Mud-lube bearings
No grease points and no seals. Most of the drilling fluid exits through the bit; 5–10% is diverted through the bearings to lubricate and cool them. The bearing set is the one routine spare.
Hunting RocKnife AT sonde housing
The dual-rod rock housing, rethought: no grease, no seals and no lid bolts. One housing family for the Ditch Witch AT line and Vermeer DR rigs.
The product
Meet the RocKnife
An AT sonde housing has the hardest seat in HDD. It carries the beacon directly behind a rock bit, passes the rotating inner drive rod through its body and routes drilling fluid to the bit. Hunting built the RocKnife on its mud-motor programme — technology already proven behind the bit in rock — and removed the classic failure points instead of reinforcing them.
A conventional dual-rod housing runs its bearings in grease behind seals and holds the beacon under a bolted lid. The RocKnife does away with all three. The bearings are lubricated and cooled by the drilling fluid itself, and the lid locks with six tabs and a roll pin — so there is nothing to grease, no seal to fail and no bolt to strip or seize.
The same housing takes Subsite, DCI and Underground Magnetics beacons, with engraved cover inserts holding each transmitter snug. When the bearings wear, the stack is swapped at the rig with workshop tools; the recommended rebuild interval is 80 hours. The RK series covers the Ditch Witch AT line from AT30 to AT100, and extension kits take the RK30 and RK60 onto Vermeer DR rigs.
- Mud-lube bearings — the drilling fluid is the lubricant
- Patented 6-tab LockingLid — beacon access with zero threaded fasteners
- Runs Subsite, DCI and Underground Magnetics electronics in one housing
- Rebuild means replacing the bearings — no specialty tools required
- Oilfield-grade manufacturing from Hunting, a global energy-services group
- Housings, rebuild parts and common spares for every RK model
What makes it different
Failure points removed, not reinforced
6-tab LockingLid
A six-tab locking lid secured with a roll pin — nothing to strip, seize or drop in the pit. Engraved cover inserts hold each transmitter model snug in the same housing.
Three beacon brands
Subsite 86B/17T, DCI 15″/19″ and Underground Magnetics Echo 70/90 all fit. A rented or borrowed locator no longer decides which housing you can run.
Rebuilt at the rig
A bearing-stack swap with workshop tools. Recommended rebuild interval 80 hours, with a measurable wear limit: rebuild at .040″/.050″ mandrel gap.
RK series
Fitment and connections
One programme for the whole dual-rod range. The RK series covers the Ditch Witch AT line from AT30 to AT100, and extension kits take the RK30 and RK60 onto Vermeer DR rigs, reusing the rig's collar. Press Get quote on any row and we come back with a quote, stock and lead time.
Ditch Witch All Terrain
RocKnife housings for the Ditch Witch AT30, AT32, AT40, AT60 and AT100.
| Model | Part number | Compatible machine | Connection | Bit box | Quote |
|---|---|---|---|---|---|
| RocKnife 30 | RK30 | Ditch Witch AT30 | 2.77-4 M | 2⅞″ Reg | |
| RocKnife 32 | RK32 | Ditch Witch AT32 | 2.36-4 M | 2⅞″ Reg | |
| RocKnife 32 | RK32L | Ditch Witch AT32 | 2.36-4 M | 3½″ Reg | |
| RocKnife 40 | RK40 | Ditch Witch AT40 | 2.95-4 M | 3½″ Reg | |
| RocKnife 60 | RK60 | Ditch Witch AT60 | 3.25-4 M | 3½″ Reg | |
| RocKnife 100 | RK100 | Ditch Witch AT100 | 3.44-4 M | 3½″ Reg |
Vermeer DR
Complete housings for the D23x30DR and D40x55DR, or an extension kit that fits an RK30 or RK60 you already own.
| Model | Part number | Compatible machine | Connection | Bit box | Quote |
|---|---|---|---|---|---|
| RocKnife 2330 | RK2330 | Vermeer D23x30DR | 2.77-4 M | 2⅞″ Reg | |
| RK30 extension kit | D2330DR_EX | Vermeer D23x30DR | 2.77-4 F – #625 | — | |
| RocKnife 4055 | RK4055 | Vermeer D40x55DR | 3.25-4 M | 3½″ Reg | |
| RK60 extension kit | D4055DR_EX | Vermeer D40x55DR | 3.25-4 F – #750 | — |
Rebuild parts — RK30 and RK32
Bearing mandrels, bearing set and housing parts for the two smaller models.
| Description | Part number | Fits | Quote |
|---|---|---|---|
| Bearing mandrel — 2⅞″ Reg | 530AT03 | RK30 | |
| Bearing mandrel — 2⅞″ Reg | 532AT03C | RK32 | |
| Bearing mandrel — 3½″ Reg | 532AT04C | RK32 | |
| Lower housing | 500AT02.1 | RK30 / RK32 | |
| Front bearing spacer | 501AT04 | RK30 / RK32 | |
| Bearing set, 4-row | M105 | RK30 / RK32 | |
| Retaining nut (2 per housing) | 501AT1804C | RK30 / RK32 | |
| Transmitter housing | 530AT05 | RK30 | |
| Transmitter housing | 532AT05 | RK32 | |
| Hex collar | 400-234-RK30 | RK30 | |
| Coiled spring pin, collar — 7/16″ x 1.5″ | 41LR44 | RK30 | |
| Locking tab washer (included with M105) | 400AT001 | RK30 / RK32 |
Rebuild parts — RK40, RK60 and RK100
The RK100 uses the 7-row M505XL bearing set, not the 5-row M505 shared by the RK40 and RK60.
| Description | Part number | Fits | Quote |
|---|---|---|---|
| Bearing mandrel — 3½″ Reg | 502AT03C | RK40 | |
| Bearing mandrel — 3½″ Reg | 560AT03C | RK60 | |
| Bearing mandrel — 3½″ Reg | 5100AT03C2 | RK100 | |
| Lower housing | 502AT02 | RK40 / RK60 | |
| Lower housing | 502AT02_2 | RK100 | |
| Front bearing spacer | 502AT31 | RK40 / RK60 / RK100 | |
| Bearing set, 5-row | M505 | RK40 / RK60 | |
| Bearing set, 7-row | M505XL | RK100 | |
| Retaining nut (2 per housing) | 502AT33C | RK40 / RK60 / RK100 | |
| Transmitter housing | 540AT05 | RK40 | |
| Transmitter housing | 560AT05 | RK60 | |
| Transmitter housing | 5100AT05 | RK100 | |
| Hex collar | 355-1050-104 | RK60 / RK100 | |
| Coiled spring pin, collar — 3/8″ x 1.0″ (2 per housing) | 41LZ92 | RK60 / RK100 | |
| Locking tab washer (included with M505) | 500AT001 | RK40 / RK60 / RK100 |
Common parts — every RK model
Lids, pins and wear parts that fit the whole series, RK30 through RK100.
| Description | Part number | Fits | Quote |
|---|---|---|---|
| Transmitter cover | 400AT21 | RK30–RK100 | |
| Coiled spring pin, transmitter cover — 1/2″ x 3″ | 41LY05 | RK30–RK100 | |
| Undercutter bit | POXX-01 | RK30–RK100 | |
| Safety bolt — 3/8-16 x 1/2″ (2 per housing) | H0014 | RK30–RK100 | |
| Punch — 3/8″ (roll-pin removal tool) | H0059 | RK30–RK100 | |
| Loctite 242, 0.5 ml | 230718 | RK30–RK100 | |
| NPT plug — 1/4″ | 40173502 | RK30–RK100 | |
| Wear pad (weld on) | RK_250500 | RK30–RK100 |
Part numbers and connections per the Hunting RK series parts reference, July 2026 — confirm the exact rig model and thread before ordering. RocKnife and LockingLid are Hunting products; product image: Hunting Energy Services. All Terrain® is a trademark of The Charles Machine Works, Inc.; Navigator® of Vermeer Corporation; DigiTrak® of Digital Control Inc.; Subsite® of The Charles Machine Works, Inc.
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