BS 4621:2010 pdf download – Aerospace series — Inserts, MJ threads, self-locking, self-broaching keys — Technical specifications
in a sampling plan, quality limit which corresponds to a specified 10 % probability of acceptance
NOTE1 lt is the limiting lot quality characteristic that the consumer is willing to accept with a low probability that a lot ofthis quality would occur.
NOTE2 For the purposes of this standard,the limiting quality quoted in Table 4 corresponds to a probability ofacceptance of 10 %.
acceptance quality limitAQL
quality limit which in a sampling plan corresponds to a specified but relatively high probability of acceptanceNOTE lt is the maximum percent defective (or the maximum number of defects per hundred units) that, for purposesof sampling inspection, can be considered satisfactory as a process average.
insert ready for use, inclusive of any possible treatments and/or surface coatings, as specified in the definitiondocument
document specifying all the requirements for finished inserts
ttorque to be applied to the associated bolt to maintain movement of rotation in relation to the part, theassembly being under no axial load and the insert locking zone being completely engaged with the bolt(minimum protrusion of two pitches, including the end chamfer)
tightening torque to be applied to the insert or bolt to introduce or to increase the axial load in the assembly
untightening torque to be applied to the insert or bolt to reduce or remove the axial load in the assembly
torque required to start unscrewing the insert or the bolt from the associated part, with the insert lockingdevice still fully engaged on the bolt, but after the axial load in the assembly has been removed by unscrewinghalf a turn followed by a halt in rotational movement
Qualification inspections and tests (requirements, methods, numbers of inserts with self-broaching keys) arespecified in Table 1.They shall be carried out on:
—each type and diameter of inserts;
—39 inserts selected from a single batch by simple random sampling.
The test programme may possibly be reduced, or the qualification be granted without inspection or testing.
Any such decision shall be based on the results obtained on similar types and diameters of inserts providedthat the design and manufacturing conditions are identical.
Table 2 indicates the allocation of insert samples for the inspections and tests.
The purpose of acceptance inspections and tests is to check，as simply as possible, by a methodrepresentative of actual use conditions， with the uncertainty inherent to statistical sampling, that the insertsconstituting the batch satisfy the requirements of this standard.
Acceptance inspections and tests (requirements, methods, numbers of inserts) are specified in Table 1.Theyshall be carried out on each batch inserts from the batch to be tested shall be selected by simple randomsampling.
Each insert may be submitted to several inspections or tests.
lf a more stringent inspection is deemed necessary, all or part of the qualification inspections and tests maybe performed during the acceptance inspections and tests. In this case, the number of inserts submitted tothese inspections and tests is the same as that submitted for qualification inspection and tests.
Acceptance inspections and tests shall be carried out by the manufacturer, or under his responsibility.4.2.4Inspection and test report
A test report showing actual numerical values shall be provided if specified in the purchase order.
See Table 1.