Screw Withdrawal Strength in 9Wood’s Assemblies · PDF file[SCREW WITHDRAWAL STRENGTH IN...

2009

Jonathan C. Gates

9Wood Inc.

July 2009

Screw Withdrawal Strength in 9Wood’s Assemblies

Test Evaluation Report

[SCREW ] WITHDRAWAL STRENGTH IN 9WOOD’S ASSEMBLIES July 2009

9Wood Inc. | 0BAbstract: ii

Abstract: This report analyzes the effect of screw withdrawal resistance and its response to

various setting practices and wood properties. A total of 294 screws were subjected to a screw

withdrawal test to evaluate the performance of their holding strength under various testing

conditions. These testing conditions included; three screw torque ranges (weak, standard,

over-torque), two penetration depths (1/2” and 5/8”), three board densities (low, standard,

high), two moisture contents (low and standard), and the use of pilot holes. Results showed

that maximum holding strength was most influenced by increasing screw penetration depth,

avoiding pilot holes, and using the proper torque when driving screws. Over-torquing the

screw had the greatest negative effect on screw withdrawal resistance with a 77% decrease in

maximum load. Screw penetration depth also had a large effect on screw withdrawal resistance

with a decrease in 32% from an average of 175 lbf ( 5/8” depth of insertion) to 118 lbf (1/2”

depth of insertion).

[SCREW WITHDRAWAL STRENGTH IN 9WOOD’S ASSEMBLIES] July 2009

9Wood Inc. iii

Table of Contents: Page Number Abstract ....................................................................................................................................................... ii

Introduction ............................................................................................................................................... 1

Literature Review ................................................................................................................................... 1-2

Materials and Methodology ................................................................................................................ 3-10

Figure 1: Testing machine used ............................................................................................................................. 3

Figure 1.1: Screws used ........................................................................................................................................ 3

Figure 2: Dimensions of sample boards ............................................................................................................... 4

Figure 3: Distance between screws ...................................................................................................................... 4

Figure 4: Diagram of sample boards with various testing conditions ................................................................... 5

Figure 5: Picture of board dimensions and screw spacing ................................................................................... 6

Figure 6: Picture of weighing mechanism ............................................................................................................. 6

Figure 7: Picture of drill bit size and machine used for pilot holes ....................................................................... 7

Table 1: Drill specifications .................................................................................................................................... 8

Figure 8: Picture of torque tester and hand drill used ........................................................................................... 8

Figure 9: Picture of the spacer used in setting the screws ................................................................................... 8

Table 2: Clutch setting and corresponding torque ranges .................................................................................. 9

Figure 10: Graph of torque ranges ........................................................................................................................ 9

Equation 1: Oven-Dry moisture content formula ................................................................................................. 10

Results and Discussion ..................................................................................................................... 10-13

Figure 11: Graph of average screw withdrawal strength for each sample batch ............................................... 10

Table 3: Average board density ......................................................................................................................... 11

Table 4: Average moisture content .................................................................................................................... 11

Table 5: ANOVA analysis for all data .................................................................................................................. 11

Figure 12: Graph of average screw withdrawal strength for significant variables .............................................. 12

Table 6: ANOVA analysis for all data excluding density and conditioning (MC) ................................................ 12

Conclusion ............................................................................................................................................... 13

Literature Cited ........................................................................................................................................ 14

Appendices ......................................................................................................................................... 15-27

Appendix I: Test Data ...................................................................................................................................... 16-19

Appendix II: All Data ANOVA Analysis ............................................................................................................. 20-24

Appendix III: All Data Excluding Density and Conditioning (MC) ANOVA Analysis ........................................ 25-27

Literature .......................................................................................................................................... 28-End


9Wood Inc. | 1BIntroduction: 1

Introduction: Screws provide an excellent method for fastening many particleboard and MDF products. The

maximum holding strength of a screw is determined in part by the panel’s internal bond (IB) strength.

In most cases, denser boards tend to have the higher screw holding strength (Eckelman, 1990). The

specifications, performance, and limits of a specific panel can be determined by testing the panel’s IB

strength against various conditions.

In this report, screw withdrawal resistance in Flakeboard VESTA FR particleboard was

investigated. The objective of this test was to evaluate the holding capacity of different screw

penetration lengths, screw torque ranges, and setting practices (i.e. pilot hole, no pilot hole) as they

are applied to Flakeboard VESTA FR particleboard. The test also examined the effects of panel

moisture content (MC) and density with each variable in an effort to characterize panel variability.

Literature Review: Previous studies have shown a strong correlation between screw withdrawal resistance,

moisture content, screw specifications, screw depth of insertion, torque strength, as well as the density

and IB strength of particleboard. Eckelman’s studies during the early 90’s have suggested that:

• There is essentially no difference in the holding strengths of seven types of #8 (0.164 in,

4.17mm) particleboard screws in a 1/2” (12.7mm) thick particleboard with a density of 49

pounds per cubic foot (pcf). All screws were inserted, with the use of a pilot hole, to the depth

of 3/32” (2.38mm). Type “A” sheet metal screws, common wood screws, and five types of

commercially available particleboard screws were included in the tests.

• Screw holding strength is strongly related to the internal bond (IB) strength of the board.

Particleboard’s density is an indicator of the panel’s IB strength. Therefore, screw withdrawal

strength can be significantly improved through the use of boards with higher density values

(i.e. high IB strength).

• The holding power of wood screws decreases with increasing moisture content. Panels of 30%

MC and subjected to 40% of their ultimate load failed within 20 days of exposure to such force.

Under identical loading conditions, there was no failure from such screws in boards with a MC

of 8%.

[SCREW ] WITHDRAWAL STRENGTH IN 9WOOD’S ASSEMBLIES July 2009

9Wood Inc. | 2BLiterature Review: 2

• Pilot holes should be at least 85% (and no larger than 90%) of the root diameter of the screw.

In the case of threaded metal connectors, manufacturers recommend that pilot hole diameter

be the same as the root diameter.

• Pilot holes should always be drilled deeper than the depth of insertion of the screw in order to

avoid splitting in the edges of a board or delamination of the face of a board.

• Although it is considered good practice to use pilot holes, it is also important to note that use of

pilot holes in the face of a board may increase withdrawal strength by only 10% to 15%.

Therefore, the use of pilot holes may not always be justified from a product engineering

viewpoint.

• The holding strength of four screw types (#8, #10, #12, and #14) was at worst 13% less when

pilot holes were not used as opposed to when the optimum size hoes were used.

• The withdrawal strength of screws is strongly related to the depth of insertion (i.e. there is

essentially a directly proportional increase in strength with depth of insertion). Increasing the

depth of insertion of a screw in the face of a board from 3/4" to 1”, for example, will increase

holding strength by approximately 30%.

• Driving force, or torque, is important in that it is desirable to have a significant difference

between the amount of torque required to “set” the screw and the amount of torque required to

“strip” the threads. Essentially, there are two solutions to the problem of overdriving: A) use a

higher dense board, or B) use guns which allow precise control of driving torque to drive the

screws.

Other studies have speculated on the correlation between screw withdrawal resistance and

density. This can be seen in the studies carried out by Johnson (1967); Yahya and Abdul-Kader

(1998); Mallari et al. (1989), Wong et al. (1999); and Poblette et al. (1996). Their findings suggest that

linear or polynomial equations incorporating board density, screw dimensions, and depth of

penetration can be derived in an effort to predict a panel’s screw withdrawal resistance (Smith et al.,

2006).

Although these equations and studies provide a starting point for evaluating the performance of

specific products under ideal conditions, particleboard properties vary widely between boards and

especially between panel manufacturers. This makes it difficult to apply these findings and equations

to the specifications of other particleboard panels. Thus, performance standards must be specific for

the panel product produced by a given manufacturer.


9Wood Inc. | 3BMaterials and Methodology: 3

Materials and Methodology: 1. Referenced Documents:

1.1. ASTM Standards: D 1037 “Standard Test Method for Evaluating Properties of Wood-Based Fiber and Particle Panel Materials.”

1.1.1. “Direct Screw Withdrawal Test” 2. Summary of Test Method:

2.1. Specimens consisted of prisms of Flakeboard VESTA FR particleboard (with face veneers) with screws driven perpendicular to panel face. The screws were withdrawn at a uniform rate of speed (0.60 in/min) by means of a certified ASTM testing machine until maximum load was recorded.

3. Significance and Use: 3.1. Refer to D 1037 “Standard Test Method for Evaluating Properties of Wood-Based Fiber and

Particle Panel Materials” under the section “Direct Screw Withdrawal Test” 4. Apparatus:

4.1. Figure 8 on page 145 (Annual Book of ASTM Standards; 1997). 4.2. Actual testing machine is shown below in Figure 1.

Figure 1: Testing machine used in screw withdrawal test. Figure 1.1: Screws used in test.

5. Test Materials: 5.1. Screws:

5.1.1. Screws were zinc plated, #8, self-piercing point, sheet metal screws. 5.1.2. The length of the screw was based on the depth of penetration (1/2” and 5/8”) into the

particleboard core (Figure 1.1).

3/4”

1”



5.2. Wood: 5.2.1. The test specimens were 3” (76mm) in width by 12” (305mm) in length by 3/4" (19mm)

in thickness (Figure 2). 5.2.2. Test specimens were made from Flakeboard VESTA FR particleboard with face and

back veneers of various wood species. 6. Sampling:

6.1. Constants: 6.1.1. Wood (3/4” Flakeboard VESTA FR particleboard with various face and back veneers) 6.1.2. Screw gauge (#8)

6.2. Variables: 6.2.1. Screw thread penetration depth (1/2” and 5/8”) 6.2.2. Torque ranges for driving screws (weak, standard, over-torque)

Note: Torque range differed with each test batch (refer to Table 1). 6.2.3. Screw setting practice (pilot hole, no-pilot hole) 6.2.4. Particleboard MC. Conditioned in Hot-Dry chamber (30˚C, 20% RH), and ASTM

standard chamber (20˚C, 65% RH) Note: RH = Relative Humidity

6.2.5. Density of particleboard (Low, Standard, High) 6.3. 6 batches of 13 sample boards were tested under various conditions and 2 batches of 10

sample boards were tested in conjunction with the 6 batches to evaluate the effects of board density (refer Figure 4).

7. Test Specimen 7.1. For the basic withdrawal tests, the specimens were 3” (76mm) in width x 12” (305mm) in

length x 3/4" (19mm) in thickness (Figure 2).

Figure 2: Dimensions of sample boards.

7.2. Three screws were driven into the panel, perpendicular to the face. Each screw was no closer

than 3 inches from the end and 1.5 inches from the side of the panel. Screws were also at least 3 inches from any neighboring screw (Figure 3).

Figure 3: Distance of screws from edges of panel and neighboring screw.

12”

3”

¾”

3” 3” 3”3”

1.5” 1.5”



7.3. A total of 98 samples were tested as follows: (Refer to Figure 4). 7.3.1. 23 samples: 1/2" screw thread penetration depth, Pilot hole, 3 torque ranges (weak,

standard, and over-torque), and 2 density ranges (standard and low). 7.3.2. 23 samples: 1/2" screw thread penetration depth, No-Pilot hole, 3 torque ranges (weak,

standard, and over-torque), and 2 density ranges (standard and high). 7.3.3. 26 samples: 5/8” screw thread penetration depth, Pilot hole, 3 torque ranges (weak,

standard, and over-torque), and 2 moisture contents (standard and low). 7.3.4. 26 samples: 5/8” screw thread penetration depth, No-Pilot hole, 3 torque ranges (weak,

standard, and over-torque), and 2 moisture contents (standard and low).

Figure 4: Diagram of sample boards and the various testing conditions for each sample batch.

Standard Over‐torqueWeak

1/2" / Pilot hole / Standard Density


1/2" / Pilot hole / Low Density


1/2" / No‐ Pilot hole / High Density


5/8" / Pilot hole / Standard Density


5/8" / No‐ Pilot hole / Standard Density

ASTM Conditioned

ASTM Conditioned

ASTM Conditioned

Hot/Dry Conditioned ASTM Conditioned

Hot/Dry Conditioned ASTM Conditioned

X 13

X 10

X 10

X 13 X 13

X 13 X 13

98 Sample Boards294 Screw‐Pulls Total

7.3.1

7.3.1

7.3.2

7.3.2

7.3.3

7.3.4


1/2" / No‐ Pilot hole / Standard Density

ASTM Conditioned

X 13



7.4. 13 samples from both the 5/8” Pilot-hole and No Pilot-hole batches were conditioned to stable weight in the Hot/Dry room prior to testing. The remaining batches were conditioned in the ASTM room prior to testing.

7.5. 10 samples of low density and 10 samples of high density from the 1/2" screw thread penetration boards were tested in conjunction with the other batches to assess the effect of density variability in the board.

8. Conditioning: 8.1. Sample boards from the 5/8” screw thread penetration batches were conditioned in both the

ASTM room (20˚C, 65% RH) and the Hot/Dry room (30˚C, 20% RH). 8.2. Sample boards from the 1/2" screw thread penetration batches were conditioned only in the

ASTM room. 9. Procedure:

9.1. Panels from various locations in 9Wood’s shop were randomly selected and 98 sample boards were cut from the panels (refer to Figure 2 and Figure 5 below for dimensions).

Figure 5: Picture showing the dimensions of the sample boards and spacing of screws.

9.2. Sample boards were numbered, weighed, and recorded immediately after cutting (refer to Figure 6).

Figure 6: Picture showing the weighing mechanism used.



9.3. Sample boards were then prepared with the correct screw spacing through the use of a template. (Refer to Figure 3 and Figure 5 for screw spacing).

9.4. From the 98 sample boards, 10 of the highest dense boards and 10 of the lowest dense boards were separated from the remaining 78 and labeled (this was done to test the effect of panel density on screw withdrawal resistance).

9.5. The remaining 78 sample boards were then randomly allocated and labeled with their testing specifications (i.e. screw penetration, density, and Pilot hole / No Pilot hole).

9.5.1. Refer to Figure 4 for sample board batches. 9.6. The 36 sample boards labeled with “Pilot hole” as well as all 10 samples from the low density

sample boards were prepared with three pilot holes (one for each screw). The pilot holes were drilled using a drill press with a 7/64” bit and a 5/8” penetration (Figure 7).

Figure 7: Size of drill bit (left) and machine used to drill pilot holes (right).

9.7. Torque ranges for a Makita 18 volt cordless driver drill were determined using an “Express Assembly Products, LLC. Torque Tester. ESP-10. Max 88.5 lbf/in” device (Figure 8). Each clutch setting was tested 5 times to establish a torque range (refer to Table 2 and Figure 10 for torque table and chart).

9.8. Torque ranges were then determined by comparing the hand drills clutch setting to the desired screw driving practice (i.e. a weak drive, a standard drive, and an over-torque drive). Each depth of screw penetration and screw setting practice (pilot hole, no-pilot hole) had its own unique clutch setting (refer to Table 1 on the following page).

9.9. Once the torque ranges and the appropriate clutch settings were determined, screws were fastened into the sample boards using the Makita 18 volt cordless driver drill to the appropriate torque range (refer to Figure 8 for drill picture). A spacer was used to ensure that there was enough clearance under the head of the screw to accommodate the gripping mechanism on the testing machine (Figure 9).

9.9.1.1. Note: Weak torque settings did not always set directly against spacer.



Table 1: Drill specifications for each screw setting practice and torque range.

Figure 8: Torque testing device used for determining the appropriate clutch setting (left) and the hand drill used in testing (right).

Figure 9: Picture depicting the use of a spacer when driving a screw into a sample board.

Makita 18 volt Drill Specs Screw Penetration

Depth Pilot hole? Torque Range Name

Drill Clutch Setting

Torque Range (lbf-in)

Speed Setting

1/2"

Yes Weak 1 9.80 - 15.90

2 Standard 4 21.25 - 30.00 Over-torque 10 43.35 - 47.10

No Weak 3 16.80 - 25.20


5/8"

Yes Weak 4 21.25 - 30.00


No Weak 6 30.15 - 36.80




Measured Torque Range (lbf-in) with Speed setting #2

Test Clutch Setting

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

1 16 15 18 30 29 37 38 43 42 45 50 55 61 55 61 65

2 10 16 17 26 33 30 31 47 47 47 51 53 58 61 65 63

3 10 18 18 29 33 34 33 37 47 45 50 48 59 62 65 64

4 12 16 23 27 26 36 36 43 40 43 47 45 55 58 61 70

5 13 11 25 21 28 31 37 35 45 47 53 53 58 61 60 67

Average 12.2 15.0 20.1 26.7 29.7 33.5 34.8 41.1 44.1 45.5 50.2 50.5 58.1 59.4 62.3 65.9

Table 2: Clutch setting and corresponding torque ranges for Makita 18 volt cordless driver drill (speed 2).

Figure 10: Each clutch setting and its comparable average torque range with confidence intervals.

Note: Speed 1 was not used in this study. Values were determined only for later reference.

9.10. Sample boards were then separated and conditioned to the desired moisture content in

either the ASTM or Hot-Dry conditioning room for at least 5 days. 9.11. Direct screw withdrawal was then performed on the sample boards using an ASTM

standard testing machine (refer to Figure 1). The maximum load received was recorded for each screw.

9.12. Sample boards were then weighed immediately after testing. 9.13. After weighing, the sample boards were then oven-dried to determine average moisture

content. Boards were left in the oven for approximately 24 hours. Moisture content was determined using oven dry method (refer to Equation 1).

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Average

Torqu

e (lb

f‐in)

Clutch Setting

Speed 1

Speed 2


9Wood Inc. | 4BResults and Discussion: 10

Equation 1: Formula used to derive Oven Dry Moisture Content.

9.14. Statistical analysis was performed to determine the significance of each variable to the maximum load received by screw withdrawal. Each variable: density, conditioning (MC), screw penetration, screw setting practice, and torque ranges were tested for statistical significance against maximum holding strength by an “analysis of variance” (ANOVA).

9.15. A second ANOVA was performed excluding density and conditioning (MC) because of their insignificance to the study. (Refer to Table 4 for ANOVA tables).

9.16. Conclusions were drawn from results.

Results and Discussion: There were noticeable differences in average maximum load (lbf) for the various treatments

(refer to Figure 11 below).

Figure 11: Average Maximum Screw Withdrawal Strengths for each Torque Range and Sample Batch.

Note: The complete data tables are presented in Appendix I.

131

149

128

153

213224

217 213

174 173164

187

247 246 246

265

4841

31 33

73

5240

86

0

50

100

150

200

250

300

ASTM ASTM Low D High D ASTM ASTM Hot/Dry Hot/Dry

1/2" Pilot 1/2" No Pilot 1/2" Pilot 1/2" No Pilot 5/8" Pilot 5/8" No Pilot 5/8" Pilot 5/8" No Pilot

Average

Maxim

um Loa

d (lb

f)

Batches

Weak Standard Over Torque

Torque Range

jgates

Stamp



The largest differences occurred in screw torque ranges and screw penetration depths.

Neither density nor conditioning to a lower MC had any significant impact on screw withdrawal load [p-

value of 0.58 and 0.77 respectively] (refer to Table 5). Density varied by 4.3 lb/ft3 among the panels;

this value was too small to affect the holding strength of the screw (Table 3). Similarly, moisture

content varied by only 4.2%OD Basis between the two conditioning methods and also had no effect on the

holding strength of the screw (Table 4). Although these results may differ from previous studies, the

variances are easily explained by the small ranges in density and MC values. However, this does not

conclude that either should be overlooked. The experimental design of this test was inconsistent

when testing the effects of both density and MC, yet did not affect the significance of the other

variables (i.e. screw penetration depth, screw torque ranges, and screw setting practice). Better

results would have come from testing panels with a wide range in MC and density.

Table 3 Table 4

Average Board Density Average Board Moisture Content

Batch Density Average (lb/ft3)

St. Dev. (lb/ft3) Conditions

Average (% OD Basis)

St. Dev. (% OD Basis)

Low 45.1 0.43 ASTM 12.5% 0.40% Standard 47.7 0.80 Hot-Dry 8.3% 0.26%

High 49.4 0.32 Range 4.2% Range 4.3

Table 3 & 15: Averages, standard deviations, and range of sample board’s density and moisture content.

Table 5: All Data ANOVA Analysis

Source Sum of Squares

Degrees of Freedom

Mean Square

F-Ratio P-Value

A: Screw torque range 1.46E+06 2 730075 497.74 <0.0001 B: Screw setting practice 2413.47 1 2413.47 1.65 0.2006 C: Screw penetration depth 125403 1 125403 85.5 <0.0001 D: Density 1587.44 2 793.722 0.54 0.5827 E: Conditioning (MC) 121.194 1 121.194 0.08 0.7740

Table 5: Analysis of variance of all variables and their significance on Maximum Load (lbf). The ANOVA table decomposes the variability of Maximum load (lbf) into contributions due to various factors. The contribution of each factor was measured having removed the effects of all other

factors. The P-values test the statistical significance of each of the factors. Since 2 P-values are less than 0.05, these factors have a statistically significant effect on Maximum load (lbf) at the

95.0% confidence level.

Since there was no significant affect on maximum load (lbf) from either moisture content or

density, the data was pooled together and reanalyzed (Figure 12). Once again, screw torque range,



screw penetration length and screw setting practice (Pilot hole / No Pilot hole) significantly affected

screw holding capacity (refer to Table 6: All Data Excluding Density and Conditioning(MC) ANOVA

Analysis). However, screw setting practice (Pilot hole / No Pilot hole) was only significant at 90%

confidence interval [p-value = 0.0568] (Refer to appendices for statistics). The data also suggests that

the use of a pilot hole decreases maximum load by 4%. These results differ from previous studies and

show that by not using a pilot hole, the panel becomes densified around the screw, creating a slightly

higher holding capacity.

Figure 12: Graph that depicts the effects of Screw Torque Ranges, Screw Setting Practice (Pilot hole / No Pilot hole), and Screw Penetration Length on Maximum Load Received by Screw

Withdrawal. Density and Conditioning were eliminated and pooled with the rest of the data due to signs of insignificancy.

Note: Error bars represent one standard deviation.

Table 6: All Data Excluding Density and Conditioning (MC) ANOVA Analysis Source Sum of Squares Degrees of Freedom Mean Square F-Ratio P-Value

A: Screw torque range 1.46E+06 2 730075 500.92 <0.0001 B: Screw setting practice 5332.5 1 5332.5 3.66 0.0568 C: Screw penetration depth 254397 1 254397 174.55 <0.0001

Table 6: Analysis of variance of all variables excluding density and conditioning (MC) and their significance on Maximum Load (lbf). Since 2 P-values are less than 0.05, these factors have a

statistically significant effect on Maximum load (lbf) at the 95.0% confidence level.

130 151 215 218170 179 247 25540 37 56 69

‐50

0

50

100

150

200

250

300

1/2" Pilot 1/2" No Pilot 5/8" Pilot 5/8" No pilot

Average

Maxim

um Loa

d (lb

f)

Batches

Weak Standard Over TorqueTorque Range


9Wood Inc. | 5BConclusion: 13

The screw torque range and screw penetration depth had the highest effect on the maximum

load (lbf). By over-torquing the screw, there was an average decrease of 163.6 lbf (or 77%) , and by

under-torquing the screw, there was an average decrease of 34.2 lbf (or 16%) (refer to appendices for

statistics). This signifies the relevance of how the screw is driven. Over-torquing the screw creates a

higher risk of failure. Screw penetration had the same effect on maximum load (lbf). When varying

from 5/8” penetration to 1/2" penetration, the average maximum load (lbf) decreased by an average of

56.71 lbf (or 32%).

This data indicates that screw torque range and screw penetration depth had the greatest

effect on the maximum holding strength of the screw [p-value in both cases are <0.001] (Refer to

Table 6).

Conclusion: Increasing screw penetration depth, avoiding pilot holes, and using the proper torque when

driving screws all significantly improve screw holding capacity.

Over-torquing screws produces the greatest decrease in average maximum load (-163.6 lbf or -

77%). Under-torqued screws also pose a threat by decreasing the maximum load by an average of

34.2 lbf (or 16%). Routine quality control checks should to be incorporated to ensure that screw guns

are properly set to fasten screws with a sufficient torque. Substantial consequences may occur if

screws aren’t properly fastened.

By increasing the screw penetration length from 1/2" to 5/8” depth, the maximum load is

increased by an average of 56.71 lbf (or 32%). This shows that depth of penetration is an important

factor when considering maximum holding capacity.

Density and conditioning (MC) had no significant effect on maximum load at the levels tested.

Note: this is in contrast with previous studies that found a correlation between density and screw

withdrawal resistance as well as MC and screw withdrawal resistance.

NOTE: Data presented is specifically related to Flakeboard’s VESTA Fire Rated Particleboard

with a face and back veneer.


9Wood Inc. | 6BLiterature Cited: 14

Literature Cited:

Annual Book of ASTM Standards. American Society For Testing and Materials: Construction. Section 4; Volume 04.10 Wood. Includes standards of the following committee: D-7 on Wood. West Conshohocken, PA 19428 (1997).

Eckelman, Carl. Fasteners and Their Use in Particleboard and Medium Density Fiberboard. National Particleboard Association. Purdue University; March 30, 1990.

Smith, D. Gregory & Semple E. Kate. Prediction of Internal Bond Strength in Particleboard from Screw Withdrawal Resistance Models. Department of Wood Science. University of British Columbia. Wood and Fiber Science, 38(2), 2006, pp. 256 – 267.


9Wood Inc. | 7BAppendices: 15

9WOOD INC.

Appendices: Copy of Test Data and Statistical Analysis


Jonathan C. Gates

July 2009



Appendix I: Test Data

1/2" / Pilot Hole / ASTM

Sample Board Number

Initial Weights (grams)

Density (lb/ft3)

Screw Penetration

Depth Pilot Hole?

Conditioning Room

Maximum Load (lbf) Weight (grams) MC (%) Screw Torque Range (lbf‐in)

10 ‐‐ 16 21 ‐‐ 30 43 ‐‐ 47 Wet OD

27 335.2 47.3 1/2 inch Yes ASTM 155.7 173.0 13.0 347.15 307.53 12.9%

36 336.6 47.5 1/2 inch Yes ASTM 134.0 180.4 18.6 348.93 312.18 11.8%

45 331.8 46.8 1/2 inch Yes ASTM 138.6 182.4 16.7 343.49 306.35 12.1%

60 329.7 46.5 1/2 inch Yes ASTM 119.3 151.5 30.5 342.21 304.21 12.5%

67 340.8 48.1 1/2 inch Yes ASTM 114.9 142.9 22.2 352.53 313.03 12.6%

68 342.3 48.3 1/2 inch Yes ASTM 136.0 201.7 187.7 354.34 313.99 12.9%

69 336.1 47.4 1/2 inch Yes ASTM 132.5 187.9 48.5 348.82 308.77 13.0%

88 330.0 46.6 1/2 inch Yes ASTM 142.1 172.8 16.1 340.64 301.97 12.8%

91 340.8 48.1 1/2 inch Yes ASTM 101.8 173.2 16.9 350.42 309.30 13.3%

93 346.4 48.9 1/2 inch Yes ASTM 126.9 184.7 24.2 358.86 319.91 12.2%

94 345.2 48.7 1/2 inch Yes ASTM 136.3 178.9 182.4 356.92 315.81 13.0%

96 347.3 49.0 1/2 inch Yes ASTM 126.2 156.3 18.8 358.97 320.70 11.9%

99 340.8 48.1 1/2 inch Yes ASTM 143.8 176.4 23.8 350.58 309.69 13.2%

Average 47.8 131.4 174.0 47.6 12.6% Placed in oven on: Thursday, June 25th @ 1:00pm

Take out of oven: Friday, June 26th @ 1:00pm

1/2" / No Pilot Hole / ASTM

Sample Board Number


Density (lb/ft3)

Screw Penetration

Depth Pilot Hole?

Conditioning Room


16 ‐‐ 25 30 ‐‐ 37 54 ‐‐ 62 Wet OD

8 347.4 49.0 1/2 inch No ASTM 156.5 174.5 48.3 360.66 321.42 12.2%

13 339.0 47.8 1/2 inch No ASTM 140.9 184.3 33.6 353.46 314.55 12.4%

15 324.3 45.8 1/2 inch No ASTM 165.1 197.1 27.6 336.98 298.42 12.9%

17 335.6 47.4 1/2 inch No ASTM 140.9 186.2 28.8 348.01 308.24 12.9%

32 337.2 47.6 1/2 inch No ASTM 160.9 155.7 33.9 350.75 312.51 12.2%

52 330.6 46.6 1/2 inch No ASTM 141.5 138.8 39.7 341.50 302.76 12.8%

57 331.2 46.7 1/2 inch No ASTM 155.7 145.0 24.9 342.08 303.42 12.7%

59 330.9 46.7 1/2 inch No ASTM 169.3 169.1 30.5 343.04 304.36 12.7%

64 335.6 47.4 1/2 inch No ASTM 170.1 202.3 30.7 348.73 310.05 12.5%

65 339.5 47.9 1/2 inch No ASTM 123.1 158.6 24.2 352.79 314.90 12.0%

74 332.4 46.9 1/2 inch No ASTM 139.8 185.8 138.1 344.50 305.25 12.9%

80 345.6 48.8 1/2 inch No ASTM 157.4 174.3 35.1 357.92 317.64 12.7%

90 345.1 48.7 1/2 inch No ASTM 117.7 173.7 31.3 358.56 319.17 12.3%

Average 47.5 149.1 172.7 40.5 12.6% Placed in oven on: Thursday, June 25th @ 1:30pm

Take out of oven: Friday, June 26th @ 1:15pm



5/8" / No Pilot Hole / ASTM

Sample Board Number


Density (lb/ft3)

Screw Penetration

Depth Pilot Hole?

Conditioning Room


30 ‐‐ 37 35 ‐‐ 47 54 ‐‐ 62 Wet OD

16 339.4 47.9 5/8 inch No ASTM 212.8 228.9 62.9 352.77 313.08 12.68%

19 335.7 47.4 5/8 inch No ASTM 244.6 246.1 58.5 347.34 308.83 12.47%

22 338.9 47.8 5/8 inch No ASTM 255.5 243.1 54.9 351.60 312.51 12.51%

23 338.1 47.7 5/8 inch No ASTM 231.6 253.2 52.4 350.34 311.49 12.47%

24 338.0 47.7 5/8 inch No ASTM 209.9 244.6 46.6 350.20 311.76 12.33%

41 342.9 48.4 5/8 inch No ASTM 236.2 276.8 35.7 355.31 318.86 11.43%

47 331.3 46.7 5/8 inch No ASTM 184.6 257.8 54.5 342.46 306.26 11.82%

48 327.9 46.3 5/8 inch No ASTM 194.7 264.2 49.9 340.04 304.20 11.78%

49 333.0 47.0 5/8 inch No ASTM 238.1 233.5 46.6 344.03 305.17 12.73%

58 337.5 47.6 5/8 inch No ASTM 246.3 231.2 61.0 350.97 311.96 12.50%

82 342.8 48.4 5/8 inch No ASTM 207.0 237.9 59.1 355.13 315.30 12.63%

84 341.3 48.2 5/8 inch No ASTM 226.2 232.9 46.8 353.14 314.42 12.31%

89 331.4 46.8 5/8 inch No ASTM 220.2 249.8 51.4 341.16 301.51 13.15%

Average 47.5 223.7 246.2 52.3 12.4% Placed in oven on: Tuesday, June 30th @ 9:00am

Take out of oven: Wednesday, July 1st @ 9:00am

5/8" / Pilot Hole / ASTM

Sample Board Number


Density (lb/ft3)

Screw Penetration

Depth Pilot Hole?

Conditioning Room

Maximum Load Received Weight (grams) MC (%) Screw Torque Range (lbf‐in)

21 ‐‐ 30 35 ‐‐ 47 54 ‐‐ 62 Wet OD

11 341.6 48.2 5/8 inch Yes ASTM 188.8 249.8 43.0 353.06 314.60 12.23%

20 339.6 47.9 5/8 inch Yes ASTM 269.9 262.4 62.1 352.58 313.02 12.64%

26 334.0 47.1 5/8 inch Yes ASTM 219.7 218.7 66.6 345.61 306.25 12.85%

29 335.6 47.4 5/8 inch Yes ASTM 204.3 267.4 47.0 348.10 311.38 11.79%

31 341.0 48.1 5/8 inch Yes ASTM 262.1 289.1 300.0 354.00 316.79 11.75%

34 334.2 47.2 5/8 inch Yes ASTM 211.6 226.6 64.5 346.00 307.79 12.41%

38 333.9 47.1 5/8 inch Yes ASTM 171.7 280.1 47.2 346.22 308.86 12.10%

42 335.1 47.3 5/8 inch Yes ASTM 207.4 237.7 43.9 347.67 309.90 12.19%

51 335.1 47.3 5/8 inch Yes ASTM 201.8 227.5 57.7 347.81 308.48 12.75%

62 335.2 47.3 5/8 inch Yes ASTM 202.4 205.3 41.6 347.39 308.95 12.44%

81 342.9 48.4 5/8 inch Yes ASTM 242.1 253.6 45.1 354.62 313.23 13.21%

83 332.9 47.0 5/8 inch Yes ASTM 235.0 239.6 72.3 342.73 302.01 13.48%

85 343.1 48.4 5/8 inch Yes ASTM 157.9 258.4 53.7 354.70 313.74 13.06%





5/8" / Pilot Hole / Hot‐Dry

Sample Board Number


Density (lb/ft3)

Screw Penetration

Depth Pilot Hole?

Conditioning Room


21 ‐‐ 30 35 ‐‐ 47 54 ‐‐ 62 Wet OD

6 341.0 48.1 5/8 inch Yes Hot/Dry 216.6 237.9 9.2 340.47 313.80 8.50%

7 347.3 49.0 5/8 inch Yes Hot/Dry 184.2 260.9 20.3 346.92 320.05 8.40%

35 339.0 47.8 5/8 inch Yes Hot/Dry 206.0 283.7 45.5 341.24 315.40 8.19%

39 333.5 47.1 5/8 inch Yes Hot/Dry 166.9 274.7 49.9 333.79 308.44 8.22%

50 336.9 47.5 5/8 inch Yes Hot/Dry 226.2 231.0 43.0 335.97 310.65 8.15%

55 333.5 47.1 5/8 inch Yes Hot/Dry 228.7 222.0 39.9 332.27 305.38 8.81%

56 333.8 47.1 5/8 inch Yes Hot/Dry 268.2 228.1 57.2 333.89 308.25 8.32%

63 330.2 46.6 5/8 inch Yes Hot/Dry 220.6 239.2 40.1 328.57 302.60 8.58%

66 324.1 45.7 5/8 inch Yes Hot/Dry 168.1 232.5 34.7 323.63 298.77 8.32%

77 333.0 47.0 5/8 inch Yes Hot/Dry 235.6 232.7 52.0 331.61 306.12 8.33%

79 333.7 47.1 5/8 inch Yes Hot/Dry 234.2 231.9 33.8 330.11 303.36 8.82%

87 346.0 48.8 5/8 inch Yes Hot/Dry 204.7 237.1 57.0 345.73 319.77 8.12%

95 342.1 48.3 5/8 inch Yes Hot/Dry 263.0 290.6 33.8 339.45 313.68 8.22%

Average 47.5 217.2 246.3 39.7 8.4% Placed in oven on: Monday, June 29th @ 8:30am

Take out of oven: Tuesday, June 30th @ 8:00am

5/8" / No Pilot Hole / Hot‐Dry

Sample Board Number


Density (lb/ft3)

Screw Penetration

Depth Pilot Hole?

Conditioning Room


30 ‐‐ 37 35 ‐‐ 47 54 ‐‐ 62 Wet OD

5 345.6 48.8 5/8 inch No Hot/Dry 233.1 232.9 43.7 345.48 318.46 8.48%

12 343.0 48.4 5/8 inch No Hot/Dry 220.4 245.9 40.7 342.12 316.51 8.09%

28 337.2 47.6 5/8 inch No Hot/Dry 177.3 273.2 32.2 337.81 311.30 8.52%

30 341.0 48.1 5/8 inch No Hot/Dry 233.5 295.6 48.0 340.95 315.35 8.12%

40 334.2 47.2 5/8 inch No Hot/Dry 168.4 313.3 33.6 334.97 309.39 8.27%

46 338.4 47.7 5/8 inch No Hot/Dry 195.1 292.4 317.1 340.77 314.93 8.20%

53 339.5 47.9 5/8 inch No Hot/Dry 222.2 300.4 340.5 342.12 317.85 7.64%

70 335.2 47.3 5/8 inch No Hot/Dry 270.9 275.5 40.9 332.51 307.11 8.27%

72 346.1 48.8 5/8 inch No Hot/Dry 195.3 244.8 50.5 344.01 316.68 8.63%

78 345.2 48.7 5/8 inch No Hot/Dry 229.3 231.0 24.9 344.34 318.19 8.22%

86 348.1 49.1 5/8 inch No Hot/Dry 185.9 241.5 64.8 348.66 321.40 8.48%

92 346.4 48.9 5/8 inch No Hot/Dry 221.8 230.6 40.1 346.20 320.13 8.14%

98 344.9 48.7 5/8 inch No Hot/Dry 214.9 260.9 36.3 342.85 315.27 8.75%





1/2" / No Pilot Hole / ASTM / High Density

Sample Board Number


Density (lb/ft3)

Screw Penetration

Depth Pilot Hole?

Conditioning Room


16 ‐‐ 25 30 ‐‐ 37 54 ‐‐ 62 Wet OD

1 353.6 49.9 1/2 inch No ASTM 195.5 187.4 37.8 365.83 324.22 12.83%

2 354.5 50.0 1/2 inch No ASTM 130.8 197.4 22.6 367.54 325.74 12.83%

3 349.4 49.3 1/2 inch No ASTM 170.9 203.9 45.3 363.50 323.36 12.41%

4 349.4 49.3 1/2 inch No ASTM 152.5 198.6 28.6 363.97 323.56 12.49%

9 352.2 49.7 1/2 inch No ASTM 188.0 162.5 15.0 364.77 322.35 13.16%

10 348.2 49.1 1/2 inch No ASTM 144.1 192.8 27.2 361.65 321.28 12.57%

71 348.9 49.2 1/2 inch No ASTM 133.7 171.1 35.1 361.26 321.27 12.45%

73 349.0 49.2 1/2 inch No ASTM 128.9 184.6 37.0 360.89 319.97 12.79%

75 348.8 49.2 1/2 inch No ASTM 154.6 188.8 57.4 361.30 320.44 12.75%

76 348.8 49.2 1/2 inch No ASTM 131.6 183.0 27.2 361.45 320.44 12.80%



1/2" / Pilot Hole / ASTM / Low Density

Sample Board Number


Density (lb/ft3)

Screw Penetration

Depth Pilot Hole?

Conditioning Room


10 ‐‐ 16 21 ‐‐ 30 43 ‐‐ 47 Wet OD

14 320.5 45.2 1/2 inch Yes ASTM 114.3 155.4 19.4 332.40 296.56 12.09%

18 317.8 44.8 1/2 inch Yes ASTM 119.7 170.4 40.7 330.68 293.73 12.58%

21 321.4 45.3 1/2 inch Yes ASTM 156.9 165.9 38.6 332.07 295.23 12.48%

25 323.8 45.7 1/2 inch Yes ASTM 133.9 185.5 12.7 335.42 298.21 12.48%

33 316.0 44.6 1/2 inch Yes ASTM 155.4 170.7 27.6 328.90 292.60 12.41%

37 316.4 44.6 1/2 inch Yes ASTM 114.9 146.0 17.3 328.96 291.94 12.68%

43 316.6 44.7 1/2 inch Yes ASTM 97.3 181.5 43.0 329.20 292.48 12.55%

54 323.2 45.6 1/2 inch Yes ASTM 138.1 162.5 50.8 335.89 298.80 12.41%

61 317.4 44.8 1/2 inch Yes ASTM 118.4 136.4 24.9 329.93 293.38 12.46%

97 322.4 45.5 1/2 inch Yes ASTM 130.8 169.8 34.5 333.43 296.20 12.57%





Appendix II: All Data ANOVA Analysis

1. Analysis Summary Dependent variable: Max load lbf Factors: Screw torque range Screw setting practice Screw penetration depth (in) Density Conditioning (MC) Number of complete cases: 294

2. Analysis of Variance for Max load lbf - Type III Sums of Squares --------------------------------------------------------------------------------

Source Sum of Squares

Degrees of Freedom

Mean Square F-Ratio P-Value

A: Screw torque range 1.46E+06 2 730075 497.74 <0.0001 B: Screw setting practice 2413.47 1 2413.47 1.65 0.2006 C: Screw penetration depth 125403 1 125403 85.5 <0.0001 D: Density 1587.44 2 793.722 0.54 0.5827 E: Conditioning (MC) 121.194 1 121.194 0.08 0.774 RESIDUAL 419496.0 286 1466.77 -------------------------------------------------------------------------------- TOTAL (CORRECTED) 2.14108E6 293 -------------------------------------------------------------------------------- All F-ratios are based on the residual mean square error.

3. Multiple Range Tests for Max load (lbf) by Screw Torque Range -------------------------------------------------------------------------------- Method: 95.0 percent LSD Level Count LS Mean LS Sigma Homogeneous Groups -------------------------------------------------------------------------------- Over Torque 98 48.6996 5.10554 X Weak 98 178.162 5.10554 X Standard 98 212.319 5.10554 X -------------------------------------------------------------------------------- Contrast Difference +/- Limits -------------------------------------------------------------------------------- Over Torque - Weak *-129.462 10.769 Over Torque - Standard *-163.619 10.769 Weak – Standard *-34.1571 10.769 -------------------------------------------------------------------------------- * denotes a statistically significant difference.



4. Multiple Range Tests for Max load (lbf) by Setting practice (Pilot hole / No Pilot hole) -------------------------------------------------------------------------------- Method: 95.0 percent LSD Level Count LS Mean LS Sigma Homogeneous Groups -------------------------------------------------------------------------------- Pilot 147 143.182 4.72829 X No pilot 147 149.605 4.72829 X -------------------------------------------------------------------------------- Contrast Difference +/- Limits -------------------------------------------------------------------------------- No pilot - Pilot 6.42308 9.85584 -------------------------------------------------------------------------------- * denotes a statistically significant difference.

5. Multiple Range Tests for Max load (lbf) by Screw penetration (in) -------------------------------------------------------------------------------- Method: 95.0 percent LSD Level Count LS Mean LS Sigma Homogeneous Groups -------------------------------------------------------------------------------- 0.5 138 118.041 4.72829 X 0.625 156 174.746 5.35023 X -------------------------------------------------------------------------------- Contrast Difference +/- Limits -------------------------------------------------------------------------------- 0.5 - 0.625 *-56.7051 12.0709 -------------------------------------------------------------------------------- * denotes a statistically significant difference.

6. Multiple Range Tests for Max load (lbf) by Density -------------------------------------------------------------------------------- Method: 95.0 percent LSD Density Count LS Mean LS Sigma Homogeneous Groups -------------------------------------------------------------------------------- Low 30 140.222 8.0351 X Standard 234 148.472 3.06633 X High 30 150.486 8.0351 X -------------------------------------------------------------------------------- Contrast Difference +/- Limits -------------------------------------------------------------------------------- High - Low 10.2636 21.8168 High- Standard 2.01333 16.928 Low- Standard -8.25026 16.928 -------------------------------------------------------------------------------- * denotes a statistically significant difference.



7. Multiple Range Tests for Max load (lbf) by Conditioning (MC) -------------------------------------------------------------------------------- Method: 95.0 percent LSD Conditioning Count LS Mean LS Sigma Homogeneous Groups -------------------------------------------------------------------------------- ASTM 216 145.512 4.01105 X Hot/Dry 78 147.275 5.90705 X -------------------------------------------------------------------------------- Contrast Difference +/- Limits -------------------------------------------------------------------------------- Hot/Dry - ASTM 1.76282 12.0709 --------------------------------------------------------------------------------

Scatterplot by Level Code

0

100

200

300

400

Max

load

lbf

Screw Torque RangeHigh Low Medium


Max

load

lbf

Setting practice

0

100

200

300

400

No pilot Pilot


Max

load

lbf

Screw penetration in

0

100

200

300

400

0.5 0.625


Max

load

lbf

Density

0

100

200

300

400

High Low Standard




Max

load

lbf

Conditioning

0

100

200

300

400

Hot/Dry StandardHigh Low Medium

Residual Plot for Max load lbf

-260

-160

-60

40

140

240

340

resi

dual

Screw Torque Range


resi

dual

Densityigh w Standard

60

-160

-60

40

140

240

340

H Lo-2


resi

dual

ConditioningHot/Dry Standard

-260

-160

-60

40

140

240

340


resi

dual

Setting practiceNo pilot Pilot

-260

-160

-60

40

140

240

340


resi

dual

Screw penetration in0.5 0.625

-260

-160

-60

40

140

240

340




-260

-160

-60

40

140

240

340re

sidu

al

0 100 200 300 400

predicted Max load lbf



Appendices III: All Data Excluding Density and Conditioning (MC) ANOVA Analysis

1. Analysis Summary Dependent variable: Max load lbf Factors: Screw torque range Screw setting practice (Pilot hole / No Pilot hole) Screw penetration depth (in) Number of complete cases: 294

2. Analysis of Variance for Max load (lbf) - Type III Sums of Squares -------------------------------------------------------------------------------- MAIN EFFECTS

Source Sum of Squares Degrees of Freedom Mean Square F-Ratio P-Value

A: Screw torque range 1.46E+06 2 730075 500.92 <0.0001 B: Screw setting practice 5332.5 1 5332.5 3.66 0.0568 C: Screw penetration depth 254397 1 254397 174.55 <0.0001 RESIDUAL 421204.0 289 1457.45 -------------------------------------------------------------------------------- TOTAL (CORRECTED) 2.14108E6 293 -------------------------------------------------------------------------------- All F-ratios are based on the residual mean square error.

3. Multiple Range Tests for Max load (lbf) by Screw Torque Range -------------------------------------------------------------------------------- Method: 95.0 percent LSD Level Count LS Mean LS Sigma Homogeneous Groups -------------------------------------------------------------------------------- Over Torque 98 49.6599 3.85884 X Weak 98 179.122 3.85884 X Standard 98 213.279 3.85884 X -------------------------------------------------------------------------------- Contrast Difference +/- Limits -------------------------------------------------------------------------------- Over Torque - Weak *-129.462 10.7342 Over Torque - Standard *-163.619 10.7342 Weak - Standard *-34.1571 10.7342 -------------------------------------------------------------------------------- * denotes a statistically significant difference.



4. Multiple Range Tests for Max load (lbf) by Setting practice (Pilot hole / No Pilot hole) -------------------------------------------------------------------------------- Method: 95.0 percent LSD Level Count LS Mean LS Sigma Homogeneous Groups -------------------------------------------------------------------------------- Pilot 147 143.095 3.15172 X No pilot 147 151.613 3.15172 X -------------------------------------------------------------------------------- Contrast Difference +/- Limits -------------------------------------------------------------------------------- No pilot - Pilot 8.51769 8.76446 -------------------------------------------------------------------------------- * denotes a statistically significant difference.

5. Multiple Range Tests for Max load (lbf) by Screw penetration (in) -------------------------------------------------------------------------------- Method: 95.0 percent LSD Level Count LS Mean LS Sigma Homogeneous Groups -------------------------------------------------------------------------------- 0.5 138 117.883 3.24981 X 0.625 156 176.825 3.05658 X -------------------------------------------------------------------------------- Contrast Difference +/- Limits -------------------------------------------------------------------------------- 0.5 - 0.625 *-58.9424 8.78094 -------------------------------------------------------------------------------- * denotes a statistically significant difference.


Max

load

lbf

Screw Torque Range

0

0

200

300

400

High Low Medium

10


Max

load

lbf

Screw penetration in

0

100

200

300

400

0.5 0.625




Max

load

lbf

Setting practice

0

100

200

300

0

No pilot Pilot

40

High Low Medium


-260

-160

-60

40

140

240

340

resi

dual

Screw Torque Range


-260

-160

-60

40

140

240

340

resi

dual

0 100 200 300 400

predicted Max load lbf

Normal Probability Plot

-70 30 130 230 330

RESIDUALS

0.115

2050809599

99.9

perc

enta

ge


resi

dual

Setting practiceNo pilot Pilot

-260

-160

-60

140

240

340

40


resi

dual

Screw penetration in0.5 0.625

-260

-160

-60

40

140

240

340

[SCR ]EW WITHDRAWAL STRENGTH IN 9WOOD’S ASSEMBLIES July 2009

9Wood Inc. | 8BLiterature:

9WOOD INC.

Literature: Copy of Cited Literature


Jonathan C. Gates

July 2009

28

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