Saturday, September 8, 2012

Starting the base - Continuing the Olive Ash Burl Table

OK,  now for the base. I actually had a base for this table about 90% done then scrapped it for a whole new design. . .a painful experience that I don't want to talk about. On my second attempt again I made a full scale drawing. I knew I wanted the legs to curve so I just played with lines in pencil until I found something I thought looked pleasing to the eye. I darkened the lines with a sharpie and then I had a good drawing to work from.

Now from that drawing I could make some patterns for the legs. Working the same way I did with the table top I made tracings of the legs and with those I could make the forms to make the tapered bent lamented legs.The reason I chose this method was the legs are much stronger then cutting them from a solid piece of wood and with the glue in between the strips its actually stronger then a steam bent piece.                                                                                                                                 

To make the forms I placed the tracing on 1/4" plywood and retraced the inside of the leg on the plywood using graphite paper. Once the arc was on the plywood I extended it out in either direction 3" so I would be able to make the form a little larger the the actual leg size. I then cut the pattern out. To make the form it was just a matter of adhering the 1/4' template to some 3/4' particle board and cutting it flush with a flush trim router bit. Once you have one piece cut I just traced it onto anther piece of particle board, cut it just out side the line with the band saw, screwed it to the first piece and flush trimmed it again. I did this until I had a stack of three pieces.
Form pattern
Now that I had the bending forms made it was time to make the 3 sleds used to taper the lamination's that make up the legs. From the full scale drawing I could get the measurement for the amount of taper in each leg. It worked out that two of the legs measured 1-1/2" at the top and the third 1-3/4". I decided that I would make all three 1-3/4" at the top. Two of the legs joined at the bottom at a little over 1" and the third was around 7/8".

OK here is the math. If I made all the legs from 6 pieces it works out like this. 1.75" (top) - .875" (bot) = .875"(amount of taper) divided by 6 = .145" (a little less than 5/32) so I rounded up to 3/16". I mean it is wood after all and I'm not a tool and die worker. The other two legs worked out like this:
1.75 - .562 (1/2 of the adjoining legs) = 1.188"( amount of taper)  divided by 6 =.198 or 3/16. From this information I decided to make the all the lamination's taper 3/16". I then got the length of each leg off  the drawing, cut a piece of particle board 4" wide by the length plus a few inches extra, and tapered the piece 3/16" on my jointer. I  started the taper a few inches in from one end so it wouldn't affect the overall taper.

I did this for all three legs and made sleds to use in my planer the same way as the rest of the forms made earlier. I chose to use oak for the base because I wanted to ebonize the base and oak has a high tannin level that makes it a good choice for this process.I cut  some 1/4' strips on the band saw to length for each of the 6 legs and ran them through the planer.
Tapering sled

  With all the pieces tapered it was just a matter of gluing them up in the forms with Unibond 800. I used a vacuum press and for some reason I could not get them to stay completely down on the forms so I had to alter my plan a little.

When the first leg went into the press it was clamped down good and tight but for some reason when it came time to take it out of the bag it was off the form a little so I decided to go ahead and do another leg and see what happened. Well as it turned out, the thickness of the strips made it hard for the pieces to stay clamped down so after the first two legs were done and almost exactly the same shape I decided to keep those two and add a 7th lamination in the rest of the legs so after all that math I had figure for one more piece and take a little more off the pieces already tapered.This made the pieces easier to clamp down and everything worked fine after. Well now of course I couldn't use the full scale drawing anymore because the legs didn't exactly match. I laid the legs out on the drawing to see how close they were. I tried a few different options until I was happy,marked them, and pushed on.


In the next post, I will explain how I did the joinery, the stretchers between the legs, and the finish. That should wrap this project up

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