure and record the distance from the front of the jig to the near edge of the spacer. The spacer establishes the angle of the sliding dovetail.
4. Make a second cut with the router and dovetail bit. This gives you a wedge-shaped female socket. SAVE THE SPACER
To cut the male part of the sliding dovetail joint:
1. Set up your router table with the dovetail bit. I built a tall auxiliary fence that attaches to the fence on my router table to keep the upright workpiece vertical.
2. Make the first cut as you would normally.
3. Measure and mark on your workpiece the distance you recorded for the placement of the spacer described in #3 step of cutting the socket above. Attach THE SAME spacer to the workpiece at that point with a piece of thin double stick tape. The spacer should ride against the router table fence when you cut the second half of the male joint.
4. Cut the second half of the joint. The spacer should cause the router table setup to replicate the angle you made when you cut the female part of the joint.
Assemble the joint:
The male member should slide into the female member loosely and tighten up as it slides home. Tap with a mallet to seat the joint. I made my male pieces a little wide in case the angle was off a little and trimmed them to the correct width after test fitting them. Mine fit well on the first try.
This would make a lot more sense if I could find my jig. I'll look harder for it this afternoon and post photos if I find it. Meanwhile, look up Hack's article in FWW. It should tell you all you need to know.
HTH.
Hank
(12-29-2017, 08:05 AM)mound Wrote: [ -> ]Thanks John. I'm having trouble visualizing what the tapering jig would look like to cut a matching taper on the edge of the cleat. For the underside of the tabletop it's just a matter of having two almost parallel fences for the router to ride between..
I would cut the taper on the male half on my table saw using a typical shop made tapering jig.
Fancier than it needs to be version. Then you cut the dovetailed profiles on the router table.
John
(12-29-2017, 01:38 PM)jteneyck Wrote: [ -> ]I would cut the taper on the male half on my table saw using a typical shop made tapering jig. Fancier than it needs to be version. Then you cut the dovetailed profiles on the router table.
John
brilliantly simple! thanks
Thanks Hank nice writeup. Makes perfect sense
