Page:Practical Treatise on Milling and Milling Machines.djvu/104

98 of replacing the broken teeth. The economy of this is of considerable importance to a shop.

If, for any reason, it becomes necessary to replace the full set of blades, or teeth, the new ones are clamped securely in position, and afterwards sharpened to correct any slight difference in height.

Teeth are released by removing the screw and inserting an extractor that threads into the bushing, and has a long end that reaches to the bottom of the hole in. the cutter body. This extractor is shown in position in Fig. 54. As the extractor is turned by means of a wrench, the bushing is forced out and the tooth can then be removed.

Another type of inserted tooth face milling cutter that can be easily made in any shop is shown in Fig. 49. The teeth in this case are simply round pieces of steel inserted in holes made in the cast iron body of the cutter, and held in place by set screws. Sometimes two sets of teeth are put in these cutters. With this arrangement on heavy work that is not wider than the diameter of the inner circle of teeth, and which does not require close limits, the outer circle of teeth can be set to take a roughing cut, and the inner circle to take the finishing cut; thus work can be finished milled at one traverse of the table. Or if an exceptionally heavy roughing cut is to be taken off, the stress can be divided between the two circles of teeth.

Method of Holding Face Milling Cutters. Face Milling Cutters

are drawn directly onto the taper nose of the spindle by a cutter driver and drawing-in bolt. driver fits into a slot in the face of the cutter and a recess in end of spindle. The shank of the cutter driver is threaded in the end to receive drawing-in bolt by which the cutter is drawn Fig- 55 onto the spindle with the aid of a wrench. Cutter, cutter driver and drawing-in bolt are shown at top of page 91.

This method of attaching face milling cutters is simple and convenient and assures a positive drive. All possibility of "freezing" is eliminated, the removal of the cutter being as easily accomplished as its placement. Diagram of section through spindle and cutter, Fig. 55, shows cutter driver in place.