Custom CNC Pump Components | Clearance, Not Size

Pump Components · Rotating Groups · Pump OEMs

Custom CNC-Machined Pump Components Made to Your Drawings

A pump part is not judged on its own dimensions. It is judged on the clearance it leaves when it is assembled with two or three other parts: the gap between the impeller and the wear ring, the fit of the shaft in the bearing bore, the runout the seal sees at the sleeve. Those are relationships spread across separate drawings, held by separate tolerances, and they only add up correctly if the parts were made with the assembly in mind. That is the subject of this page — which features carry the running behaviour, how they are controlled, and what evidence comes with them. We machine the components; the pump's hydraulic design, balancing and pressure testing belong to the pump builder.

Submit Your Pump Component Drawing Mechanical seal components →

At a Glance

What we machineImpellers, shafts, housings, covers, flanges, bushings and wear rings

Built fromYour 3D model, 2D drawing, or a measured sample for a replacement

ProcessesCNC turning · 3/4/5-axis milling · boring · grinding · drilling

Materials304 / 316L, duplex and cast-equivalent stainless, aluminum, bronze, carbon steel, PEEK / PTFE

VerificationDimensional report, bore and runout records, material certificate

Not providedPump design, hydraulic performance, balancing, pressure testing, assembly

Quick Answer

What you are buying is not five parts; it is a set of clearances that add up. A pump that runs quietly and seals properly does so because the gap between the impeller and the wear ring is right, the shaft sits in its bearing bore with the correct fit, and the seal sees a shaft surface that runs true. Each of those is a relationship between two parts, and a relationship cannot be inspected on either part alone. So three things follow for anyone quoting a pump component drawing. The critical dimensions are the mating ones — bore diameter and roundness, journal size, runout, seal-face flatness, groove depth — not the outside profile. The material has to be chosen against the medium and the temperature, not against a grade name, because 316L is the wrong answer for some chlorides and bronze is the wrong answer for some seawater. And the drawing has to state which fit applies, because a nominally correct bore and a nominally correct shaft can still be a loose or an interference assembly depending on which side of tolerance each landed. We machine to those relationships and report on them; the pump's hydraulic design, balancing and pressure test stay with the pump builder.

What This Page Covers, and What It Hands Back

Goldcattle already publishes a page on pump mechanical seal components, and a page on general CNC machining. This page sits between them, and it is worth saying at the start what each one is for, because a buyer who lands on the wrong one wastes a week.

Page	What it answers	What belongs there rather than here
This page: custom CNC pump components	Which pump parts we machine, how the running features are controlled, what the material and inspection evidence looks like	The component families, the critical features, the clearance logic, matched-part manufacturing, replacement from samples
Pump mechanical seal parts	Seal-specific components: seats, glands, sleeves, holders, seal housings	Seal-part taxonomy, wear and failure diagnosis, seal material comparison, legacy seal reproduction
CNC machining services	The plant, the equipment, the published tolerance and size tables	Machine list, envelope, general capability, floor photography
Die casting services	Aluminum, zinc and magnesium castings with CNC finishing	Housings whose route is a casting plus machining, which is a volume decision rather than a machining one

Two boundaries are worth stating plainly, because they decide whether an enquiry is even the right shape. A machined housing is not a casting route. A pump housing can be cut from solid when the annual volume is low, the wall geometry is simple, or the material is not castable in the required grade; at volume, a casting with machined interfaces is usually the cheaper route, and that decision belongs to a casting review rather than to a machining quotation. And a machined component is not a pump. We do not design the hydraulic passage, set the running clearance, balance a rotating assembly or pressure-test a casing. Where a drawing calls for those, they are the pump builder's scope; what we control is the geometry and the evidence behind it.

The Rotating Group Is the Real Unit of Purchase

Buyers send drawings one part at a time, and that is the natural way to buy. But the parts that determine whether a pump runs well are the ones that touch each other, and they are designed as a group even when they are purchased separately: shaft, bearing housing, impeller, wear ring, cover, seal interface.

What the running behaviour depends on	Which parts set it	What goes wrong when they are made independently
Radial position of the impeller in the casing	Bearing-housing bore, shaft journal, impeller hub bore	The bore and the journal are each in tolerance but at opposite limits, so the impeller sits off-center and the wear-ring gap is uneven around the circumference
Axial position of the impeller	Shaft shoulder, housing face, cover face, shim stack	Stack-up across three parts lands the impeller too close to the cover; the clearance is set by the assembly, and no single drawing owns it
Running clearance at the wear ring	Wear-ring bore, impeller eye diameter, concentricity of both	Both diameters correct, both eccentric to the shaft axis, so the gap closes on one side and opens on the other
Seal life	Shaft or sleeve surface under the seal, runout, finish	Finish is to drawing but runout is not, so the seal face oscillates and the leak appears weeks later, attributed to the seal
Vibration at running speed	Everything above, plus balance	Balance is the pump builder's operation, but poor concentricity or a bent shaft consumes the balance allowance before it starts

The sentence worth putting on a purchase order. “Parts to be machined as a matched set to drawing revision X, with runout and bore data reported per part and the assembly clearances evaluated across the set.” That single line changes what the shop does: it stops each part being optimized in isolation and forces the mating features to be measured against the same reference.

Exploded arrangement of a pump rotating group on a bench: machined bearing housing, stainless shaft, semi-open impeller, thin stainless wear ring and a machined cover plate, all spaced apart on a common axis — The group that decides the behaviour. Each part can pass its own inspection and the assembly still be tight on one side and loose on the other — that is a relationship problem, and it is solved by measuring the group against one axis.

Five Component Families, and What Decides Each One

Pump component catalogues tend to list every part name in the pump. That is not how a machining review works: what matters is which features on the part carry the running behaviour, because that is what determines the process, the inspection plan and the price. The five families below cover the parts we actually machine, and the last column is the honest answer to “what will be difficult about this one”.

Family	Typical parts	Features that carry the function	Where the difficulty sits
Impellers and rotating components	Semi-open and open impellers, closed impellers, hubs, rotors, inducer-style parts	Blade envelope, hub bore, eye diameter, back face, runout to the bore axis	Blade surfaces need multi-axis access and a consistent tool path; a closed impeller with narrow passages may not be machinable from solid at all, and that has to be established before quoting
Shafts and rotating transmission	Pump shafts, drive shafts, stepped shafts, stub shafts	Journal diameters, shoulders, keyway, thread, bearing seats, total runout	Length-to-diameter: a long shaft deflects under cutting force unless it is supported, and every support becomes a witness on the finished diameter
Housings and bearing seats	Bearing housings, bearing brackets, pump covers, end covers, seal housings	Bore diameter and roundness, bore-to-face squareness, position of the mounting pattern, seal-face flatness	Bore roundness after clamping, thin-wall distortion near a flange, and holding squareness between a bore and a face that are machined from different directions
Flanges, adapters and mounting parts	Discharge and suction flanges, adapter plates, motor adapters, spacer plates, base brackets	Bolt-circle position, spigot diameter, face flatness, parallel faces, thread depth	Bolt pattern and spigot have to keep a positional relationship; two faces parallel to each other are easy, two faces parallel to a spigot are not
Bushings, wear rings and sleeves	Wear rings, throat bushings, shaft sleeves, distance sleeves, journal bushings	Bore and outside diameter, wall thickness, roundness, concentricity, hardness and surface finish	Thin rings deflect when clamped; a ring held in a three-jaw chuck is not round by the time it leaves the machine, so they need a bore-and-mandrel sequence

Bushings, wear rings and shaft sleeves sit closest to the mechanical seal components we machine, and some of them are the same parts under a different name. That is why the seal page exists as a separate destination: if your enquiry is about a seal seat, a gland, a sleeve or a seal housing, it is answered there with the seal-specific material and wear detail, and this page links rather than repeats.

Five-axis machining center cutting a stainless steel semi-open pump impeller on a trunnion table, with one blade finished, one partly roughed and a ball-nose cutter following a blade surface under coolant — Blades are cut on a trunnion so the surface is continuous from hub to tip. The roughed blade in front shows the stepping that a finishing pass has to remove without leaving a witness line at the leading edge.

Choosing the Process From the Geometry, Not From the Machine List

The same pump part can often be made two ways, and the cheaper way is decided by the geometry and the quantity rather than by which machine is free. The table is how we route a pump enquiry.

Part condition	Route we take	Why	What it costs the buyer
Rotationally symmetric, features coaxial	CNC turning, one or two setups	Everything is generated from one axis, so concentricity is free	Nothing extra; this is the cheapest pump geometry
Shaft with a keyway, cross hole or flat	Turn, then mill; or turn-mill in one clamping	The off-axis feature has an orientation relative to the axis	A second operation unless the machine has live tooling; either way the keyway becomes a controlled position
Bore and face that must be square to each other	Single-setup boring, or bore-then-face without releasing	Squareness disappears the moment the part is re-clamped	Boring from one side only, occasionally at the expense of a larger tool overhang
Blade or vane surfaces	5-axis simultaneous milling	The surface is continuous in two directions; a 3-axis path leaves steps the seal of the flow cannot tolerate	Machine hour rate, and programming time that has to be paid once
Thin rings and bushings	Turn between centers or on a mandrel; bore, then finish outside	Clamping force is what makes a ring out of round, not the cutting	An extra operation, and a mandrel per diameter
Hardened or wear-resistant surface	Turn or mill soft, heat treat, then grind	Hardening moves the part; grinding is what restores size and roundness afterwards	A two-stage order with an allowance, and a grinding operation after heat treatment
Deep bore with a tight finish	Drill, bore, then hone or roller-burnish	A single-point tool at depth leaves a finish and a taper that a bore gauge will find	One more operation, but usually cheaper than tightening the boring tolerance
Low volume, complex housing	Machined from solid	No pattern or die to amortise	Material removal time and scrap value; at higher volume a casting review is the better conversation

CNC lathe turning a long stainless pump shaft held between chuck and tailstock center with a bronze-tipped steady rest, an indexable insert cutting a stepped diameter and a continuous chip curling away under coolant — A long shaft between centers with a steady in the middle. The steady stops the shaft deflecting away from the tool — and leaves a witness band on the diameter it bears on, which is why that band is planned into the drawing rather than discovered later.

A note on the word “precision”. Our published CNC capability includes tolerances as tight as ±0.005 mm for suitable machined features. On a pump component that number never applies to the whole part: it applies to a journal, a bore or a seal land where the drawing calls it, on a geometry and a material where it can actually be held and measured. A quotation that promises ±0.005 mm everywhere has either misunderstood the drawing or intends to interpret it later.

Critical Features: The Eight That Decide a Pump Component

This is the part of the page most worth reading before releasing a drawing, because every one of these features has a way of passing inspection and still causing a problem in the pump.

Feature	Why it matters in service	How it is normally verified	What decides whether it is achievable
Bearing bore	Sets bearing position and preload; a bore out of round transfers its shape to the outer ring	Internal micrometer or bore gauge at two depths and two directions; CMM for roundness and cylindricity	Whether the bore is finished after the part is released from the chuck, and whether the wall around it is stiff enough
Bore-to-face squareness	A bearing seated on a face that is not square to its bore tilts, and the shaft runs at an angle	CMM with a datum established on the bore, or a squareness check on a surface plate	Machining the face and the bore without re-clamping; if they must be done separately, the second operation has to be datumed on the first
Shaft journal diameter and roundness	Bearing fit and oil film; an out-of-round journal beats the bearing	Micrometer at several sections; V-block and indicator for roundness where specified	Deflection during turning, and whether the journal is ground after heat treatment
Total indicated runout	The seal, the bearing and the impeller all inherit the runout of the surfaces they sit on	Between centers or in V-blocks with a dial indicator; CMM for a full revolution scan	Whether the datum is the centers, the bearing journals or the coupling end — the number only means something with the datum stated
Seal face flatness	A seal land that is not flat leaks regardless of the elastomer	Optical flat or CMM scan; surface roughness instrument for Ra	Lapping or fine boring as a separate operation; a turned face is usually not flat enough for a hard seal
O-ring groove width and depth	Groove volume sets the compression; a shallow groove over-compresses and a wide one lets the ring move	Groove micrometer, or a profile trace on a CMM	Tool width tolerance and whether the groove is cut in the same setup as the face it sits in
Wear-ring bore and concentricity	The running clearance is set here; eccentricity closes the gap on one side	Bore gauge plus a concentricity check against the locating diameter	Holding a thin ring without distortion, and boring it in the same setup as its locating face
Keyway and thread	Transmit torque and hold the impeller nut; both fail as assemblies, not as features	Keyway width by gauge or CMM; thread by go/no-go gauges	Whether the keyway is cut after the shaft is finished, because broaching or milling it can move the shaft

Stainless pump shaft mounted between centers on a granite surface plate with a dial indicator on a magnetic base touching a machined journal, and a V-block and slip gauge beside it — Runout between centers. The number is only useful with the datum written next to it: runout measured from the centers is a different claim from runout measured from the bearing journals, and a pump drawing normally means the latter.

Stainless machined pump bearing housing on a granite surface plate with a three-point bore gauge inserted into the precision bore, a setting ring and an outside micrometer beside it — Bearing bore measured at two depths and two directions. One reading tells you the diameter; it does not tell you whether the bore is round, and the bearing will feel the difference.

Clearance Is a System Property, Not a Dimension

The single most common misunderstanding on a pump component order is that a clearance can be specified on one drawing. It cannot: a running gap is created by two or three parts, each with its own tolerance, and the assembly inherits the sum. The table shows how that arithmetic behaves, and what to do about it.

Situation	What the arithmetic does	Practical consequence	Better instruction on the drawing
Bore and shaft each at mid-tolerance	Nominal clearance, and the design intent is met	The good case; most assemblies land here	Nothing to change
Bore at maximum, shaft at minimum	Clearance at its widest; the joint can rattle or the seal can lose preload	Function loss without any dimension being out of tolerance	State the fit (for example H7/h6) rather than two independent limits
Bore at minimum, shaft at maximum	Clearance at its tightest; assembly needs force and the bearing runs hot	The part is scrapped at assembly, not at inspection	Same: replace independent limits with a fit callout
Two parts concentric individually but offset as a pair	Clearance varies around the circumference while the average stays nominal	Uneven wear-ring gap, side load, vibration	Specify concentricity or runout relative to a shared datum, not just diameters
Assembly stack-up across three parts	Three tolerances add; the axial gap is the sum	The impeller sits too close or too far from the cover	Nominate one part as the adjustable element, or specify a shim allowance

Materials Chosen Against the Medium, Not the Grade Name

Material selection is where a pump component enquiry most often contains a hidden assumption. A drawing says 316L because the last pump was 316L, and nobody checks whether the medium, the temperature or the chloride level has changed. The table below lists what we machine and, more usefully, the condition under which each is the wrong choice.

Material	Where it is the right answer	Where it is the wrong answer	What to confirm before ordering
304 stainless	Clean water, mild process fluids, general industrial service	Chloride-bearing water, brackish or marine duty, and anything that will sit wet between runs	Chloride level, temperature, and whether the part is wetted or only splash-exposed
316 / 316L stainless	Moderate chloride and chemical exposure, food-adjacent and pharmaceutical water	Warm, concentrated chlorides and some acids where pitting or stress-corrosion is likely; also not a substitute for a duplex grade in high-chloride seawater duty	Actual chloride concentration and temperature together — neither on its own decides it
Duplex / super-duplex stainless	Seawater, high-chloride and high-strength combinations	Where the grade is specified but the machining allowance was priced as 316L; duplex work-hardens and needs a different route	Whether the required grade is available in the stock form and size, and whether it is weldable in the intended assembly
Aluminum 6061-T6	Lightweight non-wetted parts, cooling-water components, adapters, brackets	Wetted surfaces in most process fluids; galvanic contact with stainless in a wet environment	Whether the part touches the medium, and whether an anodized finish is acceptable at the sealing face
Bronze and brass alloys	Wear rings, bushings, impeller wear surfaces, some seawater duty with the right alloy	Ammonia-bearing or certain chemical media; and any assumption that “bronze” means one material — the alloy family covers a wide range	The specific alloy designation, its hardness relative to the mating part, and the medium's compatibility
Carbon and alloy steel	Shafts and structural parts where strength governs and corrosion is handled by coating or by a dry environment	Wetted or humid service without a finish; also where the coating can be damaged at assembly	Heat-treatment condition, and whether the finish is protective or only cosmetic
Duplex-grade cast equivalents and cast stainless	Housings where the geometry or the volume favours a casting with machined interfaces	Prototype quantities, or where the pattern cost cannot be justified	Whether the route is casting plus machining, which is a separate quotation
PEEK, PTFE, POM	Bushings, wear pads, insulating parts, low-friction guides	High-pressure sealing faces (PTFE creeps), and any location where thermal expansion is constrained	Temperature, pressure, creep allowance, and whether the medium attacks the polymer

Three material questions we ask before quoting a pump part. What is the medium, including concentration? What is the working temperature, including cleaning and shutdown conditions? And is the part wetted, splash-exposed or dry? Those three answers move the material more often than the drawing does, and they cost nothing to ask at the enquiry stage rather than after the first batch.

Seal Faces, Bearing Seats and the Finish That Actually Matters

A drawing that says “Ra 0.8 all over” is telling the shop to waste time on surfaces that do not care, and it is not telling them enough about the two surfaces that do. Finish on a pump component should be specified where it functions.

Surface	What the finish is doing	How it is produced	What to specify
Seal land	Provides the flat, low-roughness face a mechanical seal runs against	Fine boring, then lapping where the drawing requires it	Flatness and Ra together; one without the other is not a seal face
Shaft or sleeve under the seal	The elastomer or the seal face bears on it while rotating	Turning, then grinding or polishing to size	Ra plus runout plus hardness — a soft, rough surface wears the seal packing
Bearing seat	Controls the interference fit and the seating contact	Finish boring or grinding	Diameter, roundness and Ra together; a mirror finish is not required, roundness is
O-ring groove	Retains the ring and sets its compression	Grooving tool in the same setup as the face	Width, depth and corner radius; a sharp groove corner cuts the ring at assembly
Gasket faces	Distribute bolt load without a leak path	Facing or milling	Flatness across the bolt circle, and a finish the gasket can bite into
Wear-ring bore	Sets the running clearance and takes the wear	Boring, honing where specified	Diameter, roundness and a finish that holds a lubricating film rather than a mirror
External surfaces	Corrosion resistance and appearance only	As-machined, blasting, passivation, painting	Call it once, and keep it off the functional faces

Two finishing details that change dimensions and are often discovered late. Passivation does not move a dimension; electropolishing does — it removes material, so a bore grows and an edge rounds, and a seal land that was lapped to flatness before electropolishing will not be flat after it in the same way. Coating builds on threads and fits — a plated or coated shaft journal is no longer the diameter the bearing was specified against unless the coating was masked or the allowance planned.

Machined stainless pump cover on a bench with a raised lapped sealing land, a machined O-ring groove carrying a black O-ring, and a bolt circle of countersunk holes, with a second cover behind it — Seal land and O-ring groove on one face. Both are functional surfaces with different requirements: the land needs flatness and low Ra, the groove needs width, depth and a radiused corner that will not cut the ring.

Machining Components as a Matched Set

Where a customer can supply drawings for the parts that touch each other, we will machine them as a set and evaluate the interfaces across the drawings rather than one part at a time. It is not a different process; it is a different review, and it is the cheapest way to avoid an assembly that does not close.

Set	Interface we check across the drawings	What we report
Impeller and shaft	Hub bore against shaft diameter; shoulder face against impeller back face; keyway position against impeller keyway	Measured bore and journal, and the resulting fit range across the set
Shaft and bearing housing	Journal diameter against bore; axial location of the bearing against the housing shoulder	Bore and journal data with the fit range, plus bore roundness
Impeller and wear ring	Eye diameter against ring bore; concentricity of each to the shaft axis	Radial clearance range, and runout of both parts to their locating diameters
Cover and seal interface	Seal land position and squareness against the bore axis; groove depth against the specified ring section	Squareness and flatness data, groove measurement
Flange and mounting interface	Bolt circle against spigot; face flatness against the mating face	Position data per hole and flatness across the face

What “matched” does not mean here. It does not mean we design the pump, set the running clearance, or guarantee hydraulic performance. It means the parts are machined and measured against a common interpretation of their interfaces, and the measured data is reported so the pump builder can confirm the clearance closes within the intended range. Balancing, performance testing and casing pressure tests are the builder's operations.

Replacement Components When There Is No Drawing

A large share of pump component enquiries are for replacements: the original part is worn, the OEM lead time is long, or the pump is old enough that the drawing no longer exists. That work is possible, but it starts with a measurement decision rather than with a machining decision.

The sample is not a design. A worn shaft or a scored sleeve has lost material and changed shape. Machining to the worn dimensions reproduces the wear, not the original part. The first step is deciding which surfaces can be trusted as references and which must be reconstructed.

Establish the functional references. For a shaft, that is normally the bearing journals and the coupling register, because those locate the part. Lengths and diameters between them are then rebuilt from them, not from the ends.

Use the mating parts as counter-evidence. The bearing bore, the housing seat and the seal chamber tell you what the shaft should have been. Where a mating part is also worn, both have to be measured and the difference reasoned out.

Write down the reconstructed dimensions before cutting. A one-page dimension list with the reference faces marked, sent back to the customer for confirmation, is cheaper than a second attempt and settles the argument about what “original” meant.

Report what was reconstructed. The inspection report identifies the dimensions that came from measurement of the reference surfaces and the dimensions that were reconstructed, so the customer knows which numbers carry which confidence.

Photographs, part numbers, pump model and nameplate data all help and none of them replace the measurement. Where the sample is heavily corroded or cracked, the honest answer may be that the part cannot be reproduced from it and a drawing or a mating assembly is needed.

Inspection and Traceability for Pump Components

A pump OEM's supplier quality specification usually asks for more than a dimensional report: material traceability to the heat, part marking, protection of machined surfaces in transit, calibrated instruments, in-process checks and a final inspection record. Those are reasonable, and they are the items we plan for on a pump order rather than improvise.

Document or record	What it establishes	When it is issued
Material certificate	Grade, heat number and condition of the stock	With the order; EN 10204 3.1 where the drawing or purchase order requires it
First article inspection report	Full dimensional verification of the first part against the drawing	On the first part of a new revision or a new order, before the run continues
Dimensional inspection report	The measured values of the characteristics in the agreed plan	Per batch, or per the sampling agreed at quotation
Bore and runout records	Roundness and TIR on the features that set the running behaviour	With the batch report on pump components, because diameters alone are not enough
CMM program report	Position, form and orientation against the drawing datum frame	Where the drawing carries GD&T or the geometry is not reachable with hand tools
Surface finish record	Ra on the named functional surfaces	Where the drawing specifies Ra on a seal land, journal or bore
Batch and marking record	Which parts came from which stock and which run	Per order, with the marking method agreed with the customer

The measurement has to reproduce the drawing's datum. A runout value taken between centers and a runout value taken from the bearing journals are different claims about the same shaft, and a CMM program aligned to its own convenience will report numbers that satisfy nobody at the assembly bench. That is why the datum frame is the first thing we confirm on a pump drawing, before the process is chosen. Our management system is certified to ISO 9001:2015; where a customer's industry requires a scheme approval beyond that — API, marine class, or a pump OEM's own supplier approval — it is resolved during supplier qualification for that project and is not implied by this page.

From One Prototype to a Repeat Order

Pump development usually starts before the drawings are final, which means the first parts are made from a model that will change. Knowing what changes at each stage keeps the second order from costing as much as the first.

Stage	What the customer is testing	What we do differently	What must be frozen before the next stage
Fit prototype	Whether the part physically fits the pump	Straightforward machining to the model; finish left as-machined where it does not affect fit	Nothing — this stage is expected to change
Functional sample	Whether it runs, seals and wears acceptably	Material condition and the functional finishes are fixed, because a finish can change a fit	Material grade and condition, and the datum scheme
Pre-production batch	Whether the process repeats	Fixture or soft jaws justified; first article inspected and reported; in-process checks added	Drawing revision, process route, inspection plan
Repeat production	Consistency across orders	Program, fixture and inspection plan held against one drawing revision; any change to them treated as a change	The revision itself — it becomes the controlled reference

The cost that surprises buyers. A revision arriving mid-run is more expensive on a pump component than on most parts, because the change usually lands on a mating dimension. A 0.05 mm shift on a bearing bore invalidates the program, the fixture setting and the inspection plan at once, and the parts already made are not reworkable. Freezing the revision before a repeat order is the cheapest quality control available.

What to Put in a Pump Component Enquiry

The list below is the difference between a quotation and an estimate. Every item that is missing becomes an assumption, and an assumption on a wetted part is what turns into a change order.

Item	Why the quotation changes without it
3D model and 2D drawing at a named revision	The model defines the shape; the drawing defines the datum, the fits and what is acceptable
Component type and function	A shaft, an impeller and a housing take different routes and different inspection
Material grade and condition	Grade, temper and stock form decide machinability and whether a stress-relief step is needed
Medium, concentration and temperature	Moves the material choice and the finish, more often than the drawing does
Wetted, splash or dry	Decides whether a cosmetic finish is acceptable or a corrosion-resistant one is mandatory
Critical dimensions and fits	Bore, journal, runout and seal-face calls are what the price and the inspection plan are built from
Surface finish and treatment	Lapping, grinding, passivation or coating each add an operation and may move a dimension
Inspection and documents required	FAI, CMM report, material certificate and marking are quoted separately from machining
Quantity and expected annual demand	Decides fixture investment and whether a casting route should be reviewed instead
Mating parts or the pump assembly reference	Lets the interfaces be checked across drawings instead of one part at a time
Sample, if it is a replacement	Starts the measurement decision: which surfaces are references and which are reconstructed

Frequently Asked Questions

Can you manufacture custom CNC pump components from drawings?

Yes. Send a 2D drawing and a 3D model at a named revision, plus the material grade and condition, the medium and its working temperature, the critical fits and the documents you need. The review covers the datum scheme, the mating dimensions, the route, the setups and the inspection plan before a quotation is issued. Anything that cannot be machined or measured as drawn is raised at that point rather than after the first part. STEP, IGES, X_T, DWG, DXF and PDF are all workable.

Which pump components do you machine?

Five families: impellers and rotating components; pump and drive shafts; bearing housings, bearing brackets, covers and seal housings; flanges, adapters and mounting parts; and bushings, wear rings and shaft sleeves. Mechanical seal components — seats, glands, sleeves, holders and seal housings — are covered on the dedicated mechanical seal parts page, because the material and wear questions there are seal-specific rather than pump-specific.

Can you machine a pump impeller from solid material?

Often, but not always, and the answer depends on the impeller type. A semi-open or open impeller with accessible blade surfaces is machined from solid on a five-axis machine with a trunnion, cutting the blades as a continuous surface from hub to tip. A closed impeller with narrow internal passages may not be reachable with a cutter at all, in which case it is a casting or a fabricated-and-welded part, and that has to be established before a price is given rather than discovered at programming.

What is the difference between your pump components page and the mechanical seal parts page?

This page covers the parts that set the running behaviour of the pump — impellers, shafts, housings, covers, flanges, wear rings — and how their mating features are controlled. The mechanical seal page covers seal-specific components and the seal interface: seats, glands, sleeves, holders, seal housings, and the wear and replacement questions that belong to seals. Bushings and sleeves appear on both because they are the same parts seen from two scopes; this page links to the seal page rather than repeating its material and failure detail.

What tolerances can you hold on pump components?

Capability is evaluated per feature, not promised per shop. Our published CNC capability includes tolerances as tight as plus or minus 0.005 mm for suitable machined features, depending on the material, the geometry, the part size and how the feature will be measured. On a pump drawing that call normally sits on a bearing bore, a journal or a seal land, while the rest of the part runs to general tolerance. A quotation that applies the tightest number to every dimension on the part has not read the drawing.

How do you control the running clearance between an impeller and a wear ring?

By treating it as a relationship rather than a dimension. The clearance is created by the wear-ring bore and the impeller eye diameter together, and by how concentric each is to the shaft axis. Two individually correct diameters, each eccentric to the axis, produce a gap that closes on one side and opens on the other. So the parts are bored and turned from a stated datum, concentricity is measured against the locating diameter rather than assumed from the diameter call, and where a customer supplies the drawings for both parts we machine them as a set and report the resulting radial clearance range.

Which materials do you machine for pumps, and how do I choose?

Stainless 304 and 316/316L, duplex and cast-equivalent stainless, aluminum 6061-T6, bronze and brass alloys, carbon and alloy steel, and engineering plastics including PEEK, PTFE and POM. The selection is driven by the medium and the temperature rather than by habit: 316L is not the right answer for every chloride, bronze is not a single material, and aluminum is usually wrong for a wetted surface that also touches stainless. Three questions settle most of it — what the medium is including concentration, what the temperature is including cleaning and shutdown, and whether the part is wetted, splash-exposed or dry.

Can you make a replacement pump part from a worn sample with no drawing?

Often, with one condition: the worn sample is treated as a measurement problem, not as a design. Wear and corrosion change the dimensions, so machining to the sample reproduces the damage. We establish which surfaces are functional references — normally the bearing journals and the coupling register on a shaft — rebuild the other dimensions from them, use the mating parts as counter-evidence, and send a reconstructed dimension list back for confirmation before cutting. Heavily corroded or cracked samples sometimes cannot be reproduced at all, and then a drawing or a mating assembly is needed.

How are pump components inspected and what documents come with them?

Against an agreed plan, focusing on the features that carry the function: bore diameter and roundness, journal size, total indicated runout, seal-face flatness, groove dimensions, thread gauging and bolt-circle position. The document set is agreed at quotation and may include a material certificate with heat traceability, a first article inspection report, a dimensional inspection report, bore and runout records, a CMM report where the drawing carries GD&T, and surface finish records on named surfaces. Our management system is certified to ISO 9001:2015; scheme approvals beyond that are resolved at supplier qualification for the project.

Do you balance impellers or pressure-test pump casings?

No, and we would rather say so than imply otherwise. Dynamic balancing, hydraulic performance testing, casing pressure testing, running-clearance setting and final assembly are the pump builder's operations, because they require the assembled machine and the design intent. What we do is make the parts concentric and true enough that they do not consume the tolerance those operations rely on, and report the measurements that show it.

Can you machine several pump parts as a matched set?

Yes, where the drawings for the parts that touch each other are supplied together. The parts are then reviewed as a set: impeller hub bore against shaft diameter, journal against bearing bore, impeller eye against wear-ring bore, seal land squareness against the bore axis, bolt circle against spigot. What that produces is not a design service — we do not set the running clearance or guarantee hydraulic performance — but it does mean the interfaces are machined to one interpretation and the measured fit range across the set is reported, so the builder can confirm the assembly closes where intended.

Should a pump housing be machined from solid or cast and then machined?

It depends on volume, geometry and material, and the two are different quotations rather than two prices for the same thing. Machining from solid avoids pattern or die cost and suits prototypes, low volumes and complex internal geometry with simple walls. A casting with machined interfaces becomes cheaper once the pattern is amortised, and it is the normal route for housings with internal passages that a cutter cannot reach. If the annual volume is significant, it is worth asking for both routes to be reviewed rather than defaulting to the one the supplier prefers.

Send the Drawing and Tell Us What It Runs In

A model and a dimensioned drawing at a named revision, the material grade and condition, the medium and its temperature, the critical fits and finishes, the documents you need and the quantity you expect. If it is a replacement part, send photographs, the pump model and the sample if you can. The review comes back with the route, the features that will decide the price, and anything that cannot be made or measured as drawn — before a program is written.

Request a Pump Component Quote

STEP · IGES · X_T · DWG · DXF · PDF · NDA on request

Pump mechanical seal parts

Seats, glands, sleeves, holders and seal housings, with the seal-specific material and wear detail. Seal components

CNC machining services

Equipment, envelope, published tolerance tables and the plant behind these components. Machining capability

CNC turning services

Shafts, sleeves and bushings, including slender work with steadies and between-centers turning. Turning

5-axis machining

Impeller blades, contoured passages and multi-face parts cut without re-clamping. Five-axis work

Die casting services

For housings where a casting plus machined interfaces is the right route. Die casting

Quality and certifications

What the quality system covers, which documents are issued, and what is not claimed. Quality

Surface finishing

Passivation, electropolishing, plating and blasting, and the dimensional effect of each. Finishing

Materials

The full grade library behind the materials section above. Materials

Prototype to production

How a part moves from a first-off sample to a controlled repeat process. Production support

Xiamen Goldcattle Plastic & Metal Products Co., Ltd. machines custom pump components to customer drawings on CNC turning, 3-, 4- and 5-axis milling, boring and grinding equipment, with passivation, electropolishing, plating, blasting and coating as specified, dimensional inspection including CMM, bore and runout records, first article inspection and material certification (EN 10204 3.1 on request), under an ISO 9001:2015 quality management system. Tolerances stated on this page describe capability evaluated per feature, per material and per part size at drawing review, and are not a blanket guarantee for any dimension on any part. Pump hydraulic design, running-clearance setting, dynamic balancing, casing pressure testing, assembly and scheme approvals beyond ISO 9001:2015 — including API and marine class certification — remain with the pump builder or are resolved at supplier qualification for the specific project. Materials, stock condition, finishes and inspection scope are confirmed per project.