TM 1-1500-204-23-9 NOTE A 0.002 to 0.005 inch clearance should be provided. This may be accomplished   by   scraping   or   reaming the   lead   bushing   in   the   center   of   the wheel. (5)  Mount the wheel on the shaft, and ensure that it fits without play. (6)  Install another blotter and then the outer flange. (7) Install the washer and the nut. CAUTION Do    not    overtighten    the    spindle    nut. Failure to comply may result in cracking of the grinding wheel. (8)    Tighten  the  nut  sufficiently  to  hold  the  wheel firmly. (9)  Operate the grinder for a minute or two in order to test for breakage. WARNING · Always   wear   safety   goggles   when using   grinder.      Failure   to   comply may result in serious bodily injury. · Ensure that the abrasive wheels are firmly   attached   to   the   spindles   by the  flange  nuts.    If  a  wheel  should loosen    or    detach,    serious    bodily injury could result. · Ensure  that  tool  rests  are  firmly  in place.  A loose tool rest could cause the   tool   or   piece   of   work   to   be grabbed by the wheel and cause the hand  of  the  operator  to  contact  the wheel.      Serious   bodily   injury   may result. e.    Dressing  and  Truing.    Grinding  wheels,  like  other cutting  tools,  require  frequent  reconditioning  of  cutting surfaces  to  perform  efficiently.    Dressing  is  the  term used  to  describe  the  process  of  cleaning  the  periphery of   grinding   wheels.      This   cleaning   breaks   away   dull abrasive  grains  and  smooths  the  surface  so  that  there are no grooves.  Truing is the term used to describe the removal  of  abrasive  from  the  cutting  face  of  the  wheel so   that   the   resultant   surface   runs   absolutely   true   to some other surface such as the grinding wheel shaft. (1)  Dressing procedure.  To dress a wheel, proceed as follows (see figure 6-6): (a)   Start the grinder and let it come up to speed. (b)    Set   the   wheel   dresser   on   the   tool   rest   as shown in figure 6-6 and bring it in firm contact with the wheel. Figure 6-6.  Dressing a Grinding Wheel (c)  Move the wheel dresser back and forth across the   face   of   the   wheel   until   the   surface   is   clean   and approximately square with the sides of the wheel. (2)  Wheel re-balancing.   If  grinding  wheels  get  out of  balance  because  of  out-of-roundness,  dressing  the wheel   will   usually   remedy   the   condition.      A   grinding wheel  can  get  out  of  balance  by  being  left  sitting  with part   of   the   wheel   immersed   in   the   coolant;   if   this happens, the wheel should be removed and dried out by baking.      If   the   wheel   gets   out   of   balance   axially,   it probably will not affect the efficiency of the wheel.  This unbalance  may  be  remedied  simply  by  removing  the wheel and cleaning the shaft spindle and spindle hole in the wheel and the flanges. WARNING Do  not  attempt  to  make  any  adjustment to  the  tool  rest  until  the  grinder  is  shut down and the power disconnected. Failure  to  comply  may  result  in  serious injury to the operator. 6-5