All of this relates to the task of setting up and using the horizontal spindle surface grinder.It is atthis point that you start putting together a large number of variables that through your skill andobservation can result in an accurate workpiece.As the operator,you will have more control of theoutcome in surface grinding than in nearly any other portion of the machinist's trade.This is also wherethe wheel selection and preparation：l~ocess are put to the test.
In surface grinding，it is necessary to reverse one of the more usual principles of machining used inmost of the other chip-making processes.In both turning.and milling for metal cutting volume，the machinist：tries to keep the depth of cut to a maximum,adiusting all,the other variables such as speed sand feeds to match that concept.In surface grinding，the important,thing is to match the actions of work piece speed，crossfeed,and downfeed to keep the grinding action as consistent as possible，while at the same time avoiding damage to the workpiece.The example used in this unit will be in the grinding of a vee block,but before beginning with that，some other generalities about horizontal spindle surface grinding should be considered.
Starting with a broad surface of a soft steel like AISI 1018，a suitable selection of wheel and grinding variables would be as follows：An aluminum oxide abrasive，of 46 grit sizes in a J bondhardness.The bond itself is vitrified.Tlae wheel speed for vitrified wheels is usually from 5500 to 6500sfpm；the table speed would be 50 to 100 Sfpm.The-crossfeed rate would be 0.050 to 0.500 in.per pass,with a maximum being one.fourth the wheel width.For roughing，the downfeed would be o.003 in。，andfor finishing，0.001 in.maximum.
If the salne AISI 1018 material were pack hardened（carburized）to about 55 Rockwell C，how would this change the initial recommendations？The wheel speed and the table speed would remain the same.The abrasive chosen a.nd the grit size would also remain the same，but the bond selected would beone grade softer,or I bond.The roughing downfeed would change to 0.002 in，and the finishing to0.0005 in.The greatest change in recommendation other than the grade of the wheel would be in the way that the cross feeding is done.Here the recommendation would be 0.025 to 0.250 in with one-tenth of the wheel width taken as a maximum.All of these recommendations are based on a sharp wheel prepared with a dresser that is in good condition.If the dressing is done incorrectly so that the wheel is dulled'it could make the recommendations useless.
A general observation in horizontal surface grinding is to keep the cross feed travel as large as possible，and the downfeed adjustments matched so that you cannot hear a significant change in grinding wheel speed during the work's traverse under the wheel.This procedure helps to keep，the surface of the wheel parallel to the spindle and avoids excessive dressing，providing the grade and abrasive fiiabilityare correctly matched to the work piece needs.
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