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Hollow Spheres
By Brian McEvoy
 In the last newsletter I featured the Lindsay Sphere Turning Jig and turned a solid 8 inch diameter sphere. My aim was to produce a perfect sphere that could be used for one of my 12 inch hollow globes. I've now made a number of hollow forms ranging from 6 - 13 inches in diameter, all turned to less than 1/8 inch thickness. The technique is rather simple using the method I demonstrate in my Two Piece Hollow Form DVD. Though I've turned these pieces very thin to facilitate piercing as part of the embellishment process, they could easily be left thicker if this suits your purpose as a finished piece.
 I started by coring out two half spheres so I could have three different sizes. The main reason to core out as in all cases is to achieve the most with the least waste. This beautiful butternut timber had been curing to perfection for many years and was perfectly suited to the carving I wanted to do down the road.
For this project I've chosen the middle size halves that should give me a 9 inch sphere.
 Before proceeding to turn the two pieces down to the desired thickness I was sure to true the top edges so the halves could be glued with a seamless glue joint. This was achieved using a straight edge laid across the outer edge.
 When thin work is desired, be sure to remove the wood in small stages, ensuring that the main mass is there to provide stability and minimal movement in your piece.
Work your way down in these small steps stopping and measuring for thickness regularly; you can't stop and measure too often.
Once you're close to the bottom where the foot prevents accurate measuring you have to guess at the curvature somewhat. I try to always guess on the thick side to ensure that once I remove the foot I won't be breaking through. Please note that I always start with a very small foot which might make turning the piece a little more difficult, but with smaller cuts this is of no serious consequence. Having a small foot means less guessing to achieve the thickness throughout the whole piece. 
Turn the second half the same as the first.
Note that if you try to marry the two halves in a dry run you'll find it virtually impossible to get a perfect fit and with only 1/8 inch glue surface you have very little room to play with. Because the whole piece is turned thin, it becomes quite floppy and so lining up the two halves becomes rather problematic.
To solve the fit issue I use toothpicks glued very delicately with CA glue to the half that's mounted on the lathe.
 You'll also note that I've determined the best match grain wise for the two halves and marked with a pencil a double line just to give me a reference once I have applied the glue.
With all the toothpicks in place apply the glue to both halves, ensuring good coverage.
Gently move the second half in place; you don't want to knock any of the toothpicks off at this stage.
Move the tailstock into place to act as a clamp. Good firm pressure is all that is necessary; don't over tighten as you don't want to squeeze all the glue out or, more important, you don't want to crack or break the piece.
After 15 minutes or so, remove the toothpicks and scrape off the excess glue.
At this point sand the glue joint, being careful not to create a flat spot and spoiling your perfect sphere.
Now with very gentle cuts remove the foot down to a small nub that the live center is blocking. Be very careful not to remove too much material. Err on the high side because you are going to sand off the last part to achieve a perfect sphere.
With your lathe speed very slow, sand the nub off and blend it in to the rest of the sphere. Take your time at this point, again you don't want to sand in a flat spot. Stop the lathe often and inspect your form - you'll be surprised how quickly the material disappears.
Once you're satisfied with the form, sand the whole piece down to where you are happy. I sand to 500 grit.
 There are a number of different methods to turn off the second foot. I prefer using a vacuum chuck. If this is the method you'd like to use, be very mindful that this piece is thin and high air pressure could damage it. If you don't have a vacuum chuck in your arsenal you can turn a recess in a scrap piece of timber and then carefully mount the sphere between centers using the recessed timber on the headstock end and a live center on the tailstock side. With this method you'll have to do a little hand sanding to remove the nub and achieve the desired form.
In either case gently remove the foot with small cuts as you did on the other end and then sand smooth until you're satisfied with your job.
There you have it - a very simple method to achieve what might have seemed impossible.
The techniques used to create this two piece hollow form sphere are shown in detail in our Two Piece Follow Form DVD. The piercing and airbrushing techniques are shown in our Embellishment DVD. Both are available on our websites listed below.
www.onegoodturn.ca
www.langercraftworks.com
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TWO IN ONE SAFE DRIVE AND FACEPLATE
The three adjustable pins account for the versatility and make it ideal for most between centre work such as spindle work, large logs, natural edge and regular bowls. For small work that requires attaching the face plate exactly at centre, just leave the center pin protruding a small amount to locate the center and then use three #8 or #10 screws to fasten on your work piece. 
Designed to be as versatile as possible, these boring bar set ups should suit most any lathe and shop configuration. Though they may look intimidating, in actual fact the simplicity and ease of use could surprise you. Even relatively new turners can achieve amazing results with a basic knowledge and a little practice. This boring bar is not only useful for deep vases but can be very effective when turning deep bowls or even shallow platters. I once turned a number of 16" flat serving platters with mine and found nothing as effective to achieve a perfectly flat bottom. They are also very useful when a relatively small opening, as small as two inches, if desired. 
The boring bars themselves are manufactured in two pieces that thread together to form a 1 ½ inch by 6 foot solid mass that weighs close to 50 lbs. This mass is required to reduce vibration when reaching far off the tool rest. Depending on the timber and the moisture content, up to 24 inches depth can be achieved. I usually recommend and use a steady rest when I'm turning over 18 - 20 inches. The cutter holder is bolted solidly into the end and a greater angle cutter holder is available which is very useful if you desire a small opening on a larger diameter vessel. A lot of the South West pottery is designed this way. 
The 17% HSS cutters are essentially scrapers and are very simple to sharpen with any bench grinder. For consistent angles a tool rest on the grinder close to the wheel is handy. Just set the angle once to match the angle that is ground into the cutter. 
The back floor mounted tool rest is built in five pieces to accommodate ease of shipping and storage. The bottom bar that holds the weight of the boring bar is a conveyer belt roller. The ease and smoothness of operation is hard to imagine. The beauty of this floor mounted stand is its versatility: it can be adjusted for most any height of lathe, and lathe bed length isn't an issue. Another nice advantage is the fact that you can push the roller stand well away from the lathe to achieve greater angles of attack if you want large diameter vessels with small openings. A disadvantage is that your lathe can't be up against a wall.
The secondary tool rest is also designed to accommodate most lathes. It should attach to any lathe with a split bed and is adjustable to suit lathes with 14 - 26 inch swings. The wide rest has stoppers welded on the ends to prevent the bar from accidently slipping off. Once you've made the adjustment so that the cutter tip is at center, both the secondary tool rest as well as the floor stand shouldn't have to be adjusted again unless you change lathes with a different swing or off the floor height. If you do upgrade or change your lathe a simple adjustment is all that is necessary. 
The light kit is almost essential if you plan on turning thin with translucent timber. The ease of gauging wall thickness will soon be apparent once you've tried out the light. It's also a nice way to see what's happening inside your vessel. A 12 volt battery charger combined with the automotive socket and bulb also will produce satisfactory results, though I like the higher light intensity achieved using either 18 or 24 volts. The drawback to using the higher voltage is that the bulb life is reduced considerably. I believe the trade off and final results are worth it.
For those of you who may still be a little skeptical as to the ease of use of these boring bar set ups, I'd like to relate a nice success story. A few years back when I was demonstrating at the annual Utah Woodturning Symposium I had a couple of hecklers in the front row, all in fun of course. They turned out to be Les and Judy Roberts from Australia. Les, the woodturner was quite impressed with the boring bar demonstration and said no one that he knew at home was using such a beast and he'd sure like to give it a go. A year or so later Les was instrumental in having me invited to demonstrate at Turnfest down under. The catch was, I needed a 100 lb boring bar set up to demonstrate with. Les had one built and a short time later I was over playing in his shed, as they call it. We managed to turn a number of deep vessels using Hoop Pine, a wonderful Aussie timber similar to Norfolk Pine. This summer Les and Judy gave me the pleasure of traveling over to Canada and spent 10 days hanging around, mostly playing in my shed. I hadn't mentioned that though Les was a professional turner, he'd had the misfortune of losing his arm in a boating accident a number of years back. His turning skills and eye for form put me to shame. While he was here, he managed to complete a number of birch vessels as deep as 18 inches with the 6 foot boring bar. 
