DWG_1420-0312_Supplement.docx

DWG 1420-0312 Supplement for BSS Machining Fixture Naval Foundry and Propeller Center

The following information shall be considered included as a supplement to DWG 1420-0312.

1. Machining and Fabrication Note Sheet Locations:

- Machining tolerance - see Sheet 1

- Fabrication - Note 101 and Sheet 6

2. B/M sheet 4 calls for 145.0" OD, which is the raw material size (finish machine later).

3. Top and Bottom plates machining Tolerance:

- Finished machine size is shown in VIEW 8-4A and VIEW 8-2A as Ø144.0"

- Machining tolerance - See Sheet 1

4. Sheet 8 calls for flatness and II within 002":

- Overall height requirement is 17.500/17.750

- Equal material removal from both sides (within +/-.125'' tolerance).

5. Surface finish:

- Machining surface RMS - See Sheet 1

- Fabrication/Flame cut - No need to consider surface finish

6. There is a typo error on sheet 7 detail view 7-2A drawing. Only 8 supports are required

7. There are no Painting or Finishing Requirements for the assembly.

8. ID Tag Fastening and location on assembly:

- See VIEW 8-2A and Detail View 8-1C

- Fastened with B/M item 11. See View 4-3A and Detail View 4-1A

9. For Stress Relieving assembly after fabrication step 2 (sheet 7) and before any machining, follow these steps:

a. Place the weldment flat inside the furnace. Furnace temperature shall not exceed 800°F at the time the weldment is placed in it.

b. Heat the weldment at a rate no greater than 200°F per hour from 800°F to 1200°F

c. Hold 1200°F for three hours

d. Cool furnace at a rate less than 200°F per hour to 800°F. Air cool to ambient temperature.

10. Required plate cannot be welded from 2 separate plates to create the required 120” diameter. Plate must be one piece.

11. List of material items #4 & #5 - Bolt specification: ASTM A574 ; Nut specification: ASTM A563, Grade DH heavy hex, plain