Router Plane

Monday, August 13, 2018

Large Segmented Bowl - #4 Rings & More Rings


With the second layer glued in place and the clamps removed it’s back to the lath to turn the corners off and make the layer round.  The left photo below is before I started turning and the one on the right is after I have turned the blank round.


I centered the 2-ring bowl blank on the next layer, marked the centering circle and the orientation lines as before.  Here if you look close in the center you can see one of the orientation lines marked with an “A”.  With the blank still in place I clamped the alignment blocks where they go. 


Below is after the bowl blank was removed.  This makes it a little easier to see the centering circle, where blocks are and how the bowl blank will drop in place.  Next is to add glue, drop the bowl blank in place, rotate it back and forth to spread the glue then make sure the orientation lines are in alignment, put the clamps on and finally check to make sure the layers are still in proper alignment.


The photo below shows how I have several rings in various stages of completion.  In the back is the rough-cut walnut and cherry strips for ring #7 setting to see if they are stable.  In the front left is a row of cherry and a row of walnut segments for ring #6 ready to glue together tomorrow.  At the left setting on the yellow pyramids with the metal clamp is the ring #5 that I glued together today.  To its right is ring #4 that I flattened today and will glue on tomorrow and finally at the right is the bowl blank with ring #3 that I just got done gluing on.


The next day after taking the clamps off I mounted the bowl blank on the lathe and turned the ring round.  The left photo shows that done.  Now with three rings glued on I can start to do some turning on the bowl’s inside.  On the right the bottom of the bowl is pretty well done and the second ring is roughed out.  There is a lot of refinement yet to be done especially at the transition between the bottom and the 2nd ring.  The top ring just has the inner face rounded and a small radius cut on the inner edge.  Lots left to do here but that will wait until I get more rings on.


I am not going to go through all the steps in making the rings and gluing them on since that has already been covered.  If anything that I have not covered comes up I will go over it but, in the meantime, here is where I added the 4th and 5th rings.


Making progress albeit slowly.  Here on the left is the 6th ring added and set up ready to round the outside edges.  The right image shows the 7th ring in place and the inside shaping in-progress.  The bottom layers are pretty much done while the outer three or four rings are still a work in progress.  The closer I get to the last ring added the less finished the piece is.

This is the 8th ring glued and clamped in place.  It marks the half-way point only 8 more rings to go.  If you look close at the bottom ring you can see the step between it and the layer above is getting smaller.  That is starting to cause me some problems in that I don’t have very much room to clamp the centering alignment blocks on.  It’s only going to get worse as the step continues to get smaller.

The left image has the 8th ring on with the outside rim rounded while the right image shows the 9th ring after rounding the outside rim and doing some interior tuning.  The pile of shavings is the result of interior turning and just sits there sliding along the bowl surface as I turn.


As I talked about when gluing the 8th ring on I was running out of room to clamp the centering alignment blocks on.  Well the left image is the 9th ring with blocks barely attached and the right is the 10th ring.  As you can see there is no way I can clamp the blocks on this ring.  That means that I will use a rub joint to help get an initial “tack” to reduce the piece slipping around as I clamp them up.  A rub joint is where you slide or rub the two surfaces back and forth until the glue becomes tacky and grabs.  It makes it easier to keep things aligned as the piece is clamped.  


Here is the 11th ring.  This ring represents the largest diameter of the bowl.  From here on in the rings will get smaller. 

The left photo is with the 12th ring in place.  It is just a bit smaller than the previous ring and that’s because I am working my way down toward the opening at the top.  Because the interior surface of the bowl is curving back I am having to get into some contortions to do the turning.  All along I have been finishing turning on the inside.  Now the interior surface is about 95% done up through the 8th ring and 90% done through the 11th ring while the 12th ring is about half done.  The right photo shows just how tall the stack has become.  There is right at 12” between the faceplate and the outer face of the 12th ring.  Unfortunately, as I was working on this ring I started getting some vibration and minor chattering while turning.  Changing the RPM’s, using a light touch and sharpening the tools helped but this means that I have gone as far as I want adding rings using this setup.  There are a couple of techniques that I could use to steady the bowl and dampen the vibration but I would still have the awkward turning position.   Then there is the problem of weight, as it sets including the cast iron face plate the blank is pushing 50 pounds.  Holding it up at the lathe in proper alignment with one hand while using the other to start the spindle threading into the face plate is getting pretty close to making my eyes bug out.  To resolve all these problems, I will turn the remaining four layers separately then marry the two halves together.  In retrospect I probably should have made the split between the 11th and 12th rings right at the widest point.

Next up – Adding Rings & Fitting the Halves

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