Measurement of Screw Holding Force of MDF
Medium density fiberboard-Determination of screw holding capabillty
1 Subject Content and Scope of Application
This standard specifies the method for determining the screw holding force of MDF.
This standard is suitable for indoor medium density fiberboard.
2 Reference Criteria
Preparation of MDF specimens in GB 11718.3
GB 100 countersunk wood screw
3 Equipment and measuring instruments
3.1 Wood universal testing machine.
3.2 Special fixture, see figs. 1 and 2.
Zmt8.bmp (9664 bytes)
Zmt9.bmp (5076 bytes) zmt10.bmp (3584 bytes) zmt11.bmp (4964 bytes)
4 Sampling and specimens
Sampling and cutting of specimens are carried out according to GB 11718.3.
5 test methods
5.1 The force of holding screw can be divided into front holding screw force and side holding screw force.
A. The front grip screw force is the force pulled out from the surface of the screw vertically screwed into the plate.
B. The side grip screw force is the force pulled out from the side of the screw vertically screwed into the plate.
5.2 When the nominal thickness is less than or equal to 18 mm, the two specimens should be glued together, but not when the nominal thickness is less than or equal to 9 mm.
5.3 Side grip screw force specimens, three of which are parallel to the length direction of the plate, and the other three are parallel to the length direction of the plate and the width direction. This test is not performed when the weighted thickness is less than or equal to 15mm.
5.4 The position of the screw holding the screw force under 5.4 is shown in Figure 3. Three 4*40 mm wood screw specified in GB 100 standard are used. The guide hole with a depth of 14 mm is drilled with a drill bit of 2.8 mm, and the screw is screwed into a depth of 17 mm. The guide hole and the screw must be kept perpendicular to the plate surface.
5.5 The position of the screw for measuring the side holding force is shown in Fig. 4. Two 4 x 40 mm wood screw according to GB 100 standard are adopted. Drill a 14 mm deep guide hole with a 2.8 mm bit and screw the screw into the 17 mm depth. The guide hole and the screw must be kept perpendicular to the side.
5.6 After screwing in the screw, pull the screw test immediately to keep the screw aligned with the center line of the upper and lower fixture of the testing machine.
5.7 The speed of screw pulling should be uniform, 0.25 + mm s. The maximum pulling force when the screw is pulled out is the screw holding force. The reading is accurate to 10N. In order to ensure the accuracy of test data, the screw should not be reused.
6 test results
The front grip screw force of each plate is the arithmetic average value of the front grip screw force of three specimens, and the side grip screw force of six specimens is the arithmetic average value of the side grip screw force of six specimens, which is calculated accurately to 10N.