Wednesday, September 5, 2018

Woodturning Live Center with Collet Chuck and Drawbar

I needed a means of holding and turning long thin spindles in such a way as to reduce chatter and vibration.  Live centers can introduce some problems if the tailstock is over tightened compressively.  Therefore, I wanted a means of holding the stock securely and without axial compressive forces which would contribute to vibrations and chatter.

My solution was the combination of a Collet Chuck and Live Center with a Drawbar.  Mounting this combination in the tailstock and securing the work piece in the collet chuck.  Next, move the quill on the locked tailstock  away from headstock and create some tension in the workpiece/spindle.  As a result, the workpiece is held firmly and steadily by the collet chuck.

One thing I noticed after turning very thin pieces (5/16" or 8mm) was the thin spindles demonstrated the ability to oscillate axially when the lathe was stopped.  Exerting a small amount of torque to the collet and releasing it would cause the spindle to oscillate axially in the fixture.  In any case, I have been very happy with the performance of this live center.

Live Center with Collet Chuck and Drawbar holding a spindle.

Stock mounted between OneWay Chuck with Spigot Jaws and the Collet Chuck.  This is the configuration I use
with my Lathe Duplicator, and has been used to turn spindles, balusters, stretchers and chair legs.

The complete assembly of Collet Chuck, Adapter and Live Center with Drawbar.

(A) Beall 1 1/4"-8 Collet Chuck, (B) Oneway Multi-Tip Revolving Center Chuck Adapter 3/4" 10TPI to 1-1/4 8TPI,
(C)  Oneway Live Center with 5/16" all-thread drawbar.

Wingnut on Drawbar to maintain tension on workpiece.

Holding Strength of a Collet Chuck

As an experiment, I mounted an accurate scale between the headstock and tailstock as seen in the photos below.  I drilled holes in a 3/4" piece of scrape wood and 1/2" dowel.  Baling wire was strung through the holes to form a loop for mounting the scale. The 1/2" dowel was secured in the Collet Chuck by hand tightening the chuck, and the 3/4" scrape was mounted in the Spigot Chuck.  Next, I mounted the scale, locked the tailstock and began cranking the quill away from the headstock and tightening the wingnut.  I was able to create over 100 lbs of force on this setup without the 1/2" dowel slipping in the Collet Chuck.

Scale mounted between headstock and tailstock.

Parts List and Sources:

  1.   Beall 1 1/4"-8 Collet Chuck
  2.   Oneway Multi-Tip Revolving Center Chuck Adapter 3/4" 10TPI to 1-1/4 8TPI
  3.   Oneway Live Center

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