How many figure-8 clips for this table?

[®smpr_fi_mac®]

I'm nearing completion of my trestle table build and now need to order figure-8 clips to attach the top to the base.

The top weighs in at about 135#.  The base is about 60#.

I am perfectly willing to put in as many clips as needed to ensure that when the table is lifted (if ever!) that the base will have zero risk of ripping off.

The top is 1.75" thick and the base parts where the clips will attach are the same, so I intend on using 1.25" screws with pilot holes.

Thoughts?

[Willyou]

I don't know how much weight each figure-8 will hold, but I suspect it is quite a lot; particularly with the size screws you propose. The company can probably tell you that information. Intuitively, I would say one every 10-12 inches will be very adequate.
However, a word of caution. One of the purposes of figure-8's and other clips is to allow for seasonal wood movement. When placing the figure-8's along the long side of the table (usually parallel to the grain of the top) about the only way to mount them is perpendicular to the table apron which ends up with the long axis of the figure-8 being also perpendicular to the grain of the top. In this position, the figure-8 cannot rotate to allow for seasonal movement of the top. For this purpose, I like "Z" clips better.

[FS7]

It's not the clips that you calculate load for, especially for something like this (pullout strength). A #8 screw at just over an inch of penetration will have a pullout strength of roughly 100#. Theoretically a single screw will hold the 60# base. 

I would not worry about it from a pullout perspective. Just use enough to ensure gaps are closed and it's stable. On my last table (now at the client's house) I used eight on a 36"x36" table - three each side with the grain, and one at 45 degrees on each side (allowing for expansion and contraction). That was very much overkill and the table is extremely solid.

[®smpr_fi_mac®]

I don't know how much weight each figure-8 will hold, but I suspect it is quite a lot; particularly with the size screws you propose. The company can probably tell you that information. Intuitively, I would say one every 10-12 inches will be very adequate.
However, a word of caution. One of the purposes of figure-8's and other clips is to allow for seasonal wood movement. When placing the figure-8's along the long side of the table (usually parallel to the grain of the top) about the only way to mount them is perpendicular to the table apron which ends up with the long axis of the figure-8 being also perpendicular to the grain of the top. In this position, the figure-8 cannot rotate to allow for seasonal movement of the top. For this purpose, I like "Z" clips better.

I've thought about this and in my research have found that the way to use them on the long stretches is to mount them about 15* off of perpendicular.  This way they'll have plenty of range for both expanding and contracting.

It's not the clips that you calculate load for, especially for something like this (pullout strength). A #8 screw at just over an inch of penetration will have a pullout strength of roughly 100#. Theoretically a single screw will hold the 60# base. 

I would not worry about it from a pullout perspective. Just use enough to ensure gaps are closed and it's stable. On my last table (now at the client's house) I used eight on a 36"x36" table - three each side with the grain, and one at 45 degrees on each side (allowing for expansion and contraction). That was very much overkill and the table is extremely solid.

Great.  Thanks.

[rwe2156]

I prefer buttons over figure 8's. I use my biscuit jointer to make the slots.

If I remember to, I use a mortiser before assembly.