--- title: "Milling, shaper and drilling machine operations" subject: "Manufacturing and Production Processes" chapter: 7 key: "semester_4/manufacturing_and_production_processes:milling-shaper-drilling-machines-operations" source: https://www.bctengineer.com/q/semester_4/manufacturing_and_production_processes/milling-shaper-drilling-machines-operations site: BCT Engineering --- # Milling, shaper and drilling machine operations Manufacturing and Production Processes · Chapter 7: Material Removal Processes: “ Chip-forming” - Asked in: year not given, 4+2 marks - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_4/manufacturing_and_production_processes/milling-shaper-drilling-machines-operations - Whole chapter: https://www.bctengineer.com/md/semester_4/manufacturing_and_production_processes/chapter-7 ## Question (a) Differentiate between up milling and down milling. Write the working principle of a shaper and compare it with a planer. (b) Calculate the machining time to drill a through hole of 20 mm diameter in a 40 mm thick plate with a feed of 0.15 mm/rev at 600 rpm, taking the drill point allowance as 0.3 D. ## Short answer Up milling: cutter opposes feed, chip starts thin, rougher finish; down milling: cutter moves with feed, chip starts thick, better finish, needs backlash eliminator. Shaper: reciprocating ram with quick-return; planer: work reciprocates. Drilling time for 20 mm hole: L = 40 + 0.3×20 = 46 mm, T = 46/(0.15×600) = 0.51 min. ## Answer #### (a) Milling, shaper **Milling** removes metal with a rotating multi-tooth cutter while the work is fed against it. | Point | Up (conventional) milling | Down (climb) milling | |---|---|---| | Cutter rotation vs feed | Opposite to feed direction | Same as feed direction | | Chip thickness | Zero at start, maximum at end | Maximum at start, zero at end | | Cutting force | Tends to lift the work | Presses the work on the table | | Surface finish | Poorer; rubbing at start | Better | | Backlash | Not a problem | Needs backlash eliminator | | Use | Rough surfaces, castings with scale | Finish cuts, thin parts | **Shaper:** a single-point tool is fixed on a reciprocating ram. The tool cuts on the forward stroke; on the return stroke it lifts (clapper box) and the table feeds the work sideways by a small amount. A quick-return mechanism (crank and slotted link) makes the return stroke faster. It is used for flat surfaces, slots and keyways. | Point | Shaper | Planer | |---|---|---| | Moving part | Tool (ram) | Work (table) | | Work size | Small | Large and heavy | | Tool | One | Several heads | | Feed | Work moved after each stroke | Tool moved | | Rigidity, cost | Lower | Higher | #### (b) Drilling time Length to be travelled: $$ L = t + 0.3D = 40 + 0.3\times20 = 46\ \text{mm} $$ $$ T = \frac{L}{fN} = \frac{46}{0.15\times600} = 0.511\ \text{min} \approx 30.7\ \text{s} $$ **Answer:** drilling time $= 0.51$ min. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. In down (climb) milling, what is true of the chip? A. Chip is zero at the start and maximum at the end B. Chip is thickest at the start of the cut and zero at the end C. Chip thickness is constant D. Cutter rotates opposite to the feed Answer: B. Down milling has cutter rotation in the feed direction; it presses the work down and gives better finish but needs a backlash eliminator. (Key point: Up vs down milling) 2. Why is up milling preferred for scaly cast surfaces? A. It presses the work on the table B. It gives the best surface finish C. The cutter starts with zero chip thickness and does not strike the hard scale suddenly; backlash is not a problem D. It needs a backlash eliminator Answer: C. The up-milling tooth cuts from below the surface, which suits rough castings. (Key point: Up milling use) 3. What distinguishes a shaper from a planer? A. In a shaper the work moves and is large B. A shaper has several heads and a planer one tool C. A shaper cuts on both strokes D. In a shaper the tool reciprocates and work is small; in a planer the work moves and is large Answer: D. The shaper ram carries one tool; the planer table carries heavy work. (Key point: Shaper vs planer) 4. What is the drilling time for a 40 mm plate and 20 mm drill? A. 0.51 min, using L = 40 + 0.3 x 20 = 46 mm B. 0.44 min, ignoring the drill point C. 0.33 min using L = 20 mm D. 1.0 min Answer: A. T = L/(fN) = 46/(0.15 x 600) = 0.511 min. 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