Shandong Feiteng

Author: tanya

  • Price Advantage Without Quality Risk: Writing a Specification That Protects You

    Price Advantage Without Quality Risk: Writing a Specification That Protects You

    A lower quotation is only an opportunity. Whether it becomes a real price advantage or a quality risk depends on one document: the specification you send with the enquiry. Plants that buy taphole tools for a decade without a failure usually have a short, unglamorous spec sheet, and it is the reason they can switch suppliers without switching risk.

    The fields that do the work

    • Material grade. 42CrMo, 40Cr or an agreed equivalent, with the certificate required. Grade is a strength and hardenability decision – see 42CrMo versus 40Cr.
    • Heat treatment. Quench and temper, with a hardness range and the test method. Surface hardness alone is not a specification; the core has to stay tough enough to absorb impact.
    • Thread. Profile, pitch, hand and tolerance class, checked with a gauge. Thread is where a cheap tool shows itself first: see the guide to matching thread, diameter and length.
    • Dimensions and tolerances. Length, diameter, straightness or run out limit, concentricity of the shank.
    • Cutting geometry and carbide. Tip grade, insert dimensions, brazing quality and the radius of the cutting edge.
    • Surface protection. Finish, anti-corrosion treatment and what is applied before packing.
    • Marking and traceability. Batch or heat number on the part, so that a failure can be traced to a delivery.
    • Inspection and documentation. What is measured, on what sample size, and what report accompanies the shipment – the basis of the quality control checklist.

    Two clauses that pay for themselves

    Approved sample. State that the first delivery is measured against a signed sample held by both parties, and that subsequent batches must match it. This removes the argument about what was agreed.

    Change notification. Require written notice before any change to material source, heat treatment cycle or subcontractor. Most nasty surprises in consumable supply are unannounced process changes, not deliberate shortcuts.

    How the specification changes the price conversation

    Once the spec exists, suppliers compete on the same product. Quotes that looked 15 percent cheaper usually converge when they have to include certified material, a stated hardness range and an inspection report – and the remaining difference is genuine process efficiency, which is exactly the difference a buyer wants to keep. That is the mechanism behind the structural cost advantage described in why Chinese taphole tools cost less.

    It also changes the internal conversation. A maintenance manager who can point to a hardness range and a thread tolerance class no longer has to argue about brand loyalty; the tools either meet the document or they do not.

    Putting the specification into the purchase order

    The specification should not live in a folder. Repeat the measurable requirements in the purchase order itself – material, hardness range, thread class, dimensions, inspection report, packing – so that the contract and the drawing agree. Add the approved sample and change notification clauses, and note who is responsible for measuring on arrival. Buyers who do this usually find that disputes fall in the first year and that the gap between suppliers narrows to the part which reflects real process efficiency.

    Frequently asked questions

    How long should a specification be?

    One page is usually enough. Ten measurable requirements, a sample clause and a change notification clause cover most of the risk.

    What if the supplier cannot meet a tolerance?

    Then the tolerance was doing its job. Better to find out in a quotation exchange than after a shipment reaches the cast house.

    Send us the part you buy today – a drawing, a photo or the old part itself – and we will return a specification and a quotation built on it, so the price advantage is measurable rather than assumed.

  • Lead Time as a Cost: How Distance Changes the Taphole Tool Equation

    Lead Time as a Cost: How Distance Changes the Taphole Tool Equation

    Purchasing a tool from three thousand kilometres away and from thirty kilometres away are different problems, and the difference is lead time. Treat it as a price and the arithmetic becomes simple: a cheaper tool with a six week pipeline needs a buffer, and the buffer has a cost. Plan for it properly and the same tool delivers the price advantage without the risk of a cast house standing still.

    What the timeline actually contains

    • Production: often the shortest part. Standard geometries can ship from finished stock, while a custom drawing typically needs a short tooling and machining window.
    • Inland and port: a few days to a week from factory to vessel.
    • Ocean freight: the dominant block on long routes, measured in weeks.
    • Clearance and delivery: normally days, but longer if documentation is incomplete – which is why the paperwork in the export packing guide is a schedule subject, not a formality.

    The cost of the buffer, and the cost of no buffer

    Holding six to eight weeks of consumption costs working capital, storage space and a little obsolescence risk. Running out costs a cast. For a two furnace plant drilling twelve casts a day, one lost cast is worth more than a year of storage for the entire tool set. The comparison is not close, and it is the reason a stock policy belongs in the same document as the price agreement.

    Five planning rules that work

    • Order by consumption, not by calendar. If you know your hole count, you know your monthly usage – see the consumable volume arithmetic.
    • Split the annual volume. Two or three shipments a year keep freight per tonne down and release the buffer gradually.
    • Keep one spare string per machine. Rods, adapters and connectors, not just bits. The part that stops a machine is rarely the part you stocked.
    • Use air freight deliberately. Reserve it for genuine emergencies and price it into the annual plan rather than discovering it in a crisis.
    • Qualify a second supplier. One source plus one ocean route is a single point of failure, whatever the price.

    How a supplier can shorten the pipeline

    Distance is fixed; the rest of the timeline is not. A supplier who keeps semi-finished stock for common rod profiles and can machine to drawing after the enquiry cuts weeks out of production. A supplier who quotes a realistic ship date, consolidates mixed orders into one shipment and prepares documents correctly removes days at the border. These are the qualities to test in the first order, because a supplier who is slow on a trial order will be slower at scale – and the signs are visible in how they answer the first technical question.

    Read the same logic from the maintenance side: downtime reduction practices are mostly about having the right part, in the right condition, before the cast starts.

    Making lead time a planning input

    The most useful change is procedural: treat shipping time as a fixed input in the maintenance plan rather than a surprise. Publish the pipeline on the same calendar as the cast schedule, mark the point at which a reorder must be raised, and give the store a simple rule for when to escalate to air freight. Two or three scheduled shipments a year, sized to consumption, keep a cast house supplied without tying up capital – and without the emergency premium that a stockout always charges.

    Frequently asked questions

    How much stock should a plant hold?

    Six to eight weeks of normal consumption, plus one spare string per drilling machine, plus a top-up before relines and blow-ins.

    Is it cheaper to buy a full year at once?

    Often for freight and unit price, rarely for flexibility. Two or three scheduled shipments usually beat both extremes.

    Tell us your monthly hole count and destination port, and we will propose a delivery schedule with the buffer sized to your cast rate rather than to a container.

  • The Chinese Manufacturing Advantage in Steel Plant Tooling: Scale, Drawings and Delivery

    The Chinese Manufacturing Advantage in Steel Plant Tooling: Scale, Drawings and Delivery

    The Chinese manufacturing advantage in steel plant tooling used to be summarised in one word: price. That summary is now out of date. For taphole drilling tools – bits, rods, adapters and connectors – the advantage has three layers, and buyers who understand all three get better tooling rather than merely cheaper tooling.

    Layer 1: cost structure

    The structural reasons for a lower price are real and durable: bar, cemented carbide, forging, heat treatment and precision machining sit in the same industrial cluster, so inventory is lean and handovers are short. A workshop specialising in drilling tools runs the same operations repeatedly, which reduces setup cost per part. This is the layer that shows up first in a quotation, and the mechanics are set out in why Chinese taphole tools cost less.

    Layer 2: engineering and process control

    The second layer is less visible and more interesting. Chinese tool makers now invest in the processes that decide tool life: controlled atmosphere heat treatment, calibrated hardness testing, thread gauges, run out measurement and brazing control for carbide tips. The technology is not proprietary – but the habit of documenting it is what turns a workshop into a supplier. Compare a quotation that names a hardness range and a test method against one that names only a price, and you are looking at the difference between the two layers.

    This is also the layer where the industry’s own technical evolution shows. The move from wear resistance alone toward tools designed around real operating data – covered in how rod and bit technology is changing – has been driven by customers asking better questions, and Chinese producers have answered them with drawings rather than with adjectives.

    Layer 3: production to drawing, at speed

    The third layer is flexibility. A specialist factory can take a taphole drawing – a diameter, a length, an R32 left-hand connection, a tip geometry – and turn it into a machined and heat treated part quickly, because tooling changes are small and the equipment is already set up for the family. For a steel plant, that means a tool matched to its own taphole instead of the nearest catalogue equivalent. It also means faster problem solving: when a bit starts wearing unevenly, a new geometry can be trialled in weeks.

    How a buyer turns this into an advantage

    • Bring your working conditions to the table. Taphole diameter and depth, clay type, drilling machine and connection, cast rate. The more specific the input, the more of the advantage you keep – see custom tools built to working conditions.
    • Specify to a document. Hardness range, thread tolerance, material certificate, inspection record.
    • Plan the pipeline. Match shipment size to consumption so that price and delivery both work.
    • Verify with the first batch. Measure, cut, compare against the sample – then decide.

    What to ask before you commit

    Ask for the drawing behind the part, the hardness range and its test method, the thread tolerance class and the inspection record. Ask how a change of material source or heat treatment would be communicated before it happens. Then measure the first delivery yourself. Those four questions separate a manufacturer with process control from a trading desk with a catalogue, and the answers cost nothing to obtain at the quotation stage.

    Frequently asked questions

    Is the cost advantage disappearing?

    It is narrowing on labour and energy, and holding on supply chain density and scale. For specialised parts, cost is still a real advantage – but it is no longer the only one.

    What is the biggest risk when buying from China?

    An unwritten specification. The manufacturing capability is there; ambiguity is what turns a good supplier into an unpredictable one.

    If you are reviewing taphole tooling this year, send us one part you buy today and the conditions it works in. We will return a drawing, a specification and a quote – and you can judge the manufacturing advantage on your own measurements.

  • Shank Adapters and Striking Bars: The Small Parts That Stop the Whole Rig

    Shank Adapters and Striking Bars: The Small Parts That Stop the Whole Rig

    Every blow a top hammer delivers passes through one short piece of steel before it reaches the rock: the shank adapter. It has no cutting edge, no carbide and no glamour, and when it fails the rig stops just as completely as it would with a broken bit. Yet it is the part most often left out of a purchase specification.

    What a shank adapter does

    The shank adapter – also called a shank piece, striking bar or chuck adapter, depending on the maker – sits between the rock drill and the first rod. It has three jobs:

    • Receive the piston blow on a hardened strike face and pass it into the rod string without deforming.
    • Transmit rotation from the drill’s rotation unit into the rods, usually through splines or a profiled section.
    • Pass flushing fluid from the machine’s swivel into the rod bore.

    It must do all three while being hammered thousands of times per shift, hot and wet, with the full torque of the string passing through it.

    How shank adapters fail

    Spline wear. The splines are where rotation is transmitted. As they wear, backlash grows, the adapter rattles in the rotation unit and the joint gets noisier. Worn splines also shift the load onto fewer teeth, which accelerates the wear.

    Strike face deformation. Mushrooming or erosion of the strike face absorbs part of each blow and turns it into heat instead of rock breakage. You cannot see it from the operator’s seat, but you can measure it with a straight edge.

    Cracking at the shoulder or spline root. The classic fatigue failure. It starts at a stress riser and grows quietly until the adapter breaks – almost always at the worst possible moment.

    Thread damage. Cross-threading, galling and corrosion in the front thread, which is where the adapter meets the first rod. A damaged adapter thread damages the rod thread too.

    Specifying the right one

    The shank adapter is machine-specific before it is anything else. To specify correctly you need:

    1. The rock drill model and its rotation unit, which determines the shank profile and spline count or shape.
    2. The front connection – thread or taper – which must match your rods exactly. This is the same discipline described in our thread matching guide.
    3. Length, which affects how the drill’s feed and the rod string line up.
    4. Flushing bore and porting, matched to the water or air volume the machine delivers.
    5. Material and heat treatment, chosen for the impact energy of the drill. An adapter hardened for a small hammer will crack behind a large one, and an unhardened one will deform.

    Care habits that pay

    Keep the splines and the front thread lightly lubricated, and clean them before every change – grit in a spline is a lap that cuts every revolution. Rotate two or three adapters between shifts so wear is shared rather than concentrated. Check the strike face with a straight edge at every rod change: if it is no longer flat, it is already costing you energy. And never use a worn adapter to break in new rods; the wear transfers.

    Record when each adapter is retired. The interval is the most useful indicator you have of whether impact energy is being delivered efficiently down the whole string, and it sits alongside the other joints in the chain – the coupling sleeves behind it and the rod shanks in front of it.

    Frequently asked questions

    Is a shank adapter the same as a coupling sleeve?

    No. The shank adapter couples the drill to the rod string and receives the piston blow; a coupling sleeve joins one rod to the next. They meet different loads and wear differently.

    How often should a shank adapter be replaced?

    On measurement, not on hours. Retire it when the splines show visible backlash, the strike face is no longer flat, or any crack is visible at the shoulder. As a rule of thumb, expect it to be replaced several times over the life of a rod string.

    Can a cracked adapter be welded?

    No. Welding a hardened, high-impact part introduces a new stress riser and destroys the heat treatment. A repaired adapter is more likely to break than the one you removed, and it takes the rods with it.

    Send us your drill model, rod connection and the flushing you run, and we will supply shank adapters and rods made as one system – so the blow that leaves the piston arrives at the rock instead of heating up a joint.

  • Drilling Dimensional Stone: Bit and Rod Selection for Granite, Marble and Sandstone

    Drilling Dimensional Stone: Bit and Rod Selection for Granite, Marble and Sandstone

    Dimension stone is the one branch of drilling where nobody wants the hole for its own sake. The hole exists to guide a wire, take a wedge or hold a fixing – and the granite drilling bit or marble bit you choose decides whether that hole stays on line and leaves the face unmarked. Drilling granite for aggregate is a volume business; drilling granite for a slab is a precision business.

    Three stones, three different problems

    Granite and other hard igneous stone. Highly abrasive and brittle. The bit has to resist abrasion rather than impact, and it needs continuous flushing because the cutting edge will not survive dry heat. Penetration rates are modest and predictable, and the gauge wears steadily – which is critical, because line drilling for a wire saw depends on holes of consistent diameter.

    Marble and softer crystalline stone. Cuts much faster, with less bit wear, and the risk shifts from tool life to finish. Rust, dirty water and hot cuttings can stain a pale stone; a chipped edge is expensive and permanent. Clean water and clean tooling matter more than carbide grade here.

    Sandstone and other sedimentary stone. Variable. Hard bands alternate with soft, drillable layers, so bits experience alternating load and the hole tends to wander at the transitions. A four-wing bit holds line better than a chisel in this ground.

    Which bits suit which job

    • Line drilling for wire sawing: closely spaced, accurately sized vertical holes. Consistency of diameter and straightness over the whole hole length matters more than speed, so a four-wing cross bit with controlled gauge wear is the usual choice.
    • Wedge and plug holes: the hole must be straight, clean and to size for the plug to work. Any ovality means the wedge bottoms out or the split runs off line.
    • Dowels, fixings and anchors in finished stone: hole roundness and an accurate annulus matter for the fixing, and the hole walls must not be stained. These are usually small-diameter holes in the workshop or on site.
    • Chisel bits: useful in soft stone and for quick removal work, but too prone to wander for precision lines.

    Rods, shanks and flushing

    Stone drilling is mostly done with tapered or threaded rods on hand-held or light wagon drills, and with specialised rigs for line drilling. Three practical points:

    1. Keep rod straightness high. A bowed rod in a deep line-drilling pattern translates directly into a bowed row of holes, and the wire saw then cuts badly or not at all.
    2. Water, not air, in most stone operations. Water clears cuttings and cools the bit, and it also controls dust, which matters when the dust is crystalline silica.
    3. Watch the return water. Clear return means the hole is being cleaned; milky return means you are grinding, not cutting, and the bit is heating up.

Care points that protect the block

Do not start a hole with a worn bit – a worn gauge means the first centimetres are under size and the rest of the hole has to open itself out. Keep bits and rods off the ground and away from the slurry pits, because grit on a taper or thread is the fastest way to lose accuracy. And in pale stone, check the tool: a rusty shank or flaking paint will leave marks that polishing will not always remove.

If you are running line drilling alongside wire cutting, it is worth understanding where the rest of the string actually fails – our notes on wear patterns and coupling sleeves apply to stone just as much as to mining.

Frequently asked questions

Carbide or diamond for stone drilling?

Carbide tips for production holes – line drilling, wedge holes and anchors – because they are fast and can be reground. Diamond core bits for precise, clean-edged holes in finished stone and for sampling. Most quarries use both.

How do I stop a hole wandering in a bedded stone?

Use a four-wing bit, reduce feed through the transition bands, and keep the rod as short and as straight as the depth allows.

Can worn bits be reground for stone work?

The carbide can be re-profiled, but the gauge is what your line drilling depends on. Retire bits by gauge measurement, not by appearance – see when to regrind.

Tell us the stone, the hole pattern and your rig, and we will specify bit geometry, gauge and carbide grade for stone that has to look as good as it drills.

  • Chisel Bits and Splitting Wedges: Breaking Rock Without Blasting

    Chisel Bits and Splitting Wedges: Breaking Rock Without Blasting

    Not every rock problem needs a drilling pattern and an explosive charge. Chisel bit rock breaking and wedge splitting are the quiet alternatives – cheap, portable, and permitted on sites where blasting never will be. In quarries, on site, and wherever explosives are simply not an option, rock is broken with chisels and wedges. The trick is knowing which of the two to reach for.

    Chipping and splitting are different actions

    A chisel bit works by impact and chipping. The edge concentrates the blow into a line, fractures the material and removes it piece by piece. It is the right tool for secondary breaking of oversize boulders, for trenching in rock, for removing concrete and for cutting a channel along a line.

    A wedge works by forcing a crack apart. Nothing is removed: a small crack is opened progressively along a controlled line, and the material separates. That is the right tool for splitting blocks out of a face, for reducing a boulder to a size a crusher will accept, and for cutting dimension stone to size without losing the slab to shattering.

    Confusing the two wastes both tools. A chisel driven into a block you wanted to split will simply crater it; a wedge used where you actually needed to remove material will open a crack, release a slab and leave the oversize piece still sitting there.

    Choosing a chisel bit

    • Edge angle. A sharper edge penetrates concrete and softer rock quickly but will roll over in hard, abrasive stone. A blunter edge lasts longer and delivers more energy into the break.
    • Edge width. Wide edges work well in soft or brittle material and in trenching; narrow edges concentrate force for harder rock and for cutting reinforcement-free concrete.
    • Shank and retainer. The chisel must match the breaker or hammer exactly. A loose fit in the retainer destroys the shank, then the tool.
    • Wear before edge loss. In practice a chisel is retired when the body has worn down so the edge no longer reaches the work, long before the edge itself fails.

    Choosing a splitting wedge set

    Splitting wedges come as plug-and-feather sets, as hydraulic splitters, and as simple steel wedges driven into a prepared row of holes. The rules that decide success are the same:

    • Hole line, spacing and depth. The crack follows the holes. Holes too far apart produce a wandering break; too close together and the wedges fight each other.
    • Hole diameter matched to the plug. An oversized hole lets the wedge bottom out before the rock moves.
    • Straight and square holes. A angled hole pushes the split sideways and usually loses the block.
    • Patience. Split progressively along the line instead of driving one wedge in as hard as possible – the block separates when the crack has been opened evenly across its length.

    Where the drilling comes in

    Both techniques depend on the hole that precedes them. For plug-and-feather work the hole has to be accurately sized and straight; for breaker chisel work, the material has already been produced by drilling and blasting. Bit selection for those precursor holes is covered in our dimension stone guide, and for small site work in hand-held rock drilling.

    Safety and legal notes worth repeating

    Rock breaking generates flying fragments and dust containing crystalline silica. Eye and face protection, hearing protection and dust control – water or extraction – are not optional. In urban or restricted sites, chisel and wedge techniques are often the only lawful option because they remove vibration, flyrock and the need for licenses, which is a large part of why they remain so common.

    Frequently asked questions

    Can I break a boulder with a chisel bit on a hydraulic breaker?

    Yes – that is the standard approach for oversize rock at the crusher and in trenches. Work from the edge rather than the centre, and let the tool’s weight do the work instead of forcing it.

    Are plugs and feathers obsolete now that hydraulic splitters exist?

    No. Plugs and feathers remain the cheapest and most portable option, and they are often preferred for small blocks and awkward faces where a splitter cannot be positioned.

    What causes a split to run off line?

    Almost always the holes: spacing uneven, holes not parallel, or not deep enough. The crack follows the weakest line, and the drilled line is supposed to be it.

    Tell us what you are breaking – boulder, block or trench rock – and the tools you already own, and we will recommend the chisel profile or the wedge set that suits the material rather than the catalogue.

  • Hand-Held Rock Drilling: Choosing Bits for Paving, Stone and Site Work

    Hand-Held Rock Drilling: Choosing Bits for Paving, Stone and Site Work

    Hand-held drilling is where most people meet rock bits for the first time, and where most of them are bought badly. The jobs are small – a dowel hole, a fence post, an anchor for a sign, a row of holes along a kerb line – so the instinct is to grab whatever bit is nearest. In practice these are the jobs where a wandering hole is most visible and most expensive to fix.

    Match the shank first, always

    Before tip shape, before diameter, before price: the shank has to fit the machine you own. Hand-held rock drills almost always use a hexagonal shank, either 22 mm across the flats with a 108 mm shank length, or 25 mm with a 159 mm length. Smaller hammers take smaller versions.

    Two habits save money here. Measure your chuck rather than trusting the label on the old rod, and keep shanks of different sizes in separate boxes – mixing a 25 mm rod into a 22 mm machine is a two-part failure, because the chuck jaws get hammered as well.

    Pick the tip shape for the material

    • Cross or four-wing bits are the general-purpose choice for aggregate, granite setts, kerbs, concrete and mixed ground. Four cutting edges hold the hole on line and leave a rounder hole for dowels and anchors.
    • Chisel bits cut fast in soft stone, slate, soft sandstone and clay, and are cheaper to buy. They wander more, so use them for holes where position matters less than speed.
    • Button bits bring the crushing action of larger equipment to hard, abrasive rock, and can be reground – worth having where a crew drills hard stone every day.

    For visible work – stone paving, facings, bricks – the roundness of the hole matters as much as the speed. A four-wing bit costs a little more and produces a hole that takes a dowel or anchor without packing.

    Choosing the diameter

    Work back from the fixing, not forward from the drill. A dowel or resin anchor needs a controlled annulus around it; a hole drilled two sizes too large makes the fixing depend on how much resin or grout someone happens to use. If you are drilling for a mechanical anchor, take the manufacturer’s hole diameter as the target and choose the bit to hit it – remembering that the gauge of a worn bit is smaller than its marked size.

    Practical habits that improve the hole

    1. Collar slowly. Start the hole with light feed until the bit is fully engaged. Almost every wandering hole in paving is a collaring problem, not a bit problem.
    2. Hold the machine square. A hand-held drill held off-axis drills an off-axis hole. Check the angle twice: once at the start, once at half depth.
    3. Flush properly. Even small hammers need water or air to clear cuttings, or the bit grinds its own dust. On stone and concrete this also controls the silica dust that makes this work unhealthy.
    4. Do not lean on it. Hand-held drills cut fastest at the feed the machine was designed for. Extra body weight bends the rod, wears the shank and slows you down.
    5. Retire worn bits. A cross bit with worn wings drills under size and has to be forced. Regrinding or replacement is cheaper than the extra minute on every hole.

    Buying bits for a site

    Small jobs consume bits slowly, so buy for the material you meet most often and keep one spare of each diameter on the van. Bulk packs are cheaper per piece and worth it if the work is repetitive, but only if the sizes match your fixings. If you are unsure what to standardise on, our note on colour coding and identification will at least stop you sorting the box by sight.

    Frequently asked questions

    How deep can I drill with a hand-held rock drill?

    In hard stone, a few hundred millimetres per rod is realistic; the limit is flushing and how straight you can hold the machine, not the bit. For deep holes, use extension rods and accept slower progress.

    Can I use a rock bit on reinforced concrete?

    On aggregate and unreinforced concrete, yes. On reinforcement you need a different tool: a carbide-tipped rock bit will not cut steel, and forcing it damages the wing tips.

    Do I need a different bit for marble and soft stone?

    Softer stone cuts quickly with a chisel or light cross bit, but the hole walls mark easily. Use clean water, keep the machine square and, in pale stone, avoid bits with loose rust or flaking paint. See drilling dimensional stone.

    Tell us the material, the fixing you are installing and the drill you use, and we will send the shank size, diameter and tip shape that produces the hole in one pass.

  • Hex, Round or Hollow: Choosing the Right Shank for Your Drill Rod

    Hex, Round or Hollow: Choosing the Right Shank for Your Drill Rod

    Buyers spend hours comparing rod steel, heat treatment and diameter, and then specify the shank almost as an afterthought. Yet the shank is the part that grips the machine, takes the rotation torque and absorbs the rebound of every blow. Get it wrong and nothing else about the rod matters.

    What the shank actually does

    The shank is the length of rod that goes into the drill. Three things happen there: the chuck grips it and turns it, the piston strikes the end of it, and flushing fluid enters through it. So the shank has to be dimensionally accurate in section, in length and in the bore.

    Hexagonal shanks

    Hexagon sections dominate hand-held rock drilling. The flats give the chuck jaws something positive to grip, so torque can be transmitted without slipping, and the same flats let the drill string be rotated by hand when collaring or when a rod sticks.

    The common sizes are the 22 mm hexagon shank, usually 108 mm long, and the 25 mm hexagon shank, usually 159 mm long. Which one you need is decided entirely by the drill – never by the rod you happened to have in stock. A 25 mm shank will not enter a 22 mm chuck, and a 22 mm shank in a 25 mm chuck will slip, heat up and hammer the chuck jaws out of shape.

    Round shanks

    Round shanks appear on heavier machine drills, on drifting equipment and on rods where the rotation is transmitted by a threaded or splined coupling rather than by chuck jaws. They carry higher torque and are stiffer, which matters as hole depth and rod length increase. Round rod strings are usually threaded end to end, with the connection carrying both the torque and the thrust – which is why the thread form and shoulder geometry matter so much on this type.

    Hollow versus solid

    Almost every rock drilling rod is hollow, not because hollow steel is cheaper but because the bore is the flushing channel. Water or air travels down the bore, out through the bit, and back up the outside with the cuttings. Without it, the cutting edges overheat and the hole fills up.

    Solid rods exist for short rotary work and for some auger applications where the cuttings are carried by the flights rather than by fluid. If you are choosing between them, the question is simple: does the hole need fluid to clear and cool? In rock, the answer is always yes.

    Reading a shank before you order

    Take four measurements from the machine, not from the old rod, since the old rod may be worn:

    1. Chuck aperture and section – hexagon across flats, or the diameter for a round chuck, plus the depth to the strike face.
    2. Grip length – how much of the shank the jaws actually hold.
    3. Strike face – the shape and diameter of the end that the piston hits.
    4. Bore size – the flushing hole diameter that the machine’s water or air swivel feeds.

    If a rod is worn in the chuck, the measurement tells you which part: a shank that is undersize across the flats means the chuck jaws are slipping, which is a chuck problem as much as a rod problem.

    Where rod life actually ends

    Three zones fail, in this order: the shank (hammered, oval, cracked at the collar), the thread or taper (worn, galled, cross-threaded), and the body (bent, worn thin at the couplings). Only the second of those is covered by rod selection – which is why thread matching and shank specification have to be done together. Choosing the right steel grade is also part of the picture; see 42CrMo versus 40Cr drill rod.

    Frequently asked questions

    Can a round shank be used in a hexagon chuck?

    No. The chuck transmits rotation through the flats; without them it cannot grip and will simply spin and damage both parts.

    Does shank length affect drilling performance?

    It affects how the piston energy is delivered. A shank that does not reach the strike face properly wastes part of every blow and quickly damages the end of the rod.

    How do I know when a shank is worn out?

    Measure it. Across-flats should be within the manufacturer’s tolerance, the strike face should be flat and free of mushrooming, and there should be no cracking at the collar. In practice a rod is retired when the shank stops holding, and that is normally well before the body fails.

    Photograph your chuck and measure it, or send us your drill model, and we will match the shank section, length and bore so the rods drive properly from the first blow.

  • Cost Per Metre: The Only Fair Way to Compare Drill Bit Prices

    Cost Per Metre: The Only Fair Way to Compare Drill Bit Prices

    Compare two quotations for the same bit and the cheaper one looks like the obvious decision. It usually is not, because the price on the invoice is only a part of what a bit actually costs you. The number that decides whether a drilling operation is profitable is cost per metre – and it is arithmetic anyone can do in five minutes.

    The formula

    Cost per metre is the total cost of everything consumed while drilling one metre of hole:

    Cost per metre = (bit cost + rod cost share + regrind cost + downtime cost) divided by metres drilled per bit, plus the rig’s own running cost per metre.

    The rig’s own cost – wages, fuel or power, depreciation, maintenance – is unavoidable and applies to slow drilling and fast drilling equally. That is the key insight: any bit that drills slower is charging you rig time, whether or not it appears on the invoice.

    A worked example

    Take an illustrative case. Bit A costs 100 and drills 300 m before it is finished. Bit B costs 250 and drills 900 m. Assume a rig cost of 120 per hour and a penetration rate of 30 m per hour.

    • Bit A: 100 divided by 300 m = 0.33 per metre of bit cost. Rig time: 10 hours for 300 m, so 1,200 of rig cost, which is 4.00 per metre.
    • Bit B: 250 divided by 900 m = 0.28 per metre of bit cost. Rig time: 30 hours for 900 m, again 4.00 per metre.

    On those numbers the two are closer than the price tags suggest, and the difference lives entirely in drilling speed and in the number of stops. Change one variable – say Bit B holds its penetration for the whole 900 m while Bit A slows by a third in its last 100 m – and Bit B wins by a wide margin, because the extra money bought metres drilled by a sharp bit instead of metres drilled by a hot one.

    Hidden terms most comparisons forget

    • Regrinding. Two or three regrinds per bit is normal for button bits, each with a cost and a rig stop. Add both.
    • Bit changes. Every change costs the same as a few metres of drilling. A bit that lasts three times as long cuts changes by two thirds.
    • Stuck bits and lost holes. A bit that wanders or seizes costs far more than its price: recovery time, occasionally a lost hole and a re-drill.
    • Rod and coupling wear. A bit that runs hot or off-centre wears everything behind it. Bits and rods should be costed together – our notes on wear forms explain the mechanism.
    • Stock cost. Every failure point in your replacement interval is stock you have to hold. Longer life means less capital tied up in a warehouse.

    How to run the comparison properly

    You do not need new accounting. Run a controlled trial: same rig, same operator, same ground, two bit types over a shift each, and record metres, hours, regrinds and stoppages. Four lines on a sheet. Two things make the result trustworthy – interchange the bits so the same ground is drilled by both, and record the gauge at retirement so you know when the bit actually stopped cutting rather than when it broke.

    One warning from experience: a trial run in unusual ground proves nothing. If you test in a soft patch you will conclude that the cheapest bit is best, and then discover the truth in the next seam. Run the trial in ground you would describe as typical or worse – and read the three traps behind low prices before you buy the cheapest quote in the mailbox.

    Frequently asked questions

    Is cost per metre the same as cost per hole?

    No, and cost per hole hides more than it reveals. A hole that is drilled faster but requires a second pass to reach depth is a slower hole overall.

    Should I include regrinding labour?

    Yes, if your own staff do it. The wheel, the coolant and the hour all belong in the calculation.

    What if penetration rate matters more than bit life?

    Then say so in the specification. In a bottleneck operation where the rig is the constraint, a faster bit is worth a shorter life – but do the arithmetic in advance rather than discovering it after the order. See reducing downtime in taphole drilling for how that trade-off plays out in a steel plant.

    Send us your current cost per metre, the rock you drill and your rig’s hourly rate, and we will show you which part of the string is actually costing you money.

  • Roof Bolting and Anchor Drill Bits: Choosing the Right Bit for Rock Bolt Holes

    Roof Bolting and Anchor Drill Bits: Choosing the Right Bit for Rock Bolt Holes

    In most drilling, a hole slightly over or under size is an annoyance. In roof bolting and anchor work it is a structural problem: the resin or grout has to fill the annulus between the bolt and the hole wall, and the hole diameter is what decides whether that happens. Choosing a roof bolting drill bit therefore starts with the hole, not with the bit price list.

    The hole is part of the bolt

    A rock bolt only works if the load can travel from the bolt into the rock. With resin-anchored bolts, the resin cartridge is spun through the hole and expands to fill the gap around the bar. If the hole is too small, the cartridge cannot spin and the resin does not mix. If the hole is too large, the resin layer becomes thick, the bolt sits off-centre, and anchor strength drops.

    In practice that means the bit diameter is chosen together with the bolt diameter, not afterwards. Typical bolting practice leaves a controlled annulus of a few millimetres around the bar, and the bit must hold that diameter through the whole hole – which makes gauge wear the key performance figure on a bolting bit.

    Bit types used for bolting holes

    • Tapered bits. Friction-fit on a tapered rod, quick to change, the standard for hand-held and small bolting rigs in coal and soft-to-medium rock.
    • Button bits. Crush harder rock and can be reground, which makes them the economical choice where bolts are installed in hard strata all day.
    • Cross and four-wing bits. Used where a straight, on-size hole matters more than speed, and in mixed ground where a two-wing chisel tends to wander.
    • Self-drilling anchor bits. A sacrificial bit that stays at the end of a hollow bar and becomes part of the anchor. Here the bit is a component of the support system, not a consumable, and it must match the bar exactly.

    What to specify in a bolting order

    1. Hole diameter, with a tolerance – and the bolt diameter it pairs with.
    2. Rock type and hardness, which decides button or chisel, and the carbide grade.
    3. Shank or taper exactly as measured from the drill or the existing rods.
    4. Gauge requirement: the maximum wear you are prepared to accept before the bit is retired, because that sets the replacement interval.
    5. Water or air flushing, including the pressure and volume available at the face – bolting rigs often run at lower flushing pressure than production drills, which changes the bit’s heat load.

    Why bolting bits fail early

    The failures are consistent: gauge wear that shrinks the hole so resin cartridges jam; washout from insufficient flushing; and snapped buttons from feeding a stopped or stalled string. Bolting is usually done in a hurry, in a roof that has just been exposed, by a crew with the next row waiting. Bits suffer accordingly, which is why the smartest change most mines make is a simple one: a gauge check on every bit before it goes back up, and a clean water path.

    If you cannot measure gauge at the face, mark the bits from a new box and retire them together. A bit that drills ten under-size holes has cost more than the ten bits you would have bought by checking.

    Frequently asked questions

    Can I use the same bit for roof bolting and production drilling?

    It is possible but rarely wise. The two jobs want different things – production drilling wants speed and life, bolting wants a consistent, slightly tight hole. A bit optimised for one is a compromise in the other.

    How often should a bolting bit be replaced?

    On gauge, not on time. Measure across the outer row and set a limit for your bolt and resin system. Regrinding can restore a button bit, but never regrind below your gauge limit – see when to regrind a button bit.

    What if my hole wanders in broken ground?

    Wandering usually means the bit is being pushed sideways by a hard band or a void. A four-wing cross bit supports itself better than a chisel, and a stiffer rod helps. Our comparison of bit shapes explains the geometry.

    Send us your bolt diameter, rock description, drill model and the flushing you have available, and we will specify a bolting bit that holds the hole size your anchor system needs.