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2.10 Reviewing for correct material and mechanical specifications. 

Note:  These checklists have historically pertained to drawings used as TDP elements.  With the inclusion of 3D data and solid model datasets as design deliverables in MIL-DTL-31000C comes the need to properly prepare, format, annotate, store, and transfer 3D solid model datasets.  Thus to a certain degree these checklists must pertain to solid models as well as drawings.  The following paragraph applies to all sections of the checklist that follows:

If digital 3D solid models (3D digital datasets) are included in a TDP, ensure that all of the following requirements that may pertain to models are also applied to the models.  Refer to SECTION 26 of the DRM for more specific information about and requirements for using 3D solid models as elements of a TDP. 

2.10.1 Material Specifications.  Reference ASME Y14.100.

  1. Make sure that material specifications are listed on the drawing.
  2. Check material specifications.  Ensure requirements such as class, grade and type are specified.  Ensure active specifications are used.
  3. Where applicable, ensure that the material specification correctly identifies the shape required, such as bar, sheet, rod or tubing.
  4. The tolerances and surface finishes given on specifications for commercial items must agree with those shown on the drawing for non-machined dimensions.
  5. Evaluate qualities such as to plating, painting, welding, hardening, stress relief, tempering, etc.
  6. Industry standard stock materials must be specified, when practical.
  7. Ensure that proper material is used on die formed parts.  Some heat-treated materials are not practical for die forming. Other materials are suitable and aging will meet hardness requirements.
  8. Ensure that material has been specified in the proper condition to facilitate processing operations.
  9. Check the type of raw material for compatibility with processing and machining techniques, stress requirements, and direct contact with dissimilar materials.
  10. Check the drawing notes for heat treatment and hardness specifications and requirements.

2.10.2 Cast, Forged and Molded Items.  Check the following items.

  1. Ensure that there are separate views of a rough casting or forging and the finished part.
  2. Ensure that the drawings or contract documents specify the type of casting, forging, or molding process to be used.
  3. Ensure the drawings specify draft allowances.
  4. Specified tolerances must be compatible with the types of processes and the intended use of the item.
  5. Appropriate datum reference frames must be specified.
  6. Ensure that the location and dimensions of tooling points are specified.
  7. Dimensions of draft surfaces must be taken from mold lines.
  8. Generally, duplicate dimensions and tolerances should not be shown on both the rough and finished part drawing unless one of the dimensions is specified as a reference dimension, or it is critical that an as-cast or as-forged dimension and tolerance are maintained in the final machined condition of the item. 
  9. Ensure that the grain direction of forging is indicated on the drawing.
  10. Ensure that all materials, including alloys are properly specified. Reference ASME Y14.100.
  11. Ensure that drawings specify the parting lines of castings.
  12. Ensure that the drawings show the location and dimensions of test coupons on forgings or castings.
  13. Ensure that inspection procedures are specified for casting or forgings shown on drawings.

2.10.3 Mechanical Specifications.  Reference ASME Y14.100. 

2.10.3.1 General Requirements.

  1. Check fits between all mating parts to ensure that maximum tolerance buildups will allow parts to assemble and operate without interference.
  2. Check all dimensions to ensure that material may be machined with standard tools.
  3. All machining requirements for features such as chamfers, countersinks, counterbores and radii must be properly defined and specified.
  4. Check to ensure that all mating holes for connecting hardware such as rivets and bolts are within tolerance limits.
  5. Ensure that lubrication fittings have been provided, as needed, at convenient and accessible places. 

2.10.3.2 Thread Data.  Reference ASME Y14.6. Check thread data for the following:

  1. Ensure that pipe threads are not used as pressure seals.
  2. Ensure adequate thread engagement.  Fasteners must be long enough to provide sufficient thread engagement for washers, nuts and safety wire, as appropriate.
  3. Countersink or chamfered first thread.
  4. Check uniformity in depth of tap drills and thread depth for greater efficiency in production. If possible avoid thread requirements that dictate the need to use blind taps to thread holes.

2.10.3.3 Spring Data.  Check spring data for the following information. Reference ASME Y14.13M.  

  1. Ensure that the drawings specify the type of springs to be used.
  2. Wherever possible, springs that conform to an accepted Government or industry specification or standard should be used.
  3. If nonstandard springs are used, ensure that the drawings depict their wire diameter, mean spring diameter, spring rate, unstressed length, stressed length and finish.

2.10.3.4 Gear Data.  Reference ASME Y14.2M. Check gear data for the following:

  1. Ensure that drawings specify the type of gears to be used.
  2. Wherever possible, gears that conform to an accepted Government or industry specification or standard should be used.
  3. When nonstandard gears are used, ensure that the drawings depict their pitch, pitch diameter, shaft diameter, thickness, material used, finish and any special lubrication requirements.

2.10.3.5 Bearing Data.  Check bearing data for the following information:

  1. Ensure that the drawings describe the types of bearing to be used and their rating life.
  2. Wherever possible, bearings that conform to an accepted Government or industry standard or specification should be used.
  3. Wherever nonstandard bearings are used, ensure that the drawings describe their dimensions, load rating, speed and lubrication requirements.

2.10.4 Sheet Metal Data.  Check for the minimum bend allowance and dimensions of parts formed from sheet metal.  Drawings should be functionally dimensioned and tolerance; ensuring that a finished part or assembly will function properly is the most important design consideration.  Reference ASME Y14.5M-1994.  Consider using die or investment castings rather than complex sheet metal parts or inseparable assemblies if the design requirements could be met in a more cost-effective manner.  Likewise evaluate stamping, extruding or fabricating in lieu of casting and forgings.  Ensure that welding requirements conform to applicable standards.

2.10.5 Plating and Finishing Data.  Check plating and finishing requirements for the following:

  1. Ensure that tolerance and thickness of plating is in accordance with the applicable specification.
  2. The drawings must specify the dimensions and surface finish requirements of plated parts.
  3. Precious metal plating requirements should be eliminated where practical to reduce cost.
  4. Avoid plating only selected portions of parts wherever possible.
  5. Drawings must specify if metal parts will be deoxidized, anodized, chemically filmed, barrier coated, sacrificial coated or treated in some other manner. If more than one treatment method is specified, ensue that the treatments are applied in the proper order.
  6. Check drawing notes to make sure that magnetic inspection is required for high stress heat treated parts and low micro finish parts.