Segmented Bowl – # 4 Cutting Individual Segment Blanks, Making Plywood

Next is to rip the blanks into six pieces that form the blanks for the actual segments.  This starts by ripping the piece along the glue joint between the two cherry pieces on the table saw.  The red arrow in the bottom photo points to that joint.

Using the chop saw with a stop block for accuracy each half of the just cut blank (red arrow) gets cut into three pieces.  Just to the left of the blank is a pencil.  I use its eraser end to hold the blank down when the cut is being made in case somethings wrong my fingers are away from the blade.  The three cut pieces are shown toward the bottom of the photo in front of the uncut blank. Twelve of these individual blocks will make up each of the four rings used in the bowl’s major feature band.

Using the pencil as a safety device to keep my fingers away from the blade turned out to be a really, really good idea since when I was cutting the 5th block somehow the piece got awry getting caught up in the blade, demolishing it and ripping the pencil out of my hand.  Fortunately, all that happened to me was a short-term slight numbness in my hand from the force when the pencil got yanked away.  It all happened so fast that I don’t really know what went wrong but my best guess is the shim used on the right side of the blade to level the blank somehow caused the piece to pinch against the blade causing the catch.  The result is the larger piece got thrown out to the right a few feet with the small piece nowhere to be seen.  I did find it about 15’ away from the saw when I was sweeping up at the end of the day.  After removing the shim there was no problem in making the rest of the cuts although I did have to reset the stop block as the impact moved it. 

Here is what all 59 of the pieces look like ready for their ends to be cut at 15 degrees so 12 of them per ring can be assembled into the four needed rings.  At this point the segment blanks are set aside while some other parts of the bowl are worked on.

The base of the bowl is next.  A typical ring is made up of twelve segments open in the center like the drawing on the top left.  That does not work for the bottom layer since a solid bottom is needed.  One could use a solid piece of wood here but due to differential expansion and contraction caused by changes in humidity either the rings or the base would probably crack and that’s not acceptable.  Using a ring like the one on the top right is possible but does come with its own problems.  I have used a hybrid ring with a small 1” diameter tapered plug in the center and that helps but don’t like the aesthetics.  I have gotten around that problem with the solution shown in the bottom drawing.  The blue piece is a three-layer shop made piece of oak plywood 3/16” thick.  It floats in a slot made in the bottom layer and capped with the next layer up.  The left half of the bottom drawing is before turning and the right side is a rough idea of what the finished turning will look like.

When selecting a piece of oak for the plywood I wanted a stable piece so sorted through my shorts until I found a piece that did not have the growth rings running parallel to the long face.  My first preference would be one where the growth rings are 90 degrees to the long face or quarter sawn.  The bottom photo is of the one selected and since only the left two thirds of the left side of the piece will be used most of the rings are at a 45 degree or so angle to the face which should give me a pretty stable finished part.

The plywood will be made from three layers each 1/16” thick.  To make the layers the selected piece of oak has a thin slice just over 1/16” cut off using the bandsaw.  The setup is shown in the two photos below.

To remove the bandsaw blade cut roughness out the thin piece gets run through the thickness sander.  To support the piece as it’s run through the sander a ¼” thick carrier is used.  The top photo shows it ready to go through the sander.  I have marked the bandsawn surface with a pencil to gauge when it’s smooth as it’s run though the sander.  The bottom photo is a dial caliper showing the piece being just a tiny bit under 1/16” thick.

After cutting three layers of the oak to size they are glued up with the middle layer’s grain running 90 degrees to the top and bottom layers.  The top photo shows how they will get stacked and the bottom photo is the setup for gluing.

Once the layers are glued and aligned, they get taped to a backer board that has a melamine covering the glue will not stick to.  This assembly is set in the bench vice, another backer board added and the vice tightened.  Last is to add two C-clamps to securely clamp the top edge.  The piece is left overnight for the glue to cure. 

With the floating insert glue curing I can select material to make the bottom two segmented layers.  The first step is to refer to a spreadsheet (below) that has all the information about the segments size for each ring.  The blue numbers (radius, width and thickness) are those that I entered and the rest are calculated based on them.

In the left drawing below the green is the finished profile of the bowl and the grey areas are a buffer for small changes in the design as it gets turned on the lathe.  The right side shows a cross section and sizes of each of the individual segments that make up the layers.  The dimensions that go into the spreadsheet come from this drawing.

Next Up – Making and Mounting the Bottom Layer

Segmented Bowl – # 3 Starting on Making Feature Ring Blank

With a plan in place for making the angled pieces a stop block is set on the chop saw for consistent width pieces and the first maple blank is cut.  For now, I am only going to cut one blank and take it through all the operations to make sure everything works as planned.

When I went to center the bandsaw blade between the two blanks, I ran into an unexpected snag.  Because of the bandsaw’s angled table, I couldn’t move the fence over far enough as the blade hit the bottom edge of the fence.  In the drawing below that area is circled in red. 

Since cutting a notch in the fence is not a good idea, I made a temporary spacer with a notch cut in it for the blade.  Below the left photo shows what that looks like clamped to the bandsaw’s fence.  The right photo shows the maple blank backed up to the blade before cutting.

Running the blank through the bandsaw using a light steady touch while making the cut gives me two nearly identical pieces shown in the photo below.  Pushing too hard on the blank while making the cut can cause the blade to deform resulting in a cut that is not straight. 

Next is to take each of the angled pieces and cut them to their final width with the table saw.  Not much needs to be cut off but it is necessary to make them all identical.

The thickness sander is then used to bring the angled piece down to the desired thickness.  Once that’s done the pieces are put in the angle jig and the sander is used to smooth the bandsawn surface out until the edge (red arrow) is very thin.

After cutting and sanding the maple pieces I started on the cherry parts.  As mentioned in the previous post because the cherry boards are not as wide as the maple, I need to edge glue a piece onto it to equal the maple’s width and at the same time make sure that joint lines up with where the segments will get cut apart.  Here is the first cherry glue-up.  It’s wider than needed so some will get trimmed off the top and bottom getting rid of the light-colored sap wood.  When done it will be the same size as the maple.

Once the glue cures the blanks are ripped to width.  Next the ends with the sapwood are trimmed off using the chop saw.  Since there will be six individual segments cut from the blank measurements for trimming are made from the center joint where the two boards were glued together.  That joint has the red arrow pointing to it. 

Because the cherry blanks are a little thinner than the maple ones the center line for ripping the angle pieces are not the same so the bandsaw fence had to be adjusted.  Here’s the fence reset so it’s centered between the two angled pieces.

Here are nearly all of the first group of angled pieces after being cut on the bandsaw.  They are very close in size and the ripping of the blanks went better than expected. 

The next step is to take the rough sawn pieces through the same process as described above with the first two maple pieces.  Cutting them to width on the tablesaw, sanding to thickness then using the angle jig smooth and flatten the bandsawn angled face.  Below are the finished sets of pieces ready to be glued up.

The photos below shows the sanded pieces dry stacked up using two different spacings.  One of which will be the way the bowl will look when assembled and glued together.  I just have not decided which yet.

My next step is to glue all pairs of angled pieces together using the jig made earlier.  First, one piece gets set in the jig then glue is applied to the other angled face and combed using a silicone glue spreader.  Note that the glue is applied to only the angled face.

Last is to clamp the caul in place to spread the clamping force.  That’s necessary to distribute the clamping force to make sure the thin edge of the angled piece is held in place while the glue cures.  Because of the glue on the angled pieces when the clamps are tightened, they want to slide apart but the long reference rails keep that from happening.

After the glue cures the laminated blank is removed from the jig and any glue nibs are removed from the joint where the cherry and maple meet.  The top photo shows the blank clamped in place and the scraper used to remove the glue.  The bottom photo is a closer view of the joint.  There is not a lot of glue to remove but it needs to be taken off to get a flat reference face for the next step.

Sanding starts with flattening the top and bottom of the blanks getting rid of the little lip.  That’s followed by bringing the blanks down to their final thickness.  This requires a quite a bit of care since the same amount of material needs to be taken off the top and bottom so the distance from the maple/cherry joint is the same on the top and bottom.  When finished the top photo shows what all the blanks look like and the bottom photo shows the front and back of the blanks along with an end view. 

Next Up – Cutting Individual Segment Blanks, Making Plywood

Segmented Bowl – # 2 Gluing Jig, Sample Testing & Material Selection

Once I had a pair of angled pieces sized to what’s needed the next step is to glue the two of them together.  In order to make sure the alignment is the same for all the glued-up blanks the jig below is used.   A plywood base gets covered with a piece of 6 mil polyethylene so the blank won’t get glued to the base.  A reference rail at the far side gets screwed in place.  Two end pieces are cut to the exact finished width of the blank and the front rail is held in place with the clamps shown.    These last three pieces are not fastened down in case the width needs to be adjusted.  Last is a caul that is used to apply even pressure to the glue-up.  The face of the caul towards the camera is covered with packing tape so it won’t get glued to the blank.

The glue-up has three steps:  First, one piece gets glue applied to the angled face as shown in the top photo.  Second, the other angled piece gets set in place per the bottom photo.

Last is to clamp the caul in place.  It’s here where the long reference rails come into play.  Because of the glue on the angled pieces when the clamps are tightened, the pieces want to slide apart but the rails keep that from happening.  This short glue-up is a proof-of-concept to see if everything works.  In production the blanks will run nearly the full length of the jig.

After letting the blank cure overnight, it is removed from the jig and the face joints with the tapered edges are checked to see if they came out flush which they did.  A couple quick passes through the thickness sander removed what little glue had come to the surface and bring the blank to its final thickness.  The photo below is the finished test blank where I have darkened one of the angled pieces to represent the contrasting wood.  Also, one of the finished segments is drawn on it.  In use the blanks get cut into 1.418” wide pieces then each end is angled at 15 degrees.  One thing that came up in the glue assembly is the long edge of the angled piece gets sanded to a sharp edge and that edge is very fragile. In fact in a couple of places the edge flaked off.  It ended up not being a problem here because the blank had to be taken down a few hundredths of an inch to get it to final thickness.  However, to forestall that problem I am going to make another test piece and not taper the edge to nothing but leave a tiny edge to act as a reinforcement.  It should not be a problem but the next test will let me know.

In the top photo the next test piece’s thinner edge (red arrow).  It’s only about 1/32” wide and for reference the full thickness of the piece is right at 5/8”.  After checking to see how the pieces fit in the gluing jig, I decided to thin the edge down to about 1/64” and did the glue-up using that lip.  The bottom photo is what the glued up blank looks like when pulled out of the jig before I start working on it.

The two photos below show the blank before and after running it through the thickness sander.  A good point of reference is the small knot about a quarter of the way in from the right edge.  As you can see the joint has all but disappeared.  Before I started to flatten the piece, I was a little worried that the slight raised edge might cause a rocking problem when sanding throwing the blank out of square.  Fortunately, that did not happen.  Taking what was learned from the two tests right now the plan is to slightly thicken the original angled pieces and thin down the edge even more making it as thin as possible without losing the crisp edge.  If it does get damaged during the glue-up since the assembled piece is slightly oversized that will give me some wiggle room when flattening and bringing the blank to final thickness.

Once the feature blanks are sanded to final thickness it gets cut into blocks for the segments.  In the photo a couple of the blocks are laid out showing the individual segments.  The dashed line represents the transition from one angled piece to the other.  One other note is that so far, I have only used scrap plywood and scrap 2x4 material for the jig testing.  The actual blanks will have the grain running across them rather than vertically as show in this piece.  That’s because the bottom of the segment will end up being the exposed face of the bowl which needs to be long grain and if this piece with the grain top to bottom was used the exposed face would be end grain rather than the long grain.

Selecting the material for the feature ring shown in the top drawing is next.  I need light and dark woods to provide contrast within the ring so decided to use hard maple and dark cherry.  The bottom photo shows the pieces selected and the preliminary marking of how they will be cut up.  One problem is with the width of the cherry since it and the maple pieces need to be the same width when the angled pieces are glued-up.  Since the cherry is narrower than the maple two pieces of cherry will be glued up to equal the maple’s width while at the same time making sure that joint lines up with where the segments will get cut apart. 

I had a concern with the amount of waste when ripping the blanks to their final width then cutting the angle on the bandsaw.  In the drawings below the blue indicates the waste.  The top drawing is of a single angled piece cut from a final width blank.  My solution is the bottom drawing which shows how overlapping the angled pieces on a wider blank makes less waste.  The dotted line between the two angled pieces in the bottom drawing is my bandsaw cut line.

Next Up – Starting on Making Feature Ring Blanks

Segmented Bowl – # 1 The Start, Design & a Jig

It has been some time since I had done a major lathe specific project so I decided to do another largish segmented bowl.  The difference this time is it will have a complex feature ring.  The last large-scale turning was a segmented bowl about 18” or 19" in diameter done in 2018.  It was made out of cherry and walnut.  Below on the left is it right after completion.  The photo on the right was just taken about five years later.  It’s interesting on how the wood changes color as it ages with the cherry getting darker and the walnut getting lighter.

My first step is to come up with the main feature ring and the minor feature ring then draw it up.  Once that was done working out the overall shape and proportions came next.  In the center below the shape of the bowl and the feature rings are shown.  To either side are the bowl’s profiles.  The left one is the concept section while the one on the right has a more refined section in green with the outer and inner buffer areas shown in gray.  These buffer areas allow me to make subtle changes to the profile as the turning progresses. 

The main feature ring consists of four identical layers where each layer is made from twelve segments and each of the segments has two pieces.  One made from a light wood and one from a dark wood.  All told there are 96 individual pieces in these feature rings.  The drawing below shows what a single segment looks like.

Since all those pieces are identically shaped, I will be building a jig or two to make the blanks the segments are cut from.  Below is the drawing for the first jig.  Due to the direction the grain needs to run the pieces can’t be cut out of one long piece but that’s all going to get explained later when the jig is used.

The jigs will be made from some almost 30-year-old completely dried construction 2x4’s and 2x6’s.  While they are now dry and stable as they were drying, they twisted and cupped.  Using the Planer Sled to hold them stable it’s pretty easy to get the first reference surface flat.  Here one of the 2x6’s is set in the sled ready to run through the planer.

A few passes through the planer and I have a nice straight flat reference surface to work with.  That’s shown in the photo below.  From here all that’s required is to put the reference face down in the planer then mill the second face so it ends up parallel with first face.

For the feature ring the most important part of the first jig is making the tapered piece at the correct angle so that’s what I will start with.  This piece gets rough cut with the bandsaw.  That starts by setting the angle needed which is 13.45 degrees.  In the photos below you can see the bandsaw setup to make the angled cut.  The angle gets measured with an electronic gauge.

Taking one of the flattened trued up 2x4’s that had a good straight edge the table saw is used to rip the other edge parallel to it.  The blank is then flipped over and a skim cut to the first edge cleans it up giving me a flat, true blank with square parallel edges.  The blank is then ripped with the bandsaw giving me the two pieces below.

While the bandsaw makes a pretty good cut it is still too rough and uneven for me to be able to depend on it to provide a consistent accurate reference surface in the jig.  The photo below shows what I mean.

Smoothing out the minor irregularities is not as simple as hitting it with a hand sander as I need a flat surface all in the same plane at the right angle.  To create the smooth surface the two just bandsawn pieces are put back together with the original outer faces next to each other held together with double face tape.  That puts the bandsawn faces to the outside with the angles canceling each other out resulting in the sawn faces parallel to each other.  That’s shown in the left photo below with the electronic gauge set on the cut surface reading zero degrees or level.  This means that I can run the assembly through the thickness sander to flatten and smooth out the opposing faces.  The problem is because the surfaces are rough the angle changes as the surfaces are smoothed.  The fix for that is to find out which edge needs to be raised to correct the angle and add shims along that edge.  It took a little trial and error to get the correct shim thickness shown in the right photo which ended up being a playing card plus two layers of masking tape.  Setting the gauge on the offset gave me an accurate reading of the adjusted angle.  Once the top piece angle is right the assembly gets flipped over, the shims removed and the other face made parallel giving me two angled pieces with the correct angle.

Assembling the jig is next.  One of the just finished angled pieces gets a square edge cut then screwed to a plywood base flush with the base’s edge.  The other angled piece gets ripped down so it’s just a little wider than the basee.  I did that to give me a little lip to grab onto when the jig is run through the thickness sander.  One other detail is the way the two angled pieces come together.  The piece on the right has a square edge and the one on the right has its angled edge.  I could have put the right piece in with its matching angled edge to make a nice tight joint but wanted to leave the gap so there was a space (red arrow) for sawdust to go so it does not get trapped throwing the jig’s accuracy off as it’s run through the thickness sander.  That’s all done below along with a greyed-out test piece with the pencil line on its end showing the finished piece’s final thickness.

The finishing piece on the jig is an end plate to keep the angled blank in place while the jig is being run through the thickness sander.  Note that all the jig’s pieces are screwed on and not glued.  That’s so if I need to make changes to the jig it will be easy to do.  Below is the completed jig and an angled test part  sanded to its final shape.

Next Up – Gluing Jig, Sample Testing & Material Selection