Jinan No.4: define the journal, the face and the datum together.

MK and MGK share a part-size entry, but not the wheel package

The comparison scrolls sideways on a narrow screen; focus it and use arrow keys.

The MK page explicitly covers 250 and 500 mm grinding-length versions, with 270/520 mm between-centre entries. The MGK page title says ×500, but its shared dimension block also contains 250/500 and paired dimensions/masses. Keep that inconsistency open: request the exact ×500 drawing rather than assigning both variants to the named machine.

Standard-test-part figures are different from an acceptance promise for your shaft. Compare the actual wheel, support, dressing, gauge and thermal conditions before treating MGK as an automatic upgrade. Its surface entry also needs clarification before use in an acceptance agreement.

Draw the support and the wheel approach before choosing a reference

Which configuration solves the difficult journal?

The wider current catalogue distinguishes 125, 200, 320 and 500 series, general-purpose and special grinders, internal grinding and gantry-manipulator applications. Those are separate paths: the two retained references do not establish every size, grinding surface or loading package.

Accept the released geometry and the process that produced it

Size is only one measurement

Agree journal diameter, roundness, cylindricity, taper and datum runout separately. State where and how they are measured, under what support and temperature conditions, and after which release or settling period.

Dressing and thermal state belong in the trial

Freeze material, hardness, grinding allowance, wheel and dressing arrangement, coolant and filtering. Record warm-up, dressing intervals, compensation and the inspection result across the agreed trial sample. A machine's axis repeatability does not substitute for these part results.

Output includes the whole sequence

Count loading, support setting, rough/finish grinding, dressing, inspection and rejects. If a gauge or automated loading is proposed, define it on the selected build and demonstrate its sequence; do not infer inclusion from the CNC designation.

Company context is distinct from model acceptance

The national standards platform plan 20260975-T-604 names 济南四机数控机床有限公司 among the drafting organizations for a revision of internal cylindrical grinding machine accuracy testing. The entry records a 2 March 2026 issue date and a consultation-stage plan when reviewed. It concerns internal grinding; it is not an approved new standard, a certificate or proof of conformity for the retained MK/MGK external-grinding references.

Use the complete Chinese company name when confirming the legal manufacturer and contracting seller. Similar grinder model names from a different city or builder cannot resolve this company's configuration. The company profile identifies a cylindrical-grinder manufacturer and lists internal and special grinding alongside CNC/general-purpose ranges. It also describes spindle/component manufacturing and geometrical/surface inspection equipment; this is the manufacturer’s description, not an independent site audit. Confirm the actual inspection and service package in the quotation. A separate 2016 association exhibition review names its MKS1620B/500 face-and-OD grinder; that historical model remains distinct from the current MK/MGK tables.