CAUTION Before operating a pneumatic tool, inspect the air hose and check it for leaks or damage. Blow air through the air hose to free it of foreign material  before  connecting  it  to  the  tool.  Keep the air hose clean and free from lubricants. Never point the air hose at another person. Pneumatic tools must have complete lubrication. The moving parts of pneumatic tools are fitted very closely, and they must be lubricated correctly or they will wear quickly and fail to work. Valves and pistons on pneumatic hammers require a light machine oil. Since the compressed air comes directly  in  contact  with  these  parts,  it  has  a  tendency to drive the lubricant out through the exhaust. When  working  continuously  with  a  pneumatic tool,  you  should  regularly  check  the  lubricator  to ensure there is ample lubricant available. Next, empty the  filter  assembly  as  needed. On low-pressure compressed air systems that do not have the filter, the regulator, and the lubricator assembly installed, you should disconnect the air hose every hour or so and squirt a few drops of light oil into the   air   hose   connection.   Do   NOT   use   heavy   oil because the oil will cause precision parts to either fail or  to  have  operating  troubles.  If  this  occurs,  you  have to  clean  your  tool  in  cleaning  solvent  to  loosen  the gummy  substance  that  results.  Blow  out  the  tool  with air, lubricate it with light oil, and go back to work. Keep your pneumatic tools clean and lubricated and you will have few operating problems. SHOP MACHINERY Prefabrication  of  steel  parts  and  assemblies  is typically accomplished in a steel shop where heavy steel working machinery is accessible. The steel shop is tasked with manufacturing and fabricating items, such as sheet-metal ducts, pipeline section fittings, plates, and angles. In the following sections, we will discuss some of the common types of machinery found in a well-equipped steel shop. COMBINATION  IRON  WORKER The  combination  iron  worker  is  likely  the  most valuable  and  versatile  machine  in  a  shop.  The combination  punch,  shear,  and  coper  (fig.  12-8)  is capable of cutting angles, plates, and steel bars, and it can also punch holes. The size of the angles and plates that can be safely handled by the machine depends upon its capacity. It is manufactured in various sizes and capacities, and each machine has a capacity plate either welded or riveted on it. This guide should be strictly  adhered  to.  The  pressure  and  power  the machine develops demand extreme caution on the part of  the  operator. VERTICAL BAND SAWS While  the  vertical  band  saw  is  designed  primarily for making curved cuts, it can also be used for straight cutting.  Unlike  the  circular  saw,  the  band  saw  is frequently  used  for  freehand  cutting. The band saw has two large wheels on which a continuous narrow saw blade, or BAND, turns, just as a  belt  is  turned  on  pulleys.  The  LOWER  WHEEL, located  below  the  WORKING  TABLE,  is  connected to the motor directly or by means of pulleys or gears and  serves  as  the  driver  pulley.  The  UPPER  WHEEL is the driven pulley. The saw blade is guided and kept in line by two sets  of  BLADE  GUIDES:  one  fixed  set  below  the table   and   one   set   above   with   a   vertical   sliding adjustment. The alignment of the blade is adjusted by a  mechanism  on  the  back  side  of  the  upper  wheel. TENSIONING   of   the   blade—tightening   and loosening-is provided by another adjustment located just back of the upper wheel. Cutoff gauges and ripping fences are sometimes provided for use with band saws. However, you will do most of your work freehand with the table clear because accurate cuts are difficult to make with a band saw  when  gauges  or  fences  are  used. The  size  of  a  band  saw  is  designated  by  the diameter of the wheels. Thus the 14-inch model (fig. 12-9) has 14-inch wheels. Common sizes are 14-, 16-, 18-, 20-, 30-,  36-,  42-,  and  48-inch  machines.  The 14-inch size is the smallest practical band saw. With the exception of capacity, all band saws are much alike in  maintenance,  operation,  and  adjustment. Blades,  or  bands,  for  bandsaws  are  designated  by POINTS  (tooth  point  per  inch),  THICKNESS  (gauge), and WIDTH. The required length of the blade is found by  adding  the  circumference  of  one  wheel  to  twice  the distance between the wheel centers. Length can vary within a limit of twice the tension adjustment range. Vertical  band  saws  are  comparatively  simple machines to operate. Each manufacturer publishes a technical  manual  for  their  machine.  Refer  to  the 12-3