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Hollowing Tool

Hollowing Tool


Hollowing, especially end grain timbers can be a challenge.  Entering through a small, 1” or less, diameter hole makes using a bowl gouge nearly impossible.  Handheld hollowing tools are better but still put a lot of stress on the user.  I designed and built this articulating hollowing tool to overcome the short comings of traditional and even other specialized hollowing tools on the market.

The criteria for this project were simple.  It needed to work, easy to use, and be cheap and easy to build.  For simplicity in building, I designed this project around two pivoting points and is held in the back by the tailstock.  This only required me to make a few cuts and drill a few holes.  The cost of the project was inherently low.  It only takes a few bearings and a small amount of steel.

Required parts:        

(6) 3/8” od x ¼” id bearings

1”x1” square structural steel

¼”x 1” flat structural steel

5/8” round steel

½” round steel

¼” round steel

(5) ¼” bolts

1 thumb screw

1 set screw

Paint and Primer

Pen Laser- Can be purchased HERE

¼” round tool steel

Looking at the picture, you can see the overall shape of the unit and parts needed.  Part “F” is the cutting end.  A piece of ¼” round tool steel can be inserted into the 10” long piece of 5/8” round stock labeled “F”.  This part gets support for the cut using the tool rest on your lathe. Part “G” is a small length of 1/2” round stock.  This gets secured to the Jacobs chuck in the tailstock.
I started the project with part “A” seen below.  This is made from a 1 ½” length of 1” square stock.  As shown, I drill a ½” diameter hole for the ½” round stock labeled “G”.  Part “G” is cut about 2” long and glued into the hole using gorilla glue..
Next, I drilled two ¼” through holes as shown.  These are used to bolt down the two parts labeled “B”.
Next, I cut the 2 parts “B” from 2 ¾” lengths of 1x ¼” square stock and drilled as shown.

Using ¼” bolts, I sandwich part “A” between the 2 “B” parts and bolt tightly using the two holes towards the right side of the above picture.

Next I cut part “C” from an 8” length of 1x1 square stock.  Then I drilled both ends as shown below.  I start with a shallow hole 3/8” diameter.  This is a rest for the bearings.  Drill the depth to allow about 1/32” of the top of the bearing to protrude from the surface of the 1” square stock.  This will allow clearance when the tool is in motion.  Next drill the ¼” diameter through holes in each end.

The end result should look similar to the picture.
Next, cut the 2 parts labeled “D” from 8” lengths of 1x ¼” steel.  Drill ¼” holes as shown.
Next, cut part “E” to a length of 3” from the 1” square stock as shown.  The hole on the right is made like before.  Drill a shallow 3/8” hole on the top and bottom for bearings.  Then drill the ¼” through hole.  The hole in the center of the piece is for a laser attachment added later.  The 1/8” hole on the left is tapped for a thumb screw.  This will hold the 5/8” round tool bit holder, part “F”.
Finaly, drill the 5/8” hole in the end of the stock for part “F”.
Cut part “F” to a 12” length.  Drill and tap a 1/8” hole about ½” from the end of the piece.  This will hold a set screw to secure the tool bit.  Next drill the ¼” hole in the end of the bit holder.
After all the pieces have been cut and drilled, prime and paint. Assemble the parts as shown.

Adding the laser attatchment.

This is not necessary but makes this tool extremely user friendly.

First, cut a length of ¼ round steel to a length of between 8” and 12” labeled “H” below.  For simplicity, this can be glued into the hole on part “F”.  Or, another set screw or thumb screw can be used to secure the round stock to part “F” as shown.

Next, cut a 2” length of 1”x1” square stock and drill as shown below as part “I”.  The ¼” hole allows part “I” to slide and pivot on part “H”.  The 2 1/8” diameter holes are tapped for either a set screw or thumb screw.
Next, drill a ¼” through hole in part “I” as shown.
Cut part “J” 14” long from a piece of ¼” round stock and attach to part “I”.
Lastly, cut and drill part “K” from a piece of 2” long 1” square stock as shown.  The two ¼” holes are through holes and are both off center.  This will allow part “K” to slide and twist on part “I”.  The 1/8” is tapped for yet another set screw or thumb screw.  The ¼” hole near the top of the picture gets slid onto part “I”.  The second ¼ hole near the left side is where the pen laser slides into.  This may need to be a different diameter depending on your laser.
Paint and assemble as shown.
Insert laser and tool bit.

Adjust part “K” until the laser strikes the tip of the tool bit.


Using the Hollowing Tool

Before the tool will cut, the tip needs to be ground and sharpened.  There are many shapes that the bit(s) can be ground.  Find what works for you and sharpen the tool often.  This is a scraping tool and needs to be sharp.

Grip your work piece in a 4 jaw chuck.  Bring your tool rest as close to the work piece as possible and at 90 degrees to the long axis of your weighs.  Insert the Jacobs chuck into your tailstock.  Rest the tool bit holder onto the tool rest and insert part “G” into the Jacobs chuck and tighten down.  Adjust the height of the tool rest so that the tool tip is cutting at the center line of the piece.  Start the lathe and lightly plunge the tip into the center of the work.  Gradually increase the diameter of the hole to approximately 1”.  Slowly work deeper into the vessel stopping often to clean out the chips.

Please remember to see my Turning Supplies section HERE for great prices on many woodurning supplies.