46 - Utility Workbench, страница 8
SHOP PROJECT k Tightening two "jam" nuts against each other makes it easy to install the hanger bolts. Leg Supports The legs of this shop stool are connected by two thick, triangular supports, see drawing. Actually, they're modified triangles — with sweeping curves instead of straight lines. The three curved sides create narrow arms that fit into the notches in the legs. LOWER SUPPORT In addition to providing a convenient footrest, the lower support has another (more important) job. To make the seat adjustable, the post threads into a hole in the center of the support. GLUE UP PANEL. I started work on the lower support by edge-gluing enough l1/2,l-thick stock (maple) to make an 18"-wide panel, see Fig. 5. Then, after trimming the panel to a length of 16", the next step is to lay out the shape of the lower support. LAYOUT. A large arc (83AM radius) establishes the outside ends of the arms, see Fig. 5. The only problem is the compass I ordinarily use was too small to draw the arc. So I made a compass from scrap, see Fig. 5a. To draw the arc, center the tip of the compass on the width of the blank and set it in 83/4M from one end. The point where this arc touches the end of the blank is the centerline of one arm. It's used as a starting point to locate the centerlines of the other two arms. The idea is to locate these centerlines 120° apart This isn't difficult. Just set the tip of the compass at the starting point. (You may need to move it in about 732" to "bite" into the wood.) Then draw two small arcs that intersect the large arc, see Fig. 5. SECOND: draw lines connecting centerpointto centerlines of arms FIRST: lay out end of this arm FOURTH: draw sides of triangle by connecting arms (These are just intermediate arcs.) Now place the tip of the compass on one of the intermediate arcs and draw another arc. The intersecting point establishes the centerline of the first arm. Then just repeat th<^ process for the second arm. ™ DEFINE ENDS. The next step is to lay out the narrow ends of the arms. To match the thickness of the legs, each arm is 172" wide at the end. So for one arm (the one formed by the end of the blank), all that's needed is to make a mark 3/4" to each side of the centerline, see Fig. 6. But laying out the other two arms is trickier. To do this, you'll need to draw a line that touches the circle at one point only. (Ifs tangent to the circle). This is a two-step process. First, lay out two lines that connect the center-point for the hole to the intersecting arcs made earlier. Then draw two perpendicular lines (the tangent lines) and lay out the ends of the arms. TRIANGLE. The basic groundwork is almost complete. But to make it easy to lay out the curved sides later, I drew three lines connecting the ends of the arms. (Now it's starting to look more like a triangle.) THREADED HOLE. This is also 'M good time to drill the hole for the threaded post, see Fig. 6a. Then you can cut the threads inside the hole. 8 ShopNotes No. 46 |
