Production drilling machines are of two sorts: Those designed for heavy drilling, and those for the lighter jobs.

Fig. 347. Ingersoll Horizontal Miller Doing Heavy Milling Note how lubricant floods the work in milling steel

Fig. 347. Ingersoll Horizontal Miller Doing Heavy Milling Note how lubricant floods the work in milling steel.

Heavy High-Speed Drillers

Fig. 348 is fairly representative of the type designed to use high-speed steel drills of the larger sizes to their full capacity. The frame or post of this machine is of a form similar to the frame of a punch or shear press. Pressure tests on a drill of 1 1/2-inch diameter, given a feed of 0.030 inch per revolution, have recorded a total load pressure of nearly three tons. From this it will be seen why the frame is made as shown. Feeds much in excess of 0.030 inch can be obtained in this machine. Use the coarsest feed practicable and balance the speed of cutting to it.

Light High-Speed Drillers

In the lighter jobs of drilling, a feed exceeding 0.015 inch per revolution is seldom used. Rapid production is gained in this case by maintaining a high cutting speed. Tables XVI and XVII, published by the Henry and Wright Company, show certain drilling practice where the feed does not

Fig. 348. Baker Driller Driving 2 1/2 Inch Drill through Drop Forged

Fig. 348. Baker Driller Driving 2 1/2-Inch Drill through Drop-Forged.

Wrought-Iron Saddles Courtesy of Baker Brothers, Toledo, Ohio exceed 0.016 inch per revolution. Fig. 349 shows a power feed, four-spindle high-speed driller. In designing this machine everything has been done to render its operation rapid and efficient.

Special Drillers

There are many of these, some of which are very complicated. Fig. 350 shows a machine designed for the single purpose of drilling the clearance holes in threading dies. By using four spindles and suitable work-holding table chucks, a die is completed for each stroke of the table.

Fig. 349. Four Spindle High Speed Bali Bearing Sensitive Driller Courtesy of Washburn Shops, Worcester, Massachusetts

Fig. 349. Four-Spindle High-Speed Bali-Bearing Sensitive Driller Courtesy of Washburn Shops, Worcester, Massachusetts.

Production Figures

While there are many records of high production drilling, due to the great variety of drill work, it is impossible to give a table to meet all needs.

Table XVI. Carbon-Steel Drills

Size

OF

Drill (in.)

Feed per

Rev. (in.)

Bronze Brass 150 Ft. r.p.m.

C. Iron Ann'ld r.p.m.

85 Ft.

Hard r.p.m.

C.Iron

40 Ft.

Mild Steel 60 Ft. r.p.m.

Drop Forg. 30 Ft. r.p.m.

Mal.

Iron 45 Ft. r.p.m.

Tool

Steel 30 Ft. r.p.m.

Cast Steel 20 Ft. r.p.m.

1/16

.003

....

5185

2440

3660

1830

2745

1830

1220

1/8

.004

4575

2593

1220

1830

915

1375

915

610

3/16

.005

3050

1728

813

1220

610

915

610

407

1/4

.006

2287

1296

610

915

458

636

458

305

5/16

.007

1830

1037

488

732

366

569

366

245

3/8

.008

1525

864

407

610

305

458

305

203

7/16

.009

1307

741

349

523

261

392

261

174

1/2

.010

1143

648

305

458

229

343

229

153

5/8

.011

915

519

244

366

183

275

183

122

3/4

.012

762

432

204

305

153

212

153

102

7/8

.013

654

371

175

262

131

196

131

87

1

.014

571

323

153

229

115

172

115

77

11/4

.016

458

260

122

183

92

138

92

61

11/2

.016

381

216

102

153

77

106

77

51

1 3/4

.016

327

186

88

131

66

98

66

44

2

.016

286

162

87

115

58

86

58

39