Cushion Connectors


Foremost Cushion Connectors

Threaded directly into the spindle of the rotary gearbox, the Foremost Cushion Connector helps protect the rotary drive and mast assembly against torsional and axial vibrations and shock loading in moderate and extreme drilling conditions. The result is reduced drill maintenance, increased uptime and lower drilling costs.

Disc springs are utilized which allow a range of axial movement between the drill stem and the rotary drive. The disc springs accommodate operating loads ranging from 8,000 to 120,000 lbs. (3,630 – 54,430 kg). In most cases, this is sufficient to help keep the tri-cone bit in continuous contact with the formation, thereby reducing the possibility of fracturing or breaking the carbides in the bit.



Urethane drive blocks located within the connector assembly serve to provide 100% transfer of rotary torque from the drive spindle to the drill stem as well as absorb torsional vibration transferred by the bit.

Foremost Cushion Connectors are utilized in mining applications worldwide on large and mid-range blast hole drills. In most cases, no modifications to the drill are required. The cushion connector is installed directly onto the rotary drive spindle via a threaded connection. A saver sub is usually utilized on the lower end of the cushion connector.


Models Available

Model Recommended Pulldown Torque Rating at 100 rpm Weight
14-30-6353 8,000 – 40,000 lbs
(3,630 – 18,144 kg)
265 HP (198 kW) 660 lbs (299 kg)
14-40-6353 12,000 – 50,000 lbs
(5,443 – 22,680 kg)
265 HP (198 kW) 670 lbs (304 kg)
14-50-6353 12,000 – 60,000 lbs
(5,443 – 27,215 kg)
265 HP (198 kW) 680 lbs (308 kg)
18-120-6363 20,000 – 120,000 lbs
(9,072 – 54,430 kg)
400 HP (298 kW) 1,000 lbs (454 kg)


Foremost Floating Cushion Subs (FCS)

Foremost floating cushion subs (FCS) are utilized in both slanted and vertical drilling operations to reduce vibration and wear of the drill string and drill rig components. Foremost manufactures several FCS models for mining, construction, water well and oilfield applications. The sliding spindle of the cushion sub permits the threads of the mating drill string components to float together or apart during rotation without any axial movement of the rotary drive. This decreases the impact on the rotary drive when the two mating threads are joined and decreases the load on the threads of the mating components.



The Floating Cushion Sub performs two important functions:

  • It provides a means of making up and breaking out threaded connections without damaging threads
  • It prolongs bearing and gear life of the rotary top drive

Foremost floating cushion subs are an economical accessory with the proven ability to help increase tooling life and reduce equipment downtime.


Models Available

Model Application Hoist/Pulldown Torque Stroke Weight Spec Sheet
306130 Construction, mining, oilfield, waterwell 200,000 lbs
(90,718 kg)
20,000 ft-lbs
(2,765 kg.m)
2.5 in
(63.5 mm)
195 lbs
(89 kg)
306430 Construction, mining 200,000 lbs
(90,718 kg)
30,000 ft-lbs
(4,147 kg.m)
2.5 in
(63.5 mm)
1,050 lbs
(476 kg)
359150 Oilfield 300,000 lbs
(136,078 kg)
35,000 ft-lbs
(4,839 kg.m)
3 in
(76.2 mm)
850 lbs
(386 kg)
PD6-2 Construction, mining, waterwell 125,000 lbs
(56,700 kg)
12,000 ft-lbs
(1,659 kg.m)
Light Duty: 0.75 in
(19 mm)
Heavy Duty: 1.75 in
(45 mm)
165 lbs
(75 kg)
375300 Oilfield 600,000 lbs
(272,155 kg)
32,000 ft-lbs
(4,424 kg.m)
4 in
(101.6 mm)
1100 lbs
(499 kgs)


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