Lesson 4: Precision Setup—Sine Bars & Bolt Circles
Duration of Days: 2
Lesson Objective
SWBAT: Calculate the required Gage Block height for a Sine Bar setup using the formula H = L X sin?).
Determine "Center-to-Center" distances for hole patterns arranged on a bolt circle.
How does a Sine Bar turn a triangle on paper into a physical reality on a machine?
Why is it more accurate to measure "over pins" than to measure a corner directly?
Sine bar, gage block, center-to-center, pin-to-pin, point of tangency, altitude, bisect, chord.
CTE.MFG.A.03 (Precision measuring tools)
CTE.MFG.B.07 (Apply geometric principles to layout).
Students apply trigonometry to high-precision physical setups. The purpose is to learn how to use a Sine Bar and Gage Blocks to set precise angles for inspection or machining.
DOK Level: 3 (Strategic Thinking / Hands-on)
Support: Hands-on demonstration: Have students build a "stack" of gage blocks to match a calculated height.
Extension: Calculate the "Center-to-Center" distance for a 5-hole bolt circle (requires dividing 360 degrees by 5).
"The Sine Bar Lab" – Students are given a target angle and must calculate and build the correct gage block stack to achieve it.