Turning the Tama

By far the most difficult task of this project for me was turning the tama.  I had never turned a sphere before and it proved to be more difficult than I imagined.  All of my early attempts at tamas were either egg shaped or too small.  Finally a friend came to the rescue after hearing my tales of woe and loaned me his Chefware Kits sphere turning jig. Here is a link to the ChefwareKits.com site (http://www.chefwarekits.com/Woodturning-sphere-Ball-Jig). The Chefware jig is easy to set up and on my first try I turned a perfect sphere of the exact size required.

To turn the sphere I mounted the blank between centers and rounded it into a cylinder with my spindle roughing gouge.  I formed a tenon on one end to fit into my chuck and mounted the blank in the chuck with the live center in support. 

Fig 24 thumb

 

Next with a rule I measured half of the intended diameter of the tama (1 3/16”) (see below) from the end and marked a line around the circumference of the blank.  This line is necessary to establish the centerline of the sphere for the Chefware Kits sphere turning jig. Then I marked another line around the blank to indicate the full diameter of the sphere I wanted to turn. This second line establishes the area to the left from which waste can be removed to provide clearane so that the sphere cutting jig cutter bar can traverse to form the tama. 

Fig 25 thumb

 

Once the measurements for the tama were marked on the blank I removed as much waste wood to the left of where the tama would be turned to provide clearance for the sphere cutting tool to do its job.  I left the blank about ¾” thick at this point to ensure there would be no chatter during the next step. 

Fig 26 thumb

 

Forming the Tama

With the bulk of the waste removed I knocked off the corners of the tama blank with a spindle gouge. 

Fig 27 thumb

 

Now that the tama blank was turned to a rough sphere I could finally set up the Chefware Kits sphere jig. Using the centerline I marked earlier I located the edge of the Hunter cutter on the centerline of the tama blank and locked down the tool post and tool slide into which the sphere jig was located. 

Fig 28 thumb

 

Then just by switching on the lathe and pivoting the Chefware Kits sphere jig back and forth while adjusting the cutting diameter I formed a perfect sphere for the tama ( below left) and (below center).  When the line around the blank disappeared the tama was cut to final size (below right). 

Fig 29 thumb Fig 30 thumb Fig 31 thumb

 

To ensure that my diameter was correct I carefully set my calipers to 2 ⅜” and measured the diameter of my tama sphere.  The calipers had a nice snug fit so I was satisfied. 

Fig 32 thumb

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Monday the 29th. Thanks for visiting Woodturners Unlimited.