Hamilton caliber 721 is U.S.A movement from 1940s.
Functions: N/A
Manual-winding movement with 17 jewels.
F = 18000 A/h
Power reserve: 36 hours
Dimensions: 1.00 x 0.50 mm
More information:
Hamilton Grade 721 – 21/0 Size Watch
Hamilton Grade 721 is a complete new watch in the important 21/0 size. It has been designed to eliminate certain weaknesses common to all small watches, and the many basic innovations in its design and construction insure an extremely rugged movement which is capable of maintained accuracy.
Many of the technical developments and improvements – which assure smoother operation and greater ease of repair – are also incorporated in the recent Grade 911 Hamilton movement.
Quick starting and uniform power are assured by improved escapement and newly designed center, third and fourth wheels; and third, fourth and escape pinions.
New top-grooved balance staff and a balance wheel made of the harder new alloy Aurium for greater rigidity are features of the new 721 grade movement. They also permit rapid removal of staff and greatly reduce danger of damage to balance wheel hole.
Balance pivot and jewels have been scientifically proportioned to reduce friction and insure better retention of oil. High quality ruby and sapphire olive hole jewels are used in the escapement and pallet upper and lower bearings, likewise for better oil retention of friction.
Interchangeability – Manufacturing tolerances have been closely held and all parts of the 721 movement are perfectly interchangeable with genuine Hamilton 721 grade material and parts listed on the reverse side of this sheet. Because of this and other design improvements this movement is particularly easy to repair.
Finish – Plates and bridges are rhodium plated for protection against rust and tarnish; a new damaskeening pattern adds a final mark of beauty and quality.
Special Notes
The center, third and fourth wheels; and the third, fourth and escape pinions are not interchangeable with those used in other grades. When ordering parts for this movement, consult attached material and parts list and be sure to specify Grade 721.
For instructions covering the removal and replacement of balance jewels, please refer to T.D. sheets Nos. 119 and 123.
Other links:
Hamilton caliber 721 watch parts
