By Dennis Liggett
First of all, I can not take any credit in coming up with the design of a twisted laminated goblet. Stuart Mortimer is the one that came up with the idea. I first saw the goblet at the BYU Woodturning Symposium in Provo, Utah and thought that if I could make the goblet it would be something that I would be proud. I spent two years trying different approaches to making the goblet. Finally arriving are the following method.
The object of making a twisted laminated goblet is to make four parts that eventually become the single goblet. The four parts are the top or cup, the stem, the stem insert, and the base. Most of the goblets that I make have holly inserts in the stem. Holly is a good choice because it is a fairly tough wood. It also looks good with about any wood. In the example that I am describing below, I am using cherry for the goblet wood and holly for the lighter insert. The material requirements: ½” X ½” X 7.5” holly for the insert, 5/8” X 5/8” X 7” cherry for the stem, and 3” X 3” X 6” cherry for the cup and the base.
Step 1. Creating a Drilled Stem
Always make the drilled stem first. There nothing more frustrating than to make the insert and it does not fit into the drilled stem. Mount the stem piece of wood in the chuck. It is best if the stem is perfectly square as it is gripped by the inside of the jaws. Bring the tail stock up and center the blank prior to the final tightening of the chuck. This way the stem should be centered. After centering, back the tailstock off from the piece a considerable distance because you are not going to need it for the drilling.
Move the handrest so that it can act as support for your left hand at the free end of the wood where the tailstock used to be. With the long point of a skew, enlarge the center mark of the wood that was against the tailstock to form a cone into the wood that is larger than the 3/16” drill bit size. It is important for this cone to be larger than the drill bit and it is also important that the cone that you make into the wood has no bump in the center of it. Using your left hand on the handrest to guide the drill bit, place the drill bit in the spinning cone made by the skew. If there is a bump in the bottom of the cone the drill bit will wobble. If the wood has moved off center the bit will wobble. Both of these conditions are unacceptable and you must go back and correct them. There can be no wobble to the drill bit as it sets in the spinning cone. My opinion is that the first ½” of drilling determines the path of the drill bit. So any malfunction at the start will end in the bit coming through the side of the stem. You will notice this by the bit wobbling as it gets deeper into the stem. If this happens, you must start over.
If I am using a regular aircraft engineers bit (12” long) and 3/16” in diameter. I mount these in a handle similar to a file handle or larger. I have two bits ready to drill the hole or have some method of cooling the bit. With this type of drill bit, line up the horizontal and vertical axis as close as you can by eye. Move the bit slowly forward and make very short cuts, pulling the bit entirely out of the wood after each cut and emptying the chips. I am talking about very short cuts and very quick cuts. It appears that the reason that a drill bit does not cut straight has to do with the heat build up. You can see the color of most woods change as the bit gets too hot. This is the time to switch to another bit or cool the one that you are using. It did not make sense to me but I have been shown that short quick strokes will drill a straighter hole than long deep strokes.
If I am using a gun-boring bit, which I greatly prefer, make a handle with an attached quick disconnect for compressed air at one end and a place to secure the bit at the other end of the handle. With compressed air going through the bit, align the bit in the same manner as above but with the handle slightly lower than the center. As you push forward, raise the bit handle toward the centerline. At some point the bit will start to cut by itself, this is the center and you can push the drill bit into the wood all of the way. Since I have started using gun-boring bits, I have lost very few stems due to the drill coming through the side. Also, with the compressed air the bit runs so cool that I can touch the tip after drilling through 7” of cherry or ebony and it will not burn my fingers. You can get gun-boring bits in most cities at aircraft supply outlets or on Ebay. You need one that is over 7.5” long and is 3/16” in diameter. If you are going to order a gun drill from a manufacturer, make sure that the drilling part of the bit is over 7.5” long.
Step 2. Making the 3/16” holly dowel insert.
Mount the ½” X ½” X 7.5” holly in a chuck that can get a good grip on ¼” to ½” piece of the wood. Do not tighten the piece into the chuck, just get it snug. Bring up the tailstock with a point live center. Center by eye or punch a center in the end of the holly to get it to center on the tailstock. Tighten the chuck keeping some pressure on the holly with the tailstock. After tightening the chuck, move the tailstock away from the holly so that the holly is suspended in mid air. If the holly moves as the tailstock is moved away the holly did not center in the chuck. Bring up the tailstock, readjust the chuck’s grip and repeat this process until the holly does not move when the tailstock is moved away. This is important because when reducing the size of the dowel to 3/16”, the wood must be straight to get a good dowel.
I use the taper method of reducing the size of the dowel to 3/16” at the tail stock end. I use calipers to insure that I am at 3/16” by adjusting the calipers to the drill bit that I am going to use. Once the dowel is sized at the tailstock end, I use what I call the step method of reducing the rest of the dowel to size. Using a ½” skew, I make short uphill cuts toward the headstock. I complete a ¾” section before going to the next section of the dowel. I take a light cuts reducing the size gradually. Note: As I am making the stem, I keep an eye on the livecenter. As long as the live center is spinning you have support, but as the stem gets weaker, the stem may bend slightly and if the live center stops, you have lost the support. If this happens, I gently tighten the livecenter to insure that it keeps spinning and giving support.
It is important to make sure that this dowel is 3/16”. Before removing the stem from the chuck, I remove the tailstock and slide the stem over the dowel to insure that it fits.
Step 3. Finalizing and turning the Stem
On oily wood, I run acetone through the hole before gluing. I pour a little thick super glue into the hole at one end of the stem. Place the holly dowel into the same end of the stem just slightly and cover it with enough thick super glue to cover it when it is inserted. I insert the dowel part way and rotate it and pull it out and push it back in to insure that there is glue over the entire dowel and that the glue is evenly spread. After getting glue evenly distributed on the holly insert, pull it out and put some more glue into the stem. Hold the stem upright and insert the holly from the bottom pushing up the glue to the top. I want to see glue being pushed up out of the other end of the stem. I have found that this method gives me the best lamination and usually covers the insert completely. Place the laminated stem aside to dry.
After the glue has completely dried, I mount the stem in the chuck and center it. This can be done by using the point left by the tailstock in the holly and center punching the other end. Turn the stem down to 3/8” or slightly smaller. Create a ¼” tenon on each end that is about ¼” long that is square and even. The basic stem is now complete.
Step 4. Creating the Goblet Cup
I round off the corners of a blank of 3” X 3” X 5” between centers. Keep the diameter as large a possible and cut a tendon to fit into your chuck at one end. Mount this blank into your chuck and turn the top of the goblet. There are many ways to do this. The only rules that I use are that the same look of the cup should also be used at the base. If the top is one curve, the when I make the base I only use one curve. You can experiment and come up with all kinds of designs. Some look like chalices and some look like tulips.
I drill a ¼” hole in the center of the blank to the depth of the cup as a starting point. I shape the outside of the goblet cup part way, making sure that I do not reduce the bottom part of the cup to the point that it would give me vibration. I use a spindle gouge to hollow out the cup of the goblet. As the cup gets thinner, I use my free hand to dampen any vibration that can occur and crack the cup.
After hollowing out the cup, I complete the outside of the cup. I do not part it off yet. I insure that there is enough material in the base of the cup to insert the stem to 1/4”. I have found that by putting a bead at the bottom of the cup that I can hide the glue joint between the stem and the cup.
Finish sanding and finishing the cup of the goblet before you part it off. This is the last time that you will be able to work on the inside of the cup.
Part off the goblet cup and wrap masking tape around the top edge. I use 3 wraps of tape to protect the cup from the jaws of the chuck. Folding it down into the center of the cup. You need to keep this as neat as possible because you are going to mount the rim of the cup with the protected edges in the chuck to drill the hole in the bottom for the stem to go into.
Mount the goblet cup in the chuck with the bottom facing outward. Press the cup into the jaws as far as possible to take advantage of the flat base to keep the cup centered. Gently, tighten the chuck jaws around the masking tape that protects the top edge. Tighten the jaws to the point that the cup is centered and true but not tight enough to mare the rim. Using the long point of the skew create a cone for the ¼” drill and drill a hole for the stem to fit into. Take special caution to not drill too deeply and come through the bottom of the cup. I have modified a ¼” drill bit that has a very flat point to do this with. The flattening of the drill point, I believe, lessens the possibility of the bit catching and being pulled forward through the bottom of the goblet cup. I also us a depth collar to keep the bit from being pulled in too deeply. You only have to do go through about 3 or 4 cups before you decide to modify a bit this way. Now remove the completed goblet cup.
Step 5. Creating the Goblet Base
I remount the base part of the original stock, and create the base of the goblet as a compliment to the top cup. I put a bead on the top to hide the junction of the base and the stem glue joint. Do not part this off. With the long point of a skew create a cone similar to the way that it was use to create the start of the drilling of the stem. Drill a ¼” hole to receive the base of the stem.
Step 6. Assembling the Goblet
I check to make sure that the base is running true in the chuck. There should not be any wobble to the hole in the top of the base. Turn off the lathe and insert the stem to make sure that it fits. I have found that the larger and/or darker end of the stem should be the base of the stem. If the wood has a very distinct grain that would be noticed, I align the stem as closely as possible to the grain pattern. Turn on the lathe at a low speed to check that everything is still centered and does not wobble. If it does wobble adjust the base in the chuck until there is not a wobble.
Once the base and the stem are running true. Turn off the lathe and remove the stem. Clean the stem tendon and the drilled hole with acetone if the wood is oily. Put some thick super glue on the tendon that goes into the base. Remount the stem into the base and bring up the tailstock. Turn on the lathe for a short period of time to insure that things are still in alignment. Allow the glue to set up.
Once the glue has set, remove the tailstock. Fold toilet paper into a wad that is fairly thick, square and even. Insert the toilet paper wad into the goblet cup so that you can bring up the tailstock and it will not damage the bottom on the goblet cup. Clean the drilled hole in the goblet cup and the tendon on the stem with acetone if the wood is oily. Apply thick super glue to the tendon and bring the drilled hole in the goblet cup up to fit over the tendon. Bring up the tailstock to the toilet paper inserted in the goblet cup and tighten to insure a good fit. Make sure to match the grain between the base and the cup at this point. Turn on the lathe at a low speed to insure that there is no wobble. If there is you must adjust the cup only to align the goblet.
Note: I use a modified live center to hold the goblet cup. I make this center from hard maple, a ¾ 10 nut and the Oneway live center. I buy 3/4 – 10 nuts from the hardware store and epoxy them into the end of 2” hard maple. I take a nail about the size of the insert rod provided with the live center and cut it off so that it just goes though the live center. After the epoxy has set up I wrap tape around the live center with the nail in it to prevent it from turning. I then screw on the hard maple and insert it into the head stock. I then turn the profile of the maple to what I want. I have many of they tips that I use for the live center. To make the live center point for the goblet I make a cone that is soft and not pointed at the end. I want the live center to reach the bottom of the goblet cup and not touch the sides. Or if it does it is very light because I do not want the live center to split the cup.
Once there is no wobble to the goblet, allow the glue to dry. Now you should have a complete goblet ready to apply the twist.
Step 7. Applying the Twist
I lay out the twist both the bine lines (vertical) and start lines (horizontal). I am going to describe a double barley twist, two bines and two hollows. With a diameter of 3/8” for the stem, the classic formula states the bines lines should be at 3/8”. I have found that this appearance looks OK but that the stem is a little too weak. Therefore, I stretch the bines, slightly. I stretch the bine lines to 1/2”. This also has the advantage that I can lay out a 6” space on graph paper glued to a piece of wood as a template. This also allows me to center the twist by eye as I am laying it out. Laying my template on the toolrest with the lathe running, I mark the bine lines every ½” for the 6” of the twist. With the lathe turned off, I position the tool rest as close to the 4 jaw chuck as possible but still allowing the chuck to rotate. I establish a reference point at the edge of one of the chuck jaws. From this point I draw a start line horizontally down the length of the stem. I rotate the chuck to the same reference point on the next jaw of the chuck and draw another line. Since my chuck has 4 jaws when I have drawn a line from each reference point off each jaw, I should end up with 4 equally spaced lines on the stem. (Note: This procedure is for a double barley twist. If you want to do a triple or more, I refer you to Stuart Mortimer’s book, “Techniques of Spiral Work”).
The stem should now have 13 vertical circles on it and 4 horizontal lines. This is as far as I go in the layout of this twist. You can think of the lines both horizontal and vertical as being a piece of graph paper wrapped around the stem.
Step 8. Cutting of the Twist
With the lathe stopped, pick one of the horizontal lines at the top/cup end as a start line. Number this line 1, the next 2, the next 3 and the last 4. Angle a 1/8” Abbra rasp or any thin rasp and starting at the intersection of the closest vertical line and line 1 so that as it cuts a fine line, the cut line bisects the horizontal segment line of line 2 and intersects with the next vertical line at the intersection of line 3. As you cut with your right hand you must rotate the lathe with your left hand to continue the cut. Continue this procedure to the bottom line on the stem. Make as few adjustments as possible in this initial cut and always cut across the ‘X’ formed by the vertical and horizontal lines where indicated. Do not go over the start or end lines. This will result in what the British call “untidy”. I cut this initial line once more with the 1/8” rasp to smooth out the line and get a small consistent grove. Note: This cut has nothing to do with depth; it is only for developing a path for the larger rasp to follow.
With the same 1/8” rasp repeat the above step but starting at horizontal line 3. With this cut it is important to cut all of the ‘X’ made on the stem but it is just as important to split the difference between the lines already cut from the first spiral.
Next with a ¼” rasp, start at line 1 and expand the hollow with one pass. (Note: the rasp cuts on the push stroke. You must rotate the stem as the rasp is pushed to avoid flat spots in the twist.) I then make a cutting pass on the other hollow starting at line 3. I then alternate from one to the other until one of the hollows breaks through to the holly insert. (Note: the above method is really directed at right-handers, left-handers may find it easier to move to the other side of the lathe and cut with their left hand while rotating the lathe with their right hand. I know this because I am left handed.)
Once I have broken through to the holly on one hollow, I only work on this hollow until it is completely cut I have found that by working on both hollows at the same time that sometimes the bine will split and fall off. I finish cutting the hollow that broke through so that there is a fairly consistent white line from the holly all of the way from the start to the finish. I then apply a small amount of the thin super glue in the completed grove. This fills in any places that may have been missed with the original gluing. I do not use accelerator because I want the glue to seep into the wood as deeply as possible. I set the goblet aside with just the one grove cut until the glue completely sets up. I then apply accelerator to insure that the glue is set up.
I then complete the second grove the same as the first. Applying thin super glue to the grove after the grove has been complete. I set the goblet aside and allow the glue to set up.
Step 9. Finishing the Twist
Once the glue has set, I mount the goblet in the lathe chuck and with a ¼” chain saw file, I clean the glue from both groves. I am very careful at this point not to deepen the grove much. I just want to clean it up.
With the same chain saw file, I cut straight across the bines as I am rotating the piece by hand. I do this at least twice and sometimes up to four times depending on the hardness of the wood. Each time as I push the chain saw file forward I rotate the piece to keep from allowing flat spots to form. Also on each pass I take a slightly different angle to round the edges of the bines.
From a flexible roll of sandpaper, I tear off about a ¼” strip that is about 10” long. I roll this strip into a small column and wrap it around the stem in one of its hollows. The sandpaper must go all of the way around the same grove and still have enough for you to hold. I use Vitex sandpaper which I find works the best. I start with 120-grit sandpaper. The complete wrap around the stem will smooth out the holly high spots. I count as I am sanding strokes1,2,3 and rotate the stem about a half of a turn, then do it again.
Once both grooves have been sanded with a particular grit of sandpaper, I take a piece of sandpaper of the same grit and with the lathe running at about 250 revolutions per minute. I allow the sandpaper to drop into the spirals and take the sandpaper to the other end of the stem. I hold onto the sandpaper lightly. What I am trying to do here is to allow the sandpaper to round over the bines of the stem. Sometimes I push the sandpaper to keep pressure on one side of the bine and other times I pull back on the sandpaper to get the other side of the bines. I do this 10 times or more for each grit of sandpaper that I use.
I start with 120 grit and go to 600 grit. With a particular grit I make a strip into a column, wrap it, sand the groves, sand the top of the bines and then sand the rest of the stem that may need it. Then I proceed to the next grit of sandpaper.
Step 10. Parting Off and the Bottom
I part off the base with the thinnest parting tool that I have (1/8”). I angle the cut to prevent any major work later. I make the parting cut down to about ¼” with the tailstock still in place. To finish parting off the piece, I stop the lathe and move the tailstock out of the way. I balance the stem part in my left hand. I do not attempt to hold it; I just balance it there so that when I turn on the lathe it has support. I then turn on the lathe balancing the spinning stem in my left hand, and with my right hand I finish the parting off. Note: I reduce the speed of the lathe considerably less than 250 rpm. I have found that this is easier on delicate partings off.
I inspect the base of the goblet. I usually clean up any small pieces in the very center with a knife and punch a center for the live center to seat. With the masking tape still of the top lip of the goblet, I reverse chuck the lip into the chuck and bring up the tailstock into the center mark. The tension of the goblet has to be very exact. Too much and the stem will bend and break. Too loose and you are turning in mid-air and the stem will break. What I do in bring the tailstock up gently and turn on the lathe. I watch to make sure that the livecenter is spinning. If it is not then I tighten it just a little to start the tailstock spinning.
If I have centered the goblet correctly the base will not wobble. If it does then it must be readjusted. Once the base is spinning smoothly, I very carefully sand the base of the goblet. I keep an eye on the live center because I have found that with so little pressure applied to the goblet by the livecenter that if it seat in or the pressure from the sanding moves the goblet then the live center will stop. I tighten the tailstock immediately. Once sanded I put two rings in the base with the long point of the skew.
If the stem seems particularly weak, I sometimes just sand the bottom. Under no circumstances when sanding or marking the bottom can you grab, hold or touch the stem with your hands. Any pressure will have the effect of unwinding the spiral and the goblet stem will disintegrate immediately.
The good news if you break a stem is that you can make another stem. The bad news is that 80% of the work is in the stem.
Conclusion
First, if I can, I apply an UV protectant lacquer that I get a photo store. I have found that this greatly decreases the effect of the sun on sensitive woods. I have tried this for about 2 years and it has worked well. Second, since the color of some woods is absorbed by lacquer, I have had to go over these with several coats of water based polyurethane, before the final lacquer coat. The woods that I know will color lacquer are cocobolo, Madagascar rosewood, bocote, and Honduras rosewood.
Stuart Mortimer always says that the piece should stand on its own and that the twist is added as decoration. If the piece is not done well, a twist will not save it. If the piece is done well and a twist is not done well, it would be better to leave off the twist.