Case study · Aerospace fasteners
Preventing Titanium Fastener Galling and Reducing Run-In Torque
Dicronite® dry lubrication prevented galling between titanium bolts and stainless steel nutplates during aircraft fastener testing. The treatment reduced run-in torque and enabled automated installation, supporting both production assembly and repeated removal for maintenance.
- NAS1581titanium bolts
- MS21060L6stainless steel nutplates
- Dicronite®dry lubrication
- 10CYCLES Install and removal cycles completed Twice the customer's five-cycle requirement.
- 0GALLING No galling observed In both manual and automated installation testing.
- 32IN-LB Run-in torque after cycle five Automated installation, with no galling or coating loss.
The challenge
Galling during aircraft fastener installation
An aircraft structures manufacturer encountered galling when installing NAS1581 titanium bolts into MS21060L6 threaded stainless steel nutplates. The fastener system attached a large exterior communications structure to the airframe.
The end customer required the fasteners to withstand five installation and removal cycles without galling to accommodate maintenance.
During pre-production testing, the manufacturer occasionally met this requirement. However, results were inconsistent, and installation required careful manual handling.
Application data
- Bolt
- NAS1581, titanium
- Nutplate
- MS21060L6, threaded stainless steel
- Assembly
- Large exterior communications structure to airframe
- Requirement
- Five installation and removal cycles without galling
- Problem
- Inconsistent results; careful manual handling required
The requirement
Five cycles required. Ten completed.
The end customer required five installation and removal cycles without galling. In automated testing, the Dicronite-treated fasteners completed ten, with no evidence of galling in either manual or automated installation.
The solution
Dicronite® dry lubrication
A set of titanium bolts and stainless steel nutplates received Dicronite dry lubrication for testing. The manufacturer evaluated the treated fasteners using both manual and automated installation to assess run-in torque, galling, and coating condition over repeated cycles.
Manual installation
Run-in torque fell with every cycle
The treated fasteners exhibited low run-in torque, which decreased with each installation and removal cycle.
- No evidence of galling was observed.
- The coating remained in good condition.
- Run-in torque decreased with successive cycles.
Automated installation
Ten cycles, double the requirement
During automated testing, run-in torque measured 32 in-lb after the fifth cycle. At that point, no galling or coating loss was observed. Testing continued through ten installation and removal cycles. Run-in torque increased at cycle six, then decreased consistently through cycle ten.
- No evidence of galling was observed.
- Only minimal coating degradation was noted during the additional cycles.
- The fasteners completed ten cycles, exceeding the customer's five-cycle requirement.
The outcome
Galling prevention and automated assembly
Dicronite dry lubrication was recommended for the final design after eliminating the galling problem in testing and enabling automated installation during production.
For this titanium bolt and stainless steel nutplate assembly, the treatment delivered lower run-in torque and repeatable installation and removal without galling.
Discuss your fastener application
Galling or excessive run-in torque in a threaded assembly?
Contact Dicronite Southwest to discuss dry lubrication for your fasteners, materials, and installation requirements.