ID Grinding

Internal grinding of bores, sleeves and bearing seats, where the spindle has to reach inside the part.

A bore is harder to control than a shaft: the wheel is small, the overhang is long, and the coolant has further to travel to reach the cut. Internal grinding is the process that brings a hardened bore to size and holds geometry a boring bar cannot reach.

It is usually paired with OD grinding on the same part, so concentricity between bore and outside diameter is set on one machine rather than argued between two.

What we make here

Parts that come through this department.

Bearing bores and seatsSleeves and bushingsHydraulic and pneumatic boresTool holders and colletsRing gaugesHardened housings

Typical work: hardened bores, and bore-to-OD geometry held on the same part.

How the work runs

From drawing to shipping, in this order.

Bore condition checkBore size, depth-to-diameter ratio and hardness decide the spindle and the wheel head before anything is quoted.

Setup on the faceThe part is set on its finished face or a fixture plate so the bore runs true to the datum the assembly will use.

Grind and gaugePlunge or traverse grinding with in-process gauging; taper corrected by dressing, not by re-chucking.

Check and protectBore measured at both ends for taper, checked for roundness, then plugged and packed.

Materials, equipment and inspection

The practical detail.

Materials for this process

Hardened steels, tool steels, stainless and cast iron — plus carbide where the bore has to hold size over a long run.

See the full material list

Equipment and inspection

Internal grinding spindles with a range of quill lengths, dressed on the machine. Bore size with plug gauges and bore micrometers; roundness and taper on the roundness tester.

Full equipment list

Capacity

What the department can actually hold.

Feature	Range	What to know
Bore diameter	Ø5–300 mm	Below Ø5 quoted on the jig grinder
Max depth	600 mm	Depth-to-diameter above 5:1 needs a stepped wheel and extra passes
Cylindricity	0.003 mm	On a hardened part with a stable setup
Taper	0.005 mm over 100 mm	Corrected by wheel dressing
Surface finish	Ra 0.4 µm	Ra 0.2 µm on a bearing bore
Hardness	Up to HRC 60	Hardened sleeves and bushings are routine work

Deep bores are quoted on the depth-to-diameter ratio, not on the diameter. A Ø20 × 200 mm bore is a harder job than a Ø150 × 100 mm one.

Parts we have machined

Real components, photographed on our own bench.

Where the money goes

What actually drives the price of this work.

Depth-to-diameter ratio Above 5:1 the wheel arbor deflects and the cycle slows down. This is the single biggest driver on an ID grinding quote.
Bore size Small bores need small wheels, and small wheels wear faster — more dressing, more time.
Tolerance A 0.003 mm cylindricity callout is achievable; it is bought with gauging and slower passes.
Pre-grind condition A bored hole left concentric and on size halves the grinding time. A hole that wandered costs the same to fix as to make.
Batch Steady-rest setups and gauging fixtures amortise over the run, so the tenth piece is always cheaper than the first.

Straight answers

Questions buyers ask about this work.

What is the smallest bore you can grind?

Depth matters as much as diameter. Send the drawing with the bore length and we will confirm rather than quote a number that only holds for a shallow hole.

Can you hold concentricity between bore and OD?

Yes — that is the main reason to grind both features here. Both are ground from the same setup reference and the report states the measured runout.

Do you hone as well?

We grind to size. Where the drawing calls for a cross-hatch finish we will say so at quotation rather than substitute a ground finish and hope it passes.

Keep reading

Where this usually leads next.

CapabilityOD Grinding CapabilityWire EDM IndustryMedical & Imaging

Request a quotation

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