"Five thousand double-Gloucester cheeses at fourpence-halfpenny each......"

The previous post showed the making of a bending form for three standard (or floor) lamps; since the shape of the upright gradually tapers in both width and thickness (like the table legs on which it is modelled) some thought was called for. Tapering the width is simple enough — just saw the shape from the finished lamination — but the taper in the thickness cannot be sawn. Well actually it can, but it would look singularly horrible at the points where the saw cut crosses the glue lines at a shallow angle. The answer is to taper the individual strips that make up the lamination; when glued together the total taper will be the sum of the tapers of the individual strips. 

Before this could be done, I needed to know how many strips would be required; the maximum thickness of an individual strip will be that which can be bent around the form without breaking. (Something less than this probably a good idea, given that wood is an inconsistent sort of thing; also the actual task of laying up the stack of laminations is made a good deal harder with overly springy (springful?) strips. A merely moderate pressure needed to force one strip around a sharpish bend becomes a serious test of upper body strength when multiplied by eight.) In this case I decided on a maximum thickness of just over 0.25", with each  consisting of eight strips.

Now the tricky bit: how much to taper each individual strip so that the final stack is 1.75" thick at one end and 2.375" at the other? (Hint: this is much easier in millimetres.) Also, how to cut each strip to the correct dimension? The total taper is 5/8" (.625"), and the individual taper of each strip is then one-eighth of this, or a bit over 1/16". The strips are about seven feet long.

Without being a woodworking bore, one answer is to stick an eight foot piece of 2x6 pine through the thickness planer, thus ensuring a true upper surface; then by some means* taper this piece by the required 3/32". When this is accomplished, each lamination strip in turn can be placed on this prepared board, and run through the thickness planer; the taper of the board will then be reproduced on each strip. However, a thickness planer is far from ideal for this operation; thin wood is likely to self destruct when passing under the whirling knives, and even if it successfully negotiates the cutter-head, there will be problems of chatter and grain tear out. A thickness sander sounds like a much better idea, but I don't have one.

* "By some means" also glides over an inconvenient truth: I don't have a good way of doing this. Trial and error (mostly error) was used to finally bring an individual trial strip to the proper measurement. An added complication was that the lower two thirds of the finished lamination had to have virtually no taper, the desired shape swelling gently as it starts to curve, but not before.


So, this what it looks like: the tapered pine board is on the bottom; a 1/4" piece of jatoba is sandwiched between it and the cutter head, and with any luck will emerge slightly thinner at one end than the other. There are 23 more strips to do.