Anatomy of a 3-Headed Sphere Machine
Interested in Rolling Your Own?
by Bob Keller
The sphere machine documented here is one of a trio of three-headed sphere making machines patterned on this general layout that were once manufactured by E & J (Esther and Joe) Adams Lapidary. Joe's sphere machines encompassed the $300 1" capacity marble maker illustrated here, a $500 5" capacity machine, and a $600 8" capacity machine. Unfortunately Joe passed on to that great lapidary shop in the sky some years ago and E & J Adams Lapidary sphere machines are no longer made. However, Joe's machines employed a classic architecture for 3-headed machines combined with design and fabrication approaches that are particularly interesting and germane to those with a potential interest in home-brewing their own sphere machines. All of Joe's machines were designed and constructed using a similar approach - basically the motors and parts just got scaled up in size and capacity to build the bigger ones. Quite a few machines have been built using this general approach.
The following article presents a photographic walk-about with comments adapted from my original Bob's Rock Shop product review of the E & J Adams Lapidary Marble Maker. It is not the intent of this adaptation to present what I would consider a complete or finished set of plans for a sphere machine. What I have endeavored to do is provide facilitating detail of the components and fabrication approaches employed for those with a potential interest in home-brewing a machine of this type for their own use.
An overview photo of the marble maker is presented above left. This machine is unusually compact as most lapidary equipment goes, with a base diameter of 12 inches and an overall height just exceeding 12 inches. As someone who seems forever challenged for open bench space, the compact nature of this machine is very appealing to me. Its overall design and layout is typical of larger 3-head sphere machines and I consider it to be rather "cute".
The underside of the base is detailed above right, showing the metal junction box cover unscrewed and removed from over a routed out recess that's employed to connect the motor wires to the line. The base feet are simply 2 1/2" long blocks cut from a 2x2 and attached to the base with #10 x 2 1/4" wood screws. The base disk appears to be fabricated from a 1 5/8" thick birch skinned solid core door with a particle board core. I noted the grey paint job protecting the wood surfaces on the base was rather thin on the underside of the base and feet.
Shown above left is some exterior detail of one of the Bodine Electric Company gearmotors and above right is the motor tag. These are geared parallel shaft 120VAC 60Hz continuous duty motors with an output speed of 108 rpm. The torque is specified as 30 oz in and the current draw as 125 mA. A warning on the operating instructions supplied by Joe cautions that these motors typically run hot.
The motor tags call out 1.6uF capacitors and 2.0uF 660VAC rated caps are supplied, so these
are heavy duty in terms of the requirements. The capacitor cans are mounted by gluing them to the motor cases with silicone adhesive. The capacitor terminals have also been copiously dabbed with silicone adhesive to insulate them and protect the user against a shock. The wire connections and splices connecting the line cord through the switch and to the motors are made using crimp style connectors and wire nuts.
The business end of the 30" long power cord employs a UL listed, grounded plug rated for 15A at 120V, which is heavy duty for the application. Just for a reality check I got out my trusty Simpson 260 VOM and verified the continuity of the ground circuit from the plug to each motor case. No problem there with this unit, but of course it is possible that the ground could be miswired or open on others. As this is a critical safety concern it wouldn't hurt to reality check the ground on your own sphere making and other lapidary equipment with a meter or continuity checker if you haven't already done so using a more exciting technique.
The power to the motors is switched with a UL listed, standard single pole residential 120VAC 15A wall switch, which is heavy duty for the application. The switch is mounted in a plastic junction box covered by an ordinary residential switch box cover. I was a little surprised at the junction box being attached to the base using nails. But after all, it is a nail-on style junction box... I twisted around on it some to see if I could wrench the switch box from the base using my hands. However I was unsuccessful at dislodging it and concluded the nails were in fact doing a respectable job of securing the switch box to the base. I noted that a UPC bar code tag had not been removed from the junction box. That was unsightly to my eyes but I found it readily removed.
The marble maker's electrical work exhibits appropriate overall craftsmanship and attention to electrical safety. However it is important to appreciate that while the electrical connections are insulated they are NOT WATER PROOF. These machines are typically operated using water in close proximity to line level voltages and current, so there is the possibility of receiving an electrical shock due to spilled water or if the insulation should become damaged or otherwise fails. Due to this potential hazard accompanying any line powered machinery or equipment operated in the vicinity of water, they should always be shock protected using a GFCI (Ground Fault Circuit Interrupter) device. Back when I worked as an electronics tech and engineer I used to get fairly regular shock therapy, but since taking up lapidary as a hobby I'm doing better now... ;)
Detail of the base end of a motor mount assembly is provided above left. Each motor mount assembly is fabricated from a 3 inch hinge with a 3" x 6" x 5/64" plate welded to it. A 1/2" x 1" x 1/8" "L" bracket is welded to the hinge to serve as a stop limiting the outward travel of the motors to about 10 degrees overhanging vertical.
The hinge flange is drilled to pass a mounting bolt. Above right is a close view of the welded motor mount bolt assembly consisting of a 1/2" x 1" x 1/8" strap which is drilled to pass the bolt and welded to the underside of the hex head of a 5/16" x 1" cap screw. The welded strap serves as an anti-rotational device so the mounting bolt can be tightened down via a topside nut without spinning. A 5/16" hex nut threads onto the other end with a 5/16" washer employed beneath it. This topside hex nut is what gets loosened and tightened by the operator to align and adjust the motor/cup spacing in and out. Clearance channels for the non-rotating mounting bolt heads are routed into the top of the base permit each motor mount assembly to be adjusted in and out as required to accommodate cutting various diameter marbles.
The mounting bolt clearance channels are overlapped and covered on either side with pieces of 1 1/4" x 4" x 1/8" strap which have been countersunk and screwed to the base using four #6 x 3/4" flathead wood screws per strap. These straps are spaced so there is an approximately 3/8" gap separating them, which allows the 5/16" 5/16" x 1" hex head motor mount bolts to slide freely to and fro between then. When the motor mount bolt nuts are tightened down, the steel straps welded to bolt heads are clamped against and bear on the undersides of the 1 1/4" x 4" x 1/8" straps attached along the sides of the motor mount bolt head clearance channels.
Depicted above left and right are additional motor and motor mount details shown from the sphere side of the motor mount assembly. Each motor mount plate is drilled for the 10-24 threaded attachment studs on the motor cases and a thru hole to pass the motor shaft. The motors are attached to the plates via their 10-24 threaded mounting studs using hex nuts and flat washers. The elastic "hooks" are fabricated using 3" lengths of sawed off of 1/4" hex head cap screws welded to the top of each motor mount plate.
The manner in which the 1 1/4" x 4" x 1/8" straps are positioned over the routed groove in the base and forming a trackway for the anti-rotational motor mount bolt to slide in is illustrated above left. Note the fabricated end of the anti-rotational bolt positioned on the hinge bottom with the shaft of the bolt passing through the mounting hole in the hinge flange of the detached motor mount assembly.
The larger sphere making machines produced by E & J Adams Lapidary use springs to tension and load the grinding and polishing cups against the sphere. However, the marble maker employs rubber bands for this task, as depicted above right. I've already managed to lose one of the two provided rubber bands somewhere on my patio while I was photographing this machine. But I suppose a visit to an office supply store for a box of these would have been inevitable anyway...
Shown above left is one of the brass 1/4" threaded pipe to 1/4" tubing flair fittings employed to adapt the 1/4" pipe threaded cutting and polishing cups to the 1/4" diameter output shafts of the gearmotors. An approximately .2" length of 1/4" ID rubber tubing riding on the motor shaft inside the flare side of these fittings provide some degree of off-axis flex of the grinding or polishing cups relative to the motor shafts.
Depicted above right are grinding cups positioned against a 23mm marble. The manufacturer specifies a 15 degree tilt inwards (downwards) for the motors and cup axes. I assume the reason for employing down tilt is to keep grit and swarth from running down the cups and motor shafts into the output shaft bearings in the motor cases.
Three sets of cups are provided with the marble maker, which are illustrated above left. One set specified for use with 220 grit for coarse grinding consists of metal 1/4" threaded pipe couplers. Another set specified for 600 grit fine grinding consists of 1/4" threaded to SCH 80 PVC pipe glue-on adapter couplings. Additional grinding cups should be available as standard plumbing fittings in any decent hardware store. The set specified for polishing consists of turned wood cones with dimpled ends for the marbles. The wooden polishing cones are mounted with flat head wood screws to threaded metal flanges. The polishing cup flanges are fabricated from 7/16" washers welded to 1/2" long sections of metal 1/4" pipe thread couplers. Close detail of a fabricated flange for a polishing cup is provided above right.
My general impression of the overall fit and finish of the E & J Adams Lapidary Marble Maker grades in there somewhere between "cottage industry" and "agricultural". It is not a "sleek" product in my eyes although I do appreciate some of the incorporated engineering for its simplicity and functional economy. Of course I have also come to appreciate that with tools in general, beauty is first and foremost as beauty does.
I anticipate a couple of potential stumbling blocks in the path of anyone aspiring to home-brew a machine utilizing the general layout and approach presented here. Perhaps the easiest to address of these is the requirement for welding. While most of this machine's fabrication is hacksaw, hand drill and hammer work, welded parts are employed in the fabrication of the motor mount assemblies and elsewhere. With some fortuitous scrounging or clever fabrication it might be possible to eliminate the welding, or non-welders may be successful at talking a welder friend into handling those chores for them. However, the thought occurs to me that if you don't own yet own a welder suitable for doing light fabrication like this yourself, here is just the excuse you have been waiting for to acquire one!
The more difficult to overcome potential stumbling block may be aquiring suitable geared motors without seriously denting your bank account. Geared motors are the "high technology" packages in this design approach serving to circumvent more demanding engineering and machine-shop work on the part of the home-brewer. The rest of the contraption is basically a glorified motor mount suitable for fabrication with more typical handyman type tools and facilities.
Many home-brewed machines as well as cottage industry products of this ilk have been constructed around surplus geared motors. Because surplus comes and goes, cottage manufacturers such as E & J Adams Lapidary were no doubt constantly challenged to locate and acquire reasonable supplies of suitable gearmotors at viable costs. Your own mileage will vary depending on your own definitions of "suitable" and "viable cost".
I note that Bodine Electric Company is still around and sources an extensive selection of new geared motors. They provide an online catalog with a shopping cart at their web site. Bodine Electric Company manufactures some truly awesome AC, permanent magnet DC and brushless DC type gearmotors, including a selection of parallel shaft AC gearmotors similar to those employed in the E & J Adams Lapidary sphere machines in speed and torque ranges suitable for just about any sphere machine application. But when you check them out be sure you are sitting down as you click the "add to cart" button for 3 of them and see the price...
Another manufacturer of gearmotors of potential interest to sphere machine makers is Baldor Electric Company.
If you want to explore the surplus route, you might want to check out the gearmotors at Surplus Center and Surplus Traders from time to time.
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