Tapers & Adapters: Handy Lathe Accessories

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Morse & Jacobs Tapers       

Morse Tapers offer a way to hold tools such as drill chucks, live centers, mandrels, and drive spurs inside a tapered collet when doing woodturning on a lathe. Morse Tapers come in eight sizes from 0 through 7. The most commonly used sizes for woodworkers are Morse Tapers 2 and 1 (MT#2 and MT#1).

To determine the size of the Morse Taper that you need, measure the large diameter of the hole where the taper fits into the machine. If it measures close to 3/4", it needs a MT#2; if it measures close to 1/2", use a MT#1. See the chart for other sizes.

Morse Taper #

Large Dia.

Small Dia.

Length

0

.3561”

.2520”

1.9375”

1

.4750”

.3690”

2.0625”

2

.7000”

.5720”

2.5”

3

.9380”

.7780”

3.0625”

4

1.231”

1.020”

3.875”

5

1.748”

1.475”

4.9375”

Some Morse Tapers have a threaded hole on the end of the small diameter to accommodate a drawbar – a threaded rod or bolt that fits into the small end of the arbor and is secured on the outside of the headstock or tailstock of the lathe. The drawbar applies tension to the Morse Taper to prevent it from loosening without tailstock pressure.

Morse Tapers should be kept clean, because a buildup of wood shavings or dirt can cause the taper to slip inside the collet or seat incorrectly. Some lathes have self-ejecting tailstocks that make removal of the taper for cleaning easy. For others, use a knockout bar.

The Jacobs Taper, a shorter version of the Morse Taper, is generally used to hold drill press chucks. The most common sizes are JT#3 (.811" at the large diameter) and JT#33 (.624" at the large diameter).

Chuck Adapters (Inserts)

Woodturning lathe chucks use adapters, also called inserts, that thread onto various sizes of drive spindles and allow chucks to be used on different lathes. Some manufacturers will use the same internal thread pattern on all of their chucks. Then they use inserts that will screw into the back of the chuck that will have different size thread patterns on the inside of the adapter to fit various lathes. Most adapters will not interchange with other chucks made by a different manufacturer.

The size of the adapter needed will depend on the thread pattern of the drive spindle on your lathe. The thread pattern is usually shown with the diameter followed by how many threads there are per inch. Example: 1" x 8 TPI would be interpreted as a 1" in diameter and 8 threads per inch. Common sizes are: mini lathes, 1"x 8 TPI, and larger lathes, 1-1/4" x 8 TPI.

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