Preliminary Requirements

Safety Requirements

WARNING

IT IS THE RESPONSIBILITY OF THE OPERATOR TO OBTAIN AND OBSERVE THE MANUFACTURERS MATERIALS SAFETY DATA SHEETS FOR CONSUMABLE MATERIALS INFORMATION SUCH AS, HAZARDOUS INGREDIENTS, PHYSICAL/CHEMICAL CHARACTERISTICS, FIRE, EXPLOSION, REACTIVITY, HEALTH HAZARD DATA, PRECAUTIONS FOR SAFE HANDLING, USE AND CONTROL MEASURES AND ALSO TO TAKE LOCAL REGULATIONS INTO CONSIDERATION.

WARNING

TITANIUM DUST CAN BE A FIRE HAZARD. BE SURE TO FREQUENTLY REMOVE BLEND DUST FROM THE PART, BLENDING AREA AND GLOVES WORN DURING THE REPAIR.

CAUTION

LIMITS SPECIFIED IN THIS SECTION ARE FOR GENERAL USE ONLY LIMITS SPECIFIED IN THE PART-SPECIFIC MANUALS TAKE PRECEDENCE. POST-BLEND SURFACE TREATMENT REQUIREMENTS WILL BE DETAILED WITHIN THE SPECIFIC BLEND REPAIR.

CAUTION

WHEN YOU DO THIS PROCEDURE, BE SURE TO USE GOOD SHOP PRACTICES AND COMMON SENSE. ABUSIVE BLENDING CAN CAUSE DAMAGE THAT IS HARMFUL TO THE LIFE AND FUNCTION OF THE REPAIRED PART.

CAUTION

TO CONTROL DUST AND NOISE CAUSED BY BLENDING, AND TO REDUCE THE RISK OF FIRE HAZARD FROM BLENDING DUST OF CERTAIN MATERIALS, WHENEVER POSSIBLE, DO THE BLENDING OPERATION IN A VENTILATED BOOTH. CONTACT YOUR LOCAL ENVIRONMENTAL HEALTH AND SAFETY PERSONNEL FOR SPECIFIC REQUIREMENTS.

CAUTION

USE ONLY MINIMUM PRESSURE WHEN YOU APPLY BLENDING TOOLS TO PARTS. EXCESSIVE PRESSURE AND SPEED WILL CAUSE SPARKS OR AN ORANGE PEEL EFFECT THAT CAN POSSIBLY BE HARMFUL TO THE PART. KEEP MATERIAL REMOVAL TO A MINIMUM. DO NOT EXCEED BLEND LIMITS.

CAUTION

CHECK THE PART FREQUENTLY FOR HEAT BUILD-UP. IF THE HEAT BUILD-UP IS TOO HOT TO TOUCH WITH YOUR HAND, LET THE PART DECREASE IN TEMPERATURE BEFORE YOU CONTINUE WITH THE REPAIR. OVERHEATING OF PARTS DURING BLENDING CAN CAUSE EMBRITTLEMENT.

CAUTION

DO NOT OVERHEAT THE PART BECAUSE DAMAGE CAN OCCUR.

CAUTION

BE SURE TO DRESS ABRASIVE TOOL BEFORE BLENDING TO GET THE BEST TOOL PERFORMANCE AND TO PREVENT MATERIAL CROSS-CONTAMINATION.

CAUTION

USE A SHIELD OR MASKING TO PROTECT OTHER SURFACES FROM DAMAGE BY ACCIDENTAL TOOL CONTACT DURING THE REPAIR.

Procedure

1. SUBTASK 70-35-03-220-001 Inspect the Part to Find the Level of Repair Necessary - Deleted

2. SUBTASK 70-35-03-350-001 Repair Damage - Deleted

3. SUBTASK 70-35-03-220-002 Inspect the Repair Area - Deleted

4. SUBTASK 70-35-03-380-001 Apply Surface Protection to the Repaired Area - Deleted

5. SUBTASK 70-35-03-350-002 Blending and Buffing of Steel, Nickel, Cobalt, Titanium and Aluminum Alloy Components

   1. General

      1. Blending General Guidelines

         1. Blending is an operation that is used to remove nicks, scratches, high metal and other surface irregularities by intentional removal of base metal. Manual or mechanical methods are used to make shallow and smooth surface depressions that reduce the stress concentration from the damaged area by the distribution of the stress concentration over larger, more tolerant areas.

         2. Before you start any blend repair, make sure that all applicable inspection tasks in the engine manual are completed, and that the part has no cracks.

         3. Non-toleranced enclosed areas defined in blend repairs are to corners, points of tangency between surfaces or at points opposite one of these locations. Enclosed areas will assume a tolerance of plus 0.125 inch (3.175 mm) in all directions unless adjacent areas are specified as areas where blending is not permitted.

         4. It is better to blend sharp impact damage that is within acceptable limits than it is to accept that damage. The sharper the impact, the better it is to blend the damaged area.

         5. It is recommended that you make one single blend when the adjacent damage is so close together that the minimum length-to-depth blend ratio cannot be done independently.

         6. The depth of the blend must be as deep as necessary to remove the damage within the repair limits specified.

         7. The best blends are the ones which are smooth, continuous and round bottomed and that extend outboard from the damage area as much as necessary. Refer to the subsequent steps.

         8. For rotating parts, the length of the blend must be a minimum of 15 times the maximum depth of the blend in all directions. For non-rotating parts, the length of the blend must be a minimum of 10 times the maximum depth of the blend in all directions.

         9. For local damage in the form of raised material, manual blending (that is, blending by hand) is the preferred method. Refer to the manual blending procedure.

         10. When blending on a cylindrical surface, blend in the circumferential direction.

         11. Blend engine radial members in a radial direction.

         12. For parts that are smaller than 1.75 inches (44.45 mm) in length, the subsequent manual blending procedure is recommended.

         13. Manual Blending (Blending by Hand)

             1. Manual blending is done with abrasive stones, abrasive paper, abrasive pads, files, emery cloth and/or crocus cloth.

             2. For an ergonomic alternative to remove raised material (burrs) or sharp edges from minor surface damage to make smooth, it is permitted to use the Air Turbo Lapper with flat 1/4 inch Ceramic Super Stones (80 grit or finer). This equipment is available from Boride Engineered Abrasives (E044Q). Refer to the Vendor List - Organizations Technical Information Repository source names/addresses identified by these numbers.

                NOTE

                Blending can be done with more than one grade of abrasive (coarse to fine, as necessary) to remove damage and to get the specified surface finish. Be sure to start with the least aggressive abrasive needed to remove the damage.

         14. Mechanical Blending (Power Blending)

             1. 

                CAUTION

                DO NOT OVERHEAT THE PART BECAUSE DAMAGE CAN OCCUR.

                When blending, use a power tool (electric or air) with abrasive-impregnated wheels, stones and/or pads.

                NOTE

                Blending can be done with more than one grade of abrasive (coarse to fine, as necessary) to remove damage and to get the specified surface finish. Be sure to start with the least aggressive abrasive needed to remove the damage.

             2. Use minimum pressure when you apply the blending tool to the part to prevent heat build-up. Do not let the abrasive wheels to become loaded up with any particles remaining from blending.

   2. Visual inspection of blends. Refer to the General Instruction in the SPM TASK 70-21-01-220-501).

      1. The surface finish of the blended area must be as smooth as or smoother than, the initial surface. You can compare the surface finish with adjacent non-blended surface or you can refer to the SPM TASK 70-21-01-220-501.

      2. All transitions from blended to non-blended areas must be smooth and continuous.

      3. If the blended area intersects adjacent radii, the initial radius contour must be restored. Butterfly polish holes, as necessary. Refer to the SPM TASK 70-35-19-350-501.

      4. If the blended area intersects a corner, break the sharp edges 0.003 in. - 0.015 in. (0.076 mm - 0.381 mm)

   3. Buffing/Polishing (Optional)

      1. Buffing is an optional operation that can be used to get the necessary surface finish while blending.

         1. Buff reworked area(s) with a power tool, a round nylon or tampico brush and CoMat 05-070 BUFFING POLISHING COMPOUND or CoMat 05-190 COMPOUND, SILICON CARBIDE DEBURRING (150 GRIT AND FINER).

         2. Use minimum pressure when you apply the buffing brush to the part to prevent heat build-up.

         3. Buff engine radial members in a radial direction.

         4. Buff cylindrical surfaces in a circumferential direction.

      2. Polishing is an optional operation that can be used to smooth minor (small) scratches and burrs smooth with fine grain abrasive paper, abrasive cloth, crocus cloth, emery cloth or abrasive pad (CoMat 05-125 ABRASIVE PAD, SILICON CARBIDE, ULTRA-FINE or CoMat 05-126 ABRASIVE PAD, ALUMINUM OXIDE, VERY FINE).

   4. Local Touch-Up After Blending

      1. To prevent corrosion damage after blending of aluminum anodized parts, refer to the SPM TASK 70-33-22-300-503.

   5. 
      CAUTION
      WHEN YOU BLEND ROTATING COMPONENTS DO THE PROCEDURE IN THE ORDER GIVEN IN THE PROCEDURE TO PREVENT DAMAGE TO THE PART.

      Special Instructions For The Blending Of Rotating Parts

      NOTE

      Be sure to follow all requirements in the Blending and Buffing/Polishing procedures above.

      1. In areas where peening is required by an Engine Manual repair, those blended areas are required to be shotpeened. If you are blending areas where shotpeening is critical, be sure that an approved source does the shotpeening. Refer to the specific repair details for instruction.

      2. Blend to a sufficient depth to remove all the damage that you can see plus an additional 0.002 in. - 0.003 in. (0.051 mm - 0.076 mm). Blend pits to a depth that is sufficient to remove the pits. Total material removal must not be more than the specified repair limits.

      3. Blending must start with the coarser grades of resilient flexible abrasive-impregnated wheels, brushes or points for the initial removal of damage, but not coarser than is necessary to remove the damage.

      4. Finish blending the part with the finer grades of abrasive until the surface is as smooth or smoother than the adjacent surfaces.

      5. Use grades of abrasive in the subsequent order:

         1. 80 mesh silicon carbide or aluminum oxide grit

         2. 120 mesh silicon carbide or aluminum oxide grit

         3. 180 mesh silicon carbide or aluminum oxide grit

         4. Optional: Use CoMat 05-137 POLISHING COMPOUND or CoMat 05-189 COMPOUND, POLISHING AND BUFFING or CoMat 05-191 COMPOUND - POLISHING, GREASELESS, COARSE polishing compound with a cloth wheel, cloth (non-coated) to get a surface finish, if necessary.