Tool Testing Best Practices – Skidmore-Wilhelm

Tool Testing Best Practices




EQUIPMENT SETUP

It is critical to securely fasten Skidmore-Wilhelm impact tool testers to a base with a large mass to prevent vibration from affecting the performance of the tools you are testing. Vibration can decrease torque output because all of the tools energy is not being directly exerted onto the fastener or beam.

Below are main points to keep in mind for equipment setup:

  • Use a bench or stand that weighs 200 lbs. (90 kg) or more.
  • Securely anchor the bench or stand to the floor or steel structural I-beam. We recommend using the Skidmore-Wilhelm TOOL TESTER STAND.  
  • Contact us for more details.
  • Use Grade 5 and above fasteners to securely fasten the impact tool tester to the bench or stand.

TEST TOOL REQUIREMENTS

Assure that you are following proper impact tool testing methods. There are many variables that can alter the performance of the tool you are testing, such as; improper pressure at the impact tool, insufficient air capacity at the tool, condensation is getting in the compressed air supply line, impact tool temperature too high, room temperature, length of test (inconsistent length of runs), using socket extensions, improper sockets (not used for impact tools) and altering the size of the sockets/adapters between runs.

Create a test procedure for repeatable and accurate results using the guidelines below:

  • Check the pressure and flow rate at the impact tool to assure they are sufficient.

    Follow the manufacturer’s recommendation for peak performance.

  • Perform the tool testing in equal increments of time. Use an automatic shutoff device, such as Skidmore-Wilhelm’s Air Timer. Contact Skidmore-Wilhelm if you are interested in purchasing one.

  • Use the same size impact socket/adapter (weight, length, diameter, drive size, etc.) between test runs.*

    *Changing any dimensions of the socket/adapter can alter the Mass Moment of Inertia which changes the output torque reading. Note: This only holds true when all other variables hold true (same impact tool, test bolt assembly, adapters, proper lubrication, temperature, cleanliness, etc.).

  • Allow sufficient cool down periods between test runs. Check the temperature of the impact tool to assure it is the same before each test run. Contact the manufacturer for peak operating temperature.

  • Make sure the air supply going to the impact tool is dry. Utilize an air dryer in line with the compressed air supply.

  • Maintain short lengths of air hose from the air compressor to the test tool as possible.

  • Do not use socket extensions. Use the shortest impact sockets as possible. TOOL

TESTING APPARATUS

The effective torque delivered by an impact wrench is related directly to the assembled joint stiffness. The same impact blow delivered to a hard joint will result in a different job torque than a soft joint. This is especially true when comparing the Model T (stiff joint) to the Hydraulic load cells (soft joint). Therefore, actual job torque performance can be determined only by testing the actual assembled joint. This also means that tool performance as indicated on a tester may not equal the torque delivered to the job.

Where possible, our test bolt conversion factors have been established by tightening the bolt and nut continuously through its working range at a fixed speed. The following table describes the various test bolts, tension limits and approximating factors* which can be used to estimate the applied torque based upon the Skidmore-Wilhelm unit’s gage (tension) reading. For reference, an approximate maximum torque for each test bolt is also givenbut in any case the maximum capacity of the gage should not be exceeded.

TENSION TESTER MODEL

BOLT ASSEMBLY PART NO.

TEST BOLT SIZE

HEX SOCKET (inch)

MAXIMUM "NORM" (lb-f)

TORQUE "FACTOR"

MAX. TORQUE (Ft*lb-f)

MAX. TORQUE (N-m)

S

S-105

5/16

3/8

5,000

250

20

27

J

J-110

5/8

9/16

20,000

150

130

176

J

J-114

7/8

7/8

30,000

105

300

407

RL

R-112

3/4

1-1/4

40,000

120

350

475

RL

R-116

1

1-1/2

70,000

90

800

1,085

RL

R-120

1-1/4

2

110,000

70

1,500

2,034

H

H-112

3/4

1-1/4

40,000

120

350

475

H

H-116

1

1-1/2

70,000

90

800

1,085

H

H-120

1-1/4

2

110,000

70

1,500

2,034

H

H-124

1-1/2

2-3/8

170,000

60

2,800

3,797

K

K-120

1-1/4

2

110,000

70

1,500

2,034

K

K-124

1-1/2

2-3/8

170,000

60

2,800

3,797

K

K-128

1-3/4

2-3/4

225,000

50

4,500

6,102

K

K-132

2

3-1/8

225,000

45

5,000

6,780

K

K-140

2-1/2

3-7/8

225,000

35

6,400

8,678

To estimate torque in ft-lb, divide the gage reading by the Torque Factor.  This will give an approximate equivalent in foot-pounds.  

EXAMPLE:

Normal Force Reading70,000 lb-f
Torque Factor for RL-120 = 70
CALCULATION:  70,000 lb-f (Normal Force) / 70 (Torque Factor)
Output Torque = 1000 ft-lb

 

You have achieved a normal force reading of 70,000 lb-f using a MODEL RL with the RL-120 test bolt assembly. What is the output torque? See below: 

Conversion is based on using S-W Test Bolt Lube. Components must be in good condition. Factors are best used in the midrange of the bolt’s capacity.

Note: Testing torque does not equal torque on the application.

Follow the recommendations below for best test results when using any Skidmore- Wilhelm impact tool testing equipment:

  • Use the proper size test bolt assembly in relation to the torque you are testing to. Be sure to utilize the tension to torque conversion chart above. Using the proper test bolt assembly will give you the proper resolution for the test and maximize the life of the test bolt assembly.

  • Use the proper lubrication for test bolt assemblies. See above. Reapply the lubrication in a consistent manner. Include it in the test procedure and log when it was done.

  • Keep track of the test bolt assembly life span. Log how many tests, length of test runs, etc. Set a limit on the number of test runs each test bolt assembly will be used before it is to be replaced.

  • Inspect test bolt assembly on a regular basis. Check for over exposed metal on the test bolt/nut (coating has big gouges), elongation, large divots on all mating surface of the test bolt assembly, etc.

  • Allow sufficient cooldown periods between test runs. Check the temperature of the test bolt assembly just as you checked for the impact tool to assure it is the same before each test run.* Add this in the procedure and log when this was completed.

    *Note: Temperature can have a significant impact on the test bolt assembly. If the temperature gets too high the lubrication can breakdown prematurely causing the test bolt assembly to get damaged and/or give inaccurate results.  High temperatures also decrease the lifespan of the test bolt assembly.

Cleanliness - check that all the mating surfaces are free of debris. Degrease the test bolt assembly regularly to assure no particulates get trapped in the lubrication. Add this in the procedure and log when this was completed.