Measuring Matrix screw thread dimensions

Figure 1.0 Profile Projector Machine.              Figure 1.1 Micro Profile Projector Machine

OBJECTIVE

Measuring certain dimension of a matrix screw thread

1. M24  3.0 ISO 6H
2. M5  0.8 6H

 

APPARATUS

Profile Projector Machine, Micro Profile Projector Machine, Specimen (matrix screw of M24  3.0 ISO 6H and M5  0.8 6H)

 

 

 

 

 

 

THEORY

The terminology of screw thread.

• The pitch is the distance between adjacent thread form measured parallel to the thread axis.
• The major diameter is the largest diameter of a screw thread.
• The minor diameter is the smallest diameter of a screw thread.
• Thread angle is fixed when the thread had its own standard angle. The angle is 60 degrees and the crest of the thread maybe either flat or rounded.
• The depth of cut is referred to the distance between crest and root of the thread.

   p = pitch

 

 

 

 

 

 

 

 

PROCEDURE

1. Place the screw M24  3.0 ISO 6H onto the Profile Projector Machine.
2. Set the height and location of the screw to be near the lens.
3. Suitable scale of projection is selected in order to determine appropriate projection on the screen.
4. Determine the:                                                                         
1. Major diameter
2. Minor diameter
3. Pitch
4. Thread angle
5. Depth of thread.
5. The readings for each of above are taken 5 times and the average values are calculated.
6. For the screw M5  0.8 6H, the procedure are the same as above just that it is measured using mini Profile Projector Machine.

 

RESULT

 

I. M24  3.0 ISO 6H

 

                                  Figure 1.3 Screw Matrix of M24  3.0 ISO 6H

 

 

 

 

Major	Minor	Pitch	Thread	Depth of Thread
23.992	19.841	2.996	5957’	2.083
24.069	19.792	2.998	59 29’	2.042
23.998	19.844	3.000	57 50’	2.072
23.990	19.813	2.997	59 43’	2.072
24.002	19.872	2.959	59 46’	2.064
24.010	19.832	2.990	59 21’	2.067

*all dimensions in mm

II. M5  0.8 6H

                                  Figure 1.4 Screw Matrix of M5  0.8 6H

 

Major	Minor	Pitch	Thread	Depth of Thread
4.965	3.73	0.805	57.3	0.442

*all dimensions in mm

 Figure 1.5 The projection of the screw profile.

DISCUSSION

 

            From the experiment above, both of the apparatus are used to determine the major diameter, minor diameter, pitch, thread angle and the depth of thread. The differences between these two apparatus are that the first one is used to measure bigger sample of screw and the profile is projected onto a screen which can be easily seen and measured. Whilst the second apparatus is used to measure and indicate smaller size of screw sample but the profile can only be seen through a lens such as a microscope. All of the measurements for the second apparatus are done only based on the projection through the lens. It is a little bit tougher as the scale is smaller and the adjustments of the micrometer must be done carefully and accurately to determine the deserved readings. Comparing to the first apparatus, the measurements are done easier as the readings can be taken directly from the big projection screen and the adjustment for certain axis is taken from a digital micrometer, means that the readings is more accurate.

 

CONCLUSION

 

Some of the readings for screw profile measurements vary due to several factors. One of the main factors that caused such matter is ralax parallax. Even some of the readings were taken 5 times, each of the readings show minor differences. It can be said that the person who operates the measurements did not measure accurately as sometimes mistakes happen when reading the measurements on the screen projection as it was not 100% clear and precise.  Besides that, it is said that the screw itself do not have consistent measurements, in order words the screw itself does not have the accurate readings as the given dimension and it is assumed to be under the permissible percentage of errors because the differences were very small.