Pet Carrier Comb: Detangling

Pet carrier production desk · Updated 2026-10-06 · 15 min read

Most buyers ask a pet bag supplier the same opening question: can the pet carrier accessory line be reordered in the original colour six months later? The answer depends on dye-lot control, not on goodwill.

Tooth Geometry: Pitch, Taper and Section

A comb is a row of cantilevers and it is specified by the same parameters as any beam: length, section, spacing and end condition. The four interact, and setting one without the others is what produces a comb that breaks or one that does nothing.

Pitch is the centre-to-centre spacing of the teeth, at 1.2-6.0 millimetres across the category. A fine pitch of 1.2-2.0 millimetres is a finishing or a flea comb; a medium of 2.5-4.0 is a general detangling comb; a wide of 4.5-6.0 is a coarse comb for a heavy coat. Pitch is also the number that creates a pinch geometry, and it is a compliance variable as much as a functional one.

Tooth length is 12-45 millimetres of exposed length, and it is set by the depth of the coat rather than by the size of the comb root. A long tooth at 30-45 millimetres has a slenderness ratio that makes it a flexible cantilever: it deflects 3-12 millimetres at a 10 newton tip load, and it takes a permanent set at 20-45 newtons.

Tooth section is rectangular, round or lenticular. A rectangular section of 1.2 by 2.5 millimetres is the stiffest in the direction of the load and the most likely to present a square edge; a round section of 1.5-2.5 millimetres diameter is 40-60% less stiff but has no edge at all; a lenticular section is between the two and it is what most moulded combs use.

Taper is the variable that reconciles the conflict. A tooth that tapers from 2.5 millimetres at the root to 0.8-1.4 at the tip is stiff where the bending moment is highest and fine where the work is done. A taper of 2:1 to 3.5:1 over the tooth length is the standard, and it is produced by grinding on a steel comb and by the mould geometry on a plastic one.

Tip geometry follows from the taper and it is the compliance figure. A ground and polished tip has a radius of 0.25-0.70 millimetres; a moulded tip has 0.30-0.90; a stamped and deburred tip has 0.10-0.40. A tip produced by shearing alone, with no deburring step, has a radius below 0.08 millimetres and it is a sharp point.

Root fillet is the detail that decides whether teeth break off. A tooth meeting the spine at a sharp corner has a stress concentration factor of 2.2-3.4 and it fractures at 40-60% of the load it would otherwise carry. A fillet of 0.4-1.2 millimetres radius at the root reduces the factor to 1.1-1.5 and it is drawn rather than left to the toolmaker.

A taper of 2:1 to 3.5:1 with a tip radius of 0.25-0.70 millimetres and a root fillet of 0.4-1.2 millimetres is the tooth geometry that is stiff at the root, fine at the tip and compliant at both determinations.

Manufacturing Route: Stamped, Machined and Moulded

Three processes make a comb and the choice decides the tip quality, the edge quality, the tooling cost and the unit cost at the same time. It is the first decision in the programme.

Stamping from a steel strip is the volume route. A coil of 1.0-2.5 millimetres thickness in 420 or 304 stainless is blanked in a progressive die at 20-60 strokes per minute, producing the tooth profile and the spine in one operation. Tooling is 8,000-28,000 USD for a progressive die and the unit cost is 0.35-2.20 USD at 3,000 units.

The stamped route's problem is the edge. A blanked edge carries a burnished band, a fracture band and a burr, and the burr is 0.05-0.40 millimetres high on an unmaintained die. Burr height is a function of die clearance at 4-10% of material thickness and of die wear, and it is controlled by a clearance specification and a sharpening interval measured in strokes rather than in weeks.

Deburring is therefore a specified operation rather than an optional one. A vibratory or a tumbling deburr of 20-90 minutes removes a burr of up to 0.25 millimetres and produces an edge radius of 0.05-0.20 millimetres; a magnetic abrasive or a brush deburr is faster at 3-12 minutes and gives 0.03-0.12. The acceptance is a burr under 0.03 millimetres and an edge radius above 0.05.

Machining from a solid bar is the low-volume and the premium route. A bar of aluminium or stainless is milled on a four-axis or a five-axis machine at 4-18 minutes per unit, giving a tip radius and an edge break that are programmed rather than incidental. Unit cost is 2.40-14.60 USD and tooling is 400-2,600 USD for fixtures. It is the route for a short run and for a premium finish.

Injection moulding is the high-volume route and the one with the best inherent safety geometry. A comb in polyamide, polypropylene or acrylonitrile butadiene styrene is moulded at 2.0-4.0 millimetres spine and 1.0-2.5 millimetres tooth section, with a cycle of 25-70 seconds and a tool of 12,000-46,000 USD. The tip radius is in the tool and it does not vary with wear in the way a stamped edge does.

Moulded teeth have a stiffness problem rather than a safety one. A polyamide at 2,800-3,400 megapascals flexural modulus is 22-28 times less stiff than steel, so a moulded tooth of the same section deflects 22-28 times more; the section has to be 2.2-3.5 times thicker to compensate, which is why a moulded comb is visibly chunkier.

Glass filling is the fix for stiffness. A polyamide with 15-35% glass fibre reaches 6,000-11,000 megapascals flexural modulus and it holds a thinner section, at 8-22% more material cost and a surface finish that is rougher by 0.4-1.6 micrometres of average roughness. The rougher surface is a snag risk and it has to be measured rather than assumed.

Stamping is the volume route at 0.35-2.20 USD but it needs a specified deburr to reach a burr under 0.03 millimetres; moulding gives the tip radius in the tool but needs glass filling to reach usable tooth stiffness.

Radius, Edge Break and the Sharpness Determinations

The compliance question on a comb is not whether it is sharp in a general sense; it is whether it fails two specific measurements, and both are decided in manufacturing rather than in design.

The sharp-point determination is a pass or fail made with a slotted gauge at a specified contact force of 4.45 newtons. A tooth tip enters the slot and, if it penetrates far enough to trigger the indicator, it is a sharp point. The criterion is binary and it is applied to the tip as manufactured rather than as intended.

The practical margin is narrower than it looks. A tip at 0.25 millimetres radius passes with little margin; one at 0.15 is borderline; one below 0.10 fails. Because a stamped tip varies by plus or minus 0.05-0.15 millimetres across a production run and by 0.10-0.30 as a die wears, a specification written at the passing threshold will fail in production. It has to be written at 0.30 minimum with the process capability to hold it.

The sharp-edge determination applies to the edges of the teeth and the spine, and it is made by drawing a specified tape across the edge under a load of 6.67 newtons over a 25 millimetre stroke. An edge cutting more than 50% of the tape in one pass is a sharp edge.

An edge break is the manufacturing answer and it is cheaper than a radius. A chamfer or a radiused break of 0.10-0.40 millimetres on every accessible edge takes an edge from a tape-cutting condition to a non-cutting one, and it is produced by the tumbling operation that does the deburring, at no extra cost provided the cycle time is specified for it rather than for deburring alone.

Accessibility is the gate that decides which edges are tested. A jointed probe of specified dimensions is applied at a stated force; an edge it cannot reach is not tested. This is why the spine edge behind the teeth is often the one that fails, because the probe reaches between the teeth, and why the tooth root geometry matters as much as the tip.

The procedural reference for both determinations is published by the U.S. Consumer Product Safety Commission, and the instruments and the procedure are standardised within the ISO quality and conformity system under which the inspection records are held.

Verification is a lot-by-lot activity rather than a first-article one. A comb programme tests 8-20 tips and 4-10 edges from every production lot, because a die that wears or a deburr cycle that is shortened to meet a schedule produces a failure that no first-article report will catch.

Specify a tip radius of 0.30 millimetres minimum with the process capability to hold it, an edge break of 0.10-0.40 millimetres on every accessible edge, and lot-by-lot verification on 8-20 tips rather than a first-article report.

Spine, Handle and the Structural Load Path

A comb carries a bending load from the teeth into the spine and from the spine into the handle, and the load path is short enough that every joint in it is a failure candidate.

The spine is a beam of 3-12 millimetres depth and 1.5-5.0 millimetres thickness, spanning the width of the tooth row at 40-140 millimetres. Under a distributed load from the teeth it deflects 0.4-3.0 millimetres at 100 newtons and it returns; the acceptance is a residual deflection under 0.3 millimetres after load removal.

Spine depth is the variable that controls it and it is cheap. Increasing a spine from 4 to 7 millimetres depth reduces deflection by 82% for 18% more material, because the second moment of area scales with the cube of depth. A comb that feels flexible is almost always a spine that is too shallow rather than teeth that are too thin.

The handle is either an extension of the spine or a separate moulding or scale attached to it. An integral moulded handle is the safest because there is no joint; a riveted scale on a steel comb is the traditional construction and it introduces two joints, each of which is tested to 150-450 newtons of pull and 2-8 newton-metres of torque.

Rivet specification is the detail that decides it. A solid rivet of 2.0-3.5 millimetres diameter in brass or stainless, peened over a washer, holds 300-900 newtons; a tubular rivet of the same diameter holds 150-500 and it is the one that comes loose after 6-24 months. The rivet is 0.03-0.18 USD and the difference is not worth the claim.

Tooth fracture is the field failure and it is a root-fillet problem rather than a tooth-strength problem. A tooth tested to failure at its root breaks at 40-140 newtons on a steel comb and at 15-60 on a moulded one, and the fracture surface shows whether the fillet was present. A batch that breaks at the low end has a tooling problem, not a material problem.

Brittle fracture is the material risk on a moulded comb and it is tested rather than assumed. A notched specimen is struck by a pendulum and the absorbed energy is recorded; a polyamide at 4-12 kilojoules per square metre is tough and one at 2-4 is brittle. A glass-filled grade drops by 30-60% against its unfilled base, which is the price of the stiffness.

A spine of 5-8 millimetres depth, a solid rivet at 2.0-3.5 millimetres holding 300-900 newtons, and a root fillet that puts the tooth fracture load at 40-140 newtons, is the load path specification that does not break in the hand.

Surface Finish, Burr Control and Static Behaviour

Three surface properties decide whether a comb feels finished and whether it stays that way: roughness, burr height and surface resistivity. All three are measurable and all three are usually left unspecified.

Roughness on a steel comb is 0.2-1.6 micrometres of average roughness after polishing. A finish at 1.6-3.2 catches on a fibre and it drags; one at 0.2-0.8 does not. Polishing is a tumbling operation of 60-240 minutes with a ceramic or a steel medium, and the specification is a roughness figure with a measurement position on the tooth flank rather than on the spine.

Roughness on a moulded comb is set by the tool surface and it rises with tool wear. A new tool at 0.1-0.4 micrometres produces a part at 0.2-0.8; a tool after 200,000-800,000 cycles produces 0.8-2.4. The control is a tool polishing interval and a first-and-last-piece roughness measurement on each run.

Burr control is the second property and it is the one with a compliance consequence. A burr of 0.05-0.40 millimetres on a blanked tooth is a cutting edge at the tip and it is what turns a passing tip radius into a failing one. The control is die clearance at 4-10% of material thickness, a sharpening interval measured in strokes, and a downstream deburr with a specified cycle time rather than a visual standard.

Surface resistivity is the third and it is the one that produces the static complaint. A moulded polyamide has a surface resistivity of 10 to the power of 12 to 10 to the power of 15 ohms per square, and it charges to 2-15 kilovolts by triboelectric effect in a dry environment. A steel comb at 10 to the power of negative 7 to 10 to the power of negative 5 does not charge at all.

An antistatic additive is the intervention on a moulded comb. A permanent antistatic agent at 1-4% loading reduces the surface resistivity to 10 to the power of 9 to 10 to the power of 11 and the charge to 0.2-2 kilovolts, at 6-18% more material cost and with a dependence on ambient humidity that makes it ineffective below 30% relative humidity.

Coating is the alternative and it is more durable. A conductive or a hydrophilic coating at 2-12 microns applied by dipping or spraying holds the resistivity at 10 to the power of 8 to 10 to the power of 10 for 6-24 months, at 0.10-0.55 USD per unit, and it is the specification where the comb is sold in a dry climate.

A roughness of 0.2-0.8 micrometres on the tooth flank, a burr under 0.03 millimetres controlled by die clearance and a specified deburr cycle, and either steel or an antistatic treatment, is the surface specification that stays finished.

Small Parts, Broken Components and Detachable Pieces

A comb is a single part and that is its structural advantage, but it is also a part that can break into a piece small enough to be a small part, and it is often sold with accessories that are not.

The small-parts determination is made with a cylinder of specified internal dimensions. An item that fits entirely within it at any orientation, without compression, is a small part. A complete comb at 150 millimetres is not; a single tooth at 12-45 millimetres and 1.2-2.5 millimetres section is, once it is out of the comb.

Fragmentation is therefore the risk and it is assessed by a specified abuse sequence rather than by a visual inspection. The product is subjected to a drop of 1.0-1.5 metres onto a hard surface, a flexure of the spine through a stated angle, and a torque applied at the handle, and it is then examined for liberated fragments. A tooth that comes off in the abuse sequence is a small part.

This is why the root fillet and the tooth fracture load are compliance figures and not only durability figures. A tooth with a fracture load of 40-140 newtons at the root does not liberate in the abuse sequence; one at 12-30 does, and a programme that discovers that at the abuse test rather than at the drawing stage has lost 8-16 weeks.

Detachable accessories are the second exposure and they are routinely underestimated. A comb sold in a kit with a removable cap, a detachable handle scale or a small cleaning pick is a product with components that are small parts in their own right, and each one has to be assessed separately rather than as part of the assembly.

A cap or a sleeve is the common case. It is a separate moulding of 0.8-2.0 millimetres wall that fits over the tooth row, and on its own it is a small part unless it is retained. The retention solutions are a friction fit of 2-12 newtons, a snap bead giving 8-30, or a tether. A tether of 40-90 millimetres keeps the cap attached and it costs 0.03-0.14 USD.

Age grading decides whether any of this applies and it is made on the product's characteristics and its marketing. A comb sold in a grooming kit alongside other tools is more likely to attract a determination than the same comb sold alone, which is a packaging decision with a compliance consequence.

Assess the comb after a specified abuse sequence rather than as supplied, hold the tooth root fracture load at 40-140 newtons so no fragment liberates, and tether any cap or accessory that is a small part on its own.

Labelling, Instructions and Packaging

A comb carries the same labelling obligation as any hand tool with points, and its packaging has the same job as a brush pack: protect the teeth and show them at the same time.

The permanent marking is moulded into the spine or laser-etched into a steel one, at 2-4 millimetres character height, carrying the model and the origin. A moulded marking costs nothing per unit and it survives the product; a printed one at 0.02-0.10 abrades off in 20-120 hours of handling and it is the reason a returned unit often cannot be identified.

The on-pack warning states the hazard, the consequence and the avoidance, at 2-4 millimetres character height for the signal word and 1.5-3 for the body. It has to be visible at the point of purchase, which on a carded pack means the front face, and it must not be obscured by the product itself. A warning partly behind the comb has failed on placement.

The instruction leaflet carries the storage, the cleaning and the disposal statements in the languages of every destination market on the shipment. It is a folded sheet at 80-160 grams per square metre and 0.06-0.34 USD. A single-language leaflet on a multi-market shipment is a recall risk rather than a paperwork gap.

Return handling closes the documentation set. A comb with a broken or a sharp tooth is a safety return and the procedure is defined in advance: quarantine the unit, record the lot code, and trace the lot to its die or tool maintenance record. Without a lot code mapping to a tooling interval, a single defect becomes a whole-shipment action.

Packaging protects the teeth and it is specified by clearance. A blister of 0.25-0.60 millimetres thermoformed over the tooth row with 1-3 millimetres of clearance at the tips survives a drop of 800-1,500 millimetres; a pack touching the tips bends teeth at 200-500. A comb with a tooth protector sleeve at 0.06-0.38 USD survives anything the carton survives.

Carton arithmetic is favourable. A carded comb at 200 by 100 by 30 millimetres is 0.0006 cubic metres and a master carton of 60-160 units is 0.036-0.096, giving 700-1,890 cartons per 40-foot high-cube before pallet losses. Weight is 25-140 grams per unit and it never binds, so every millimetre of blister depth is units per container.

A moulded permanent marking, a complete front-face warning, a multi-language leaflet, a lot code mapped to the tooling maintenance record, and 1-3 millimetres of blister clearance, is the labelling and packaging set that holds up on a return.

Range Structure, Tooling and Programme Economics

A comb range is a set of tooth pitches on a shared spine and handle platform, and the economics are unusually favourable because the tooling is cheap and the variants are nearly free.

Spine and handle tooling is 12,000-46,000 USD for a moulded platform and 8,000-28,000 for a progressive die on a stamped one. Within that, a pitch variant is a change to the tooth-forming insert or the die station: 1,800-9,000 USD on a moulded platform and 1,200-6,500 on a stamped one, and the two common pitches are usually built into the first tool.

A dual-pitch comb is the cheapest variant of all. A single spine carrying a fine pitch of 1.2-2.0 millimetres on one half and a coarse pitch of 4.5-6.0 on the other costs nothing in tooling, nothing in assembly and 0.05-0.30 USD in material, and it carries a 4-14 USD retail step. It is the highest-margin line in the range.

The table below sets out the range on the parameters that decide the structure.

The machined row shows why it is a premium rather than a volume route: 2.40-14.60 USD of unit cost against 0.90-3.90 for a stamped comb, bought for a tip radius that is programmed rather than incidental and for a finish that reads as a premium product.

The protector row is the best value line in the table. At 0.06-0.38 USD it removes bent-tooth arrivals, which run at 3-11% on a carded comb with insufficient blister clearance and at 0.1-0.8% with a sleeve, and it is reused by the customer as a storage cover.

Compliance testing across the range is the line that is under-budgeted. Sharp point, sharp edge, abuse and small-parts assessment on one platform costs 380-1,700 USD and takes 12-30 days, and each additional pitch on the same spine needs the sharp-point and abuse work repeated at 160-620 USD rather than being cleared by the existing report.

A dual-pitch comb costs nothing in tooling and 0.05-0.30 USD in material while carrying a 4-14 USD retail step, and a protector sleeve at 0.06-0.38 USD removes a 3-11% bent-tooth arrival rate, which together are the two best lines in the range.