Spiraled Bar

Both 1/8" x 3/4" and 1/4" x 1" aluminum bar make attractive ornamental spirals. Simply clamp one end in a bench vise, and twist the other end with a large wrench. To prevent "snaking" and to keep spirals straight and even, slip 1" outside diameter tube over 3/4" bar or 11/4" tube over 1" bar before twisting, as in Fig. 3-20.

Twist sufficiently to obtain a uniform spiral, but do not overtwist. Remember, one full twist (360°) produces two spiral edges as shown in Fig. 3-20. To make parts with matching spirals, count twists exactly .... as two full twists, 21/£ or 3 or 31/2, etc.....for each matching part.

Sharpening Or Flattening Angles

Both the 1/8" x 3/4" x 3/4" and the 1/16" x 1" x 1" angles sometimes require adjusting the 90° to some other value for certain projects, such as the exhaust hood in Fig. 7-2.

Figure 3-21 shows how to close the 90° angle; Fig. 3-229 how to open it. This method will provide accurate work if you count the exact number of turns on the vise handle. If the legs of the angle section become distorted, drive them through a saw slot cut lengthwise in a scrap piece of 2" x 4" about 12" to 16" long.

Fig. 3-22.

Bending 1/2" Rod

Face the jaws of a mechanic's vise with small pieces of 1/4" plywood, hardwood preferred. This will prevent marring the %" rod when clamping for bending by hand as shown in Fig. 3-23.

Pull up tightly against the wood while making the bend with the hands. Rod will assume a natural radius of bend. To duplicate this natural radius when making several pieces or when bending two curves to match, place hands the same distance from the vise and apply bending force in same amount and direction. For sharp bends, hammer with a rubber or wood mallet while applying bending force with the hand.

Forming 1/2" Rod

To make other than a plain 90° bend, as for the legs of the nesting table (Fig. 11-13) use a wood plane or a wood rasp to produce the exact curve desired on a form block. Then wrap the rod around this block while clamped in a vise as in Fig. 3-24, using a monkey wrench as shown for precision forming.

For compound forming where more than one curve is wanted, clamp two large wood screws or 1/4" diameter bolts in a vise. Make the first bend as shown in Fig. 3-23 or 3-24. Then make the second bend or curve as shown in Fig. 3-25, the first bend accurately positioning the second bend.

Fig. 3-23.

Fig. 3-24.

Precise Rod Bending

Various projects involve a number of lengths of 3/8" rod with 90° bends on each end, all to exactly the same dimensions. To make such rods match perfectly, drill a hardwood block to the depth required for the bend. Saw a slot part way through this block as in Fig. 3-26. Cut all rods to exact over-all length. Insert rod end into jig full depth, and clamp in vise. Slot allows vise grip to be applied to rod. Make the bend freehand, or hammer down with a rubber mallet if a sharp 90° bend is desired.

Where the end of the bent rod will be longer than the distance easily handled in a block, drill the hole clear through the block. Then mark rod where bend is to start, and insert rod through hole in jig until bend mark comes even with top of jig. Then clamp tightly with vise, and bend.

Fig. 3-25.

Shaping Rod Tips

Pointed, round, or smooth flat tips are easy to shape on an ordinary disk sander. Ends of bar, tube, and angle stock can be shaped in same manner.

Grinding Rod, Bar, Tube

As a general rule, avoid prolonged grinding of aluminum on a regular emery wheel because the "gummy" characteristic of the metal tends to load up the wheel, especially with heavy feeds. A power sander, either disk or belt type, is much superior for shaping aluminum. With a fairly coarse abrasive, loading will be no problem, yet cutting will be clean and fast.

Tube Bending

Figure 3-27 shows the simple jig which makes tube bending easy .... a straight "back" block and a form block. Anchor both securely to bench top, and space just far enough apart to accommodate the size tube to be bent. There are two things to do to prevent the tube from "kinking" when bending is attempted .... first, clamp it securely to the back block, preferably using two or more C-clamps. Use a scrap block of wood between clamps and tube; otherwise clamps will simply collapse the tube when they are tightened. For best results, saw a V lengthwise in the face of both back block and clamping block to reduce the tendency of clamping pressure to collapse the tube.

Second, use a clamp block long enough to wedge up against the form block. This will prevent any tendency of the clamp block to slide and allow the tube to move. Warning: Any movement of the tube lengthwise as you apply the bend will result in kinking and a spoiled piece of material.

To prevent tube collapse at the bend, avoid using too small a bend radius. Recommended minimum radius for 3/4" tube is 21/2" when packed with sand, 5" if unpacked; for 1" tube, about 43/4" packed, 91/2" unpacked; for 11/4" tube, 51/2" packed, 11" unpacked. These are safe minimum radii even for the inexperienced, providing the accompanying instructions are followed.

Packing the tube with sand helps prevent collapse and so permits radii about half those practicable without packing. Poke the tube up and down in a bucket of semiwet sand. If sand does not tamp well into tube, it probably is too wet; add more dry sand to mixture. If it tamps in but falls out, it may be too dry. Tap tube on concrete floor or sidewalk to pack sand down firmly. After bending, shake out sand or wash out with a hose.

For best results, the surface of the form block around which the tube is bent should be turned on a lathe or worked with a wood rasp to the same radius as the contour of the tube (3/8",1/2", or 5/8", respectively, for 1", and tube). This contacting jig surface will then support the tube better and prevent collapse. With skill and such a jig, appreciably smaller radii than those listed above become practicable.

Most important .... when making bends without sand, screw jig to bench top so tube sticks straight out over edge of bench at start of bend. Use your body and left hand to apply bending pressure as you start the bend, and with your free right hand strike sharp blows with a heavy rubber mallet on tube exactly over the point where bending is occurring. This helps the metal to upset on the inside of the bend and so keeps the bend smooth and uniform without collapsing. Watch as you make the bend .... if tube tends to collapse, stop further bend movement while you hammer vigorously to work the metal and control tube contour. Then renew your bending action . . . . work slowly. With a little practice you can easily make smooth, small-radius bends without difficulty.