ASTM D6205-20

Standard Practice for Calibration of the James Static Coefficient of Friction Machine

SIGNIFICANCE AND USE
5.1 This practice is used to calibrate the James Machine for determination of static coefficient of friction of polish surfaces in accordance with Test Method D2047. Over considerable time and repeated use the James Machine may tend to mechanical misalignment, giving self-evident, anomalous readings. The periodic accumulation and comparison of data generated by this practice provides an indication of when the machine is no longer within the calibration limits and can no longer be expected to provide accurate and reliable data.  
5.2 Semi-automated James machines may perform an internal calibration/alignment test. These automated tests should be routinely run per the manufacturer's recommendation. If the repeatability tests of this practice indicate that the machine is out of calibration, the manufacturer should be contacted and their suggestions followed. Unqualified disassembly, modification, or adjustment may void the instrument warranty of semi-automated James Machines.
SCOPE
1.1 This practice covers the testing of the James Machine for repeatability of static coefficient of friction, relative to a standard reference interface consisting of the working surfaces of Borco2 board and standard leather shoe sole material, or a control polish film and standard leather shoe material. The practice provides basis data on the stability of the James Machine to ensure accurate static coefficient of friction determinations over time and repeated use and for determining if the James Machine is mechanically calibrated and properly aligned.  
1.2 This practice is written specifically for James Machines with manual or motorized test table transport. Variations of this practice for the calibration of versions of James Machines which are semi-automated are obvious. Calibration practices suggested by the manufacturer of semi-automatic James Machines should be followed in preference to this practice.  
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 14-Jun-2020
• ICS: 19.060 - Mechanical testing
• ICS: 61.060 - Footwear
• Technical Committee: D21 - Polishes
• Drafting Committee: D21.06 - Slip Resistance

Relations

• Refers: ASTM D2047-17 - Standard Test Method for Static Coefficient of Friction of Polish-Coated Flooring Surfaces as Measured by the James Machine
• Effective Date: 01-Nov-2017
• Refers: ASTM D4103-17 - Standard Practice for Preparation of Substrate Surfaces for Coefficient of Friction Testing
• Effective Date: 01-Mar-2017
• Refers: ASTM D4103-90(2016) - Standard Practice for Preparation of Substrate Surfaces for Coefficient of Friction Testing
• Effective Date: 01-Oct-2016
• Refers: ASTM E178-16 - Standard Practice for Dealing With Outlying Observations
• Effective Date: 01-Jun-2016
• Refers: ASTM D2825-13 - Standard Terminology Relating to Polishes and Related Materials
• Effective Date: 01-Jan-2013
• Refers: ASTM D2825-11 - Standard Terminology Relating to Polishes and Related Materials
• Effective Date: 01-Oct-2011
• Refers: ASTM D2047-11 - Standard Test Method for Static Coefficient of Friction of Polish-Coated Flooring Surfaces as Measured by the James Machine
• Effective Date: 01-Oct-2011
• Refers: ASTM D4103-90(2009) - Standard Practice for Preparation of Substrate Surfaces for Coefficient of Friction Testing
• Effective Date: 01-Mar-2009
• Refers: ASTM E29-08 - Standard Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
• Effective Date: 01-Oct-2008
• Refers: ASTM E178-08 - Standard Practice for Dealing With Outlying Observations
• Effective Date: 01-Oct-2008
• Refers: ASTM D2825-02(2008) - Standard Terminology Relating to Polishes and Related Materials
• Effective Date: 01-Mar-2008
• Refers: ASTM E29-06b - Standard Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
• Effective Date: 15-Nov-2006
• Refers: ASTM E29-06a - Standard Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
• Effective Date: 15-Sep-2006
• Refers: ASTM E29-06 - Standard Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
• Effective Date: 01-May-2006
• Refers: ASTM E29-04 - Standard Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
• Effective Date: 01-Dec-2004

Overview

ASTM D6205-20: Standard Practice for Calibration of the James Static Coefficient of Friction Machine outlines procedures for calibrating the James Machine, a key instrument used to measure the static coefficient of friction of polished surfaces. Proper calibration ensures ongoing accuracy and reliability when assessing slip resistance, especially when using Test Method ASTM D2047. Over time, mechanical misalignment or wear can cause anomalous readings, so periodic calibration is essential for maintaining consistent and trustworthy results.

This standard addresses calibration for James Machines with manual or motorized test table transport and highlights best practices for semi-automated models. Adhering to this standard supports laboratories and facilities in upholding slip resistance test validity and safety, meeting regulatory and performance-based requirements.

Key Topics

• Purpose of Calibration: Ensures the James Machine provides accurate static coefficient of friction (SCOF) readings over time, especially after repeated use which could affect mechanical alignment.
• Reference Surfaces: Calibration is performed using a standard interface, which may include a Borco board and standard leather shoe material or a control polish film with standard leather. These interfaces are critical references for establishing the repeatability of the machine.
• Calibration Procedure: Includes rigorous cleaning, assembly, alignment checks, and a standard sequence of friction measurements. The procedure emphasizes minimizing contamination and mechanical errors.
• Repeatability and Accuracy Checks: Multiple test sequences are required to calculate averages and standard deviations, ensuring measurements remain within specified limits for both accuracy and repeatability.
• Troubleshooting: The standard lists common issues such as contamination, irregular table transport, wear at pivots or guides, improper table speed, and environmental influences, guiding users through diagnostic checks.

Applications

ASTM D6205-20 is widely used in:

• Product Testing Laboratories: Provides a standardized method for certifying the performance of the James Machine when measuring the static coefficient of friction for flooring, polishes, and related materials.
• Quality Assurance: Facilities manufacturing or treating floor surfaces rely on regular calibration according to this standard to ensure slip resistance tests meet safety and regulatory standards.
• Research and Development: Accurate testing of new flooring materials or coatings requires calibration as described in ASTM D6205-20 to provide dependable SCOF data.
• Facility Safety: Entities responsible for workplace or public area safety utilize calibrated James Machines to support slip resistance measurements for risk assessment and accident prevention.

Proper use of this calibration standard helps organizations demonstrate due diligence in floor safety and slip resistance certification.

Related Standards

• ASTM D2047: Standard test method used in conjunction with the James Machine for measuring the static coefficient of friction of polish-coated flooring.
• ASTM D2825: Terminology standard for polishes and related materials, providing definitions for consistent communication.
• ASTM D4103: Practice for the preparation of substrate surfaces prior to coefficient of friction testing, enhancing test validity.
• ASTM E29: Guidelines for using significant digits in test data to determine specification conformance.
• ASTM E178: Procedures for dealing with outlying data points in test results to ensure robust analysis.
• Federal Spec KK-L-165C: Specification for standard leather materials used in the test interface, ensuring consistency in reference components.

These related standards form a comprehensive framework for friction measurement, calibration, and terminology, supporting the validity and repeatability critical to slip resistance testing.

Keywords: ASTM D6205, James Machine, static coefficient of friction, calibration, slip resistance, SCOF, Borco board, standard reference leather, flooring safety, friction testing, ASTM D2047, laboratory calibration.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D6205 − 20
Standard Practice for
Calibration of the James Static Coefficient of Friction
Machine
This standard is issued under the fixed designation D6205; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
1.1 This practice covers the testing of the James Machine 2.1 ASTM Standards:
for repeatability of static coefficient of friction, relative to a D2047 Test Method for Static Coefficient of Friction of
standard reference interface consisting of the working surfaces Polish-Coated Flooring Surfaces as Measured by the
of Borco board and standard leather shoe sole material, or a James Machine
control polish film and standard leather shoe material. The D2825 Terminology Relating to Polishes and Related Mate-
practice provides basis data on the stability of the James rials
Machine to ensure accurate static coefficient of friction deter- D4103 Practice for Preparation of Substrate Surfaces for
minationsovertimeandrepeateduseandfordeterminingifthe Coefficient of Friction Testing
James Machine is mechanically calibrated and properly E29 Practice for Using Significant Digits in Test Data to
aligned. Determine Conformance with Specifications
E178 Practice for Dealing With Outlying Observations
1.2 This practice is written specifically for James Machines
2.2 Federal Specification:
withmanualormotorizedtesttabletransport.Variationsofthis
KK-L-165C Leather, Cattlehide, Vegetable Tanned and
practice for the calibration of versions of James Machines
Chrome Tanned, Impregnated, and Soles
which are semi-automated are obvious. Calibration practices
suggested by the manufacturer of semi-automatic James Ma-
3. Terminology
chines should be followed in preference to this practice.
3.1 Definitions:For general definitions, see Test Method
1.3 This standard does not purport to address all of the
D2047 and Terminology D2825.
safety concerns, if any, associated with its use. It is the
3.2 Definitions of Terms Specific to This Standard:
responsibility of the user of this standard to establish appro-
3.2.1 Borco, n—special 5-ply vinyl drawing board cover.
priate safety, health, and environmental practices and deter-
3.2.2 Borco/standard leather reference interface,
mine the applicability of regulatory limitations prior to use.
n—working interface consisting of the white side of the Borco
1.4 This international standard was developed in accor-
material, mounted as described in this practice, and the
dance with internationally recognized principles on standard-
standard leather shoe sole material, mounted on a precision
ization established in the Decision on Principles for the
shoe pad as described in Section 7 of Test Method D2047.
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
3.2.3 control polish, n—a reference polish of known or well
Barriers to Trade (TBT) Committee.
established Static Coefficient of Friction, as determined by
repeated determinations using Test Method D2047 over a long
period of time and preferably by determinations on multiple
This practice is under the jurisdiction of ASTM Committee D21 on Polishes
and is the direct responsibility of Subcommittee D21.06 on Slip Resistance.
James Machines.
Current edition approved June 15, 2020. Published July 2020. Originally
3.2.4 control polish/standard leather reference interface,
approved in 1998. Last previous edition approved in 2012 as D6205- 12. DOI:
10.1520/D6205-20.
n—working interface consisting of a dried film of control
Borco is a registered trademark for a Danish product imported into the United
polish, applied according to the procedures of Practice D4103
States by Sierra Group, a division of Wallace Leisure Products, Inc.Available from
on standard vinyl composition tile, and the standard leather
Papyro-TexA/S, DK-2730, Herlev, Denmark; distributed in NorthAmerica through
drafting and office supply stores under the trade names “Borco,” “Vyco,” and
“Altex” board covers.
The sole source of supply of Borco known to the committee at this time is For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Phipps’s Reprographics 6920 Plainfield Rd, Cincinnati, OH 45236. If you are aware contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
of alternative suppliers, please provide this information to ASTM International Standards volume information, refer to the standard’s Document Summary page on
Headquarters.Your comments will receive careful consideration at a meeting of the the ASTM website.
1 4
responsible technical committee, which you may attend. See also: https:// Available from Standardization Documents Order Desk, Bldg 4 Section D, 700
www.thehcpa.org/resources/#1517763820809-cf4141f9-4ecb. Robbins Ave., Philadelphia, PA 19111-5094, Atten: NPODS.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6205 − 20
sole material, mounted on a precision shoe pad as described in 6.1.3 Improper Rate of Test Table Transport—Even when
Section 7 of Test Method D2047. uniform, the use of an improper rate of test table transport will
result in changes in the readings. This is most often seen in
3.2.5 standard test sequence, n—series of not less than eight
manually cranked test table transports, where the rate of travel
consecutive Static Coefficient of Friction (SCOF) determina-
is difficult to judge subjectively without training and practice.
tions made on the Borco/standard leather interface or control
Many motor driven test tables have an electrical motor speed
polish/standard leather interface in accordance with this prac-
control to adjust the rate of table travel, and this can be
tice. The arithmetic average and standard deviation of one
inadvertently changed. Too rapid a rate of travel will result in
standard test sequence is the Static Coefficient of Friction
high readings, and too slow a rate of travel will result in low
(SCOF) of the interface.
readings.
4. Summary of Practice
6.1.4 Wear or Binding—Wear or binding at the following
bearing surfaces will result in deviations from calibration and
4.1 The performance of the James Machine, in the standard
loss of machine repeatability: upper strut pivot, upper strut ball
configuration for the determination of Static Coefficient of
bearings,backplate,strutrackandpiniongearassembly,lower
Friction (SCOF), is tested relative to a standard working
strut pivot, and shoe pad cups for lower strut pivots. These
interface consisting of the surface of white Borco material in
problems are most often the result of the normal, repeated use
contact with a standard leather shoe pad, or a control polish
of the James Machine, but they can also be caused by heavy
film in contact with a standard leather shoe pad. The static
impacts, improper use, improper or inadequate periodic clean-
coefficient of friction values generated provide a basis to
ing and lubrication, or inadequate protection of the machine
establish the repeatability of the mechanical configuration of
from dirt. Wear resulting in excessive play in the bearing
the James Machine and determine whether the machine re-
surfaces will cause lower readings. Sporadic binding of the
mains within the calibration limits.
bearing surfaces and pivot points will result in loss of machine
5. Significance and Use
repeatability. Consistent binding of the bearing or pivot sur-
faces can result in high readings.
5.1 This practice is used to calibrate the James Machine for
6.1.5 Test Table not Flat—Test tables are warped out of
determination of static coefficient of friction of polish surfaces
flatnessbyheavyimpactsontothetable,storageofheavyitems
in accordance with Test Method D2047. Over considerable
on the edges of the test table, or storage of the James Machine
time and repeated use the James Machine may tend to
with the weight and strut in the upright position resting on the
mechanical misalignment, giving self-evident, anomalous
test table.Test table flatness may be assessed visually or by use
readings. The periodic accumulation and comparison of data
of a machinist’s dial gage attached to the strut rack gear and in
generated by this practice provides an indication of when the
contact with the traversing test table. Lack of adequate test
machine is no longer within the calibration limits and can no
table flatness will result in poor repeatability of data as a
longer be expected to provide accurate and reliable data.
function of the test specimen (tile) placement on the table.
5.2 Semi-automated James machines may perform an inter-
6.1.6 Test Table not Level—This is often due to the entire
nal calibration/alignment test. These automated tests should be
James machine not being level. Otherwise, this problem is
routinely run per the manufacturer’s recommendation. If the
usually caused by wear of the table transport guides, an impact
repeatability tests of this practice indicate that the machine is
on the table, or improper use of the test table for storage.Atest
out of calibration, the manufacturer should be contacted and
table which is not level will result in abnormal readings. The
their suggestions followed. Unqualified disassembly,
deviation from accurate readings will depend on the magnitude
modification, or adjustment may void the instrument warranty
and direction of the deviation of the test table from level.After
of semi-automated James Machines.
many adjustments are made to level the Test Table, use the
6. Interferences (Troubleshooting)
machinist’s square to ensure that the plane of strut motion is
perpendicular to the Test Table.
6.1 Deviations in calibration data and anomalies in machine
6.1.7 Excess Play or Movement in the Strut Rack Gear—
accuracy and repeatability are due to the following interfer-
This results from wear in the strut rack and pinion gear
ences:
assembly, loss of lubricant, or use of an improper lubricant in
6.1.1 Contamination of the Test Surfaces—These are most
the gear box. Care must be taken that there is enough freedom
commonly due to fingerprints or other soils on the working
in the movement of the strut rack gear so that the vertical
leather surface or the working surface of the Borco board, or
motionofthestrutrackgearisnotimpeded.Excessplayinany
the presence of residual materials on the Borco board from use
direction perpendicular to the vertical motion of the strut rack
of an improper cleaning solution. Generally, contamination of
gear will result in low readings.
the working surfaces will result in low readings.
6.1.2 Irregular Test Table Transport—This problem is most 6.1.8 Test Table Travel is not in the Plane of Strut Motion—
common on James Machines that derive test table transport This is usually caused by excessive movement in the strut rack
from manual cranking, which may not be smooth and uniform, gear assembly so that the plane of strut motion is rotated (see
but it may also be caused by localized wear or grit and dirt in 6.1.7), binding or excessive movement in at least one of the
thedrivemechanismoronthetransportguidesofthetesttable. upper strut pivots (see 6.1.4), or wear of the test table transport
Test table movement that is not smooth and uniform will guides (see 6.1.6). This problem results in low readings, since
provide low readings. the slipping motion of the shoe pad on the test surface is
D6205 − 20
compounded by a skewing action (greater lateral forces are 7.7 Cleaner Solution—Alcoholandwater-basedcleanerthat
applied at the interface than are recorded by the linear table does not leave a non-volatile residue, such as household
displacement shown on the chart). window glass cleaner, or equivalent.
6.1.9 Chart Board (or Chart) is not in a Plane Parallel to
7.8 Cleaning Cloth—Clean, lint-free, absorbent cloth or
the Plane of the Strut Motion—This problem is usually due to
white paper towel.
a heavy impact on the chart board, but it can also be due to the
7.9 Shoe Pad Stop—Metal block, approximately 15 cm (6
use of a pad of charts (rather than an individual sheet) attached
in.) wide and long enough to fit between the James Machine
to the chart board. The magnitude and sign of deviations in
test table retaining bar and the leading edge of the metal shoe
readingsthatresultfromthisproblemdependonthemagnitude
pad when the strut is in the full upright position and the test
and direction of the deviation of the chart board from a parallel
table is in the start position. The shoe pad stop end shall be
configuration with respect to the plane of strut motion.
constructed so that it contacts only the machined shoe pad and
6.1.10 Warped, or “Out of True” Back Plate, Chart Board,
not the leading edge of the leather. See Fig. 2. The shoe pad
Strut Arm, or Strut Rack Gear—Though this problem can be
stop prevents slippage of the shoe pad during movement of the
the result of heavy impact, it is most commonly the result of
test table during calibration of the James Machine.
not maintaining the James Machine in a controlled temperature
7.10 Spring Clips or Drafting Tape.
environment. The James Machine is a complex assembly of
parts that are rigidly held in alignment by bead welds or bolts. 7.11 Machinist’s Square.
Since many of the parts are constructed of different metals,
8. Test Surface
temperature changes (and the different coefficients of thermal
expansion) will result in very large forces being applied to the
8.1 For James Machine calibration the test surface assembly
joints or to the components themselves. This can result in a
will consist of the working interface between the standard
distortion or warping of the parts, particularly those which are
reference leather, mounted on the shoe pad, and the mounted
large or have at least one long dimension.
Borco board reference surface, or between the mounted stan-
dard reference leather and the control polish applied and
7. Apparatus
equilibrated on a Vinyl Composition Tile as described in Test
Method D2047 and Practice D4103.
5,6
7.1 James Machine —See Fig. 1.
8.2 The test surfaces shall not be altered, adulterated, or
6,7
7.2 Standard Reference Leather —Leather sole material
contaminated in any matter, except for the cleaning procedure
conforming to Federal Specification KK-L-165C (Type 1,
which begins
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D6205 − 12 D6205 − 20
Standard Practice for
Calibration of the James Static Coefficient of Friction
Machine
This standard is issued under the fixed designation D6205; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This practice covers the testing of the James Machine for repeatability of static coefficient of friction, relative to a standard
reference interface consisting of the working surfaces of Borco board and standard leather shoe sole material, or a control polish
film and standard leather shoe material. The practice provides basis data on the stability of the James Machine to ensure accurate
static coefficient of friction determinations over time and repeated use and for determining if the James Machine is mechanically
calibrated and properly aligned.
1.2 This practice is written specifically for James Machines with manual or motorized test table transport. Variations of this
practice for the calibration of versions of James Machines which are semi-automated are obvious. Calibration practices suggested
by the manufacturer of semi-automatic James Machines should be followed in preference to this practice.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D2047 Test Method for Static Coefficient of Friction of Polish-Coated Flooring Surfaces as Measured by the James Machine
D2825 Terminology Relating to Polishes and Related Materials
D4103 Practice for Preparation of Substrate Surfaces for Coefficient of Friction Testing
E29 Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
E178 Practice for Dealing With Outlying Observations
2.2 Federal Specification:
KK-L-165C Leather, Cattlehide, Vegetable Tanned and Chrome Tanned, Impregnated, and Soles
3. Terminology
3.1 Definitions:For general definitions, see Test Method D2047 and Terminology D2825.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 Borco, n—special 5-ply vinyl drawing board cover.
This practice is under the jurisdiction of ASTM Committee D21 on Polishes and is the direct responsibility of Subcommittee D21.06 on Slip Resistance.
Current edition approved Oct. 1, 2012June 15, 2020. Published October 2012July 2020. Originally approved in 1998. Last previous edition approved in 20062012 as
D6205- 06.12. DOI: 10.1520/D6205-12.10.1520/D6205-20.
Borco is a registered trademark for a Danish product imported into the United States by Sierra Group, a division of Wallace Leisure Products, Inc. Available from
Papyro-Tex A/S, DK-2730, Herlev, Denmark; distributed in North America through drafting and office supply stores under the trade names “Borco,” “Vyco,” and “Altex”
board covers.
The sole source of supply of Borco known to the committee at this time is Phipps’s Reprographics 6920 Plainfield Rd, Cincinnati, OH 45236. If you are aware of alternative
suppliers, please provide this information to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of the responsible technical
committee, which you may attend. See also: https://www.thehcpa.org/resources/#1517763820809-cf4141f9-4ecb.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from Standardization Documents Order Desk, Bldg 4 Section D, 700 Robbins Ave., Philadelphia, PA 19111-5094, Atten: NPODS.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6205 − 20
3.2.2 Borco/standard leather reference interface, n—working interface consisting of the white side of the Borco material,
mounted as described in this practice, and the standard leather shoe sole material, mounted on a precision shoe pad as described
in Section 7 of Test Method D2047.
3.2.3 control polish, n—a reference polish of known or well established Static Coefficient of Friction, as determined by repeated
determinations using Test Method D2047 over a long period of time and preferably by determinations on multiple James Machines.
3.2.4 control polish/standard leather reference interface, n—working interface consisting of a dried film of control polish,
applied according to the procedures of Practice D4103 on standard vinyl composition tile, and the standard leather sole material,
mounted on a precision shoe pad as described in Section 7 of Test Method D2047.
3.2.5 standard test sequence, n—series of not less than eight consecutive Static Coefficient of Friction (SCOF) determinations
made on the Borco/standard leather interface or control polish/standard leather interface in accordance with this practice. The
arithmetic average and standard deviation of one standard test sequence is the Static Coefficient of Friction (SCOF) of the interface.
4. Summary of Practice
4.1 The performance of the James Machine, in the standard configuration for the determination of Static Coefficient of Friction
(SCOF), is tested relative to a standard working interface consisting of the surface of white Borco material in contact with a
standard leather shoe pad, or a control polish film in contact with a standard leather shoe pad. The static coefficient of friction
values generated provide a basis to establish the repeatability of the mechanical configuration of the James Machine and determine
whether the machine remains within the calibration limits.
5. Significance and Use
5.1 This practice is used to calibrate the James Machine for determination of static coefficient of friction of polish surfaces in
accordance with Test Method D2047. Over considerable time and repeated use the James Machine may tend to mechanical
misalignment, giving self-evident, anomalous readings. The periodic accumulation and comparison of data generated by this
practice provides an indication of when the machine is no longer within the calibration limits and can no longer be expected to
provide accurate and reliable data.
5.2 Semi-automated James machines may perform an internal calibration/alignment test. These automated tests should be
routinely run per the manufacturer’s recommendation. If the repeatability tests of this practice indicate that the machine is out of
calibration, the manufacturer should be contacted and their suggestions followed. Unqualified disassembly, modification, or
adjustment may void the instrument warranty of semi-automated James Machines.
6. Interferences (Troubleshooting)
6.1 Deviations in calibration data and anomalies in machine accuracy and repeatability are due to the following interferences:
6.1.1 Contamination of the Test Surfaces—These are most commonly due to fingerprints or other soils on the working leather
surface or the working surface of the Borco board, or the presence of residual materials on the Borco board from use of an improper
cleaning solution. Generally, contamination of the working surfaces will result in low readings.
6.1.2 Irregular Test Table Transport—This problem is most common on James Machines that derive test table transport from
manual cranking, which may not be smooth and uniform, but it may also be caused by localized wear or grit and dirt in the drive
mechanism or on the transport guides of the test table. Test table movement that is not smooth and uniform will provide low
readings.
6.1.3 Improper Rate of Test Table Transport—Even when uniform, the use of an improper rate of test table transport will result
in changes in the readings. This is most often seen in manually cranked test table transports, where the rate of travel is difficult
to judge subjectively without training and practice. Many motor driven test tables have an electrical motor speed control to adjust
the rate of table travel, and this can be inadvertently changed. Too rapid a rate of travel will result in high readings, and too slow
a rate of travel will result in low readings.
6.1.4 Wear or Binding—Wear or binding at the following bearing surfaces will result in deviations from calibration and loss of
machine repeatability: upper strut pivot, upper strut ball bearings, back plate, strut rack and pinion gear assembly, lower strut pivot,
and shoe pad cups for lower strut pivots. These problems are most often the result of the normal, repeated use of the James
Machine, but they can also be caused by heavy impacts, improper use, improper or inadequate periodic cleaning and lubrication,
or inadequate protection of the machine from dirt. Wear resulting in excessive play in the bearing surfaces will cause lower
readings. Sporadic binding of the bearing surfaces and pivot points will result in loss of machine repeatability. Consistent binding
of the bearing or pivot surfaces can result in high readings.
6.1.5 Test Table not Flat—Test tables are warped out of flatness by heavy impacts onto the table, storage of heavy items on the
edges of the test table, or storage of the James Machine with the weight and strut in the upright position resting on the test table.
Test table flatness may be assessed visually or by use of a machinist’s dial gage attached to the strut rack gear and in contact with
the traversing test table. Lack of adequate test table flatness will result in poor repeatability of data as a function of the test
specimen (tile) placement on the table.
6.1.6 Test Table not Level—This is often due to the entire James machine not being level. Otherwise, this problem is usually
caused by wear of the table transport guides, an impact on the table, or improper use of the test table for storage. A test table which
D6205 − 20
is not level will result in abnormal readings. The deviation from accurate readings will depend on the magnitude and direction of
the deviation of the test table from level. After many adjustments are made to level the Test Table, use the machinist’s square to
ensure that the plane of strut motion is perpendicular to the Test Table.
6.1.7 Excess Play or Movement in the Strut Rack Gear—This results from wear in the strut rack and pinion gear assembly, loss
of lubricant, or use of an improper lubricant in the gear box. Care must be taken that there is enough freedom in the movement
of the strut rack gear so that the vertical motion of the strut rack gear is not impeded. Excess play in any direction perpendicular
to the vertical motion of the strut rack gear will result in low readings.
6.1.8 Test Table Travel is not in the Plane of Strut Motion—This is usually caused by excessive movement in the strut rack gear
assembly so that the plane of strut motion is rotated (see 6.1.7), binding or excessive movement in at least one of the upper strut
pivots (see 6.1.4), or wear of the test table transport guides (see 6.1.6). This problem results in low readings, since the slipping
motion of the shoe pad on the test surface is compounded by a skewing action (greater lateral forces are applied at the interface
than are recorded by the linear table displacement shown on the chart).
6.1.9 Chart Board (or Chart) is not in a Plane Parallel to the Plane of the Strut Motion—This problem is usually due to a heavy
impact on the chart board, but it can also be due to the use of a pad of charts (rather than an individual sheet) attached to the chart
board. The magnitude and sign of deviations in readings that result from this problem depend on the magnitude and direction of
the deviation of the chart board from a parallel configuration with respect to the plane of strut motion.
6.1.10 Warped, or “Out of True” Back Plate, Chart Board, Strut Arm, or Strut Rack Gear—Though this problem can be the
result of heavy impact, it is most commonly the result of not maintaining the James Machine in a controlled temperature
environment. The James Machine is a complex assembly of parts that are rigidly held in alignment by bead welds or bolts. Since
many of the parts are constructed of different metals, temperature changes (and the different coefficients of thermal expansion) will
result in very large forces being applied to the joints or to the components themselves. This can result in a distortion or warping
of the parts, particularly those which are large or have at least one long dimension.
7. Apparatus
5,6
7.1 James Machine —See Fig. 1.
6,7
7.2 Standard Reference Leather —Leather sole material conforming to Federal Specification KK-L-165C (Type 1, Class 6).
7.3 Leather/Shoe Pad Assembly—Reference leather mounted on the machined shoe pad.
7.4 Borco Board —drafting and drawing board working surface cover.
6,8
7.5 Reference Surface —Aluminum plate, 30.48 by 30.48 by 0.3175 cm (12 by 12 by 0.125 in.), which has been machined
flat, to which 30.48 by 30.48 cm (12 by 12 in.) Borco board has been mounted, white side up.
6,9
7.6 Chart.
7.7 Cleaner Solution—Alcohol and water-based cleaner that does not leave a non-volatile residue, such as household window
glass cleaner, or equivalent.
7.8 Cleaning Cloth—Clean, lint-free, absorbent cloth or white paper towel.
7.9 Shoe Pad Stop—Metal block, approximately 15 cm (6 in.) wide and long enough to fit between the James Machine test table
retaining bar and the leading edge of the metal shoe pad when the strut is in the full upright position and the test table is in the
start position. The shoe pad stop end shall be constructed so that it contacts only the machined shoe pad and not the leading edge
of the leather. See Fig. 2. The shoe pad stop prevents slippage of the shoe pad during movement of the test table during calibration
of the James Machine.
7.10 Spring Clips or Drafting Tape.
7.11 Machinist’s Square.
8. Test Surface
8.1 For James Machine calibration the test surface assembly will consist of the working interface between the standard reference
leather, mounted on the shoe pad, a
...