8 Unit 12 Structural Metals . . . . . . . . . . . . . . . . . . . 163 What is Metal? 163 Metals Supplied for Welding 166 Metal Specifications 166 Unit 13 Common Types of Joints and Welds . . . 169 Joint Types 169 Weld Types 169 Joints and Grooves 171 Terms Used to Describe Welds 171 Unit 14 Welding Symbols . . . . . . . . . . . . . . . . . . . 175 Elements of a Welding Symbol 175 Reference Line 177 Weld Symbol 177 Arrow 178 Tail 180 Supplementary Symbols 180 Dimensions 182 Contour and Finish Symbols 183 Notations 183 Nonpreferred Weld Symbols 183 Reading and Explaining a Welding Symbol 186 Unit 15 Fillet Welds . . . . . . . . . . . . . . . . . . . . . . . . 191 General Use of Fillet Weld Symbol 191 Intermittent Fillet Welds 194 Fillet Welds in Holes and Slots 194 Specifying Fillet Weld Contours 194 Combination Weld Symbols 195 Unit 16 Groove Welds . . . . . . . . . . . . . . . . . . . . . . 203 Root Opening, Groove Angle, and Bevel Angle 204 Preparation Size and Effective Throat of Groove Welds 204 General Use of Groove Weld Symbol 205 Groove Dimensions 206 Surface Finish and Contour of Groove Welds 207 Melt-Through, Back, and Backing Welds 207 Backing, Joint Spacers, and Runoff Weld Tabs 208 Flare-Groove Welds 209 Combination Weld Symbols 210 Unit 17 Plug and Slot Welds . . . . . . . . . . . . . . . . . 219 General Use of the Plug and Slot Weld Symbol 220 Size of Plug Welds 220 Countersink Angle of Plug Weld 220 Slot Weld Details 222 Filling Depth of Plug or Slot Welds 222 Spacing Plug or Slot Welds 223 Surface Contour of Plug or Slot Welds 223 Unit 18 Spot, Seam, and Projection Welds . . . . . 235 Spot Welds 236 Size and Strength of Spot Welds 236 Spacing of Spot Welds 236 Extent of Spot Welding and Number of Spot Welds 236 Flush Spot Weld Joints 237 Multiple Member Joint Spot Welds 238 Seam Welds 238 Size and Strength of Seam Welds 238 Length of Seam Welds 239 Dimensioning of Intermittent Seam Welds 239 Orientation of Seam Welds 240 Flush Seam Weld Joints 240 Multiple Joint Seam Welds 240 Projection Welds 240 Stud Welds 242 Side Significance 243 Stud Size, Spacing, and Number of Studs 243 Location of Stud Welds 243 Unit 19 Surfacing Welds . . . . . . . . . . . . . . . . . . . . 253 General Use of Surfacing Weld Symbol 254 Surfacing Weld Dimensions 254 Location, Extent, and Orientation of Surfacing Welds 254 Unit 20 Edge Welds . . . . . . . . . . . . . . . . . . . . . . . . 259 Multiple Member Edge Welds 259