Fig. 21. Two Types of Floating Reamer Holders
There are many different designs of floating holders but the general principle upon which they are based is illustrated by the two types shown in [Fig. 21]. The reamer and holder shown to the left has a ball-shank A which bears against a backing-up screw B inserted in the end of holder C through which the driving pin passes. The lower end of the reamer shank is also spherical-shaped at D, and screw-pin E secures the shell reamer to this end. It will be noted that the hole in the shank for pin E is “bell-mouthed” on each side of the center and that there is clearance at F between the shank and reamer shell; hence the reamer has a free floating action in any direction. This holder has given very satisfactory results.
The holder shown to the right is attached to the face of the turret by four fillister-head screws. Sleeve C is held in plate A by means of two steel pins B which are tight in plate A and made to fit freely in bayonet grooves D. Reamer holder E floats on sleeve C, the floating motion being obtained through the four steel pins G extending into driving ring F. Two of the pins are tight in the holder E and two in sleeve C. The faces of sleeve C, driving ring F, and reamer holder E are held tightly against each other by means of spring H which insures the reamer being held perfectly true. Spring H is adjusted by means of nut I which is turned with a spanner wrench furnished with each holder. The reamer is so held that its axis is always maintained parallel to the center of the hole, and, at the same time, it has a slight self-adjusting tendency radially, so that the hole and reamer will automatically keep in perfect alignment with each other.
Fig. 22. Multiple-spindle Cylinder Boring Machine
Multiple Cylinder Boring Machine.—In automobile and other factories where a great many gasoline engine cylinders are required, multiple-spindle boring machines of the vertical type are commonly used. The machine shown in [Fig. 22] is a special design for boring four cylinders which are cast en bloc or in one solid casting. The work is held in a box jig which has a top plate equipped with guide bearings for holding the spindles rigidly while boring. The lower end of each spindle has attached to it a cutter-head and the boring is done by feeding the table and casting vertically. This feeding movement is effected by power and it is disengaged automatically when the cutters have bored to the required depth. The particular machine illustrated is used for rough boring only, the cylinders being finished by reaming in another similar machine. The cylinders are bored to a diameter of 35/8 inches, and about 3/8 inch of metal is removed by the roughing cut. The spindles have fixed center-to-center distances as the machine is intended for constant use on cylinders of one size, so that adjustment is not necessary. Of course, a special machine of this kind is only used in shops where large numbers of cylinders of one design are required continually. Some cylinder boring machines of the vertical type have spindles which can be adjusted for different center-to-center distances if this should be necessary in order to accommodate a cylinder of another size.