Machinery's Handbook, 31st Edition
Cutter Grinding 905 between centers while mounted on a mandrel. The cutter is rotated to the position where the vertical indicator contacts a cutting edge. The second indicator is positioned with its spindle axis horizontal and with the contact point touching the tool face just below the cut ting edge. With both indicators adjusted to read zero, the cutter is rotated a distance equal to the checking distance, as determined by the reading on the second indicator. Then the indicator drop is read on the vertical indicator and checked against the values in the tables. The indicator drops for radial relief angles ground by a disc-type grinding wheel and those ground with a cup wheel are so nearly equal that the values are listed together; values for the eccentric-type relief are listed separately, since they are larger. A similar procedure is used to check the relief angles on the side and end teeth of milling cutters; however, only one indicator is used. Also, instead of rotating the cutter, the indicator or the cutter must be moved a distance equal to the checking distance in a straight line. Table 4. Indicator Drops for Checking Rake Angles on Milling Cutter Face
Indicator Drop
Set indicator to read zero on horizontal plane passing through cutter axis. Zero cutting edge against indicator.
Measuring Distance Move cutter or indicator measuring distance.
Measuring Distance, inch
Measuring Distance, inch
Rate Angle, Deg.
Rate Angle, Deg.
.031
.062
.094
.125
.031
.062
.094
.125
Indicator Drop, inch
Indicator Drop, inch
1 2 3 4 5 6 7 8 9
.0005 .0011 .0016 .0022 .0011 .0022 .0033 .0044 .0016 .0032 .0049 .0066 .0022 .0043 .0066 .0087 .0027 .0054 .0082 .0109 .0033 .0065 .0099 .0131 .0038 .0076 .0115 .0153 .0044 .0087 .0132 .0176 .0049 .0098 .0149 .0198 .0055 .0109 .0166 .0220
11 12 13 14 15 16 17 18 19 20
.0060 .0121 .0183 .0243 .0066 .0132 .0200 .0266 .0072 .0143 .0217 .0289 .0077 .0155 .0234 .0312 .0083 .0166 .0252 .0335 .0089 .0178 .0270 .0358 .0095 .0190 .0287 .0382 .0101 .0201 .0305 .0406 .0107 .0213 .0324 .0430
10 .0113 .0226 .0342 .0455 Relieving Attachments.— A relieving attachment is a device applied to lathes (especially those used in tool-rooms) for imparting a reciprocating motion to the tool-slide and tool, in order to provide relief or clearance for the cutting edges of milling cutters, taps, hobs, etc. For example, in making a milling cutter of the formed type, such as is used for cutting gears, it is essential to provide clearance for the teeth and so form them that they may be ground repeatedly without changing the contour or shape of the cutting edge. This may be accomplished by using a relieving attachment. The tool for “backing off” or giving clearance to the teeth corresponds to the shape required, and it is given a certain amount of reciprocating movement, so that it forms a surface back of each cutting edge, which is of uniform cross section on a radial plane but eccentric to the axis of the cutter sufficiently to provide the necessary clearance for the cutting edges.
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