Router Plane

Monday, March 4, 2019

2 Piece Turned Bowl - #1 The Blanks & a Snag


This blog series is going to cover another lathe project.  I plan on making a large diameter hollow form.   Typically, you turn a solid block of wood round then working from one end hollow out the center.  So, if you want a small opening at the top then the removal of all the material from the inside has to come out of that small hole.  However, that’s not the way I plan on doing this project.

The short sequence for the way I am going to do it is to:
  1. Take two pieces, a top and bottom then on the lathe rough turn the outside of each one.
  2. Next, turn the inside part of the top half and bottom half.
  3. Stain and finish the inside of each half.
  4. Glue the two halves together.
  5. Final turn the outside then finish it.

There are a lot more steps than this but it’s a good overview.

I had done a small-scale prototype some time ago so had an approximate design done.  With that in mind I start by selecting the material.   When I built the combination Dining/Gaming table for my son I had some 6/4 or just under 1½” rough sawn red oak cutoffs.  They had been laying around for the better part of a couple of years and were roughly the right size for the project.  Here are the three pieces I started with.  Not so good looking and a couple were cupped really badly with just a little twist to complicate things.  Oh yes, the ends were split and cracked too.

Below is a photo of the best-looking piece which will be used for the top half with the prototype setting on it.

To get the bottom half I needed to recut, flatten and glue these two ugly boards together.


Taking the left-hand piece, I marked out where I needed to make the cut to get the majority of the cup removed.  Fortunately, the cupping was not even across the board but much more sever towards one side.  Cutting to an approximate length also helped get rid of some of the twist and the end splits too.  Here you can see how much it helped in removing the cup.  Also, if you take a look at either edge of the cut-out piece you can see where the surface has been smoothed out for about an inch.  That is where I used a hand plane to take out the twist so there is a flat surface when it gets run through the thickness sander to flatten.  Since the pieces are so rough and cupped, I used a 36-grit belt.  Not quite as rough as a gravel road but pretty close.

Here are the pieces now just over 1 3/16” thick flattened, squared up and marked with the bowl blank diameter.  The two pieces on the right are matched so the grain flows from one to another and should be nearly invisible when glued up.

The glue up is pretty simple as shown here just one joint with four clamps to keep everything aligned.


Once the glue had cured, I checked for flatness made a couple of small adjustments and redrew the bowl blanks on each piece.


To speed the process of turning the blanks round I used the bandsaw to cut the blanks close to final size.

The next step is to drill a 2 ½” diameter hole on the inside of the blank for mounting in the scroll chuck.  That is not an arbitrary number it is based on matching the arc of the chuck’s jaws to a specific diameter circle.  That way you get maximum surface contact between the jaws and the piece of wood which makes the mounting more secure.  Having a 1 ¼” thick, 11 ½” diameter piece of oak come flying off the lathe at me is not my idea of a good time.  Anyway, when I went to get the drill bit, boy was I surprised as my set did not have one that size.  Closest was a 2 3/8” one which is too small for the oak blank to even mount on the chuck.  I know I tried it with a piece of scrap.  Much to my disappointment a Fostner bit that size was not available locally so I ordered one on-line which ground the project to a halt until the bit arrived.


About a week or so later thanks to the internet and Amazon the new 2 ½” bit arrived.  This is what it looked like after cleaning the protective oil off all ready to use, or not. 

After inspecting the bit, I found it needed some modification before it was usable for my purpose.  There are two things that need to be done.  First, in the photo below you can see the center point is pretty good size.  It is about 5/16” above the cutting edge on either side which for most applications is OK but here since the bottom of the drilled hole is going to be pretty close to the bottom of the bowl it needed to be shortened.  I sure did not want to have it come through the bottom and needed to be able to later turn the divot it leaves out.  This may not make a lot of sense now but it will later on.  Second, the long horizontal cutting edges need to be cleaned up so the little chips and nicks are gone then sharpened as right now they leave a little to be desired.

This is after about an hour of grinding, hand filing and honing.  The center point is 1/8” shorter and the long cutting edges have been honed using a diamond file.  There are still a few nicks on the leading cutting edge but it is way better and a whole lot sharper.

With the bit ready I can finally start making some shavings.

Next up – Turning the Bottom Half

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