FES Kelly bars may be made in friction type and locking type, in 3,
4, 5 or 6 elements for some special occasion. For sake of common
application, the external diameter is designed to be in universal
dimension, such as **3mm, **9mm, **0mm, **7mm, **6mm, **9mm, **0mm,
**0mm, **8mm, etc. High strength steel tube material is picked and
heat-treated to arrange production, which enables the Kelly bars to
work well under maximum torque of the torque output. Kelly keys and
guides inside Kelly joints are made in highly wear-resistant
material for a prolonged maintenance time. Special tooling is set
up to ensure the straightness of tubes during welding process.
