A Comprehensive Guide to Machining Technical Requirements!

General Technical Requirements

1. Remove scale from the part.

2. The machined surfaces of parts shall be free from defects such as scratches, abrasions, or other damage to the surface.

3. Remove burrs and flash.

Heat Treatment Requirements

1. Quenched and tempered, HRC 50–55.

2. The parts are subjected to high-frequency quenching, followed by tempering at 350–370°C, achieving a hardness of HRC 40–45.

3. Carburized depth: 0.3 mm.

4. Perform high-temperature aging treatment.

Tolerance requirements

1. Unspecified geometric tolerances shall comply with the requirements of GB 1184-80.

2. Unmarked length dimensions are permitted to have a tolerance of ±0.5 mm.

3. The casting tolerance zone is symmetrically positioned with respect to the basic dimension of the blank casting.

Part edges and corners

1. The radius of the fillet, R5, is not indicated.

2. All unmarked chamfers are 2×45°.

3. Deburr acute angles, sharp corners, and sharp edges.

Assembly Requirements

1. All seals must be thoroughly soaked in oil before assembly.

2. When installing rolling bearings, oil‑bath heating may be used for hot mounting, but the oil temperature must not exceed 100°C.

3. After gear assembly, the contact pattern on the tooth surfaces and the side clearance shall comply with the requirements of GB 10095 and GB 11365.

4. When assembling the hydraulic system, sealing compounds or sealants may be used, but care must be taken to prevent them from entering the system.

5. All parts and components entering assembly, including purchased and outsourced items, must be accompanied by a certificate of conformity issued by the inspection department before assembly may proceed.

6. Before assembly, all parts must be thoroughly cleaned and free of burrs, flash, scale, rust, chips, oil, coloring agents, and dust.

7. Prior to assembly, the principal mating dimensions of components and parts, particularly interference fit dimensions and associated dimensional accuracy, shall be rechecked.

8. During assembly, parts must not be subjected to impacts, collisions, scratches, or rust.

9. When tightening screws, bolts, and nuts, striking them or using inappropriate screwdrivers and wrenches is strictly prohibited. 10. For fasteners with specified torque requirements, a torque wrench must be used, and the fasteners must be tightened to the prescribed torque value.

11. When securing the same part with multiple screws (bolts), each screw (bolt) shall be tightened in a crosswise, symmetrical, gradual, and uniform manner.

12. During the assembly of taper pins, a color‑checking procedure shall be performed; the contact area shall cover no less than 60% of the pin’s engagement length and shall be evenly distributed.

13. The flat key shall make uniform contact with both sides of the keyway on the shaft, and there shall be no clearance between the mating surfaces.

14. The number of tooth surfaces in simultaneous contact during spline assembly shall be no less than two-thirds, and the contact ratio in both the length and height directions of the spline teeth shall not be less than 50%.

15. After assembly, the sliding-fit flat key (or spline) shall allow the mating parts to move freely, with no uneven looseness or tightness.

16. After bonding, any excess adhesive that has oozed out should be removed.

17. The outer ring of the bearing shall not be jammed in the semicircular holes of the open-type bearing housing and bearing cover.

18. The outer ring of the bearing shall make good contact with the semi-circular holes in the open-type bearing housing and the bearing cover. When checked by means of a color‑checking method, uniform contact shall be ensured within a 120° sector symmetric about the centerline for the housing and a 90° sector symmetric about the centerline for the cover. Within these specified areas, when inspected with a feeler gauge, a 0.03 mm gauge shall not be able to penetrate more than one-third of the outer ring’s width.

19. After the bearing outer ring is assembled, it shall make uniform contact with the end face of the locating bearing cap.

20. After the rolling bearing is installed, it should rotate smoothly and freely when turned by hand.

21. The mating surfaces of the upper and lower bearing shells shall be tightly fitted, with no gap detectable when checked using a 0.05 mm feeler gauge.

22. When securing bearing shells with locating pins, drill and ream the holes and fit the pins only after ensuring that the shell‑seat surfaces and end faces are flush with the mating surfaces and end faces of the corresponding bearing bores. Once installed, the pins must remain securely in place without any looseness.

23. The bearing housing and the bearing pedestal of a spherical roller bearing shall be in uniform contact; when checked by the color‑checking method, the contact area shall not be less than 70%.

24. Alloy bearing liners shall not be used when their surfaces have turned yellow; within the specified contact angle, no core‑free zones are permitted; and outside the contact angle, the area of core‑free zones shall not exceed 10% of the total non‑contact area.

25. The reference end face of the gear (worm wheel) shall be in close contact with the shaft shoulder (or the end face of the locating sleeve), and no gap shall be detected when checked with a 0.05 mm feeler gauge. Furthermore, the perpendicularity requirement between the gear’s reference end face and the axis must be ensured.

26. The mating surfaces of the gearbox and its cover shall be in good contact.

27. Before assembly, thoroughly inspect and remove any sharp edges, burrs, and foreign particles remaining from the machining process. Ensure that the seals are not damaged or abraded during installation.

Casting Requirements

1. The casting surface shall be free of cold shuts, cracks, shrinkage cavities, and through‑going defects, as well as severe surface imperfections such as underfilling and mechanical damage.

2. Castings shall be thoroughly cleaned, with no burrs or flash; risers and sprues on non-machined surfaces shall be removed flush with the casting surface.

3. Cast markings and symbols on the unmachined surfaces of castings shall be clearly legible, with their locations and fonts conforming to the drawing requirements.

4. The surface roughness of the non-machined surfaces of castings, for sand casting, shall not exceed 50 μm.

5. Castings shall be cleaned of risers, sprues, and flash. Residual material from risers and sprues on non‑machined surfaces must be chipped off and ground smooth to meet the required surface finish.

6. The molding sand, core sand, and core supports on the casting shall be thoroughly removed.

7. For castings with inclined surfaces, the dimensional tolerance zones shall be symmetrically arranged relative to the inclined plane.

8. The molding sand, core sand, core supports, excess metal, and adhering sand on the casting shall be scraped and ground smooth and thoroughly cleaned.

9. Features such as undercuts and raised bosses with casting misalignment shall be corrected to ensure smooth transitions, thereby guaranteeing surface quality.

10. Wrinkles on the unmachined surfaces of castings shall have a depth of less than 2 mm and a spacing greater than 100 mm.

11. All non-machined surfaces of castings for machinery products shall undergo shot blasting or tumbling to meet the Sa2 1/2 cleanliness requirement.

12. Castings must undergo water toughening treatment.

13. The casting surface shall be smooth, and risers, burrs, sand adhesion, and other defects shall be thoroughly removed.

14. Castings shall not contain casting defects such as cold shuts, cracks, or porosity that impair serviceability.

Painting Requirements

1. Prior to painting, all steel components requiring coating must be thoroughly cleaned to remove rust, scale, grease, dust, dirt, salt, and other contaminants.

2. Prior to rust removal, first use organic solvents, alkaline solutions, emulsifiers, steam, and other agents to remove oils and contaminants from the surface of steel components.

3. The time interval between surface preparation by shot blasting or manual rust removal and the application of primer shall not exceed 6 hours.

4. The surfaces of riveted components that come into contact must be coated with a rust‑preventive paint having a thickness of 30–40 μm prior to assembly. Overlapping edges shall be sealed with paint, putty, or an adhesive. Any primer damaged during fabrication or welding must be recoated.

Piping Requirements

1. Prior to assembly, all tubing shall have its ends deburred, chamfered, and cleaned of burrs. The interior walls of the tubing shall be cleared of debris and loose rust using compressed air or other suitable methods.

2. Prior to assembly, all steel pipes, including prefabricated piping, shall undergo degreasing, pickling, neutralization, water rinsing, and rust‑preventive treatment.

3. During assembly, tighten all threaded connections, including pipe clamps, supports, flanges, and fittings, to prevent loosening.

4. All welded joints of prefabricated pipes shall undergo pressure testing.

5. When piping is disconnected or transferred, the pipe openings must be sealed with adhesive tape or plastic caps to prevent foreign matter from entering, and labeled accordingly.

Requirements for Repair Welds

1. Prior to welding, all defects must be completely removed, and the groove faces shall be ground smooth and rounded, with no sharp edges permitted.

2. Depending on the nature of defects in steel castings, defects in the weld zone may be removed by chipping, grinding, carbon‑arc gouging, oxy‑acetylene cutting, or machining.

3. Any adhering sand, oil, water, rust, or other contaminants within 20 mm of the weld zone and the groove must be thoroughly removed.

4. Throughout the entire welding process, the temperature in the preheating zone of the cast steel component shall not fall below 350°C.

5. Whenever conditions permit, weld in the horizontal position whenever possible.

6. During repair welding, the electrode should not be swung excessively from side to side.

7. When performing overlay welding on the surface of steel castings, the overlap between weld passes shall be no less than one-third of the weld pass width. The weld bead shall be full and well‑formed, with no burn‑in, cracks, or obvious weld nodules on the weld face. The weld appearance shall be neat and free from defects such as undercut, slag inclusion, porosity, cracking, and spatter; the weld ripple shall be uniform.

Forging Requirements

1. The sprue and riser of the ingot shall be trimmed to an adequate extent to ensure that the forging is free from shrinkage cavities and severe segregation.

2. Forgings shall be formed on forging presses with sufficient capacity to ensure thorough internal forging penetration.

3. Forged parts shall not exhibit visible cracks, laps, or other surface defects that impair serviceability. Local defects may be removed, provided that the removal depth does not exceed 75% of the machining allowance. Defects on the non‑machined surfaces of forged parts shall be thoroughly removed and blended to ensure smooth transitions.

4. Forgings shall not contain white spots, internal cracks, or residual shrinkage cavities.

Requirements for Machined Parts

1. Parts shall be inspected and accepted at each process step; only after passing inspection in the preceding process may they proceed to the next.

2. Machined parts shall be free of burrs.

3. After finishing, parts shall not be placed directly on the floor; appropriate support and protective measures must be taken. The machined surfaces shall be free from rust, pitting, and any defects—such as dents or scratches—that could compromise performance, service life, or appearance.

4. The surface subjected to roller burnishing shall show no peeling after the process.

5. After the final heat‑treatment process, the part’s surface shall be free of oxide scale. The finished mating surfaces and gear teeth shall not exhibit any signs of annealing.

6. The machined threaded surface shall be free from defects such as black scale, dents, stripped threads, and burrs.