46 - Utility Workbench, страница 11
thick, wood cylinder that raises and [lowers the seat
ROLLING PIN. This cylinder is like a giant rolling pin with a different length handle at each end. At the top end, a short tenon fits into the hole in the collar, see detail 'a.' And a long shaft on the bottom end threads up and down through the hole in the lower support, see detail 'b.' To prevent the post from flexing, a thick barrel (in the middle) fits inside the hole in the upper support.
DOWEL The barrel determines the size of the dowel used to make the post. I used a 2"-dia. maple dowel and cut it to a rough length of 22", see drawing at right.
The next step is to turn the shaft and tenon to size. The shaft is sized to fit a lW'-dia. threadbox (or router jig) that's used to cut the threads. And the tenon will fit in the lV^'-dia. hole in the collar.
TABLE SAW "TURNING." You could use a lathe to size the shaft and tenon. But I took a different approach that involves "turning" them to size using a table saw and a dado blade.
To do this, set the dado blade to make a very shallow (Vie") cut, see Figs. 13 and 13a. I also mounted an L-shaped fence to the miter gauge to support the post during the cut.
Why not use a regular fence? (You know, a scrap attached to the miter
gauge.) Well, I tried that. But with the dowel close to the miter gauge, I got a cramp in my hands from spinning it The L-shaped fence prevents that by supporting the dowel out in front (away from the miter gauge).
Before you get started, make sure the fence is clamped in place. I positioned it so the dowel would be centered over the saw blade, see Fig. 13a. Also, lock the rip fence in place and use it as a stop to establish the shoulder of the shaft (or tenon).
SHAFT. To form the shaft, hold the end of the dowel against the fence and lower it onto the spinning blade. Now slowly rotate the dowel toward you as if you're nibbling kernels off an ear of corn. After one full revolution, lift the dowel, move it away from the fence, and repeat the process.
To prevent the dowel from tipping into the blade, leave a band of waste to support the end of the shaft. Just be sure it's wide enough that it doesn't drop into the miter gauge slot. (A lV2"-wide band is plenty.)
After working your way to the end of the shaft, raise the blade another Vie" and make another series of passes. Then continue this process until the shaft is the correct diameter to fit into the threadbox. Note: The tenon is made in the same way.
CUT THREADS. Once everything is sized correctly, it's time to cut the
REMOVE WASTE AFTER TURNING TENON AND SHAFT TO SIZE
threads in the shaft. To fit the shaft into the threadbox, you'll need to trim the waste off the end. Then thread about an 8"-long section of the shaft, see Step 2 in drawing above. (For more on this, see page 14.)
TRIM POST. This threaded section is longer than what's actually needed. So before attaching the seat,
I used a hand saw to trim the post to final length, see Step 2 above.
GLUE IN POST. Now it's just a matter of gluing the post into the collar. The tenon should fit snugly in the hole, so no clamps are needed. But after applying glue and inserting the tenon in the hole, twist the post around to distribute the glue evenly.
ASSEMBLY. Once the glue dries, all thaf s left is to lower the end of the post down through the hole in the upper support and thread it into the hole in the lower support
FINAL DETAILS. Applying a finish and some paste wax will make the post spin freely. Finally, to prevent the post from threading out of the hole, screw a stop (G) to the bottom end. (I just used a toy wheel.)
TRIM POST TO A FINAL LENGTH OF 191/4"
THREAD S"-LONG SECTION OF SHAFT