MACH 118: Lathe & Mill 1 Lathe Workholding

Explain the uses and care of independent and universal chucks. OBJECTIVES tab After completing this unit, you should be able to… Explain the uses and care of independent and universal chucks. Explain the limitations and advantages of collets and describe a collet setup. Explain the use of a face driver or drive center. Explain the uses and differences of drive plates and face plates.

Lathe Spindle Nose LATHE SPINDLE TOOLING tab The lathe spindle nose is the carrier for a variety of work- holding devices, fastened to it in several ways. The spindle is hollow and has an internal Morse taper at the nose end, which makes possible the use of taper shank drills or drill chucks. This internal taper is also used to hold live centers, drive centers, or collet assemblies. Fig. I-107 Section view of the spindle.

Lathe Spindle Nose LATHE SPINDLE TOOLING tab The outside of the spindle nose can have either a threaded nose (Fig. I-108), a long taper with key drive (Fig. I-109), or a camlock (Fig. I-110). Threaded spindle noses are used mostly on older lathes. The chuck or face plate is screwed on a coarse right-hand thread until it is tight. The tapered key drive spindle nose relies on the principle that a tapered fit will always repeat its original position. The key gives additional driving power.

Lathe Spindle Nose LATHE SPINDLE TOOLING tab Fig. I-109 Long taper with key drive spindle nose. Fig. I-108 Threaded spindle nose. Fig. I-110 Camlock spindle nose.

Lathe Spindle Nose LATHE SPINDLE TOOLING tab Two disadvantages of the threaded spindle nose: The spindle cannot be rotated in reverse against a load. It is sometimes difficult to remove a chuck or face plate. Fig. I-111 The chuck can be removed by using a large monkey wrench on one of the chuck jaws while the spindle is locked in a low gear. A long steel bar may also be used between the jaws. The knockout bar should never be used to remove a chuck, as it is too light and will bend.

LATHE SPINDLE TOOLING tab Lathe Spindle Nose All spindle noses and their mating parts must be carefully cleaned before assembly. Small chips or grit will cause a work-holding device to run out of true and be damaged. A spring cleaner is used on mating threads for threaded spindles. Fig. I-112 A spring cleaner is used for cleaning internal threads on chucks.

Independent Chucks LATHE SPINDLE TOOLING tab Independent four-jaw & universal three-jaw chucks are mounted on the spindle nose of engine lathes. Each of the four jaws moves independently of the others, which makes it possible to set up oddly shaped pieces. Fig. I-113 Four-jaw independent chuck holding an offset rectangular part.

Independent Chucks LATHE SPINDLE TOOLING tab Concentric rings on the chuck face help set the work true. Each jaw of the chuck can be removed & reversed to accommodate irregular shapes.

Independent Chucks LATHE SPINDLE TOOLING tab Some types are fitted with top jaws that can be reversed when bolts on the jaw are removed, to grip larger-diameter workpieces. The independent chuck will hold work more securely for heavy cutting than the three-jaw universal chuck. Fig. I-114 Four-jaw chuck in reverse position holding a large-diameter workpiece.

LATHE SPINDLE TOOLING tab Universal Chucks Universal chucks usually have three jaws, but some are made with two jaws, or six jaws. All the jaws are moved in or out equally in their slides by means of a scroll plate located in back of the jaws. Fig. I-115 Two-jaw universal chuck. (Courtesy of Hardinge Inc.) Fig. I-116 Six-jaw universal chuck. (Courtesy of Buck Chuck Company)

Universal Chucks LATHE SPINDLE TOOLING tab The scroll plate has a bevel gear on its reverse side that is driven by a pinion gear. Universal chucks provide quick and simple chucking and centering of round stock. Uneven or irregularly shaped material will damage them.

Universal Chucks LATHE SPINDLE TOOLING tab The jaws of universal chucks will not reverse, so a separate set of reverse jaws is used to hold larger diameter pieces. The chuck & each of its jaws are stamped with identification numbers. Fig. I-118 Universal three-jaw chuck (Adjust-tru) with a set of outside jaws (Courtesy of Buck Chuck Company).

LATHE SPINDLE TOOLING tab Universal Chucks Removing & Replacing Jaws

Universal Chucks LATHE SPINDLE TOOLING tab A universal chuck with top jaws is reversed by removing the bolts in the top jaws & reversing them. They must be carefully cleaned when this is done. Soft top jaws are frequently used when special gripping problems arise. Fig. I-119 Universal chuck with top jaws. (Courtesy of Haas Automation, Inc.)

Universal Chucks (machinable or soft jaws) LATHE SPINDLE TOOLING tab Universal Chucks (machinable or soft jaws) Because the jaws are machined to fit the shape of the part they can grip it securely for heavy cuts. A disadvantage is loss of accuracy when the scroll & jaws wear. Normally there is no compensation for wear other than re-machining the jaws. Fig. I-120 Machining soft jaws to fit an oddly shaped workpiece on a jaw turning fixture.

Independent And Universal Chucks LATHE SPINDLE TOOLING tab Independent And Universal Chucks The three-jaw adjustable chuck shown here has a compensating adjustment for wear or misalignment. Fig. I-121 Universal chuck (Adjust-tru) with special adjustment feature (G) makes it possible to compensate for wear (Courtesy of Buck Chuck Company).

Other Chucks And Chuck Components LATHE SPINDLE TOOLING tab Other Chucks And Chuck Components Drive plates are used together with lathe dogs to drive work mounted between centers. The live center fits into the spindle taper and turns with the spindle. A sleeve is sometimes used if the spindle taper is too large in diameter to fit the center. Fig. I-123 Drive plate for turning between centers.

Other Chucks And Chuck Components LATHE SPINDLE TOOLING tab Other Chucks And Chuck Components To machine the entire length of work mounted between centers without the interference of a lathe dog, special drive centers or face drivers can also be used to machine a part without interference. Quite heavy cuts are possible with these drivers, especially for manufacturing purposes. Fig. I-125 Face driver is mounted in headstock spindle, and work is driven by the drive pins that surround the dead center.

Other Chucks And Chuck Components LATHE SPINDLE TOOLING tab Other Chucks And Chuck Components Unlike drive plates that have only slots, face plates have T slots and are more heavily built. Face plates are made of cast iron & so must be operated at relatively slow speeds. If the speed is too high, the face plate could fly apart. Fig. I-126 T-slot face plate. Workpieces are clamped on the plate with T-bolts and strap clamps.

Other Chucks And Chuck Components LATHE SPINDLE TOOLING tab Other Chucks And Chuck Components Collet chucks are accurate work-holding device, used in producing small high-precision parts. Steel spring collets are available for holding & turning hexagonal, square, and round workpieces. They are made in specific sizes with a range of only a few thousandths of an inch. Fig. I-127 Side and end views of a spring collet for round work.

Other Chucks And Chuck Components LATHE SPINDLE TOOLING tab Other Chucks And Chuck Components An adapter called a collet sleeve is fitted into the spindle taper & a draw bar inserted in the spindle at the opposite end. The collet is placed in the adapter and the draw bar is rotated, which threads the collet into the taper and closes it. Never tighten a collet without a workpiece in its jaws, as this will damage it. Fig. I-128 Cross section of spindle showing construction of draw-in collet chuck attachment.

Other Chucks And Chuck Components LATHE SPINDLE TOOLING tab Other Chucks And Chuck Components The rubber flex collet has a set of tapered steel bars mounted in rubber. It has a much wider range than the spring collet, each collet having a range of about 1/8 in. Fig. I-129 Rubber flex collet.

Review Describe the purpose and advantages of: 3 jaw chuck 4-jaw chuck Collet chuck What is a face plate and how is it used? What three types of spindle noses are found on lathes? Which type of spindle nose is not suited for reverse turning? Which type of spindle nose is most common? What type of taper is found on the common lathe spring collet? Which type of chuck has the most holding power relative to the others?

Internet Resources tab Information on lathe spindle tooling: http://www.workholding.com http://www.buckchuckusa.com http://www.royalprod.com