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6061 Aluminum Holder: Stepped Bores & Ra 1.6 DFM Review

The drawing was reviewed before quoting, and five points were raised first (A to E below). The part was planned as two setups on a dedicated fixture, and the first article passed CMM inspection against the drawing.

Grant Lv Reviewed by Grant Lv · 10+ years CNC machining & programming
  • 6061
  • stepped bores
  • Ra 1.6
  • Qty 10
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Client details withheld under NDA unless a client has agreed to be named. Tolerance values are identified as drawing requirements or inspected results, as applicable.

The drawing, annotated

Section W-W of drawing OA-00491 Rev A, marked A at the 0.25 × 45° chamfer, B at the three Ra 1.6 callouts, C at the stepped concentric bores and E at the 11.360 height dimension
Section W-W of the drawing. Click or tap to enlarge.
Six more crops of the drawing: the three other places where 0.25 appears (A), the finish field and note 4 (D), and the general tolerance table (E)
Other places on the sheet. Click or tap to enlarge.

Drawing OA-00491 Rev A. OpenCPC™ © 2024 by OpenAeros LLC, licensed under CC BY-SA 4.0. Cropped and annotated by MachForge (markers A to E added); the annotated images are shared under the same license.

Five points raised before quoting

  • AThe same “0.25” appears in the title block, as a 0.25 × 45° chamfer, as a 0.25 +0.20/0.00 dimension on the front view, and beside the general 0.254 mm edge-break note. Which one controls is asked before quoting, not assumed.
  • BThree Ra 1.6 callouts on the stepped faces. More than one finishing route can reach Ra 1.6 and the route changes cost, so it is confirmed before quoting.
  • CStepped concentric bores: one setup or re-fixturing, and how stack-up between the Ra 1.6 faces and the bores is controlled.
  • DThe finish field in the title block says none, while note 4 says all tolerances apply after finishing and treating. Whether any finish or treatment is intended is asked before quoting.
  • EDimensions written to three decimals fall under a tighter general tolerance (±0.013 mm) than those written to two (±0.125 mm), and one height dimension (11.360) is written to three decimals with no tolerance of its own. Whether that tightness is intended is asked before quoting.

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Grant Lv
MACHFORGE Grant Lv Manufacturing Engineer Every DFM review is done by Grant, with 10+ years of CNC machining and programming experience. Shenzhen, China LinkedIn

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