Thread: A Coffee Table With A Twist

Since my last post I routed a roundover on both top and bottom edges of the tabletop as can be seen in the two photo's below:

66IMG_E0273.jpg 67IMG_E0272.jpg

Everything rested on the next part of this project being as accurate as possible with all parts working correctly. My choice of hinges were the SOS Concealed type The Soss-brand invisible hinges face the wall when the tabletop is folded and are concealed when the top is open.: they're pretty strong little thing but have two mortise depths. So mortising is a two step process and the face has to be completely flush to the frame edge.

68IMG_0269.JPG 69IMG_0270.JPG

Initially I was going to use a Forstner bit to drill two holes and then chisel the rest of the mortise but I was worried of splitting the wood as it's endgrain. I also could have paid for the SOS concealed hinge jig but what would have been the fun in that!, So I built my own which I believe is much better than the SOS one. I also had to figure out a way to clamp the jig and clamp the table tops in my bench vise while I mortised everything.

In the first photo you can see what I had to build just to get the hinges attached. The second photo is a picture of the first jig and second jig I built, the first one worked ok but I found a solution to get more accurate stops. You can see some of my many efforts to perfect this jig before commencing with the actual table, not risking anything!. incidentally the jig needed a bushing attached to the router.

70IMG_0256.jpg 71IMG_E0253.jpg

Here's a photo of the clamp up. You can see the two boxes I made so the tabletop was raises to a workable
level for my bench vise. What a carfuffle!, all this just to get a small job done. I'm sure there's a better solution but this is the one I came up with at the time. Second photo shows the hinge fitted and flush with the edge.

72IMG_E0249.jpg 73IMG_0267.jpg

I was relieved to see both table leaves open and close perfectly, alignment was spot on in both open and closed states. Next I needed to route a 2mm groove for both open table sides. The reason the ends were filled was because of the mortising that had to take place on the edges and I was unsure how much room I had to play with after the hinge mortise was completed. This is just more for aesthetics than anything as I didn't want an interrupted rail lines.

74IMG_0252.jpg

As mentioned before in this thread I was going to use some geometry to find the exact location of the pivot point. Also Auscab in post#69 mentioned you can draw the base dimension on a piece of scrap board to scale to find the pivot point, I believe this was is the traditional way of finding the pivot point however I dipped my feet into abit of geometry. hopefully the following explains how I found the pivoting point.

Point (A) is the midpoint of the hinge line with the table folded in the two-seat position, while point (B) is the midpoint of the hinge line with the tabletop rotated and in the six-seat position. I then draw lines from both points at 45° to the line A-B; their intersection marks the pivot point (C).
75MG_0257.jpg

With all that in mind, I measured and marked the pivot point on both bottom table leaf and carcass tray. I then drilled a hole into the centre of the marked pivot point to accept an M10 bearing. As I understand it the traditional way would have been to use a metal plate instead of a bearing but I decided to go this route, I figured it would make for a smother pivot action anyway. For the pivot pin I used a brass M10 hex bolt which passed through the bearing and out the other side of the carcass tray. The bolt would then screw into a block with a threaded insert on the underside of the bottom coffee table leaf.

CA Glue was used to secure the bearing to the tray:

76MG_0257.jpg

The pivot block and stops attached to the bottom of the coffee table leaf:

77MG_E0259.jpg 78IMG_0258.jpg

Just a matter of laying the leaf down, taking out a draw and screwing in the M10 pin:

79IMG_0265.jpg

With everything attached it was time to test it all!.

And with a twist and a flip, a coffee table for two becomes a coffee table for eight!. I'm happy and releived to say it works beautifully!. Beacuse its a dynamic piece of furniture I will be making a video of the table working when its completly finished.

I'll be revisiting the drawers in my next post.