Demco: Bolt Grades and Torque-Chart Conditions
- Select torque using bolt size, head markings, and applicable instructions.
- Verify thread condition and account for locking elements.
- Replace bolts with matching grades and check tightness periodically.
- Torque wrench — Apply the selected torque after checking chart conditions and any overriding instruction.
- Socket set — Engage bolt heads and nuts securely during tightening.
- Combination wrench — Hold the mating fastener while applying torque.
- Caliper — Check bolt diameter for chart selection.
- Inspection light — Examine head markings, locking elements, and evidence of oil or grease.
- Shop rag — Wipe loose dirt from hardware to make markings and surface conditions visible.
Demco directs users to tighten bolts to the chart values unless another specification is provided. Check bolt tightness periodically, and replace hardware with bolts of the same grade.
Unless otherwise specified, the equipment uses high-strength Grade 5 hex bolts. Bolt and capscrew head markings identify their grade or class, so the chart selection depends on more than diameter alone.
The listed torque figures apply to threads and heads that are not greased or oiled unless the manual specifies otherwise. Do not lubricate bolts or capscrews without such an instruction. When locking elements are used, the manual calls for a 5 percent torque increase.
For a 5/8-inch standard bolt, the chart lists 95 lb-ft for Grade 2, 150 lb-ft for Grade 5, and 225 lb-ft for Grade 8. These are chart values subject to the manual's stated conditions and any otherwise-specified torque.
How It Works
Instruction precedence and bolt identification
Demco directs users to apply chart torque unless another specification is provided; a specific instruction therefore takes precedence over the general chart. Unless otherwise specified, the equipment uses high-strength Grade 5 hex bolts, but technicians must still identify diameter and head markings before selecting an entry. Replace hardware with the same bolt grade rather than treating a matching diameter as sufficient.
Friction controls the relationship between torque and clamp load
Tightening torque must overcome friction while stretching the bolt to develop clamp load, so lubrication changes the relationship between wrench torque and joint loading. Demco's listed values apply to threads and heads that are not greased or oiled unless otherwise specified; do not add lubricant without that instruction. When locking elements are used, apply the manual's 5 percent torque increase.
Chart examples and continued inspection
For a 5/8-inch standard bolt, the chart lists 95 lb-ft for Grade 2, 150 lb-ft for Grade 5, and 225 lb-ft for Grade 8, subject to the stated conditions and any overriding specification. These differences show why diameter alone cannot determine the correct torque. Check bolt tightness periodically because loss of clamp load can permit joint movement and accelerate wear.
Step-by-Step Procedure
0/7 doneDemco Standard-Bolt Chart Examples
| 5/8-inch Grade 2 | 95 lb-ft, chart value |
| 5/8-inch Grade 5 | 150 lb-ft, chart value |
| 5/8-inch Grade 8 | 225 lb-ft, chart value |
| Adjustment when using locking elements | Increase torque by 5% |
Diagnostic Chart
| Symptom | Check | Spec / Expected | Likely cause & fix |
|---|---|---|---|
| The proposed torque was selected using bolt diameter alone. | Read the head markings, confirm diameter, and check for a specific torque instruction before selecting the chart entry. | For a 5/8-inch standard bolt: Grade 2 uses 95 lb-ft; Grade 5 uses 150 lb-ft; Grade 8 uses 225 lb-ft, subject to chart conditions and overriding instructions. | The selected chart entry may belong to a different bolt grade. Basis: Demco-Coupler-Manual-1 |
| Oil or grease is visible on threads or beneath the bolt head. | Determine whether the applicable manual explicitly specifies lubrication before using the chart. | Chart values apply to threads and heads that are not greased or oiled unless otherwise specified. | Unspecified lubrication changes friction and can produce excessive bolt loading at the listed torque. Basis: Demco-Coupler-Manual-1 |
| A locking element is present, but the work instruction lists only the base chart value. | Verify the applicable torque instruction and confirm that the locking-element adjustment has been included. | Apply the manual's 5 percent increase when using locking elements. | The torque selection may have omitted the required locking-element adjustment. Basis: Demco-Coupler-Manual-1 |
| Replacement hardware has different head markings from the specified hardware. | Identify the replacement bolt grade and compare it with the required grade before installation. | Replace hardware with bolts of the same grade; equipment uses high-strength Grade 5 hex bolts unless otherwise specified. | Hardware may have been selected by fit alone rather than by both fit and grade. Basis: Demco-Coupler-Manual-1 |
At the Bay: Diagnose the Case
CASE 1 / 4
The proposed torque was selected using bolt diameter alone.
- Test
- Compare
- Correct
Select the next check
Basis: Demco-Coupler-Manual-1. A likely cause is a hypothesis; confirm it with the applicable service procedure before repair.
Common Bay Mistakes
- ✕ Selecting torque by diameter without reading head markings.
- ✕ Adding oil or grease to make tightening easier without manual authorization.
- ✕ Forgetting the locking-element adjustment or an overriding torque instruction.
- ✕ Substituting a different bolt grade because it fits the hole.
Quick Check
Practice only — not scored.
Plan the Service Sequence
Planning practice only. Follow the applicable manufacturer's instructions, employer safety program and qualified supervision on real equipment.
Plan the first action. Compare the service steps with the bay mistakes.
Source: Demco-Coupler-Manual-1 — 7