Lathe chucks are used to accurately clamp a workpiece on a lathe for turning operations or can be used on an indexing fixture for milling operations. Manual lathe chucks manually open or close jaws with a screw or pinion. Power lathe chucks use hydraulics, pneumatic or electricity to close the jaws. They have a high gripping accuracy and are designed for mass production.
Parts of a Lathe Chuck
Material:
- Cast Iron (Semi-Steel) is the industry standard for chuck body material.
- Forged Steel or steel chucks have greater accuracy, less wear and can be operated at higher RPMs.
To determine which type of spindle nose mounting your lathe requires, consult the diagrams and general measurement information.
American Standard “A” Series Spindle
Type A: Tapped holes in flange without inner bolt circle.
Type B: Tapped holes in flange and inner bolt circle.
| Spindle nose size | B max. [in] | E1 (UNC-3B) | F1 [in] | E2 (UNC-3B) | F2 [in] |
|---|---|---|---|---|---|
| 3 | 2.13 | 7/16-14 | 2.78 | 7/16-14 | - |
| 4 | 2.50 | 7/16-14 | 3.25 | 7/16-14 | - |
| 5 | 3.25 | 7/16-14 | 4.13 | 7/16-14 | 2.44 |
| 6 | 4.19 | 1/2-13 | 5.25 | 1/2-13 | 3.25 |
| 8 | 5.50 | 5/8-11 | 6.75 | 5/8-11 | 4.37 |
| 11 | 7.75 | 3/4-10 | 9.25 | 3/4-10 | 6.50 |
| 15 | 11.25 | 7/8-9 | 13.00 | 7/8-9 | 9.75 |
| 20 | 16.25 | 1-8 | 18.25 | 1-8 | 14.50 |
| 28 | 23.00 | 1-1/4-7 | 25.50 | 1-1/4-7 | 20.87 |
Camlock “D” Series Spindle
| Spindle nose size | B max. [in] | E1 (UNC-3B) | F [in] |
|---|---|---|---|
| 3 | 2.13 | 3 x 0.59 | 2.78 |
| 4 | 2.50 | 3 x 0.66 | 3.25 |
| 5 | 3.25 | 6 x 0.78 | 4.13 |
| 6 | 4.19 | 6 x 0.91 | 5.25 |
| 8 | 5.50 | 6 x 1.03 | 6.75 |
| 11 | 7.75 | 6 x 1.22 | 9.25 |
| 15 | 11.25 | 6 x 1.41 | 13.00 |
| 20 | 16.25 | 6 x 1.66 | 18.25 |
Long Taper Key Drive “L” Series Spindle
| Spindle nose size A | A. [in] | B. [in] |
|---|---|---|
| L00 | 2.750 | 3-3/4" - 6" |
| L0 | 3.250 | 4-1/2" - 6" |
| L1 | 4.125 | 6" - 6 |
| L2 | 5.250 | 7-3/4" - 5" |
| L3 | 6.500 | 10-3/8" - 4" |
Threaded Spindle
| Spindle nose size A | B [in] |
|---|---|
| 1" - 10" UNS-2B | 1.015 |
| 1-1/2" - 8" UN-2B | 1.515 |
| 2-3/16" - 10" UN-2B | 2.2025 |
| 2-1/4" - 6" UN-2B | 2.2600 |
| 2-3/16" - 6" UN-2B | 2.2025 |
| 2-3/4" - 8" UN-2B | 2.7600 |
Chuck Application
Self centering scroll chucks are ideal for gripping cylindrical or concentric work because all jaws work in unison and automatically center the piece. The jaws on the scroll open and close with a wrench that is turned on a pinion.
- 2-jaw self-centering are used for rectangular shaped parts as a stationary fixture.
- 3-jaw self-centering are the most versatile and ideal for holding round parts (bars, rings and pipes.)
- 4-jaw self-centering are used for square parts
- 6-jaw self-centering are used for thin-walled parts. More gripping points allow for even distribution of clamping forces and prevention of distortion.
Independent chucks are designed with jaws that move independently of one another. Ideal for gripping irregularly shaped workpieces or eccentric operations. They have a longer setup time than self-centering chucks.
Combination chucks (self-centering with individual jaw adjustment), allow each jaw to be operated independently or move simultaneously as a self-centering scroll chuck. Ideal for repeatable centering of oddly shaped parts. Individual jaw adjustment also allows for reducing runout on regular jobs.
Chuck Mounting and Spindle Nose Information
- Direct mount chucks do not require additional adapter plates. They can only mount on one particular spindle nose type (eg. D1-6).
- Plain back chucks require adapter plates to mount on a spindle nose. The same chuck can be used on different machines.
- Plain back chucks (front-mounting) are designed with mounting bolts that go from the face through the chuck body. They are used with A-type adapter plates and mount on base plates or indexing fixtures.
- Radially adjustable mounting chucks are designed so that the chuck body can be moved by utilizing adjusting screws to reduce runout. Requires a matching adapter plate.
Fully finished adapter plates do not require any machining to work. They do not allow for any adjustment or compensation of possible run-out of the spindle. They only fit plain back chucks with matching mounting dimensions.
Semi-machined adapter plates are machined on the spindle nose’s side and blank on the chuck’s side. They require machining to work and can be used with wide selection of chucks.
Radially adjustable chuck adaptor plates only work with the same manufacturer’s chucks. They do not require machining.
Lathe Chuck Jaws
Hard Lathe Chuck jaws are used for holding a workpiece on a lathe chuck. They are made of a case-hardened steel and have serrated clamping surface for securing the work during a machining operation. Ideal for rough-finished parts.
Lathe Chuck Jaw Designs:
- Solid jaws are designed to ensure the best rigidity, but take longer to replace.
- 2-piece jaws (with tongue-and-groove interface) are easy to swap and allow for having multiple jaw setups.
Soft (Machinable) Lathe Chuck jaws are used for holding a workpiece while turned on a lathe. They are made of soft materials such as aluminum or mild steel and can be machined to precise specifications for accurately aligning the workpiece during an operation. They can be cut to match the diameter of the specific part, maximizing surface of contact. Ideal for use on fine-machined parts.
Mounting Instructions:
Chuck Mounting Information: Using Intermediate Plates for Standard Flat Back Lathe Chucks: Lathes must be leveled with a precision level.
NOT for "Adjustable RunOut" models (see separate instructions).
When using a Chuck Adapter Plate to mount a flat back lathe chuck:
- The lathe must be levelled with a precision level; this assures machining accuracy.
- Adapter plate or chuck plate is to be mounted on lathe spindle.
- A skim facing cut across the full face of the adapter must be made. This assures that the face is at 90° to the centerline of the lathe spindle.
- The chuck plate has a boss onto which the recess in back of the chuck must mount. Turn the boss to fit tightly into the chuck body. The accuracy of this operation is directly relative to best results.
- Turn the O.D. of the chuck plate to match the chuck — not always the same size of the chuck body, especially with 4-jaw independent chucks.
- In most cases the chuck has threaded holes in the chuck body, to accept mounting bolts, or the chuck plate has threaded holes, for chucks having through holes in the body for front insertion. In some instances, it may be necessary to transfer hole locations and drill clearance holes.
- "A" type adapters come in two versions: A-1 has two bolt circles (inner and outer), A-2 has a single bolt circle (outer) of tapped holes. The chuck adapter is fastened to the spindle separately, then the chuck is fastened to the plate.
- Lathes having threaded spindle noses follow similar procedures 1 thru 6.
Adapter Plate Information
Chuck Mounting Information: Using Intermediate Adapters - For ADJUSTABLE RunOut Chucks, known as: “Adjust-Tru,” “Set-Tru,” “Zero-Set,” “Set-Rite,” “Hi-Tru,” “Accu-Chuck,”
This type of chuck is designed so that the chuck body can be moved by utilizing adjusting screws. A ground pin is held firmly in the chuck mounted on the lathe. The pin is trammed with a test indicator and the adjusting screws used to correct the runout. The design of the chuck adapter permits the chuck adjusting screws to contact an extended boss on the plate, facilitating adjustment. Each brand chuck requires its matching adaptor — same manufacturer or specific identification — they are not interchangeable (unless so indicated).
These adapters are to be "zeroed in" prior to actually mounting the chuck by taking a skim facing cut across the flange. All other dimensions should be compared to the back of the specific chuck and machined accordingly, if necessary. Once the mounted chuck has been “zeroed-in” in all respects, the chuck must be “locked” into the adjusted position. Double check with ground pin and test indicator.