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Sky Box as a 7 page pdf

SKY BOX

Sky Box

INTRODUCTION:  Haven’t you always wanted a sky box?  Too bad you can’t use this one to watch the super bowl, although you could place it next to your best bowl.  Bad jokes aside, I think this box has some interesting features.  The first is the magnetic closure.  With magnets you don’t have to worry about minor wood movement messing up the fit, and the somewhat different feeling as you open the box is a pleasant surprise.  The second is the decoration.  I’m not quite sure what to call it—it’s closest to Intarsia, I guess, but on a curved surface.  I picked anthropomorphic sky elements because I like them as a motif.  An additional benefit of using something cute is that the execution requirements are less stringent than realistic.

Briefly the box starts as a normal turned box, although I hope you find the sanding method interesting.  A groove is cut just under the rim of the box and 1/16” steel wire is inlaid in the groove.  The lid is turned with a not-tight fit and three small magnets are glued in the lid.  To make the sky elements blanks are first temporarily glued to a scrap block to enable safe cutting of the necessary curved back on the band saw.  The designs are then cut out and shaped with various sanders and then glued to the side of the box.  A similar element is attached as a finial to the lid.

TURNING THE BASE:  Start with a 3” x 3” x 4-5/8” turning square of a dark wood such as walnut.  (If you don’t have or can’t find such a large turning square, consider gluing up four 1-1/2” turning squares with contrasting veneer in between and using four design elements instead of three around the box.  The veneer will frame each element.)  Mount the turning square between centers and turn to a cylinder.  Turn a 7/16” long x 2” diameter tenon on each end.  Then measure 2-3/8” from the shoulder of one of the tenons and make a parting tool cut most of the way through as in Fig. 1.   The design calls for a 2-1/4” height, but some wiggle room is nice to allow for.  Then cut the rest of the way through with a hand saw.  You could cut all the way through with the parting tool, but the two pieces of such a thick cylinder tend to catch on the parting tool and rattle disturbingly.

Fig01

Figure #1:  The turning square prepared for chuck mounting.

Mount the larger piece, which will be the base, in a 4-jawed chuck, and true the cylinder if necessary.  Measure 1/4” away from the tenon shoulder and make a parting tool cut to the left of the measurement 1/4” deep (if you ended up with a 3” cylinder this would be a 2-1/2” diameter, but prioritize having  1/4” for a bead to set off the elements).  Make another parting tool cut of the same diameter at the other end as in Fig. 2  Reduce the area between the parting tool cuts to cylinder leaving a 1/4” x 1/4” flange proud of the cylinder as in Fig. 3.  Then round over the flange into a bead.

Fig02

Figure #2:  Define the base dimensions with parting tool cuts.

Fig03

Figure #3:  Reduce the area between the parting tool cuts to a cylinder.

Clean up the face of the base.  Set a 3/16” (or so) drill bit in a pair of locking pliers as in Fig. 4 to use as a depth drill.  The point of the drill should be 1/8” shy of the bead.  Make a starting dimple in the center of the face of the base with a pointed tool and then use the depth drill to mark how deep to hollow as in Fig. 5.

Fig04

Figure #4:  Set the depth drill.

Fig05

Figure #5:  Mark the hollowing depth.

Now hollow the box.  You want to leave a generous 1/8” of wall thickness.  Use whatever tools you’re comfortable with to hollow.  Fig. 6, from left to right, shows the sequence I used.  I first used a small bowl gouge until it started to get jumpy.  Then I switched to a scraper to finish rough hollowing the box and then finished with a shear scraper to reduce sanding on the bottom end grain.

Fig06

Figure #6:  Hollow the box.

If you had a catch whilst hollowing then clean up the rim.  If you didn’t, reduce the height above the bead to 2”.  Now use a 1/16” parting tool to make a groove for 1/16” steel wire that makes half of the magnetic closure for the lid.  Make a cut a little over 1/16” deep just below the rim.  Fig. 7 shows making the groove and testing the depth of the cut with a short bent length of wire.

Fig07

Figure #7:  Make and test a groove for the wire.

Now sand the box.  I made a specialized sander for rough sanding the inside which worked quite well.  Follow the sequence for a foam cone sander (see References) except make the core a cylinder.  After putting two layer of craft foam on the cylinder and trimming it, also put two layers on the end.  Cover with duct tape and then use spray adhesive to attach separate cloth backed abrasive to the walls and cap.  The diameter of the sander should be more than half the diameter of the box interior so that you can sand the entire bottom while keeping the sander in contact with the side walls for stability.  To use the sander, mount it in a drill.  Turn the lathe on at a slow to moderate speed and the drill on maximum speed.  Fig. 8 shows the box after sanding with the first grit and the foam cylinder sander.

Fig08

Figure #8:  Power sand with the first grit.

Once the tooled surface has been sanded with the first grit, subsequent grits don’t usually require as aggressive treatment, so I didn’t think it was worth recovering the foam cylinder.  Instead of just using hand held abrasives, I used a non-powered sanding aid to keep my fingers out of the box.  It’s just a turned cylinder about 6” long x 1” diameter covered with a couple of layers of 2mm craft foam.  One end is cut at 90 degrees and the other at 45 degrees (to get into corners) and the ends are also covered with foam.  To use I folded abrasive into about 1” wide strips, folded the strip over an end and held it by hand as shown in Fig. 9. Then sand the outside of the box with hand held abrasives.  The result is shown in Fig. 10.

Fig09

Figure #9:  Hand held interior sanding aid.

Fig10

Figure #10:  Sand the base.

Now insert steel wire into the groove.  Cut the wire a little over size (say by wrapping it around the outside of the box).  File or grind the ends flat across.  Try the fit and remove the excess a little at a time until it fits as in Fig. 11.  You can secure it with a few dots of CA glue.

Fig11

Figure #11:  Insert the wire.

To reverse the base to turn the bottom, first make a pad to avoid marking the already turned and sanded surfaces of the box.  Cut a piece of flexible sheet metal such as aluminum flashing 1/2” wide and long enough to go around the box rim.  Use spray adhesive to attach 2mm craft foam to the strip.  Wrap the padded strip around the box rim, aluminum side out, and trim the length so it’s about 1/2” short of going all the way around.  Then put the wrapped base rim in your 4-jawed chuck with the gap in the pad between jaws.  Tighten the chuck until the base feels secure but don’t crank on it as hard as you can on the chuck key or you may crack the box. 

Bring up your tailstock center for support and turn the original mounting tenon down to a nub as shown in the left image of Fig. 12.  Then remove the nub and sand the bottom of the base as in the right image of Fig. 12.  The foam cylinder sander worked nicely for the initial sanding of the bottom.

Fig12

Figure # 12:  Turn the bottom of the base.

TURN THE LID:  Remove the base from the chuck and mount the lid blank by its tenon.  Measure the diameter of the box opening (inside the wire, which may be proud a bit) and use a parting tool to turn a tenon a little larger than that diameter on the end of the lid blank.  The tenon should be 3/8” deep.  Clean up the side of the tenon with a skew (or other tool) and check the fit of the base on the tenon.  It should fit loose enough to come off easily, but not fall off if you leave it there.  Fig. 13 shows the tenon and testing the fit.

Fig13

Figure #13:  Turn a tenon on the lid and test the fit.

Set up a drill guide, as in Fig. 14, if you have one to drill holes for the 3/16” magnets.  A drill guide is more precise, but drilling by hand will probably be okay if you use your indexing system to mark the locations and are careful about drilling depth.  Try to keep the holes close to the flange of the lid.  A steel object smaller than the diameter of the magnet seeks a position in the middle of the magnet.  If you drill the holes away from the flange, even if you don’t have problems with the drill breaking out of the short grain, the lid will tend to “float” the lid rather than rest on the rim.

Fig14

Figures #14:  Drill 3/16” diameter x 3/16” deep holes for the magnets.

Now hollow the inside of the lid to remove some weight as in Fig. 15.  A penciled line 3/16” in from the edge of the tenon will help avoid hollowing too wide.

Fig15

Figure #15:  Hollow the lid.

Now set your calipers to the diameter of the body of the base.  Use a parting tool to cut to this diameter 1/4” back from the edge of the flange of the lid.  Round over the result into a 1/4” bead.  Then sand the parts of the lid turned so far.  Fig. 16 shows after turning the bead and sanding.

Fig16

Figure #16:  Turn the lid bead and sand.

Reverse mount the lid the same way as the base.  You could trim the mounting aid if you plan to never make another box or prepare a new one.  Shape the top of the box into a dome.  Use a pointed tool to dimple the top center of the lid for mounting the moon finial.  Then sand the top of the lid.  Fig. 17 shows the lid reverse mounted and then turned and sanded.

Fig17

Figure #17:  Reverse mount the lid and then turn and sand the top of the lid.

To insert the magnets you need some CA glue, and something steel to use as a handle such as a hex wrench as shown in Fig. 18.  Put a piece of tape on your work surface to protect it and put a drop of CA glue on the tape.  Place a magnet on the end of the hex wrench and dip it in the CA glue, then press it into the hole.  Repeat for the other two magnets.  Fig. 19 shows the box without the sky elements.

Fig18

Figure #18:  Insert the magnets.

Fig19

Figure #19:  Skyless box.

 

CUE THE SUN:  The applied sky elements are much like intarsia, except for the curved substrate.  Since the box is a cylinder, only curved in one direction, it doesn’t add too much difficulty.  Begin by copying Drawing A or download it (see references) and print it out.  Drawing A has a Cloud element if you need an extra one because you’re using a glued up turning square.  Or just if you need a choice.

Drawing A

Drawing A:  The sky patterns.

Prepare blanks for the sky elements.  I used Holly, except for Tulipwood as the orb of Saturn.  Substitutions are allowed.  The blanks, shown in Fig. 20, are all 1-1/2” x 1-1/2” x 1/2”.  The grain runs parallel to one long side so that it matches the grain direction of the box.

Fig20

Figure #20:  Cut out blanks for the sky elements.

Cut out four of the arc patterns (one blank, for the moon finial, is not arced).  Glue them to an end grain surface to three Holly blanks and the Tulipwood blank.  Wrap original blue masking tape around the blanks but don’t cover up the pattern.  Cut a piece of scrap wood that’s 1-1/2” high and 3” or 4” long to use as a handle so you can cut the arcs safely on the band saw.  Make sure that the scrap block has a flat bottom and one face 90° to the bottom.  Glue the 90° face of the scrap block to a blank with the arc pattern facing up and the concave side of the arc towards the scrap blank as in Fig. 21.  Since you’re gluing to end grain of the scrap, hot melt glue is probably the quickest reliable glue.

Fig21

Figure #21:  Glue the blanks to a scrap handle for safe sawing.

If the throat of your band saw looks like mine then temporarily attach a zero clearance throat made of 1/4” Masonite.  Holding on to the handle so your fingers stay well away from the blade, cut the arcs of the blanks as in Fig. 22.  Be sure to do the convex cut on the side away from the scrap block first.  Remove the offcut that’s attached to the scrap block and save it for the next step.

Fig22

Figure #22: Saw the sky blanks into arcs using temporary handles for safety.

Nest the arced blank and the convex offcut together and wrap with tape in both directions.  Then glue the pattern piece to the blank as in Fig. 23.  Also glue the Moon finial blank to the flat blank.

Fig23

Figure #23:  Attach the patterns to the blanks.

Drill holes for the interior cuts.  Use the smallest drill that your scroll saw blade can fit through at the corners of the mouths on the Sun and Star.  Match the drill size to the circle of the pattern for the eyes of the Moon, Sun, Star and Saturn Orb blank.  Be careful, as the Star’s eyes are smaller.  Also drill a hole in the bottom of the Moon blank that matches the diameter of a bamboo skewer.  This hole should intersect the lowest part of the Moon pattern and should be deep enough to use to mount it on the box but not so deep as to run into the mouth.  It’s easier and safer to drill into a square blank than a shaped one.  The pieces after drilling are shown in Fig. 24.

Fig24

Figure #24:  Drill holes for the interior cuts and to mount the Moon.

Now cut out the pieces.  A scroll saw is easiest, but a fret saw would work.  As some of the pieces are very small it is prudent to use a zero clearance throat with the blade set at a fresh, rather than worn location.  For any given element, do the inside cuts, such as eyes and mouth, first.  The eye cuts, as in Fig. 25, generally start tangent to the hole.

Fig25

Figure #25:  Make the inside cuts first.

Once the inside cuts are complete, work on the other cuts from the outside in—both in the sequence of pieces removed and which part of a piece is cut first as in the left image of Fig. 26.  To avoid shifting pieces retape after making cuts as in the right image of Fig. 26.  For the Sun I suggest numbering the four sun ray pieces like a clock as in the left image of Fig. 27 so you can assemble them in the correct location.  After cutting the pieces out transfer the number to the back of the piece before removing the pattern.  Where really sharp corners are desired, such as the Star, make separate cuts, as in the right image of Fig. 27, rather than turning the blade.

Fig26

Figure #26:  Cut outside first and retape after cutting.

Fig27

Figure #27:  Number similar pieces and make separate cuts if sharpness is required.

Keep multiple pieces together.  I suggest moving the piece to safe location and tossing away the scrap before moving on to the next piece to avoid confusion.  Fig. 28 shows all the cut out pieces.

Fig28

Figure #28:  The cut out pieces.

Sand the pieces to shape using power sanding.  As some of the pieces are small it would be prudent to clean up where the sander might toss them.  You at least want to round all of them over.  They will look better if background pieces, such as the Sun’s rays and the orb of Saturn, are reduced in thickness.  You can hold the pieces by hand or temporarily glue the pieces to dowel stubs.  For thicknessing, rough shaping, and convex areas use a relatively big sander such as the Oscillating Spindle Sander with 3” drum shown in Fig. 29.  It’s around 100 grit.  A lathe mounted drum sander (such as the one used to sand inside the box) would also work well.  Keeping the speed down doesn’t reduce sanding efficiency much but does increase confidence that you won’t sand off your fingers.

Fig29

Figure #29:  Rough sand on a relatively large drum.

For details and concave areas I used a small pointed foam cone sander as in Fig. 30 (to make one use the same procedure as the Foam Cone Sander:  see references).  Alternately use drum sanders mounted in a Dremel or similar tool.

Fig30

Figure #30:  Sand details and concave areas with a smaller sander.

After the pieces are power sanded to shape you can finish sanding with handheld progressively finer sandpaper.  They’re small, so it will go quickly.  Fig. 31 shows the completed design elements.

Fig31

Figure #31:  The completed pieces.

ASSEMBLE:  Mark equal intervals around the rim of the box base to aid in positioning the Sun, Saturn and Star.  I drew lines at 120° intervals and centered the box on it but it would have been easier to wrap tape around the box, remove the tape, divide into intervals and replace the tape.  For each motif pre-position the major elements to center them top to bottom.  Then put a few drops of CA glue on the back of the element and glue in place on the box.  Then add additional pieces.  For small pieces, such as the rays of the Sun it will be easier to pick up the piece by stabbing it with a small knife as in Fig. 32.  This will make the small pieces easier to put in place and keep your fingers free of CA glue as well. 

Fig32

Figure #32:  Glue on the sky.

Measure the thickness of the box lid under the dimple with calipers.  Then mark a bamboo skewer sized drill for less than this depth and drill a hole using the dimple to start the drill as in the left image of Fig. 33.  Put a piece of tape on your work surface to protect it, and put a drop of CA glue on the tape.  Dip a bamboo skew in the drop of glue and insert into the hole drilled earlier in the bottom of the Moon.  Trim the skewer protruding from the Moon to less than the drilled depth in the top—diagonal pliers work fine for trimming.  Then dip the trimmed end of the skew in the CA glue as in the right image of Fig. 33 and glue the Moon finial to the box lid.

Fig33

Figure #33:  Glue on the Moon finial.

Apply the finish of your choice.  Spray lacquer is probably the easiest, at least for the Sky motifs.  The finished box is shown in Fig. 34.

Fig34

Figure #34:  The completed box.

REFERENCES: 

Foam Sander Article:  http://davidreedsmith.com/Articles/FoamConeSander/FoamConeSander.htm

Sky patterns:  http://davidreedsmith.com/Articles/skybox/drawingA.pdf