Preliminary Requirements

Safety Requirements

WARNING

IT IS THE RESPONSIBILITY OF THE OPERATOR/USER TO GET AND OBEY THE HEALTH AND SAFETY DATA FOR THE MATERIALS IN USE AND TO REFER TO LOCAL REGULATIONS FOR A SAFE WORK PROCEDURE. ALL HEALTH AND SAFETY DATA GIVEN IN THIS DOCUMENT ARE GENERAL GUIDELINES ONLY.

WARNING

ALWAYS FOLLOW THE INSTRUCTIONS IN THE SUPERFINISHING EQUIPMENT AND CONSUMABLE SUBSTANCE MANUFACTURER'S HEALTH, SAFETY, AND ENVIRONMENTAL DATA SHEETS.

Procedure

1. SUBTASK 70-38-25-860-001 Introduction

   1. This process gives the method One or Two for the Superfinishing (also known as Vibropolishing or Vibrobarrelling) of blade and vane airfoils. The process uses non-metallic media to produce a fine surface finish. Superfinishing must only be used where specified in the applicable Engine Manual or Repair Scheme, or damage to the parts may result. The superfinishing of coated components usually specifies special precautions to prevent damage. For example, certain coating systems (for example, Silicon-modified Aluminides) must not be superfinished after coating.

   2. Superfinishing media usually consists of aluminum oxide bonded in a ceramic, porcelain, or plastic and is available in many types of shapes and sizes. The choice of media is controlled by the material to be finished and the component geometry. The finish produced by superfinishing is directly related to the old surface condition of the component but is affected by the media composition and geometry.

      1. If the applicable Engine Manual or Repair Scheme work instructions do not specify the applicable polishing media, it is the responsibility of the operator to select the applicable polishing media. Trials are necessary to identify the optimum media and process time. You can improve the effect of the process by the addition of chemical polishing solutions.

2. SUBTASK 70-38-25-860-003 Equipment and Materials

   1. Equipment used in process.

      1. A suitable superfinishing machine of sufficient size to hold the parts and polishing media.

      2. NOTE

         It is the responsibility of the operator to select suitable equipment.

         A suitable electronic surface measuring machine.

3. SUBTASK 70-38-25-380-001 Makeup and Control of the Superfinishing Media

   1. Refer to Step (Introduction) and Step (Materials and equipment used).

   2. Load the machine with the quantity of media specified by the equipment manufacturer to makeup the necessary volume. The maximum size of the media to be used is specified in the Engine Manual.

      1. It is permitted to polish with smaller sizes of media than specified. However, the time necessary to produce the finish specified will be longer.

   3. It is necessary to prepare (also known as conditioning) new media before the superfinishing of engine parts to remove sharp edges from the media. Prepare (condition) the media as specified by the media manufacturer.

      1. NOTE

         Keep the machine drain open to prevent unwanted material building up in the equipment.

         If no instructions to prepare/condition the new media are given, then prepare the media for a minimum of 3 hours at 80 percent to 100 percent machine running speed. The actual time required will be dependent on the amount of media to be prepared. As you prepare the media, it is necessary to add a liquid compound compatible with the superfinishing media to the media. This may be a one-off addition of compound and water in the case of a small barrel, or a continuous flow, at the specified proportions, of compound and water, while the machine is ON. Add the quantity of the liquid compound as specified by the compound manufacturer.

   4. Add media, as necessary, to one of the procedures that follows:

      1. For additions of media up to 20 percent of the working volume by weight, preparation of the media is not necessary.

      2. For additions of media of more than 20 percent by weight, preparation of the media is necessary and must be carried out as follows:

         1. Prepare the media as specified by the media manufacturer.

            1. NOTE

               Keep the machine drain open to prevent unwanted material building up in the equipment.

               If no instructions are given, prepare the media for a minimum of 3 hours at 80 percent to 100 percent machine running speed. The actual time necessary is applicable to the amount of media to be prepared. As you prepare the media, it is necessary to add a liquid compound compatible with the superfinishing media must be added to the media. This may be a one-off addition of compound and water in the case of a small barrel, or a continuous flow, at the specified proportions, of compound and water, while the machine is ON. Add the quantity of the liquid compound as specified by the compound manufacturer.

   5. Removal of unwanted material from the working chamber.

      1. For machines which do not flow the water/compound mixture continually to drain, it is necessary to drain the liquid after each batch of parts and to wash the media with water before you start superfinishing. For continuous flow machines, keep the drain open. Permit the excess solution to flow to the drain through via a settlement tank to catch solid material.

      2. NOTE

         Be sure to follow local regulations when you discard the effluent from the process.

         To prevent blockages in the finishing equipment drain pipes, it is important to keep the superfinishing equipment clean, particularly equipment used with chemical additives.

4. SUBTASK 70-38-25-380-002 Control of the Superfinish Produced

   1. NOTE

      Due to the variability of types of machine and media used, it is not possible to define exactly the necessary parameters. For guidance on typical parameters, see Step for guidance.

      For each type of part (for example, H.P.3 stators, or H.P.5 compressor blades), a test batch of parts must be done to assess the effectiveness of the parameters.

   2. Be sure to record the test parameters which must include:

      1. Part number/name and quantity in test batch.

      2. Any preparatory surface treatment (include masking and surface finish).

      3. Media shape and size.

      4. Liquid compounds or additives and dilution.

      5. Superfinishing machine, make and size.

      6. Machine operation time.

      7. Machine operation speed (Hz).

      8. Maximum number of parts for each cubic meter (or cu.ft.) of media.

      9. The surface finish to be produced.

   3. Superfinish the parts. Refer to Step (Superfinishing Procedure) or Step (Superfinishing Procedure).

   4. After superfinishing all of the test batch, dimensionally inspect the parts for chordal width, trailing edge thickness, and surface finish.

      1. The necessary surface finish is specified in the Repair Scheme. Chordal width and trailing edge thickness is specified in the Engine Manual.

5. SUBTASK 70-38-25-380-003 Set-up of the Surface Measuring Machine

   1. Assemble the surface finish measuring machine to the manufacturer's instructions. Then do as follows:

      1. For additions of media of more than 20 percent by weight, preparation of the media is necessary and must be carried out as follows.

         1. Be sure that the measuring probe is horizontal relative to the test piece, and that the stylus touches the surface; use a piece of CoMat 02-181 MODELLING CLAY, for example, to make sure the test piece is horizontal.

      2. Measure the surface finish of the test piece; operate the machine to the manufacturer's instructions.

      3. Read off the surface finish and record the results.

         1. If the equipment indicates a false reading:

            1. Check the set up of the test piece and the machine.

            2. Adjust the machine and test piece, as necessary.

            3. Do the set-up test again.

6. SUBTASK 70-38-25-380-004 Measure the Surface Finish of the Parts

   1. Set-up and test the surface finish checking machine. Refer to Step.

   2. NOTE

      The part must be set up so that the area of airfoil required is horizontal with the convex surface uppermost.

      Set-up the part to be measured.

      1. NOTE

         Operate the machine to the manufacturer's instructions.

         Adjust the measuring probe of the surface finish measuring machine so that it runs horizontally over the area to be measured. On small highly curved blades, it may be necessary to run the probe axially along the length of the airfoil.

   3. Measure the surface finish of the part as follows:

      1. Measure the surface finish, in the area indicated by the shading in Figure, and record the surface finish.

         1. If the measuring equipment indicates a false reading, reset the measuring equipment (refer to Step) and do the surface finish measurement again.

      2. Make two more surface finish measurements within the defined area and record the surface finish values.

      3. Calculate the mean surface finish as follows:

         Mean Surface Finish = Sum of reading obtained divided by the number of readings taken.

   4. Measure and record the surface finish of the other parts in the batch.

   5. Calculate the mean surface finish for the batch as follows:

      Mean Surface Finish = Sum of reading obtained divided by the number of readings taken.

      1. If the mean surface finish produced is worse than that specified, then do again Step (Superfinishing Procedure) from the paragraph titled Masking to the end of the subtask and examine again, refer to Step (Inspection Procedures).

         1. NOTE

            If there is a significant difference in the recorded surface finish between different parts or between areas on a part, review the choice of media.

            Set the time for the additional superfinishing by comparison of the measured surface finish to the time to get the finish.

   6. Process Guidance Notes.

      1. For an initial mean surface finish achievement of 1-4 microinches better than the specified surface finish, do not change the parameters as this will permit batch variation and minor process deterioration.

      2. If the mean surface finish achieved is better than the specified surface finish by 5 microinches (or more), it is permitted to reduce the process time provided the surface finish necessary is still achieved.

7. SUBTASK 70-38-25-380-005 - 001 Superfinishing Procedure Method One

   1. 

      CAUTION

      EFFECTIVE MASKING FOR CHEMICAL SUPER POLISHING IS DIFFICULT. STAGNANT CHEMICALS UNDER THE MASKING MUST CAUSE NO DAMAGE TO THE PART.

      

      CAUTION

      MEDIA USED TO PROCESS TITANIUM, ALUMINUM, OR ALUMINUM COATED COMPONENTS MUST NOT BE USED TO PROCESS NICKEL OR COBALT BASE COMPONENTS.

      

      CAUTION

      BLOCKAGE AND THEREFORE BUILD UP OF CHEMICALS IN A MACHINE CAN CAUSE UNACCEPTABLE LEVELS OF HYDROGEN IN TITANIUM ALLOYS.

      

      CAUTION

      YOU MUST NOT ABRASIVE BLAST OIL SYSTEMS OR PARTS THAT HAVE A COMPLEX SHAPE IN WHICH THE MEDIA CAN GET CAUGHT AND REMOVAL IS NOT POSSIBLE. ALSO IT MUST BE POSSIBLE TO EXAMINE THE PARTS FULLY TO MAKE SURE ALL OF THE MEDIA HAS BEEN REMOVED. IF YOU DO NOT OBEY THIS INSTRUCTION, YOU CAN CAUSE DAMAGE TO THE PART(S).

      Before you start any Superfinishing process, refer to Step (Introduction), SUBTASK 70-38-25-860-02 (Safety Precautions) and Step (for Materials used).

   2. Initial cleaning.

      1. Initially clean the parts by the procedures in the SPM TASK 70-11-03-300-503, if necessary, to remove grease, oil, and dirt.

   3. 
      CAUTION
      DO NOT ABRASIVE BLAST THE AIRFOIL SURFACES OF PARTS WHICH HAVE ALREADY BEEN PEENED.

      NOTE

      An abrasive blast is optional. It is only necessary when the surface finish is unsatisfactory for immediate superfinishing. An unsatisfactory surface finish for immediate superfinishing can be the result of:

      Local blending or dressing operations.

      Components that have been chemically etched for inspection purposes.

      Minor pitting or damage of the airfoil.

      Abrasive blast.

      1. Mask before abrasive blasting.

         1. Mask off areas for which abrasive blasting is not necessary. Whenever possible, use superfinishing masks specially made for the parts. If the masks are not available use CoMat 02-002 ADHESIVE TAPE GENERALPURPOSE PAPER or CoMat 02-003 ADHESIVE TAPE BLACK WATERPROOF, as applicable.

      2. Abrasive blast the parts, by one of the methods that follow:

         1. All parts except aluminized turbine blades and aluminized nozzle guide vanes. For the abrasive blasting of Aluminized Turbine Blades and Aluminized Nozzle Guide Vanes refer to paragraph 2(c).

            1. Wet abrasive blast by one of the methods in the SPM TASK 70-12-01-120-501, or SPM TASK 70-12-06-120-501; use the media in CoMat 05-003 ABRASIVE MEDIUM ALUMINUM OXIDE, 120/220 GRADE, or CoMat 05-004 ABRASIVE MEDIUM, ALUMINUM OXIDE, 140/400 GRADE, or CoMat 05-198 ALUMINUM OXIDE, 320-GRIT, or CoMat 05-199 ALUMINUM OXIDE, F500 GRIT, or CoMat 05-230 ABRASIVE MEDIUM ALUMINUM OXIDE, 280/500 GRADE.

         2. All parts except titanium, aluminized turbine blades and aluminized nozzle guide vanes. For the abrasive blasting of Aluminized Turbine Blades and Aluminized Nozzle Guide Vanes refer to paragraph 2(c).

            1. Dry abrasive blast by one of the methods in the SPM TASK 70-12-01-120-501, or SPM TASK 70-12-02-120-501, or SPM TASK 70-12-09-120-501; use CoMat 05-003 ABRASIVE MEDIUM ALUMINUM OXIDE, 120/220 GRADE, or CoMat 05-004 ABRASIVE MEDIUM, ALUMINUM OXIDE, 140/400 GRADE, or CoMat 05-198 ALUMINUM OXIDE, 320-GRIT, or CoMat 05-199 ALUMINUM OXIDE, F500 GRIT, or CoMat 05-230 ABRASIVE MEDIUM ALUMINUM OXIDE, 280/500 GRADE.

         3. Aluminized Turbine Blades and Aluminized Nozzle Guide Vanes.

            1. Glass bead or ceramic bead peen aluminized turbine blades and aluminized nozzle guide vanes by the method in the SPM TASK 70-12-03-120-501, or SPM TASK 70-12-12-300-503; refer to the Repair Scheme or Engine Manual for required bead size.

      3. Remove any masking from parts.

   4. Visual Inspection.

      1. After blasting, do a check to see that the blasting pattern is even.

      2. Make sure all the blast media has been removed from the parts.

   5. Mask prior to superfinishing.

      NOTE

      It is necessary for some parts to have a mask for abrasive blasting but not during superfinishing. Specific masking instructions will be given in the Engine Manual.

      1. Mask off areas for which superfinishing is not necessary; use superfinishing masks specially made for the part. If these are not available, use CoMat 02-003 ADHESIVE TAPE BLACK WATERPROOF.

   6. 
      CAUTION
      DO NOT DROP THE PARTS ONTO THE MEDIA TO PREVENT DAMAGE MAY BE CAUSED TO THE PARTS.
      
      CAUTION
      DO NOT PUT TOO MANY PARTS IN THE SUPERFINISHING MACHINE.

      Superfinish cycle.

      1. Set the required parameters and start the superfinishing machine; refer to Step.

      2. Make sure the necessary water/compound quantity is added to the media (small machines) or is running continuously (large machines with automatic compound additions).

      3. Carefully put the permitted maximum number of parts into the moving superfinishing media.

      4. Superfinish the parts for the specified time.

   7. 
      CAUTION
      DO NOT PERMIT THE PARTS TO RATTLE AGAINST EACH OTHER DURING REMOVAL FROM THE MACHINE.
      DO NOT DROP THE PARTS INTO PROCESS BASKETS BECAUSE EDGE DAMAGE CAN OCCUR.

      Removal from superfinishing machine.

      1. Carefully remove the parts from the media by hand. Removal by an automatic removal (weir discharge) system is permitted, if no damage occurs to the parts.

   8. Remove masking.

      1. After the removal of all masking, carefully place the parts in protective containers to prevent damage. If adhesive tape has been used as masking, it may be necessary to clean the masked areas by means of a suitable solvent to remove any remaining adhesive.

   9. Rinse.

      1. Rinse with cold water, then air-water blast or pressure wash to remove all superfinishing material residues.

   10. Hot Rinse.

       1. Put the parts fully into hot water, at 176 deg F (80 deg C) minimum, for sufficient time to be sure the parts reach the temperature of the water.

   11. Dry the parts.

       1. After the hot rinse, blow dry the parts with a blast of clean, dry compressed air.

   12. Inspection.

       1. Examine the parts by the procedure in Step (Inspection Procedures).

8. SUBTASK 70-38-25-380-005-002 Superfinishing Procedure Method Two option for HPC Airfoils

   1. 
      CAUTION
      DO NOT DO THIS VIBRATORY FINISHING PROCESS BEFORE FLUORESCENT PENETRANT INSPECTION.

      NOTE

      To provide a smooth surface finish for all model engines front and rear compressor blade and variable vane airfoils (excluding Fan Blades).

      NOTE

      This airfoil refurbishment process increases performance of front and rear compressor blade and variable vane airfoils because it gives a better surface finish. This operation is not for the repair of leading edge erosion.

      Introduction.

      1. This procedure gives two vibratory finishing process methods for surface finish improvement.

         1. METHOD 2A is a cut-down process.

         2. METHOD 2B is a refinement polishing process.

      2. Method selection is determined by the average surface roughness (Ra) condition of the blade or variable vane airfoil at the start of the process. Refer to Ra qualification limits in Procedure METHODS 2A and 2B, that follow.

      3. Consumable materials, media and cleaning or burnishing compounds are identified separately for each method.

   2. Prerequisites.

      1. Remove antigallant and clean airfoil. Refer to Engine Manual cleaning requirements.

      2. Do fluorescent penetrant inspection. Refer to Engine Manual requirements.

      3. Peen airfoil, if specified by the Engine Manual.

      4. Do an airfoil surface roughness inspection to determine the Average Roughness (Ra) surface condition for the quantity of parts before the vibratory finishing process. This determines whether to use METHOD 2A or 2B.

      5. Mask the variable vane trunnion before vibratory finishing the airfoils.

   3. Definitions.

      1. ROUGHNESS WIDTH: The distance parallel to the nominal surface between the successive peaks or ridges which constitute the predominant pattern of the roughness.

      2. ROUGHNESS WIDTH CUTOFF (INSTRUMENT CUT-OFF): The greatest spacing of repetitive surface irregularities to be included in the measurement of average roughness height. Roughness width cutoff corresponds to the low frequency cutoff of the instrument and is specified in inches.

   4. Equipment:

      1. Vibratory finishing machine, bowl-type, 10 cu.ft (0.28 cu.m.) capacity recommended Surface roughness instrument

   5. Consumable Materials

      For METHOD 2A:

      Table 2.

      CoMat 05-254 Media - Quartz-abrasive, Barrel-finishing, Triangular-shaped	Plastic, Quartz-abrasive, Barrel-finishing, Triangular-shaped (alternate to CoMat 05-255)
      CoMat 05-255 Media - Ceramic, Cone-shaped, Lightweight	Media - Ceramic, Lightweight, Cone-shaped (alternate to CoMat 05-254)
      CoMat 05-259 Liquid Detergent for Barrel Finishing	Liquid Detergent for Barrel Finishing

      For METHOD 2B:

      Table 3.

      CoMat 05-256 Media - Aluminum Oxide Barrel Finishing	Aluminum Oxide Barrel Finishing Media
      CoMat 05-257 Polishing Compound (for Refinement step)	Polishing Compound (for Refinement step)
      CoMat 05-258 Burnishing Compound (for Final Polish step)	Burnishing Compound (for Final Polish step)

   6. Procedure METHOD 2A: Repair Blade Or Variable Vane Airfoil (With Surface Finish Roughness More Than 30Ra)

      1. Makeup and control media as follows:

         1. Fill the vibratory finishing machine, to 3.0 in. (76.2 mm) from the top of the outside rim of the machine or by the manufacturer's instructions, with CoMat 05-254 Media - Quartz-abrasive, Barrel-finishing, Triangular-shaped or CoMat 05-255 Media - Ceramic, Cone-shaped, Lightweight.

         2. Set up the vibratory finishing machine. Refer to the manufacturer's instructions.

         3. Adjust the water flow rate to 20 gallons/hour (75.7 liters/hour).

         4. Add CoMat 05-259 Liquid Detergent for Barrel Finishing at a rate of 1 - 1.5 fluid ounces of detergent/gallon of water/hour (7.7 ml - 11.55 ml of detergent/liter of water/hour) for a 10 cu.ft (0.28 cu.m.) machine. Adjust proportionately for other size machines.

         5. Open the drain valve, as necessary.

         6. Start the vibratory finishing machine.

      2. 
         CAUTION
         IF NEW MEDIA IS IN THE MACHINE, IT MUST FIRST HAVE ITS SHARP/ROUGH EDGES REMOVED. OPERATE THE MACHINE FOR A MINIMUM OF TWO HOURS WITH A WATER FLOW OF 20 GALLONS/HOUR (75.7 LITERS/HOUR) BEFORE YOU START TO BURNISH.
         
         CAUTION
         IF NEW MEDIA IS ADDED TO KEEP UP THE OPERATIONAL VOLUME OF THE MACHINE, A BREAK-IN CYCLE TO REMOVE SHARP/ROUGH EDGES IS RECOMMENDED WHEN THE ADDED MEDIA IS GREATER THAN 10 PERCENT BY WEIGHT OF OPERATIONAL VOLUME. NO BREAK-IN IS NECESSARY WHEN NEW MEDIA WEIGHT IS LESS THAN 10 PERCENT OF THE OPERATIONAL VOLUME.
         
         CAUTION
         IF THE MACHINE DOES NOT FLOW THE WATER MIXTURE CONTINUOUSLY TO DRAIN, THE WATER MIXTURE MUST BE DRAINED AFTER EACH QUANTITY OF PARTS AND THE MEDIA FLUSHED WITH WATER BEFORE THE NEXT QUANTITY OF PARTS IS PROCESSED.
         
         CAUTION
         MAKE SURE THAT BLADES HAVE EQUAL DISTANCES BETWEEN THEM IN THE MEDIA AND THAT THE MACHINE IS NOT TOO FULL. THIS IS TO PREVENT DAMAGE TO THE BLADES AND VARIABLE VANES.

         Put the blades, one at a time (with airfoil first), into the media in the vibratory finishing machine as follows to prevent part damage:

         1. In lots of up to two complete blade sets for each cycle of any one stage or

         2. In lots with mixed blades of other stages that are the equivalent of up to two blade sets.

      3. Operate the vibratory finishing machine up to three hours.

      4. Remove the blades and/or variable vanes and do one of the steps that follow:

         1. Flush in cold water and air-dry with filtered shop air.

         2. Put in hot water, 150 deg F - 200 deg F (66 deg C - 93 deg C) to flash dry.

         3. Clean by TASK 70-11-03-300-503.

      5. Do the airfoil roughness inspection per Step.

      6. A scheduled screening procedure is recommended to remove media which has been worn to 3/8 in. (9.128 mm) or less in size.

         NOTE

         Be sure to calibrate the surface roughness gage against a Standard before use.

   7. Procedure Method 2B: Repair Blade Or Variable Vane Airfoil (With Surface Finish Roughness Of 30Ra Or Less)

      1. Makeup and control media as follows:

         1. Fill the vibratory finishing machine, to 3.0 in. (76.2 mm) from the top of the outside rim of the machine or by the manufacturer's instructions, with CoMat 05-256 Media - Aluminum Oxide Barrel Finishing.

         2. Set up the vibratory finishing machine. Refer to the manufacturer's instructions.

         3. Close the drain valve, as necessary.

         4. Add 3 gallons (11.355 liters) of water for every 10 cu.ft (0.28 cu.m.) of machine capacity (medium water level).

         5. To the water added above, add 8 oz.wt./gallon (60 grams/liter) of CoMat 05-257 Polishing Compound (for Refinement step).

         6. Start the vibratory finishing machine.

      2. Put the blades, one at a time (with airfoil first), into the media in the vibratory finishing machine as follows to prevent part damage:

         1. In lots of up to two complete blade sets for each cycle of any one stage or

         2. In lots with mixed blades of other stages that are the equivalent of up to two blade sets.

      3. Operate the vibratory finishing machine up to two hours.

      4. Open the drain valve and remove the water.

      5. Adjust the makeup and control the media as follows:

         1. Adjust the water flow to 10 gallons/hour (37.85 liters/hour).

         2. Add CoMat 05-258 Burnishing Compound (for Final Polish step) at a rate of 1 - 1.5 fluid ounces/gallon of water/hour (7.7 - 11.55 ml/liter of water/hour) for a 10 cu.ft (0.28 cu.m.) machine. Adjust proportionately for other size machines.

         3. Start the vibratory finishing machine.

      6. Operate the vibratory finishing machine up to one hour.

         NOTE

         For vibratory finishing machines that have more than a 10 cu.ft (0.28 cu.mm) capacity, a minimum flow of 1 gallon/hour/ cubic foot (3.785 liters/hour/0.03 cubic meter) of machine capacity is necessary.

      7. Remove the blades and/or variable vanes and do one of the steps that follow:

         1. Flush fully in cold water and air-dry with filtered shop air.

         2. Put fully in hot water at 150 deg F- 200 deg F (66 deg C - 93 deg C) to flash dry.

         3. Clean by TASK 70-11-03-300-503.

      8. Do the airfoil roughness inspection per Step.

         NOTE

         If the surface finish is not smooth enough, the METHOD 2B vibratory finishing process can be done again one more time. (Refer to Definitions).

9. SUBTASK 70-38-25-380-006 Inspection Procedures

   1. NOTE

      Too many parts in the superfinishing machine or rough handling during loading, unloading and post superfinishing washing can cause damage to occur.

      Examine leading and trailing edges for damage.

   2. Examine the chordal width.

   3. Examine 5 percent minimum of the airfoils for the surface finish produced, refer to Step and Step. Measure within the areas given in Figure. The surface finish requirement will be given in the Engine Manual or Repair Scheme.

      1. Accept/Reject Criteria.

         Accept superficial scuffing or surface marking that cannot be felt with a non-metallic scriber or finger nail drawn across the scuffing or marking.

         Reject any scuffing or marking that can be felt with a non-metallic scriber or finger nail drawn across the scuffing or marking.

         NOTE

         If the parts are not immediately necessary for further operations, apply an approved preservative, refer to the engine manual. For short-term protection, refer to the SPM TASK 70-62-00-620-501 and SPM TASK 70-38-37-300-503.

   4. Place parts in protective containers to prevent damage.

10. SUBTASK 70-38-25-380-007 Suggested Start Conditions for Superfinishing

    1. The start parameters that follow are included for guidance and do not constitute actual conditions for production purposes.

       1. For suggested start parameters to produce a 0.5 micrometer (20 micro inch) finish for steel or nickel base alloys or aluminized nickel base alloys and titanium, refer to the tables as follows.

          Table 4. Table 1: Machine Volume is 3 cu.ft (0.085 cu.m.)

          Media size		Material to Superfinish		Polish Time at 25 Hz
          up to 10 mm		Steel		4 hours
          		Nickel base alloys		4 hours
          		Aluminized nickel base alloys		6 hours
          		Titanium		3 hours

          Table 5. Table 2: Machine Volume is 9 cu ft or 18 cu ft (0.25 cu m or 0.5 cu m)

          Media size		Material to Superfinish		Polish Time at 25 Hz
          up to 10 mm		Steel		4 hours
          		Nickel base alloys		4 hours
          		Aluminized nickel base alloys		6 hours
          		Titanium		3 hours

          Table 6. Table 3: Machine Volume is 9 cu ft or 18 cu ft (0.25 cu m or 0.5 cu m)

          Media size		Material to Superfinish		Polish Time at 25 Hz
          10 mm to 15 mm		Steel		2 hours 30 minutes
          		Nickel base alloys		2 hours 30 minutes
          		Aluminized nickel base alloys		3 hours 30 minutes
          		Titanium		2 hours

          Table 7. Table 4: 9 cu ft or 18 cu ft (0.25 cu m or 0.5 cu m)

          Media size		Material to Superfinish		Polish Time at 25 Hz
          15 mm to 25 mm		Steel		2 hours
          		Nickel base alloys		2 hours
          		Aluminized nickel base alloys		3 hours
          		Titanium		1 hour 30 minutes

    2. On a glass bead peened surface, blasted immediately before superfinishing, decrease the suggested polishing time by 50 percent.

Figure: Areas in which Superfinishing must be measured, on convex side of Airfoil Fig 70-38-25-990-002

Areas in which Superfinishing must be measured, on convex side of Airfoil Fig 70-38-25-990-002