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Bowl Bottom Finding Jig

Bowl Bottom Finding Jig

 This jig is ideal for finding the inside bottom of a bowl relative to the outside.  It aids in getting the correct wall thickness near the bottom.  This is easy to build, cheap, easy to use, and very effective.

 

I start out making the base and vertical member.  The base was made from a piece of 8"x8" plywood.  The vertical member is made from a 20" long 2"x2" piece of maple.  The height of the jig depends on the swing of your lathe.  My lathe has a 20" swing.  If you have a smaller lathe, a smaller jig can be made.

 

The two holes seen in the picture below are needed for dowels.  The hole in the middle of the vertical piece is centered to your spindle.  I use a 1/4" wooden dowel in this hole.  The hole near the top will be the support arm for the pen laser.  For added strength, I used a 3/8" steel dowel for the added weight of the laser and laser support.

The picture below shows the dowels in place.

I added set screws to the vertical members to secure the dowels in place.  Thumb screws would work just as well.  This allows for adjustment of the dowels when aligning the laser.

Next, I add the laser support.  I used a piece of 1 1/2"x 1 1/2" x 2" piece of maple.  I drilled a through hole along the long axis of the piece to fit over the top dowel.  I drilled a second through hole 1/2" from the end of the piece.  This will hold the laser in place.  The hole is slightly oversized.  The keychain pen laser I used, click HERE, has a button that needs to be pressed and held to keep the laser on.  A larger hole size allows me to slide the laser in and the interior wall of the hole keeps the button compressed and laser on.  Lastly, I add another set screw to the side of the laser support to lock it in place on the dowel.
To use this jig:

After hollowing out the interior of your bowl to an approximate depth, place the base of the jig onto the ways of your lathe.  Adjust the laser so that the red light shines on the tip of the bottom dowel.

Slide the entire jig towards the bowl until the bottom dowel is touching the interior bottom of your bowl.  Find where the laser light meets the exterior of your bowl.  This is the interior bottom of your bowel.

 

Other uses of these handy lasers:

The same principles described above can be added to other woodturning tools in your shop.  I have made simular adjustable laser arms for:

Hollowing tools

Bowl coring tools

Jacobs Chucks

Drill press

 

Find a great deal on pen lasers and other useful woodturning products HERE