1. John O’Brien – Skidmore Wilhelm

2.  Overview - Tension vs. Torque
 Bolt Tension Calibrator (Skidmore)
 4 Methods of Pre-Installation Verification
◦ Each method can be compromised without
proper diligence
 Best Practices (how to keep the inspector
happy)

3.  What’s the difference between tension &
torque?
 Is it a big deal?
 90% of torque overcomes
friction (not tightening)
 Conditions outside control
of bolt manufacturer
affects performance

4.  What does a Skidmore do?
◦ Simulates bolted joint
◦ Measures Force in Lbs
 How does a Skidmore work?
◦ Hydraulic Load cell
 Why is it used?
◦ Test Bolts
◦ Verify bolt tensioning

5.  Are bolts so different?
 Live Demonstration – Effect of Lubrication
Photo courtesy of Robert Shaw, President,
Steel Structures Technology Center Inc.
Photo courtesy of Chris Curven, Vice President,
Applied Bolting Technology

6.  Rusty bolts okay? Can’t I just lube them?
Photo courtesy of Chris Curven, Vice President,
Applied Bolting Technology
.
Photo courtesy of Chris Curven, Vice President,
Applied Bolting Technology

7.  Rusty bolts okay? Can’t I just lube them?
Photo courtesy of Chris Curven, Vice President,
Applied Bolting Technology
.

8.  Which bolts maintain lubricity?
Photo courtesy of Robert Shaw, President,
Steel Structures Technology Center Inc.
Photo courtesy of Chris Curven, Vice President,
Applied Bolting Technology

9.  Wrenches Compatible with Skidmore Units
◦ Hand Torque Wrenches
◦ Impact Guns
◦ Electric Wrenches
◦ Hydraulic Wrenches

10.  Turn of the Nut
 Calibrated Torque Wrench
 Direct Tension Indicators (DTI’s or “squirter
washers”)
 Tension Control Bolts

11.  Turn of the Nut
◦ Snug bolt
◦ Mark bolt/nut/plate
◦ Turn nut required amount– make sure
tension is at least 5% over required
amount (see table)
◦ In structure bolt head must be prevented
from turning

13.  Calibrated Wrench
◦ Snug bolt
◦ Tighten to tension plus 5%
◦ Measure torque to move additional 5
degrees
◦ Average 3 bolts assemblies

15.  DTI
◦ Snug bolt – Verify gaps with feeler gage
◦ Tighten to tension plus 5%
◦ Verify gaps with feeler gage
◦ Squirter washers

17.  Tension Control (TC) Bolt
◦ Snug bolt
◦ Tighten to spline break
◦ Verify tension is correct

19.  Proper setup of Skidmore
◦ Seat parts
◦ Proper Clamping
◦ Oil Leaks (small leak okay…get fixed
when able)
 Spacers – Don’t stack washers!!
 Torque reaction arms?
 Spacer Bushings

20.  Frequently Asked Questions
◦ Temperature Effect
◦ Calibrate the Skidmore? How often?
◦ Is there a source for information on proper bolting?
 www.boltcouncil.org Research Council Structural
Connections (RCSC)
 Structural Bolting Handbook – by SSTC
 Questions?