How to Install Figure 8 Table Top Fasteners

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Introduction: How to Install Figure 8 Table Top Fasteners

About: Hi, I'm Brian. My goal is to make fine woodworking — and especially Japanese kumiko woodworking — accessible and fun.

As their name suggest, Figure 8 fasteners are generally used to safely and securely fasten the solid wood top of a table to its solid wood base.

In this instructable, I want to walk you through the simple steps to install them, and share something I haven't seen many talk about: exactly where on the base you should place your figure 8 clips.

Supplies

Step 1: Measure & Mark the Base for Fasteners

The first step is to lay out where the fasteners will go. Set a marking gauge, a combo square, or a ruler like I have here to just smaller than the radius of your figure 8s.

The fasteners I bought have a five eighths inch diameter, so I’m setting my ruler to just less than the radius of 5/16”. This will allow the fastener to pivot easier, which is how it protects from potential damage caused by wood movement.

Where to Install Figure 8 Fasteners on the Base

Notice I’m only marking on the short stretchers of the base. The purpose of these fasteners is to pivot to allow for seasonal wood movement, and the short stretchers are the best place to do that. Generally speaking, you’ll always want to install figure 8s on the stretchers that are perpendicular to the grain lines on the top, because that’s the direction most of the wood movement will occur.

Also notice that I’m marking the inner side of the rails. Doing this will hide the fastener in the final piece.

With all of the spots marked, I can come back with an awl to make a starter hole for my forstner bit.

Step 2: Drill a Shallow Recess With a Forstner Bit

Although most figure 8s don’t come with detailed instructions, they do tell you to use a forstner bit the size of the diameter, or slightly larger, to make a shallow recess for one side of the fastener.

As you’re drilling, go slow and check the fit often. The figure 8 should sit just below the surface of the base. It can’t be too far below because it will need to contact the tabletop as well. So just sneak up on the fit and stop when the entire fastener is below the surface.

Oh, and you may need to knock off the ears of the recess with a chisel like I did here to get enough clearance, especially if the forstner bit you used is the exact size of the diameter. So do that now.

Step 3: Drill Holes for Mounting Screws on the Base

In the point that the forstner bit left in each recess, drill a pilot hole for the small screws.

Once all the holes are drilled, you can attach the clips to the base. I'd recommend using a screwdriver instead of a drill to drive the screws; you want to avoid stripping these small holes.

Step 4: Drill Holes for the Mounting Screws on the Top

With all the fasteners installed to the base, now we can mate it to the top. Lay the top upside down on a protective surface. Turn the base over and place it on the top.

Align the two, then mark for the screws on the bottom of the top. Remove the base for a moment, and drill the holes for screws. One tip to make sure you don’t drill all the way through the top is to use a piece of tape like I did as a depth gauge.

Step 5: Attach the Base to the Top With Screws

Return the base to the top, screw to attach, and you’re done. Now the table and the top are securely together while still being allowed to move independently. It's as simple as that!

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    21 Comments

    0
    Stevens Workshop
    Stevens Workshop

    9 months ago

    Nice Instructable, I've done a couple of tables and never knew about figure of 8 fasteners. Thanks for the heads up

    0
    stanwitham
    stanwitham

    9 months ago on Step 5

    Thanks for sharing your project. I was not aware of how they were used.

    0
    bikecitywoodworks
    bikecitywoodworks

    Reply 9 months ago

    My pleasure! Hopefully you took away something from the video!

    0
    David R
    David R

    9 months ago on Step 5

    Very nice instructable. Best framed explanation for the function of figure 8 fasteners I’ve ever seen. Good job.

    0
    burzurk
    burzurk

    9 months ago

    Great good looking stuff man!

    0
    MarcR
    MarcR

    9 months ago

    If the top is plywood, wood movement is not much of an issue but otherwise, one cannot emphasize enough the importance of properly choosing the placement of the fasteners as you rightfully so recommend. Well done!

    0
    bikecitywoodworks
    bikecitywoodworks

    Reply 9 months ago

    Totally, I didn't mention it, but MDF, plywood, or OSB won't experience enough movement to warrant this!

    0
    williamhdixon
    williamhdixon

    Reply 9 months ago

    So, using the desk in your Instructable, if the top had been plywood, OSB or MDF, how would you have attached it? Pocket screws? Glue? Drill all the way through your frame and use long screws? Or would you just go ahead and use these fasteners?

    0
    bikecitywoodworks
    bikecitywoodworks

    Reply 9 months ago

    I wouldn't use glue just because of the difficulty of getting a good glue joint all around the table, but if it was a stable material like those you mentioned, I'd probably choose either pocketholes or long screws. Either one will work.

    Even on a solid wood top like this, long screws can work. The trick is, you a) also need to put them in the base stretchers perpendicular to the grain, and you need to create elongated holes so the screws can move inside the hole. I had considered it for this desk build, but ultimately decided not to because the process would have been the following:
    1. Purchase screws that are long enough to go through the base and into the top but not through the top.
    2. On the underside of the base, drill an elongated counterbore for the heads of the screws (they have to be flat, they can't be countersunk in this case)
    3. On the underside of the base, drill each hole for the screw, then elongate the holes in the direction perpendicular to the grain.
    4. Mark the holes on the underside of the top.
    5. Drill and attach.

    Seemed like so much more work to me!

    0
    RandyPerson
    RandyPerson

    9 months ago

    I've seen these fasteners for years, but until your intro photo, I did not realize I have a ready source for them. In a past life, I worked on motorcycles quite a bit. Drive chains wear, and are a routine replacement item. A Figure 8 fastener could substitute for a motorcycle drive chain side plate. Flip side - a worn out chain is a free source for hundreds of the fasteners. A cheap chain comes apart easily with a "chain breaker," like a small gear puller that pushes the pin out of the side plate. On tougher chains, you may have to grind the ends of the pins off, then push or punch them through. Free hardware, and reuse keeps the material out of the waste stream. Score!

    0
    burzurk
    burzurk

    Reply 9 months ago

    hahaha I was thinking similar :) "...what the eff is he doing with motorcycle chain links!?!"

    0
    mikesmithfl
    mikesmithfl

    9 months ago

    Thanks for the details. I didn't know about these either and agree with kenbob - the cleanliness of these is much better than other plates.

    Also, thank you for referring to the action as "drill a pilot hole" instead of 'pre-drilling'.
    I wish more people used the term.

    0
    stanwitham
    stanwitham

    Reply 9 months ago

    Re: your second sentence: I have seen a lot of work that would have turned out much better had the person, myself included, drilled a pilot hole first. It prevents splitting. I agree that " drilling a pilot hole" is a better term than "pre-drilling". It is more descriptive and helpful.

    0
    bikecitywoodworks
    bikecitywoodworks

    Reply 9 months ago

    Haha, you don't hear "pilot hole" much anymore! I'm super interested in what value Z-clips have now, because there must be a place for them?

    0
    kenbob
    kenbob

    9 months ago on Step 5

    Wow, did not even know such a thing existed. ( a perk of Instructables is the discovery of new tools and parts :) ) I have used the flat metal plates that insert into a slot in the base, but i like the cleanliness of these better. Thanks for sharing!