Drill core tray sizes decoded: NQ, HQ, BQ, PQ and how to rack them

Drill core tray sizing looks like a hardware question, but it starts with a drilling code. The letter — B, N, H or P — sets the diameter family, and a “Q” on the end means a wireline system, so NQ, HQ, BQ and PQ are simply the wireline cousins of the older conventional sizes. Get the size language right and the rest follows: slot width, rows per tray, lift weight, and how the loaded trays map onto pallets and racking in the core farm. This guide decodes the codes and turns them into a storage plan.

How do drill core tray sizes actually work?

A core tray is sized around one number: the diameter of the core it has to cradle. The tray is a set of parallel slots (channels), and each slot has to be just wide enough to hold the core in clean order without letting it roll or ride up. Pick the wrong slot width and either the core rattles loose and loses its sequence, or it won’t seat at all — so the drilling size is the first spec, and everything else on the tray is built around it.

That single number then cascades. A wider core needs wider slots, which means fewer rows across the same tray footprint and fewer metres of core per tray. A wider core is also heavier per metre, so a tray fills to a sensible manual-lift weight sooner. And because the core farm is a long-term archive, the tray and the way it stacks and racks have to stay consistent for years — Australia’s geoscience agencies keep core precisely because the physical sample outlives the rig, with Geoscience Australia maintaining national drill-core and sample collections as a long-term scientific asset (Geoscience Australia, ga.gov.au). Size the tray well at the start and it indexes the same way for the life of the program; size it badly and every retrieval fights you. (For the rig-to-shed integrity side of this — keeping runs oriented and labelled through every transfer — see our companion guide on drill core tray handling.)

What do NQ, HQ, BQ and PQ mean — vs B/N/H/P?

The size code is two pieces of information in one label: a letter for the diameter family and an optional “Q” for a wireline system. The letters run smallest to largest — B, N, H, P — and each names a standard hole-and-core diameter. The “Q” suffix tells you the core was drilled with a wireline rig, where the inner tube carrying the core is winched up the rods rather than tripping the whole drill string. So NQ is the wireline form of the N family, HQ of H, BQ of B and PQ of P.

Why this matters for trays: diameter sets slot width, and the wireline sizes are the ones you’ll meet in practice, because most modern diamond drilling is wireline. The recovered core for the common sizes is roughly:

• BQ — core ≈ 36.5 mm (hole ≈ 60 mm). The slimmest common size; lots of rows per tray, lightest per metre.
• NQ — core ≈ 47.6 mm (hole ≈ 75.7 mm). The everyday exploration workhorse; the size most “standard” trays are built around.
• HQ — core ≈ 63.5 mm (hole ≈ 96 mm). Larger sample for better recovery and orientation; noticeably heavier trays.
• PQ — core ≈ 85 mm (hole ≈ 122.6 mm). Big-diameter core for met work and difficult ground; widest slots, fewest metres before a tray gets heavy.

The bare conventional letters (B, N, H, P) describe the older non-wireline equivalents and sit at slightly different diameters again — a real difference if you inherit legacy core, but for new programs the Q-series numbers above are what drive a tray order. The practical takeaway: tell your tray supplier the core diameter, not just the hole size or the rig type, because the slot is cut to the core.

How many slots and rows fit per tray?

Once you fix the core size, the tray becomes a slot-counting exercise: a wider core means a wider slot, which means fewer rows across a given footprint and fewer metres of core per tray. The table below works from the standard wireline core diameters to show how size drives slot width, the rows a typical multi-row tray carries, the relative core mass per metre, and the handling consequence. These are planning figures to size a tray order and a core-farm footprint — your specific tray’s published row count and capacity govern — but the direction is fixed by physics: diameter up, rows and metres down, weight up.

Two lessons fall out of the table. First, row count is a direct function of core size: drop from PQ to NQ and you roughly double the rows — and the metres — the same external tray carries, which is why slimmer programs generate so many more trays per hole. Second, mass per metre rises far faster than diameter: a metre of PQ core is roughly three times the mass of a metre of NQ, so a PQ tray reaches a sensible manual-lift weight on a much shorter run length. Both point the same way when you size: choose the tray to your dominant core size, and let the heaviest size set your lift limit and stack height.

How do I map tray size to storage racking?

Storage is where tray sizing pays off or bites: the goal is a clean size map from the tray profile, to its external footprint, to the pallet it stacks on, to the rack bay. When every loaded tray in the farm shares one external footprint and sits on one pallet family, the whole archive racks, scans and retrieves the same way — regardless of whether the core inside is BQ or PQ. When tray footprints vary, you lose that consistency and the core farm becomes a one-off-shelving problem.

The table below shows how core size flows through to the storage decision. Note the move that makes a mixed program manageable: hold the external tray footprint constant and let the slot width (and therefore the core inside) be the only thing that changes. The pallet under the column is then chosen for the heaviest loaded stack — usually the large-diameter trays — so a single rack layout safely carries every size.

The pallet at the bottom of every column is the load-bearing link in that map, and it carries its trays unsupported across the beam span — which is why a pallet’s racking rating is far lower than its floor (static) rating. The international pallet test method, ISO 8611, sets out how static, dynamic and rack loads are measured and caps how far a deck may deflect, and Australian steel racking is governed by AS 4084; both treat the unsupported span as the limiting case (ISO 8611, iso.org). So size the pallet under your core trays to its racking figure, not its headline static number — we walk through that exact distinction in plastic pallet load ratings: static vs dynamic vs racking.

Which pallet base goes under a stack of core trays?

Choose the pallet for the heaviest loaded column you’ll rack, with a published racking rating that clears it at your beam span. A rackable Australian-standard pallet on the 1165 mm family — like the medium-duty unit above, rated 10,000 kg static but 2,000 kg racking — gives real headroom under a dense column of loaded trays while keeping the whole farm on one footprint. The flat, square deck keeps the bottom tray from walking, and the rackable rating is the number that actually governs once the pallet goes on a beam.

Where the core is large-diameter and the bays are dense, step up to a heavy-duty, full-perimeter base and add beam pallet-support bars so the rack — not the plastic — carries the concentration. The 1165 mm footprint is deliberate: it palletises neatly, squares up in the rack, and runs the same forklift tine setting as the rest of your site bins. Standardise the tray and the pallet together and you buy one rack layout for the life of the program; browse the rackable options across the plastic pallet range, and see how the whole resources kit fits together in the mining and resources range.

How do I standardise sizes across a mixed program?

Standardise on one or two tray profiles and one external footprint, sized to your dominant core size, and accept that a smaller core simply leaves a little spare room in the slot. Almost every program drills more than one size over its life — NQ for the bulk of exploration, HQ or PQ for metallurgical and geotechnical holes — and the mistake is letting each size dictate a different tray footprint. That fragments the core farm into incompatible shelving and breaks consistent racking and retrieval.

The pattern that works is to fix the things that touch storage (external footprint, stacking, pallet, rack bay) and vary only the thing that touches the core (slot width). Bulk and oversize sample material — coarse rejects, met lots, RC chip bags — then lives in rigid containers on the same footprint family, so one forklift setting and one rack plan cover trays and bins alike. That is the same durability-and-standardisation logic we apply to the bins themselves, and it keeps a multi-year program on a single, predictable storage system.

For the bulk material that doesn’t go in trays, a one-piece HDPE pallet box like this one suits coarse-reject storage and large metallurgical sample lots: 1,400 litres of capacity, a 7,000 kg static rating for dense material, and a moulded body with no timber to rot or steel to rust on a wet pad. Keeping these on the same 1165–1300 mm footprint family as your core-tray pallets means one storage plan across the whole core farm. See the full range of rigid options in the IBC and bulk container range, and the resource-recovery fit — where the same rugged bins sort and store recovered material — on the recycling and resource recovery page.

How do I brief a supplier on core tray sizing?

Give a supplier four things and the tray, pallet and rack spec falls into place: your core size(s), your run length per tray, your storage method, and your site conditions. Those decide slot width, lift weight, the pallet’s racking rating and whether you need a UV-stabilised grade — and they’re the difference between a tray order that racks cleanly for a decade and one that fights you from the first hole.

• Core size(s). BQ, NQ, HQ, PQ or a mix — this sets slot width, rows per tray and the metres you can plan around.
• Run length per tray. Balances trays-per-hole against a sensible manual-lift weight for your heaviest core size.
• Storage method. Free-standing stacks or beam racking — this sets the pallet’s racking rating and the safe stack height.
• External footprint. Hold it constant across sizes so the whole core farm racks and retrieves the same way.
• Site conditions. Outdoor, remote, high-UV core farm versus a covered shed — this sets whether you need a UV-stabilised grade.

Tell us your core sizes and program scale and we’ll match trays, pallets and bulk-sample bins to one footprint — use the guided product finder to shortlist by load and application, or send your core size, metres and freight postcode for a spec-backed quote. Need a tray or bin profile that isn’t standard? We manufacture, import and source to spec.

Common questions

What is the difference between NQ, HQ, BQ, PQ and B, N, H, P?

The letters B, N, H and P are the diameter families (smallest to largest), and the “Q” suffix means a wireline system, where the inner tube and core are winched up the rods instead of pulling the whole string. So NQ is the wireline version of the N family, HQ of the H family, and so on. In practice most modern diamond drilling is wireline (Q-series), which is why you see NQ, HQ and PQ on core-tray orders far more often than the bare conventional letters.

What core diameter does each size give?

For the common wireline sizes the recovered core is roughly BQ 36.5 mm, NQ 47.6 mm, HQ 63.5 mm and PQ 85 mm. The hole is larger again (PQ drills a hole over 120 mm). Those core diameters are the numbers that set your tray slot width — the tray has to cradle the core, not the hole.

How many rows of core are in a tray?

It depends on the slot width, which is set by your core size. A tray sized for slimmer NQ core fits more rows across the same footprint than one sized for chunky PQ core, so the same external tray holds fewer metres as diameter goes up. Most trays are built in fixed multi-row profiles (commonly four to six rows) so they stack and rack consistently across a program.

Do I need a different tray for each core size?

Not necessarily — many programs standardise on one or two tray profiles sized to their dominant core size, and accept that a smaller core simply leaves a little extra room in the slot. What you want to avoid is a different external footprint for every size, because that breaks consistent stacking, racking and retrieval in the core farm.

How does core size affect storage and racking?

Larger core is denser per metre, so a PQ tray reaches a sensible lift weight and a higher per-bay load far sooner than an NQ tray of the same length. That feeds straight into how high you stack and what the pallet under the column has to carry — which is why you size the pallet to its racking rating, not its headline static figure, the same way you would for any beam-racked load.

Sources: Geoscience Australia (national drill-core and sample collections, maintained as a long-term scientific asset). ISO 8611 (Pallets for materials handling — Flat pallets; static, dynamic and rack test methods and deflection limits) and AS 4084 (steel storage racking) for the storage-and-racking guidance. Drill core and hole diameters (BQ core ≈ 36.5 mm, NQ ≈ 47.6 mm, HQ ≈ 63.5 mm, PQ ≈ 85 mm) are standard wireline diamond-drilling sizes; the “Q” suffix denotes a wireline system versus the conventional B/N/H/P letter sizes. Slot width, rows-per-tray and core-mass figures are planning estimates and vary with your specific tray profile, core recovery and program design. Capacity and load figures for named products are the manufacturer’s tested ratings and vary with load distribution, beam span and storage method. Treat this as general guidance for sizing and storage planning, not a rack design or a quote.