figure 8 fasteners to attach table top

[Tyler Davis]

I am building a hutch and need to attach the top next. The aprons and top are both white oak. The top is three pieces edge-glued to a total width of 20".

I have used a pocket screw at the center of each of the short aprons to securely attach the top. Now I need to secure the top to the long aprons, while allowing for movement across-grain.

I have not routed a groove to use traditional S-shaped tabletop fasteners, and it seems the Figure-8 fasteners would be my best option at this point. I have not used them before.

1. do you think Figure-8's will be strong enough to support the weight of the hutch? The furniture will be lifted by the tabletop when it needs to be moved.

2. how do I attach them? I'm hoping I can chisel a recess to house one side of the Figure-8's

[Doug Shepard]

I think you just typically use a forstner bit off-center to make the recess for the figure-8 type but I've always used the other type so somebody else will know for sure. But if you have a biscuit joiner you can still use the other type. I've always called them Z-clips but I think we're talking about the same type. I've never run a full length slot for them but just put them where I needed the clips, which you can still do after assembly unless your case is so shallow it wont allow the biscuit jointer to get between the sides.

[Prashun Patel]

You can use a forstner or a spade bit off center as suggested above. Clamp a sacrificial piece of wood to the inside of the apron to help support the bit. Then you clean up with a sharp chisel. Pretty easy.

Those fasteners, though, have 1/2-3/4" screws, which won't provide much holding power when you lift the top. You should really lift the piece by the aprons. Or - use those magic sliders and save your back altogether!

The simplest would actually be to use pocket screws. Drill your hole, then use a straight pilot bit to elongate the hole in the direction of the movement.

[glenn bradley]

I also use a Forstner but do it on the DP prior to assembly. Don't forget to chisel out the "points" to allow a slight rotation during movement. As to lifting the hutch by the top and expecting the figure 8's to hold, I guess that depends how many you plan to use, fastener type/size and how often you plan to move it. I would expect it to be the fastener that fails, not the figure 8(?). I have never had a top fail but don't move my tables like I do dining chairs ;-)

[Mike Henderson]

I use them too, and never had any problem with them coming loose when you pick up the table. As Glenn said, just use enough.

Try to figure out where you want the movement to occur and trim out the edges (points) in that location, like Glenn mentioned. For example, if you're making an expanding table with a couple of leaves, you want the movement to occur on the outside and not on the inside (you want the top to stay aligned with the apron on the inside).

Mike

[Tyler Davis]

good advice to use the Forstner bit. I will use 4 figure-8's along each long apron - hopefully that will be enough to support the lift. Lifting by the aprons is not an option since there are panels and doors under them.

so does the figure-8 allow movement based only on the oversized screw holes? Or are they expected to rotate within their recesses when the humidity changes?

[Prashun Patel]

Expected to rotate.

[Frank Drew]

I don't think these fasteners allow as much movement as the z-type fasteners, since they only rotate.

[Chris Tsutsui]

I use a spade bit and it works fine. The best tip I have is to make a starter hole with a center punch so your bit doesn't wander. The strength of the figure 8 is probably associated with the length of screws you use.

It would take quite a bit of weight to really bend or break the figure 8.

I'm talking about the ones from Lee Valley.

[glenn bradley]

Or are they expected to rotate within their recesses when the humidity changes?

You can sort of see the chiseled out forstner holes at the rear of this nightstand. The pivot allows for well over 1/4" of movement in this install. More could be allowed.

There are only 2 fig-8's used here as the hidden stretcher acts as an attaching point as well.

http://www.sawmillcreek.org/attachment.php?attachmentid=103542&d=1229207222