Tip #26
Drill Press (continued)
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Metal Drilling

Figure 7-50. Always be sure that metal to be drilled is firmly supported clsoe to the cutting area.

Metal drilling requires a firm support as close to the cutting area as possible (Figure 7-50). Warning: The workpiece should always be clamped or gripped in a device such as a drill press vise or locking pliers. Backup scrap should be used so the torque of the bit, as it breaks through, does not jerk the metal.

Figure 7-51. To drill metal, use a twist bit and feed it into the workpiece slowly while applying plenty of oil.

When drilling metal, set the speed to the maximum recommended or slower and use a sharp, high-quality twist bit. To determine the maximum recommended speeds for various metals, use the following formula: high-quality twist bit. To determine the maximum recommended speeds for various metals, use the following formula: Caution: Feed the bit very slowly into the workpiece and apply plenty of oil to the tip of the bit while you're drilling. This will keep the bit from dulling (Figure 7-51).

If the bit catches, back it out quickly; then feed it more slowly with less pressure. If the bit stalls completely and the quill won't retract, quickly turn off the Mark V. Back the bit out of the hole, turning it counterclockwise by hand. Once the bit is free, turn on the machine and feed the bit very slowly back into the workpiece. Once the bit goes through the workpiece, turn off the Mark V and let it come to a complete stop before you remove the workpiece.

Metal Drilling Layout
A scriber is usually used for marking metals, but often the line won't show clearly unless you bear down on the scriber. Since this might scratch the material more deeply than desired, special dyes are used to coat the metal (Table 7-4). Apply the dye coater. Don't "paint" the metal; a thin but even coat is sufficient. Allow it to dry then scribe the lines. The scribe lines should be just light enough to remove a tiny thread of the coating and thus reveal the metal beneath. The metal itself is not harmed. Warning: Prepare the dyes care-fully. Always follow safety cautions that may be on the container of the material you use.

Figure 7-52. Working with the scale flat and using the scriber to scratch a dimension mark can lead to inaccuracies.

When marking a dimension point, don't place the scale flat on the work and then scratch with the scriber to form the mark (Figure 7-52). A precise method is shown in Figure 7-53. Set the scale on its edge and then run the point of the scriber down the graduation groove. This will leave a fine dot as a dimension point, which is all you need.

Figure 7-53. When you work with the scale on edge and the scriber sliding down the groove in the scale, the dimension mark will be a fine point, which is all you need.

Figure 7-53. Work with an angle gauge or similar measuring device to mark lines parallel to an edge.

An angle gauge or similar marking tool (Figure 7-54) can be used as an edge-marking gauge when you need a line parallel to the edge or end of a piece of work. Maintain the scriber's contact as you move the gauge along. Dividers can be used to gauge the distance between holes (Figure 7-55) or to mark the locations of equally spaced holes.

Figure 7-55. Use dividers to gauge the distance between holes or to mark the locations of equally spaced holes.

Figure 7-56. Methods of working that do much to assure accurately drilled holes.

Drilling Preparations
After hole locations have been established, a prick punch is used to mark the hole's center. The prick punch has a slender, sharp point which is easy to place at the correct drilling spot. The small spot it makes is enlarged with a center punch, which forms a small well that serves as a seat for the point of the bit (Figure 7-56A).

Positive accuracy, especially when drilling large holes, is assured by using the method shown in Figure 7-56B. After the hole location has been prick-punched, scribe a circle the same size as the hole you want, or a bit larger, around the center mark. The scribed circle is a guide that will reveal any tendency of the bit to drift off center.

A way to work, should the bit start to drift, is shown in Figure 7-56C. Make a series of small chisel or prick punch marks as the illustration shows; then continue drilling.

Centering Pin Use

Figure 7-57. How a centering pin is used. The wood block under the stock is there to back up and keep the stock level.

A precise way to position work so the hole location will be centered with the bit point is to use a centering pin (Figure 7-57). The pin itself is a short length of 1/8" or 1/4" steel rod, sharpened to a fine point at one end. The work is gripped in a holding device, in this case a drill press vise, and is positioned indentation made with the prick punch. Clamp the vise firmly in place; then do the drilling after substituting the bit for the pin (Figure 7-58).

Figure 7-58. The bit is substituted for the centering pin after the stock has been positioned.

The drill press vise is a unique tool in that it is easily bolted to the worktable. The replaceable jaws have vertical and horizontal V-grooves so they can securely grip round stock, triangular pieces, and flat material.

Concentric Drilling
A drill press vise is commonly used to hold short pieces of round bar stock vertically for concentric drilling. But, a unique and practical way to work, if stock diameter permits, is to use a lathe faceplate as shown in Figure 7-59. An advantage is assurance that the stock will be in true, vertical position. Place the faceplate on a flat surface as you insert the stock and secure it with the faceplate's locking setscrew.

Figure 7-59. Use a lathe faceplate to hold round bar stock for concentric drilling. If the stock is positioned carefully, this idea can be used for stock with a diameter that is less that the hole size in the faceplate.

V-Block Drilling

Figure 7-60. The table and fence form a V-block so you can accurately drill diametric holes in round stock.

The combination of the rip fence and table as a V-block works for woodworking as well as metal-working. With the table tilted 45° and the fence secured, perfect support is created for drilling round stock (Figure 7-60).

Be sure that the setup is situated under the spindle so the bit meets the work at its highest point, which is the centerline of the work. Caution: If the hole is to go through the stock, use scrap wood under the work to protect the table and fence.

Countersinking

Figure 7-61. When countersinking metal, be sure to use a countersink that will cut at the correct angle for fasteners like machinge screws or stove bolts.

Machine screws and stove bolts often have countersunk heads, so they need a seat in the work if they are to be flush with work surfaces. Countersinking is done after the holes for the fasteners have been drilled. As with all metal work, be sure the workpiece is secure in a holding device and that the holder is clamped to the table (Figure 7-61).

Countersunk heads on stove bolts and machine screws have a different angle than those on wood screws, so be sure to use a countersink designed specifically for metalwork.

Spot Polishing

Figure 7-62. Spot polishing creates a distinctive finish on soft metal surfaces.

Spot polishing, or "damaskeening,"is an attractive finish easily accomplished on soft metals by working as shown in Figure 7-62. The spot-polishing tool being used is made by following the plan in Figure 7-63. The final appearance of the finish will depend on the uniformity of the application and how much you overlap the spots. Use a backup block under the work and set the rip fence so each set of spots will have a common centerline.

Figure 7-63. Construction details of the spot polishing tool.

Figure 7-64. Three examples of other types of homemade spot-polished tools.

You'll be able to judge immediately, by checking the first spot, just how much feed pressure you should use. Figure 7-64 shows some other types of spot-polishing tools you can make. When abrasive paper or steel wool is used to abrade the spots, the work is done dry. If a straight rod is used, a mixture of emery dust and light oil is used on the work. The turning rod causes the mixture to abrade the metal which, in turn, causes the spot to appear.

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