reading would be the circumference of a circle with a diameter  of  3  inches  and  would  be  the  length  of  a stretch-out   for   a   cylinder   of   that   diameter.   The dimensions for the stretch-out of a cylindrical object, then,  are  the  height  of  the  cylinder  and  the circumference. CUTTING TOOLS Various types of HAND SNIPS/HAND SHEARS are used for cutting and notching sheet metal. Hand snips are necessary because the shape, construction, location,  and  position  of  the  work  to  be  cut  frequently prevents  the  use  of  machine-cutting  tools. Hand  snips  are  divided  into  two  groups.  Those  for straight   cuts   are   as   follows:   straight   snips, combination  snips,  bulldog  snips,  and  compound  lever shears. Those for circular cuts are as follows: circle, hawk’s bill, aviation, and Trojan snips. These snips are shown  in  figure  2-15.  The  following  is  a  brief description of each type of snip. STRAIGHT  SNIPS  (fig.  2-15,  view  A)  have straight  jaws  for  straight  line  cutting.  To  ensure strength, they are not pointed. These snips are made in various sizes and the jaws may vary from 2 to 4 1/2 inches. The overall length will also vary from 7 to 15 3/4 inches. The different size snips are made to cut different thicknesses of metal with 18 gauge steel as a minimum  for  the  larger  snips.  These  snips  are available  for  right-  or  left-hand  use. COMBINATION SNIPS (fig. 2-15, view B) have straight jaws for straight cutting but the inner faces of the  jaws  are  sloped  for  cutting  curves  as  well  as irregular shapes. These snips are  available in the same sizes and capacities as straight snips. BULLDOG SNIPS (fig. 2-15, view C) are of the combination type, They have short cutting blades with long handles for leverage. The blades are inlaid with special alloy steel for cutting stainless steel. Bulldog snips can cut 16 gauge mild steel. The blades are 2 1/2 inches long and the overall length of the snip varies from 14 to 17 inches. COMPOUND  LEVER  SHEARS  (fig.  2-15,  view D)  have  levers  designed  that  give  additional  leverage to ease the cutting of heavy material. The lower blade is bent to allow the shears to be inserted in a hole in the bench or bench plate. This will hold the shear in an upright position and make the cutting easier. The cutting blades are removable and can be replaced. The capacity is 12 gauge mild steel. It has cutting blades that are 4 inches long with an overall length of 34 1/2 inches. CIRCLE SNIPS (fig. 2-15, view E) have curved blades and are used for making circular cuts, as the name  implies.  They  come  in  the  same  sizes  and capacities  as  straight  snips  and  either  right-  or left-hand  types  are  available. HAWK’S  BILL  SNIPS  (fig.  2-15,  view  F)  are used to cut a small radius inside and outside a circle. The  narrow,  curved  blades  are  beveled  to  allow  sharp turns without buckling the sheet metal. These snips are useful  for  cutting  holes  in  pipe,  in  furnace  hoods,  and in  close  quarters  work.  These  snips  are  available  with a 2 1/2-inch cutting edge and have an overall length of either 11 1/2 or 13 inches and have a 20 gauge mild steel  capacity. AVIATION  SNIPS  (fig.  2-15,  view  G)  have compound  levers,  enabling  them  to  cut  with  less effort.  These  snips  have  hardened  blades  that  enable them to cut hard material. They are also useful for cutting  circles,  for  cutting  squares,  and  for  cutting compound   curves   and   intricate   designs   in   sheet metal.  Aviation  snips  come  in  three  types:  right hand, left hand, and straight. On right-hand snips, the  blade  is  on  the  left  and  they  cut  to  the  left. Left-hand  snips  are  the  opposite.  They  are  usually c o l o r - c o d e d    i n    k e e p i n g    w i t h    i n d u s t r y standards-green   cuts   right,   red   cuts   left,   yellow cuts straight. Both snips can be used with the right hand. The snips are 10 inches long and have a 2-inch cut and have a 16 gauge mild steel capacity. TROJAN   SNIPS   (fig.   2-15,   view   H)   are slim-bladed  snips  that  are  used  for  straight  or  curved cutting. The blades are small enough to allow sharp turning  cuts  without  buckling  the  metal.  These  snips can be used to cut outside curves and can also be used in place of circle snips, hawk’s bill snips, or aviation snips  when  cutting  inside  curves.  The  blades  are forged high grade steel. These snips come in two sizes: one  has  a  2  1/2-inch  cutting  length  and  a  12-inch overall length and the other has a 3-inch cutting length and  a  13-inch  overall  length,  They  both  have  a  20 gauge  capacity. Modern  snips  are  designed  to  cut  freely  with a  minimum  curling  of  the  metal.  The  snips  are generally  held  in  the  right  hand  at  right  angles  to the  work  (fig,  2-16).  Open  the  blades  widely  to obtain  maximum  leverage.  Do  not  permit  the  ends to  close  completely  at  the  end  of  a  cut  or  a  rough 2-6