Broaching fundamentals — function of rear teeth What do the rear (trailing) teeth of a broach primarily do during a pass?

Introduction / Context:
A broach is a multi-tooth tool with progressively increasing tooth height. Its tooth arrangement splits work between roughing, semi-finishing, finishing, and sometimes burnishing lands. Recognizing the role of each section is key to process design and surface integrity control.

Given Data / Assumptions:

• Standard pull-type internal broach with roughing teeth, finishing teeth, and burnishing (sizing) lands at the rear.
• Feed per tooth (rise-per-tooth) is front-loaded; burnishing lands have zero rise.

Concept / Approach:
Roughing teeth remove the bulk allowance. Finishing teeth remove a small, uniform allowance to achieve size and reduce tool load. The last ‘‘rear’’ teeth are burnishing lands with no additional rise; they plastically smooth asperities and size the hole by ironing rather than cutting, hence removing essentially no metal.

Step-by-Step Solution:
Identify tooth sequence: rough → finish → burnish.Note burnish lands have zero chip load (rise-per-tooth = 0).Therefore, rear teeth do not cut; they size and smooth, removing no measurable metal.

Verification / Alternative check:
Surface roughness after burnishing typically improves by 1–2 grades without corresponding chip formation; chips end before the burnish zone.

Why Other Options Are Wrong:
Burnishing is a plastic deformation/ironing action, not metal removal; finishing teeth do remove minimum metal, but they are not the very rear burnishing lands; roughing removal is at the front.

Common Pitfalls:
Using the term ‘‘rear teeth’’ for finishing teeth; in many texts, ‘‘rear’’ specifically refers to the final, zero-rise burnishing lands.

Final Answer:
Remove no metal at all