42CrMo Precision Knurled Locating Sleeve

From concept to production in 25 days High-quality, cost-efficient rapid tooling solution.

25 Days

Total Lead Time

±0.02 mm

Precision Tolerance

100K+ Shots

Mold Life

0 PPM

Quality Target

Project Overview

Manufacture of AAT-005, a 90 mm long precision locating sleeve from 42CrMo alloy steel. The component combines a Ø32 mm internal bore, Ø42 mm front/grip section, a knurled operating surface, a radial M8×1.25 through-threaded hole with countersink, and an M14×1.5-6H axial threaded feature. The part is heat treated to HRC 35–40 and finished with nickel plating.

The customer drawing does not state the final equipment or exact function. From the geometry, we treat the component as a precision locating / clamping sleeve that may be used in inspection fixtures, gauges, alignment tools or other repeatable positioning assemblies.

Drawing Feature	Requirement / Manufacturing Focus
Part No.	AAT-005
Material	42CrMo alloy steel
Heat Treatment	HRC 35–40
Surface Finish	Nickel plated finish
Overall Length	90.00 mm
Internal Bore	Ø32.00 mm
Front / Grip OD	Ø42.00 mm
Knurled Section	18.00 mm axial length shown on drawing
Radial Thread	M8×1.25 THRU with Ø8.50 × 90° countersink
Axial Thread	M14×1.5-6H
Profile	R75.40 transition; 2.0 × 45° chamfers shown
General Tolerance	±0.05 mm unless otherwise noted; break all other edges 0.2 mm

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The Challenge

1. Long internal locating bore: the Ø32 mm bore extends through most of the 90 mm body. Bore size, straightness and surface condition must remain consistent so a mating shaft or inspection element can enter smoothly without local binding.

2. Bore-to-OD concentricity: although no explicit coaxiality callout is shown, the internal bore and turned external profile are functionally related. Excess eccentricity could cause uneven wall thickness, poor alignment or inconsistent clamping.

3. Heat-treatment distortion: 42CrMo must reach HRC 35–40. A relatively thin-walled sleeve can change roundness or straightness during heat treatment, especially around the open bore and threaded cross-hole.

4. Knurling deformation: the 18 mm knurled section improves grip, but knurling applies radial forming forces. If the process is too aggressive, it can distort the nearby bore or change the external diameter.

5. Intersecting threaded features: the radial M8×1.25 through hole and the axial M14×1.5-6H feature require clean thread form and controlled deburring. Burrs entering the bore can interfere with a mating component.

6. Nickel plating after precision machining: plating changes functional dimensions and thread fit. Critical bore and thread conditions therefore need allowance, masking or post-plating verification.

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Our Solution

Rough-turn the 42CrMo blank and rough-bore the internal diameter while leaving controlled finishing allowance. Keep wall thickness as uniform as practical before heat treatment to reduce distortion.

Heat treat to HRC 35–40, verify hardness, then check bore straightness/roundness before final finishing. Finish-turn the external profile and finish-bore the Ø32 mm locating surface from a controlled datum setup.

Use suitable boring support and multiple light finishing passes for the long bore. Inspect the bore at the entrance, middle and deep end rather than measuring only one section.

Produce the knurl with controlled pressure and feed, preferably after the main geometry is stable. Recheck the internal bore after knurling to confirm that the forming load has not created measurable distortion.

Machine the M8×1.25 through-threaded hole and Ø8.50 × 90° countersink in a rigid secondary setup. Produce the M14×1.5-6H internal thread with controlled tool alignment and verify both threaded features with appropriate GO/NO-GO gauges.

Coordinate nickel-plating thickness with the finishing supplier. Use masking or pre-plating dimensional allowance where required, then carry out final checks of the Ø32 bore, thread fit, overall geometry, coating quality and edge condition after plating.

Project Results

The resulting component combines a hardened 42CrMo structure, repeatable locating bore, secure threaded locking features and a durable nickel-plated finish. Controlling heat treatment, bore finishing, knurling and plating as one process chain reduces the risk of bore distortion, thread interference and inconsistent assembly.

For precision fixture or inspection-related use, the finished sleeve provides a robust interface for positioning and clamping a mating cylindrical element while allowing convenient manual handling through the knurled grip. Documented bore, thread and hardness inspection also supports repeat production and traceability.

Project Photos

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