Sheet Metal (C-43) · Lesson 7 of 8

Metal Shear Guarding: the 3/8-Inch Rule and Table G-3 (8 CCR 4227, 4186)

"Metal Shear Guarding: the 3/8-Inch Rule and Table G-3 (8 CCR 4227, 4186)" is lesson 7 of 8 in the Sheet Metal (C-43) Learning Hub. It opens with "Why the Shear Is Guarded at the Point of Operation" and works through 5 short steps, then a worked example you can check yourself against.

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Steps in this lesson

  1. Why the Shear Is Guarded at the Point of Operation
  2. Metal Shears: Section 4227
  3. Table G-3: Opening Size Grows with Distance
  4. What a Good Guard Looks Like
  5. Controls, Sharpness, and Repairs

The worked example in the course applies this lesson to a realistic job in 6 steps, from "Read the maximum opening" through "Choose a fix".

What you'll be able to do

  • Explain the main idea of "Metal Shear Guarding: the 3/8-Inch Rule and Table G-3 (8 CCR 4227, 4186)" in plain language you can use on the exam.
  • Apply this step with confidence: "Table G-3: Opening Size Grows with Distance".
  • Apply this step with confidence: "What a Good Guard Looks Like".
  • Apply this step with confidence: "Controls, Sharpness, and Repairs".
  • Test yourself on the worked example and the quick-check quiz inside the classroom.
Metal Shear Guard Openings, Table G-3Squaring shear, side viewtableknifefixed guard bar3/8 inmaxrear barrieroperator sideFixed barrier: not more than 3/8 in above the table,or self-adjusting up to the material thickness.Table G-3 (8 CCR Sec. 4186)Distance of opening from pointof operation hazard (inches)Maximum widthof opening (in)1/2 to 1-1/21/41-1/2 to 2-1/23/82-1/2 to 3-1/21/23-1/2 to 5-1/25/85-1/2 to 6-1/23/46-1/2 to 7-1/27/87-1/2 to 12-1/21-1/412-1/2 to 15-1/21-1/215-1/2 to 17-1/21-7/817-1/2 to 31-1/22-1/8Red row: slot at 3 in fails at 5/8. Green row: 4 in passes.Bar at 1/2 in fails; 5/8 in slot at 3 in failsFix: lower the bar to 3/8 in, and set the finger guard 4 in from the knife (5/8 in allowed).8 CCR Sec. 4227(a), 4186(b), 4207(a)(2), Table G-3. Guarding starts 1/2 in from the point of operation.CC
The diagram for this lesson, exactly as it appears in the Learning Hub.

The first steps of this lesson

Step 1: Why the Shear Is Guarded at the Point of Operation

Title 8 General Industry Safety Orders Section 4184(a) requires machines with a grinding, shearing, punching, pressing, squeezing, drawing, cutting, rolling, or similar action, in which an employee comes within the danger zone, to be guarded at the point of operation. Section 4184(b) extends that to machines in any industry with similar hazards. In a sheet metal shop the squaring shear, the press brake, and the forming rolls are exactly the machines these orders were written for. The Group 8 orders on points of operation are what an inspector checks in the shop.

Step 2: Metal Shears: Section 4227

Section 4227(a) says mechanical power and foot and hand power metal shears must have a guard that prevents the operator hands from entering the zone traveled by the knives while they are in motion. The guard may be a fixed barrier set not more than 3/8 inch above the table (or per Figure G-8 and Table G-3 of Section 4186), or a self-adjusting barrier with a 3/8 inch limit that rises to the thickness of the material. Hydraulic or pneumatic hold-downs are guarded by U-shaped guards coming down to not more than 3/8 inch from the table (Section 4227(b)). Partial enclosure guards must stop anyone reaching around or behind the guard (Section 4227(d)), and chains, barriers, or other means must prevent entry to the rear of the shear during operation (Section 4227(e)).

The remaining 3 steps, the worked example and the quiz are in the course. This is a preview. The full lesson, with the step-by-step explanations, a worked example and a quick-check quiz, is inside the classroom.

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