Geometric Chuck 7:2 ratio

UPDATES: See below…

The geometric chuck is used as an accessory to an ornamental or rose engine lathe. It can create circular patterns by offsetting the workpiece from the lathe center, while at the same time turning the workpiece at a different rate than that of the lathe. This chuck is designed to turn at a fixed ratio of 7:2. It also has the capability to change direction, which will change the orientation of the loops it creates and therefore the design. Although the gear ratio on this chuck is set, hundreds of different patterns and designs can still be created. 

Features:

• 7:2 gear ratio.
• 1 x 8 teeth per inch spindle.
• Directional change feature.
• 120 position main gear.
• Eccentric pivot. 

Print details:

• Material: PETG (PLA may also work but I have not tested it thoroughly.)
• Layer height: 0.20mm
• Supports: Yes, on many of the parts.
• Infill: 20% in most cases. 100% for smaller parts and gears, and around holes and bearing openings.
• Perimeters: Should be increased to at least 3 for additional strength. 

All parts shone were printed on a Prusa i3 MK3S+.

Additional parts needed:

Bearings-

• 8x22x7 - 5
• 6x22x7 - 1
• 35x62x18 - 1
• 25x52x15 - 2

Bolts-

• M3 - 12
• M8x37 - 1
• M6x37 - 1
• M4 - 3
• M6x25 - 3
• M8x19 - 5
• M6x30 - 1

Threaded inserts for plastic-

• M3 - 9
• M4 - 3

8mm Steel shaft-

• 105mm long - 1

Nuts-

• M6 square nuts - 4
• M3 square nuts - 2
• M8 lock nuts - 6
• M6 lock nuts - 1

Lock collars-

• 8mm - 2

6x9x13 steel tubing spacer for gear 3

You may want to test and tune your printer to make sure it prints correctly. Tolerances are very close on some parts, gears must mesh correctly, and bearings must fit snuggly without slipping. A method to hold the main gear motionless will need to be in place for the chuck to operate. Because there are so many different configurations of ornamental lathes, I have not included this method, and it will have to be made by the user for thier particular lathe.

I did not include a build guide for this model, but if you need help you can refer to the build guide for my other geometric chuck model that is also posted to this site. The two models are constructed much the same.

Remember to work safe. 

This chuck was not designed for and should not be used on a high-speed lathe! Most conventional wood lathes do not turn slowly enough to use this chuck. Do not attempt to turn this chuck faster than 5 rpm!

• This design has many pinch points. Be aware of moving parts while machines are running.
• Do not overreach or use excessive force to perform any machine operation.
• Never wear loose clothing, watch, rings, or gloves when operating a lathe.
• Tie back long hair or anything which could be caught in moving parts.
• Keep small children away from machinery, and away from small loose parts which could be a choking hazard. 
• Always wear eye and face protection when operating a lathe.

UPDATES:

• 7/5/23 - Added metric (30-3.5) parts.