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2009

Screw Withdrawal Strength in 9Wood's Assemblies

Test Evaluation Report

Jonathan C. Gates 9Wood Inc. July 2009

[SCREW WITHDRAWAL STRENGTH IN 9WOOD'S ASSEMBLIES]

July 2009

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).

9Wood Inc. | 0BAbstract:

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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.

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[SCREW WITHDRAWAL STRENGTH IN 9WOOD'S ASSEMBLIES]

July 2009

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%.

9Wood Inc. | 1BIntroduction:

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[SCREW WITHDRAWAL STRENGTH IN 9WOOD'S ASSEMBLIES] ·

July 2009

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. | 2BLiterature Review: 2

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

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.

3/4" 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). 9Wood Inc. | 3BMaterials and Methodology: 3

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

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).

3" ¾" 12"

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).

3" 3" 3" 3" 1.5" 1.5"

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

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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).

Weak Standard Overtorque ASTM Conditioned 1/2" / Pilot hole / Standard Density

X 13

7.3.1

Weak

Standard

Overtorque ASTM Conditioned

X 10

7.3.1

1/2" / Pilot hole / Low Density

Weak

Standard

Overtorque ASTM Conditioned

X 13

7.3.2

1/2" / No Pilot hole / Standard Density

Weak

Standard

Overtorque ASTM Conditioned

X 10

7.3.2

1/2" / No Pilot hole / High Density

Weak

Standard

Overtorque Hot/Dry Conditioned ASTM Conditioned

7.3.3

X 13 X 13

5/8" / Pilot hole / Standard Density Weak Standard Overtorque Hot/Dry Conditioned ASTM Conditioned 5/8" / No Pilot hole / Standard Density Total

7.3.4

X 13 X 13

98 Sample Boards 294 ScrewPulls

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

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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. 9Wood Inc. | 3BMaterials and Methodology: 6

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

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. 9Wood Inc. | 3BMaterials and Methodology: 7

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

Makita 18 volt Drill Specs

Screw Penetration Depth Pilot hole? Yes 1/2" No Torque Range Name Weak Standard Over-torque Weak Standard Over-torque Weak Standard Over-torque Weak Standard Over-torque Drill Clutch Setting 1 4 10 3 6 14 4 8 14 6 8 14 Torque Range (lbf-in) 9.80 - 15.90 21.25 - 30.00 43.35 - 47.10 16.80 - 25.20 30.15 - 36.80 54.80 - 61.95 21.25 - 30.00 35.05 - 47.20 54.80 - 61.95 30.15 - 36.80 35.05 - 47.20 54.80 - 61.95 Speed Setting 2

2

Yes 5/8" No

2

2

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. 9Wood Inc. | 3BMaterials and Methodology: 8

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

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

Test 1 2 3 4 5 Average Clutch Setting 1 16 10 10 12 13 12.2 2 15 16 18 16 11 15.0 3 18 17 18 23 25 20.1 4 30 26 29 27 21 26.7 5 29 33 33 26 28 29.7 6 37 30 34 36 31 33.5 7 38 31 33 36 37 34.8 8 43 47 37 43 35 41.1 9 42 47 47 40 45 44.1 10 45 47 45 43 47 45.5 11 50 51 50 47 53 50.2 12 55 53 48 45 53 50.5 13 61 58 59 55 58 58.1 14 55 61 62 58 61 59.4 15 61 65 65 61 60 62.3 16 65 63 64 70 67 65.9

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

80.00 70.00 Average Torque (lbfin) 60.00 50.00 40.00

Speed 1

30.00 20.00 10.00 0.00 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Speed 2

Clutch Setting

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). 9Wood Inc. | 3BMaterials and Methodology: 9

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

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).

300

Torque Range

Weak 250 Average Maximum Load (lbf)

Standard

Over Torque

265 247 213 246 224 246 217 213

200 174 150 173 149 131 128 164

187 153

100 73 50 48 41 52 31 33 40

86

0 ASTM 1/2" Pilot ASTM 1/2" No Pilot Low D 1/2" Pilot High D 1/2" No Pilot ASTM 5/8" Pilot ASTM 5/8" No Pilot Hot/Dry 5/8" Pilot Hot/Dry 5/8" No Pilot

Batches

Figure 11: Average Maximum Screw Withdrawal Strengths for each Torque Range and Sample Batch. Note: The complete data tables are presented in Appendix I. 9Wood Inc. | 4BResults and Discussion: 10

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

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 [pvalue 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

Batch Density

Average (lb/ft3) St. Dev. (lb/ft3)

Average Board Moisture Content

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 Sum of Mean Degrees of Source F-Ratio P-Value Freedom Squares Square 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, 9Wood Inc. | 4BResults and Discussion: 11

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

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.

300

Torque Range

250

Weak

Standard

Over Torque

Average Maximum Load (lbf)

200

150

100

50 130 0 1/2" Pilot 50 1/2" No Pilot Batches 5/8" Pilot 5/8" No pilot 170 40 151 179 37 215 247 56 218 255 69

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.

9Wood Inc. | 4BResults and Discussion:

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

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. | 5BConclusion:

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

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.

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9WOOD INC.

Appendices:

Copy of Test Data and Statistical Analysis

Test Evaluation Report

Jonathan C. Gates July 2009

9Wood Inc. | 7BAppendices:

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

Appendix I: Test Data

1/2" / Pilot Hole / ASTM Sample Board Number 27 36 45 60 67 68 69 88 91 93 94 96 99 Average Initial Weights (grams) 335.2 336.6 331.8 329.7 340.8 342.3 336.1 330.0 340.8 346.4 345.2 347.3 340.8 Density 3 (lb/ft ) 47.3 47.5 46.8 46.5 48.1 48.3 47.4 46.6 48.1 48.9 48.7 49.0 48.1 47.8 Screw Penetration Depth 1/2 inch 1/2 inch 1/2 inch 1/2 inch 1/2 inch 1/2 inch 1/2 inch 1/2 inch 1/2 inch 1/2 inch 1/2 inch 1/2 inch 1/2 inch Pilot Hole? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Conditioning Room ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM Maximum Load (lbf) Screw Torque Range (lbfin) 10 16 21 30 43 47 155.7 134.0 138.6 119.3 114.9 136.0 132.5 142.1 101.8 126.9 136.3 126.2 143.8 131.4 173.0 180.4 182.4 151.5 142.9 201.7 187.9 172.8 173.2 184.7 178.9 156.3 176.4 174.0 13.0 18.6 16.7 30.5 22.2 187.7 48.5 16.1 16.9 24.2 182.4 18.8 23.8 47.6 Weight (grams) Wet 347.15 348.93 343.49 342.21 352.53 354.34 348.82 340.64 350.42 358.86 356.92 358.97 350.58 OD 307.53 312.18 306.35 304.21 313.03 313.99 308.77 301.97 309.30 319.91 315.81 320.70 309.69 12.9% 11.8% 12.1% 12.5% 12.6% 12.9% 13.0% 12.8% 13.3% 12.2% 13.0% 11.9% 13.2% 12.6% MC (%)

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 8 13 15 17 32 52 57 59 64 65 74 80 90 Average Initial Weights (grams) 347.4 339.0 324.3 335.6 337.2 330.6 331.2 330.9 335.6 339.5 332.4 345.6 345.1 Density 3 (lb/ft ) 49.0 47.8 45.8 47.4 47.6 46.6 46.7 46.7 47.4 47.9 46.9 48.8 48.7 47.5 Screw Penetration Depth 1/2 inch 1/2 inch 1/2 inch 1/2 inch 1/2 inch 1/2 inch 1/2 inch 1/2 inch 1/2 inch 1/2 inch 1/2 inch 1/2 inch 1/2 inch Pilot Hole? No No No No No No No No No No No No No Conditioning Room ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM Maximum Load (lbf) Screw Torque Range (lbfin) 16 25 30 37 54 62 156.5 140.9 165.1 140.9 160.9 141.5 155.7 169.3 170.1 123.1 139.8 157.4 117.7 149.1 174.5 184.3 197.1 186.2 155.7 138.8 145.0 169.1 202.3 158.6 185.8 174.3 173.7 172.7 48.3 33.6 27.6 28.8 33.9 39.7 24.9 30.5 30.7 24.2 138.1 35.1 31.3 40.5 Weight (grams) Wet 360.66 353.46 336.98 348.01 350.75 341.50 342.08 343.04 348.73 352.79 344.50 357.92 358.56 OD 321.42 314.55 298.42 308.24 312.51 302.76 303.42 304.36 310.05 314.90 305.25 317.64 319.17 12.2% 12.4% 12.9% 12.9% 12.2% 12.8% 12.7% 12.7% 12.5% 12.0% 12.9% 12.7% 12.3% 12.6% MC (%)

Placed in oven on: Thursday, June 25th @ 1:30pm Take out of oven: Friday, June 26th @ 1:15pm

9Wood Inc. | 7BAppendices:

16

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

5/8" / No Pilot Hole / ASTM Sample Board Number 16 19 22 23 24 41 47 48 49 58 82 84 89 Average Initial Weights (grams) 339.4 335.7 338.9 338.1 338.0 342.9 331.3 327.9 333.0 337.5 342.8 341.3 331.4 Density 3 (lb/ft ) 47.9 47.4 47.8 47.7 47.7 48.4 46.7 46.3 47.0 47.6 48.4 48.2 46.8 47.5 Screw Penetration Depth 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch Pilot Hole? No No No No No No No No No No No No No Conditioning Room ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM Maximum Load (lbf) Screw Torque Range (lbfin) 30 37 35 47 54 62 212.8 244.6 255.5 231.6 209.9 236.2 184.6 194.7 238.1 246.3 207.0 226.2 220.2 223.7 228.9 246.1 243.1 253.2 244.6 276.8 257.8 264.2 233.5 231.2 237.9 232.9 249.8 246.2 62.9 58.5 54.9 52.4 46.6 35.7 54.5 49.9 46.6 61.0 59.1 46.8 51.4 52.3 Weight (grams) Wet 352.77 347.34 351.60 350.34 350.20 355.31 342.46 340.04 344.03 350.97 355.13 353.14 341.16 OD 313.08 308.83 312.51 311.49 311.76 318.86 306.26 304.20 305.17 311.96 315.30 314.42 301.51 12.68% 12.47% 12.51% 12.47% 12.33% 11.43% 11.82% 11.78% 12.73% 12.50% 12.63% 12.31% 13.15% 12.4% MC (%)

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 11 20 26 29 31 34 38 42 51 62 81 83 85 Average Initial Weights (grams) 341.6 339.6 334.0 335.6 341.0 334.2 333.9 335.1 335.1 335.2 342.9 332.9 343.1 Density 3 (lb/ft ) 48.2 47.9 47.1 47.4 48.1 47.2 47.1 47.3 47.3 47.3 48.4 47.0 48.4 47.6 Screw Penetration Depth 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch Pilot Hole? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Conditioning Room ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM Maximum Load Received Screw Torque Range (lbfin) 21 30 35 47 54 62 188.8 269.9 219.7 204.3 262.1 211.6 171.7 207.4 201.8 202.4 242.1 235.0 157.9 213.4 249.8 262.4 218.7 267.4 289.1 226.6 280.1 237.7 227.5 205.3 253.6 239.6 258.4 247.4 43.0 62.1 66.6 47.0 300.0 64.5 47.2 43.9 57.7 41.6 45.1 72.3 53.7 72.7 Weight (grams) Wet 353.06 352.58 345.61 348.10 354.00 346.00 346.22 347.67 347.81 347.39 354.62 342.73 354.70 OD 314.60 313.02 306.25 311.38 316.79 307.79 308.86 309.90 308.48 308.95 313.23 302.01 313.74 12.23% 12.64% 12.85% 11.79% 11.75% 12.41% 12.10% 12.19% 12.75% 12.44% 13.21% 13.48% 13.06% 12.5% MC (%)

Placed in oven on: Tuesday, June 30th @ 8:30am Take out of oven: Wednesday, July 1st @ 9:00am

9Wood Inc. | 7BAppendices:

17

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

5/8" / Pilot Hole / HotDry Sample Board Number 6 7 35 39 50 55 56 63 66 77 79 87 95 Average Initial Weights (grams) 341.0 347.3 339.0 333.5 336.9 333.5 333.8 330.2 324.1 333.0 333.7 346.0 342.1 Density 3 (lb/ft ) 48.1 49.0 47.8 47.1 47.5 47.1 47.1 46.6 45.7 47.0 47.1 48.8 48.3 47.5 Screw Penetration Depth 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch Pilot Hole? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Conditioning Room Hot/Dry Hot/Dry Hot/Dry Hot/Dry Hot/Dry Hot/Dry Hot/Dry Hot/Dry Hot/Dry Hot/Dry Hot/Dry Hot/Dry Hot/Dry Maximum Load (lbf) Screw Torque Range (lbfin) 21 30 35 47 54 62 216.6 184.2 206.0 166.9 226.2 228.7 268.2 220.6 168.1 235.6 234.2 204.7 263.0 217.2 237.9 260.9 283.7 274.7 231.0 222.0 228.1 239.2 232.5 232.7 231.9 237.1 290.6 246.3 9.2 20.3 45.5 49.9 43.0 39.9 57.2 40.1 34.7 52.0 33.8 57.0 33.8 39.7 Weight (grams) Wet 340.47 346.92 341.24 333.79 335.97 332.27 333.89 328.57 323.63 331.61 330.11 345.73 339.45 OD 313.80 320.05 315.40 308.44 310.65 305.38 308.25 302.60 298.77 306.12 303.36 319.77 313.68 8.50% 8.40% 8.19% 8.22% 8.15% 8.81% 8.32% 8.58% 8.32% 8.33% 8.82% 8.12% 8.22% 8.4% MC (%)

Placed in oven on: Monday, June 29th @ 8:30am Take out of oven: Tuesday, June 30th @ 8:00am

5/8" / No Pilot Hole / HotDry Sample Board Number 5 12 28 30 40 46 53 70 72 78 86 92 98 Average Initial Weights (grams) 345.6 343.0 337.2 341.0 334.2 338.4 339.5 335.2 346.1 345.2 348.1 346.4 344.9 Density 3 (lb/ft ) 48.8 48.4 47.6 48.1 47.2 47.7 47.9 47.3 48.8 48.7 49.1 48.9 48.7 48.2 Screw Penetration Depth 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch 5/8 inch Pilot Hole? No No No No No No No No No No No No No Conditioning Room Hot/Dry Hot/Dry Hot/Dry Hot/Dry Hot/Dry Hot/Dry Hot/Dry Hot/Dry Hot/Dry Hot/Dry Hot/Dry Hot/Dry Hot/Dry Maximum Load (lbf) Screw Torque Range (lbfin) 30 37 35 47 54 62 233.1 220.4 177.3 233.5 168.4 195.1 222.2 270.9 195.3 229.3 185.9 221.8 214.9 212.9 232.9 245.9 273.2 295.6 313.3 292.4 300.4 275.5 244.8 231.0 241.5 230.6 260.9 264.5 43.7 40.7 32.2 48.0 33.6 317.1 340.5 40.9 50.5 24.9 64.8 40.1 36.3 85.6 Weight (grams) Wet 345.48 342.12 337.81 340.95 334.97 340.77 342.12 332.51 344.01 344.34 348.66 346.20 342.85 OD 318.46 316.51 311.30 315.35 309.39 314.93 317.85 307.11 316.68 318.19 321.40 320.13 315.27 8.48% 8.09% 8.52% 8.12% 8.27% 8.20% 7.64% 8.27% 8.63% 8.22% 8.48% 8.14% 8.75% 8.3% MC (%)

Placed in oven on: Monday, June 29th @ 8:30am Take out of oven: Tuesday, June 30th @ 8:30am

9Wood Inc. | 7BAppendices:

18

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

1/2" / No Pilot Hole / ASTM / High Density Sample Board Number 1 2 3 4 9 10 71 73 75 76 Average Initial Weights (grams) 353.6 354.5 349.4 349.4 352.2 348.2 348.9 349.0 348.8 348.8 Density 3 (lb/ft ) 49.9 50.0 49.3 49.3 49.7 49.1 49.2 49.2 49.2 49.2 49.4 Screw Penetration Depth 1/2 inch 1/2 inch 1/2 inch 1/2 inch 1/2 inch 1/2 inch 1/2 inch 1/2 inch 1/2 inch 1/2 inch Pilot Hole? No No No No No No No No No No Conditioning Room ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM Maximum Load (lbf) Screw Torque Range (lbfin) 16 25 30 37 54 62 195.5 130.8 170.9 152.5 188.0 144.1 133.7 128.9 154.6 131.6 153.1 187.4 197.4 203.9 198.6 162.5 192.8 171.1 184.6 188.8 183.0 187.0 37.8 22.6 45.3 28.6 15.0 27.2 35.1 37.0 57.4 27.2 33.3 Weight (grams) Wet 365.83 367.54 363.50 363.97 364.77 361.65 361.26 360.89 361.30 361.45 OD 324.22 325.74 323.36 323.56 322.35 321.28 321.27 319.97 320.44 320.44 12.83% 12.83% 12.41% 12.49% 13.16% 12.57% 12.45% 12.79% 12.75% 12.80% 12.7% MC (%)

Placed in oven on: Tuesday, June 30th @ 8:00am Take out of oven: Wednesday, July 1st @ 9:00am

1/2" / Pilot Hole / ASTM / Low Density Sample Board Number 14 18 21 25 33 37 43 54 61 97 Average Initial Weights (grams) 320.5 317.8 321.4 323.8 316.0 316.4 316.6 323.2 317.4 322.4 Density 3 (lb/ft ) 45.2 44.8 45.3 45.7 44.6 44.6 44.7 45.6 44.8 45.5 45.1 Screw Penetration Depth 1/2 inch 1/2 inch 1/2 inch 1/2 inch 1/2 inch 1/2 inch 1/2 inch 1/2 inch 1/2 inch 1/2 inch Pilot Hole? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Conditioning Room ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM Maximum Load (lbf) Screw Torque Range (lbfin) 10 16 21 30 43 47 114.3 119.7 156.9 133.9 155.4 114.9 97.3 138.1 118.4 130.8 128.0 155.4 170.4 165.9 185.5 170.7 146.0 181.5 162.5 136.4 169.8 164.4 19.4 40.7 38.6 12.7 27.6 17.3 43.0 50.8 24.9 34.5 31.0 Weight (grams) Wet 332.40 330.68 332.07 335.42 328.90 328.96 329.20 335.89 329.93 333.43 OD 296.56 293.73 295.23 298.21 292.60 291.94 292.48 298.80 293.38 296.20 12.09% 12.58% 12.48% 12.48% 12.41% 12.68% 12.55% 12.41% 12.46% 12.57% 12.5% MC (%)

Placed in oven on: Monday, June 29th @ 9:00am Take out of oven: Tuesday, June 30th @ 8:30am

9Wood Inc. | 7BAppendices:

19

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

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 -------------------------------------------------------------------------------Sum of Mean Degrees of Source Freedom Squares Square A: B: C: D: E: Screw torque range Screw setting practice Screw penetration depth Density Conditioning (MC) 1.46E+06 2413.47 125403 1587.44 121.194 2 1 1 2 1 730075 2413.47 125403 793.722 121.194

F-Ratio 497.74 1.65 85.5 0.54 0.08

P-Value <0.0001 0.2006 <0.0001 0.5827 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. 9Wood Inc. | 7BAppendices: 20

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

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.

9Wood Inc. | 7BAppendices:

21

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

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

400

Scatterplot by Level Code

400

Max load lbf

Max load lbf

300 200 100 0 High Low Medium

300 200 100 0 No pilot Pilot

Screw Torque Range

Setting practice

Scatterplot by Level Code

400

Scatterplot by Level Code

400

Max load lbf

300 200 100 0 0.5 0.625

Max load lbf

300 200 100 0 High Low Standard

Screw penetration in

Density

9Wood Inc. | 7BAppendices:

22

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

Scatterplot by Level Code

400

340 240

Residual Plot for Max load lbf

Max load lbf

residual

300 200 100 0 Hot/Dry Standard

140 40 -60 -160 -260 High Low Medium

Conditioning

Residual Plot for Max load lbf

340 240

340 240

Screw Torque Range

Residual Plot for Max load lbf

residual

residual

140 40 -60 -160 -260 No pilot Pilot

140 40 -60 -160 -260 0.5 0.625

Setting practice

Residual Plot for Max load lbf

340 240

Screw penetration in

Residual Plot for Max load lbf

340 240

residual

140 40 -60 -160 -260 High Lo w Standard

residual

140 40 -60 -160 -260 Hot/Dry Standard

Density

Conditioning

9Wood Inc. | 7BAppendices:

23

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

Residual Plot for Max load lbf

340 240

residual

140 40 -60 -160 -260 0 100 200 300 400

predicted Max load lbf

9Wood Inc. | 7BAppendices:

24

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

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 A: Screw torque range B: Screw setting practice C: Screw penetration depth 1.46E+06 5332.5 254397 2 1 1 730075 5332.5 254397

F-Ratio 500.92 3.66 174.55

P-Value <0.0001 0.0568 <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.

9Wood Inc. | 7BAppendices:

25

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

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.

Scatterplot by Level Code

400

400

Scatterplot by Level Code Max load lbf

Max load lbf

300 200 100 0 High Low Medium

300 200 100 0 0.5 0.625

Screw Torque Range

Screw penetration in

9Wood Inc. | 7BAppendices:

26

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

Scatterplot by Level Code

400

340 240

Residual Plot for Max load lbf

Max load lbf

residual

300 200 100 0 No pilot Pilot

140 40 -60 -160 -260 High Low Medium

Setting practice

Screw Torque Range

Residual Plot for Max load lbf

340 240

340 240

Residual Plot for Max load lbf

residual

residual

140 40 -60 -160 -260 No pilot Pilot

140 40 -60 -160 -260 0.5 0.625

Setting practice

Residual Plot for Max load lbf

340 240

Screw penetration in

Normal Probability Plot

99.9 99 95 80 50 20 5 1 0.1 -70 30 130 230 330

140 40 -60 -160 -260 0 100 200 300 400

predicted Max load lbf

percentage

residual

RESIDUALS

9Wood Inc. | 7BAppendices:

27

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

9WOOD INC.

Literature:

Copy of Cited Literature

Test Evaluation Report

Jonathan C. Gates July 2009

9Wood Inc. | 8BLiterature:

28

Information

Screw Withdrawal Strength in 9Wood's Assemblies

31 pages

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