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Tips for Ordering Drill Chucks and Arbors

Arbor and Chuck

The basics:
Drill Chucks are often connected to a machine's spindle with a removeable Drill Chuck Arbor. The arbor is simply a double-ended shaft of steel, with one end machined to fit up into a machine's spindle, and the other end machined to fit into the back of a drill chuck. A second common type of machine has no removable arbor: the chuck instead mounts directly onto a male projection machined into the spindle itself.

For machines with removeable, interchangeable arbors:
To find an arbor/chuck combination that works for a given machine, first identify the type of spindle on the machine. (For instance, a milling machine might have an R8 spindle; a drill press might have a #3 Morse Taper (MT) spindle; a lathe tailstock might hold 2MT tooling.) If you have questions about identifying the spindle of your machine, consult your machine's documentation and/or measure the dimensions of relevant parts and compare them to the reference charts below.

After identification of the machine's spindle, select a chuck. (Choose a chuck based on holding capacity, machine torque, keyed vs keyless, etc.) Note how the selected chuck mounts to the machine's spindle/arbor assembly. Most chucks intended for use on a drill press will mount via a female Jacobs Taper (JT) hole in the back of the chuck. (Some chucks have female-threaded backs instead; these chucks are often used on hand-held drills with threaded spindles.)

With both the machine spindle and drill chuck mount identified, choose an arbor that matches both specifications. For instance, to use a 3JT chuck with an R8-spindled mill, the only arbor that will work is an R8-3JT arbor. To use a 33JT chuck with a 3MT-spindled drill press, the only arbor that will work is a 3MT-33JT arbor.

For machines with no removable arbor:
These machines are often smaller benchtop drill presses. The spindle-integrated male chuck mounts are usually 33JT, but this should be confirmed with actual measurements. Select a 33JT chuck to mount on a 33JT-spindled machine.

Taper Size Charts and Diagrams

MT-JT Arbor Diagram

            (A)         (B)        (C)
  0        .250"       .228        .438
  1        .384        .333        .656
2 short    .549        .488        .750
  2        .559        .488        .875
  3        .811        .746       1.219
  4       1.124       1.037       1.656
  5       1.413       1.316       1.875
  6        .676        .624       1.000
 33        .624        .561       1.000

            (A)        (B)        (C)
  0        .356"      .252       1.938
  1        .475       .369       2.063
  2        .700       .572       2.500
  3        .938       .778       3.063
  4       1.231      1.020       3.875
4-1/2     1.500      1.266       4.313
  5       1.748      1.475       4.938
  6       2.494      2.116       7.000
  7       3.270      2.750       9.500

B+S         LARGE      SMALL
             (A)        (B)       (C)
  1         .239"      .200       .938
  2         .230       .250      1.188
  3         .375       .313      1.500
  4         .402       .350      1.250
  5         .523       .450      1.750
  6         .600       .500      2.375
  7         .725       .600      3.000
  8         .899       .750      3.563
  9        1.067       .900      4.000
 10        1.289      1.045      5.688
 11        1.532      1.250      6.750
 12        1.797      1.500      7.125
 13        2.073      1.750      7.750
 14        2.344      2.000      8.250
 15        2.615      2.250      8.750

Helpful Hints and Links

Just replacing an old chuck?
Check the old chuck body for specification labeling. The capacity and mounting specs are usually stamped or etched onto the chuck, making it fairly easy to choose a suitable replacement. Confirm any specification labels with actual measurements.

Measuring Morse and Jacobs tapers:
With a caliper, measure the large and small ends of the taper and match the dimensions to the correct chart. (For instance, when trying to match a tapered part that inserts into a spindle or tailstock, it's most likely a Morse Taper part and that chart should be consulted first. When trying to identify a taper that is known to fit into a drill chuck, consult the Jacobs Taper chart.) Make sure to take the large and small measurements with the proper distance between them; i.e. if you think you have a 33JT mount, take the large measurement 1" from the small. If you are trying to match a 3MT part, take the large measurement about 3-1/16" from the small.

How does it stick?
In drill presses, it's common for the spindle/arbor/chuck assembly to be held together solely by the friction between the mating surfaces of tapered tooling.

Removing tapered arbors from spindles:
A Drill Drift can be used to knock removeable tapered arbors free from a spindle.

Removing chucks from JT arbors or integrated JT spindles:
Properly sized Drill Chuck Removal Wedges can be forced together between the chuck body and the arbor shoulder to push the chuck off the tapered arbor. (For example, 33JT wedges are used to remove a chuck from a 33JT arbor.) Wedges will NOT separate a threaded-back chuck from a threaded arbor. If you are having difficulty separating your old chuck from a drill press or portable drill, here are Jacobs' instructions for mounting or removing a drill chuck.

Links to some of our related tooling:
If you are looking for a drill chuck, we offer Jacobs key-type drill chucks as well as quality import drill chucks. We also carry several types of keyless drill chucks.

We stock various accessories for drill presses: chuck removal wedges, drill drifts, morse taper arbors, straight shank arbors, and R8 drill chuck arbors.