Need the NQ drill rod size before you order rods, bits or casing? This chart gives hole diameter, core diameter, rod OD and ID, approximate weight per 3 m rod and the usual thread for BQ, NQ, HQ and PQ wireline coring. The rod and hole figures are cross-checked between Boart Longyear data and other published manufacturer tables.
What BQ, NQ, HQ and PQ mean
The letters come from the Diamond Core Drilling Manufacturers Association (DCDMA) size system. Boart Longyear states that its hole sizes follow the DCDMA “W” series, which was adopted into ISO 3551 (1992) and British Standard BS 4019 (1993).
The first letter is the size group. From small to large, the common groups are A, B, N, H and P. The second letter is the system:
- W (BW, NW, HW, PW): conventional rods and casing.
- Q (BQ, NQ, HQ, PQ): wireline coring rods and barrels.
- 3 suffix (NQ3, HQ3, PQ3): triple-tube barrels. A split inner tube holds the core, so the core is slightly smaller in the same hole.
In wireline coring the rods stay in the hole. The inner tube full of core is pulled up through the rods on a wire. That makes rod ID as important as rod OD, because the inner tube assembly has to pass through it.
Q-series wireline size chart
| Size | Hole diameter | Core diameter | Rod OD | Rod ID | Approx. weight per 3 m rod | Common thread |
|---|---|---|---|---|---|---|
| BQ | 59.6–60.0 mm (2.35 in) | 36.4–36.5 mm (1.43 in) | 55.6 mm (2.19 in) | 46.1 mm (1.81 in) | 18.0 kg (about 40 lb) | Q |
| NQ | 75.3–75.7 mm (2.97 in) | 47.6 mm (1.88 in) | 69.9 mm (2.75 in) | 60.3 mm (2.38 in) | 23.4–23.5 kg (about 52 lb) | Q; RQ on NRQ rods |
| HQ | 95.6–96.1 mm (3.76–3.78 in) | 63.5 mm (2.50 in) | 88.9 mm (3.50 in) | 77.8 mm (3.06 in) | 34.5–35.0 kg (about 76 lb) | Q; RQ on HRQ rods |
| PQ | 122.0–122.6 mm (4.80–4.83 in) | 85.0 mm (3.35 in) | 114.3 mm (4.50 in) | 101.6–103.2 mm (4.00–4.06 in) | 52.2–52.5 kg (about 115 lb) | Q; PHD heavy-duty rods |
How to read the chart:
- Hole diameter is the standard core bit OD. The range covers standard and reaming-shell sizes from different makers. Oversize bits run larger: Boart Longyear lists HQ oversize bits at 97.3 mm and 98.9 mm.
- Core diameter is for a standard double-tube barrel.
- Weight is for a standard straight-wall steel rod. Internally upset rods are lighter. Boart Longyear lists NQ V-Wall at 20.42 kg and HQ V-Wall at 27.22 kg per 3 m.
- Rod ID for PQ varies most between makers, from 101.6 mm to 103.2 mm. Check it against your inner tube and overshot.
Triple-tube core sizes
Triple-tube barrels use the same rods and drill the same hole. The extra split tube reduces the core diameter slightly. Figures below are Boart Longyear’s.
| Size | Hole diameter (standard bit) | Core diameter |
|---|---|---|
| NQ3 | 75.3 mm | 45.1 mm (1.78 in) |
| HQ3 | 95.6 mm | 61.1 mm (2.41 in) |
| PQ3 | 122.0 mm | 83.1 mm (3.27 in) |
Choose triple tube in broken, soft or clay-rich ground, where keeping the core intact matters more than the last 2–3 mm of diameter.
NQ drill rod thread specifications
Standard BQ, NQ, HQ and PQ rods use the Q thread, a tapered wireline rod thread. Many makers produce Q-compatible rods. Heavy-duty versions use upgraded threads:
- RQ thread (NRQ and HRQ rods): Boart Longyear describes a coarse thread with 3 threads per inch and increased taper for easier make-up and break-out. The pin crest is case-hardened to a nominal 60 HRC and the box ends are heat-treated.
- PHD: Boart Longyear’s heavy-duty P-size rod.
- XQ: a newer Boart Longyear thread that the maker says is stronger and easier to make and break than RQ.
Three rules keep a rod string safe:
- Do not mix rods from different makers or thread generations in one string. Boart Longyear warns against mixing its rods with other makers’ rods.
- Gauge pins and boxes when rods arrive and at each service. Retire rods with worn or galled threads.
- Use a rod thread compound on every joint and keep thread protectors on during transport.
HQ core size and choosing a size
NQ and HQ are the two most common wireline sizes. Each size trades depth capacity against core volume:
- BQ (36.5 mm core): the lightest common rod. Suits deep, small-diameter holes where a small core is acceptable.
- NQ (47.6 mm core): a general-purpose exploration size. Rods weigh about two-thirds as much as HQ, so a given rig reaches greater depth.
- HQ (63.5 mm core): more core per metre for assays, logging and geotechnical testing. HQ core is about 1.8 times the cross-section of NQ core.
- PQ (85.0 mm core): large samples for metallurgical or bulk testing, usually in shallower holes.
The cross-section figure is simple geometry: (63.5 ÷ 47.6)² ≈ 1.78.
Frequently asked questions
What is the size of an NQ drill rod?
A standard NQ wireline rod is 69.9 mm (2.75 in) OD and 60.3 mm (2.38 in) ID. It drills a 75.3–75.7 mm hole and cuts a 47.6 mm core with a double-tube barrel.
How much does an NQ drill rod weigh?
A standard 3 m NQ rod weighs about 23.4–23.5 kg (about 52 lb). A lighter NQ V-Wall rod weighs 20.42 kg per 3 m, according to Boart Longyear figures.
What is HQ core size?
HQ core is 63.5 mm (2.5 in) in diameter from a double-tube barrel. HQ3 triple tube gives 61.1 mm core. Both drill a hole of about 96 mm.
What is the difference between NQ and NW?
Both belong to the DCDMA N size group. NQ is a wireline coring rod. NW refers to conventional rods and casing in the same size group. They are separate products and do not share threads.
ATR Drill supplies BQ to PQ wireline rods and casings, core barrels and diamond core bits to drilling teams across the Middle East and Africa. Browse the geotechnical rods and casings range or the matching diamond core bits. To get a quote, send the rod size, length, quantity and thread type through the contact page.
