Comparators are the devices which are used to find only dimensional difference between the actual manufactured component and standard or master component.
Sine bar
Wednesday 13 April 2016
Sine bar is an instrument which is used for measuring smaller taper angles. Here taper means slant(inclined). So, the smaller angles are determined accurately by using Sine bar.
While using a Sine bar for finding the taper angles, some other intermediate equipment are required. Those are Surface plate, Slip gauges and a Dial indicator. By using all these tools a proper arrangement is made to find the taper angle value.
Methodology:
First we should clean the surface plate by using oil or grease to remove dust particles on the plate. Now, take the Sine bare and clean it too and place it on the surface plate. The cleaning of the tools is very important to confirm the accuracy in the measurement. Take the tapered object whose angle is to be measured and place it on the sine bar. Now, take the dial indicator and place it on the surface plate. Arrange the plunger of the dial indicator on the taper object where the smallest height of the taper surface takes place. While arranging the plunger at this end, apply some initial pressure to the plunger. After that make the indicator on the dial pad to coincide with zero by rotating the bezel of the dial indicator. When you rotate the bezel, the dial pad also rotates. Now move the indicator on the taper object from initial end to final end and observe the reading on the dial indicator. This reading gives you the height of the slant of the tapered surface. What ever the value we get on the dial indicator according to that we need to select the number of slip gauges to that value. The thickness of the slip guage would be given its surface. By observing its thickness select the slip guages by joining which we get the same value as we observed on the dial indicator.
Now, take those slip gauges and arrange them below one of the rollers of the sine bar where the smallest height of the taper object is taking place. When you do this the taper surface of the object becomes parallel to the surface plat. To confirm the accuracy of the parallelism once again move the dial indicator over the tapered surface. If any fluctuations are there in dial indicator in clockwise or anti clockwise, we should add or remove the gauges for confirming the parallelism of the taper surface with the surface. Once there is no fluctuation the dial indicator while moving over the taper surface from one end to another end, then we can confirm the parallalism. The total arrangement is given in the figure below provided.
Now, we need to apply the sine rule by constructing a right angle triangle with the help of height of the slip gauges and distance between the rollers of the sine bar as shown in figure below. Then we can find the what is the theta value which is only the required value.
The distance between the rollers is in between a range of 100 mm to 150 mm.
While using a Sine bar for finding the taper angles, some other intermediate equipment are required. Those are Surface plate, Slip gauges and a Dial indicator. By using all these tools a proper arrangement is made to find the taper angle value.
Methodology:
First we should clean the surface plate by using oil or grease to remove dust particles on the plate. Now, take the Sine bare and clean it too and place it on the surface plate. The cleaning of the tools is very important to confirm the accuracy in the measurement. Take the tapered object whose angle is to be measured and place it on the sine bar. Now, take the dial indicator and place it on the surface plate. Arrange the plunger of the dial indicator on the taper object where the smallest height of the taper surface takes place. While arranging the plunger at this end, apply some initial pressure to the plunger. After that make the indicator on the dial pad to coincide with zero by rotating the bezel of the dial indicator. When you rotate the bezel, the dial pad also rotates. Now move the indicator on the taper object from initial end to final end and observe the reading on the dial indicator. This reading gives you the height of the slant of the tapered surface. What ever the value we get on the dial indicator according to that we need to select the number of slip gauges to that value. The thickness of the slip guage would be given its surface. By observing its thickness select the slip guages by joining which we get the same value as we observed on the dial indicator.
Dial Indicator
Slip gauges box
Now, take those slip gauges and arrange them below one of the rollers of the sine bar where the smallest height of the taper object is taking place. When you do this the taper surface of the object becomes parallel to the surface plat. To confirm the accuracy of the parallelism once again move the dial indicator over the tapered surface. If any fluctuations are there in dial indicator in clockwise or anti clockwise, we should add or remove the gauges for confirming the parallelism of the taper surface with the surface. Once there is no fluctuation the dial indicator while moving over the taper surface from one end to another end, then we can confirm the parallalism. The total arrangement is given in the figure below provided.
Now, we need to apply the sine rule by constructing a right angle triangle with the help of height of the slip gauges and distance between the rollers of the sine bar as shown in figure below. Then we can find the what is the theta value which is only the required value.
surface integrity
Monday 27 October 2014
Surface integrity means it is a condition of surface of a component after manufacturing process. After manufacturing process the surface may be consisting of smoother surface or surface with irregularities. These conditions depends on the process characteristics of manufacturing process we have selected for the component.
Generally, a component is made by casting operation or any other machining operations. By taking care of the process characteristics for these two processes we can get the desired surface finishing for the component. For the casting operation what are the process characteristics means preparation of proper mould cavity with high compact strength, passage ways with smoother surface inside, proper cross sectional areas for the passage ways which provides uniform flow of the molten form of metal, getting totally converted form of metal etc. For machining operation process characteristics are constant speed ratio between worpiece and tool, uniform feed rate and proper depth of cut etc. So, maintaining all these process characteristics in optimum condition we can avoid the irregularities may take place on the surface of component.
Surface integrity is considered in two forms based on the irregularities and reasons for getting irregularities on the surface of a component after manufacturing process. Those two forms are Topography characteristics and surface layer characteristics. The topography characteristics are related to the irregularities related to roughness, waviness, flaws and lays. Surface layer characteristics are those irregularities which are due to the high heat applied to component which causes the change in crystal structure, grain structure and ultimately causes the variation of properties of metal of component.
Measurment of Pitch:
Monday 13 October 2014
A pitch value a screw thread can be measured in so many ways like by using screw pitch gauges, screw plug gauges and also by Tool Maker's Microscope. The screw pitch gauges are provided in a form of number of blades. Each blade provided with different thread profiles having different pitch values. The pitch value of each thread profile is mentioned on the blade. After manufacturing desired threads, the pitch value is checked by matching the profile with the number of pitch gauges.
Screw pitch gauges
A pitch value of external threads can also be determined by using Tool Maker's Microscope. In this method the pitch value can be measured by using two micrometers provided in longitudinal and traverse direction. By using the same cross mark, we should place the cross mark on any crest point or root point and then we should move that cross mark to the successive crest or root point by using the longitudinal micrometer. In between these two positions we should take micrometer readings as initial and final reading. The difference between these two readings is the desired pitch value.
Using a Pitch measuring machine:
A pitch measuring machine consists of two vertical slides provided with two screws. These two screws are provided for fixing a threaded component. It means we have to adjust the component in between the two screws of slides. These slides be sliding on the guide of base of this machine. This machine is also consisting of an indicator provided with stylus. According to the movement of the stylus the reading on the indicator will be changing. This indicator is provided on a guide way which will be sliding in traversing direction. Here one of the sliding is provided with a micrometer head.
After adjusting the threaded component in between the screws, we should insert the stylus of indicator in the thread and we should make the reading on indicator as zero. Then we should rotate micrometer so that the thread component moves in longitudinal direction. So, the reading on indicator changes. We should move the component until the reading again becomes zero. It means the stylus moved from a point on a flank surface to the next successive point on the next flank surface. Here, in between these two positions we should take two micrometer readings. The difference between two micrometer readings is the desired pitch value.
A pitch measuring machine consists of two vertical slides provided with two screws. These two screws are provided for fixing a threaded component. It means we have to adjust the component in between the two screws of slides. These slides be sliding on the guide of base of this machine. This machine is also consisting of an indicator provided with stylus. According to the movement of the stylus the reading on the indicator will be changing. This indicator is provided on a guide way which will be sliding in traversing direction. Here one of the sliding is provided with a micrometer head.
After adjusting the threaded component in between the screws, we should insert the stylus of indicator in the thread and we should make the reading on indicator as zero. Then we should rotate micrometer so that the thread component moves in longitudinal direction. So, the reading on indicator changes. We should move the component until the reading again becomes zero. It means the stylus moved from a point on a flank surface to the next successive point on the next flank surface. Here, in between these two positions we should take two micrometer readings. The difference between two micrometer readings is the desired pitch value.
Measurement of Thread angle:
Monday 13 October 2014
A Thread angle of a given screw thread can be determined by using Tool Maker's microscope. The microscope gives an enlarged view of the thread profile. In Tool Maker's microscope an illuminating unit is provided below a measuring table. This illuminating unit will focus the edge profile or contour shape of the thread. By getting the contour shape we can find the thread angle.
The Tool Maker's microscope is provided with a cross mark(x) on its primary eye piece. In this cross line, we have to adjust one line to one flank surface as it is aligning to it. In this position we should take the protractor disc reading as initial reading. Then after we should rotate the protractor as the same line of cross mark aligns with the opposite flank surface. In this second position again we should take the protractor reading as final reading. The difference between the two readings will be the desired angle value.
The Tool Maker's microscope is provided with a cross mark(x) on its primary eye piece. In this cross line, we have to adjust one line to one flank surface as it is aligning to it. In this position we should take the protractor disc reading as initial reading. Then after we should rotate the protractor as the same line of cross mark aligns with the opposite flank surface. In this second position again we should take the protractor reading as final reading. The difference between the two readings will be the desired angle value.
Tool Maker's Microscope
Measurement of Minor diameter of External and Internal Threaded component
Sunday 12 October 2014
Minor Diameter of External Threaded component:
The minor diameter of external threads can be determined by using a special type of micrometer which is provided with number of V-peices. These V pieces are changeable according to the root diameter of the thread profile. This method is used for British standard and British association threads. While measuring the minor diameter, the V pieces are connected to micrometer anvil and the screw is adjusted in between the anvils as tip diameter of V pieces matches with the root diameter of thread profile. If it is not exactly matching we should change the V pieces until a perfect match is obtained. Once the perfect match is obtained, then we should take the reading on micrometer which gives the minor diameter of screw or external threaded component.
Measurement of Minor Diameter of Internal Threaded component(Nut):
Minor diameter of an internal threaded component can be measured by two methods as they are by using Tapered Parallels and using Rollers & Slip gauges.
In the method of using tapered parallels, the tapered plates are placed at initial position on each other as they give minimum height and then they are inserted into a nut component. After inserting in a nut, they are slide on each other as the height be increasing. The sliding of tapered parallels is done until their top and bottom surfaces touch the crest points of the internal threads. Once they touch there will be no movement and in this position we should find the height of the plates by using micrometer. The micrometer anvils are to be arranged on the plates and reading should be taken.This reading will give the minor diameter of the Internal threaded component(nut).
In the method of using rollers and slip gauges, the two rollers are adjusted inside a nut with the help of slip gauages. It means in between the rollers number of slip guages are arranged as per gap taking place between the rollers. Here the diameter of rollers and width of slip gauages are known. By adding all these values we can find the minor diameter of an internal threaded component or a nut.
The minor diameter of external threads can be determined by using a special type of micrometer which is provided with number of V-peices. These V pieces are changeable according to the root diameter of the thread profile. This method is used for British standard and British association threads. While measuring the minor diameter, the V pieces are connected to micrometer anvil and the screw is adjusted in between the anvils as tip diameter of V pieces matches with the root diameter of thread profile. If it is not exactly matching we should change the V pieces until a perfect match is obtained. Once the perfect match is obtained, then we should take the reading on micrometer which gives the minor diameter of screw or external threaded component.
Measurement of Minor Diameter of Internal Threaded component(Nut):
Minor diameter of an internal threaded component can be measured by two methods as they are by using Tapered Parallels and using Rollers & Slip gauges.
In the method of using tapered parallels, the tapered plates are placed at initial position on each other as they give minimum height and then they are inserted into a nut component. After inserting in a nut, they are slide on each other as the height be increasing. The sliding of tapered parallels is done until their top and bottom surfaces touch the crest points of the internal threads. Once they touch there will be no movement and in this position we should find the height of the plates by using micrometer. The micrometer anvils are to be arranged on the plates and reading should be taken.This reading will give the minor diameter of the Internal threaded component(nut).
In the method of using rollers and slip gauges, the two rollers are adjusted inside a nut with the help of slip gauages. It means in between the rollers number of slip guages are arranged as per gap taking place between the rollers. Here the diameter of rollers and width of slip gauages are known. By adding all these values we can find the minor diameter of an internal threaded component or a nut.
Measurement of major diameter of internal thread
Sunday 5 October 2014
There is no perfect method for finding the elements of internal threads. But even we can find them by using screw pitch gauages and screw plug gauges. By using pitch gauges we can measure or check pitch value and by using the screw plug gauge we can measure or check major diameter.
Screw pitch gauges
Screw plug
Another approximation method is preparing the cast of the internal thread profile and following the same procedure as for the external threads. For preparing the cast of the internal thread, the nut is fixed in between two wooden blocks with certain gap. Through this gap molten form of metal like wax or sulphur is poured into the nut. Before pouring the molten metal, the internal thread profile should be properly cleaned and brushed from all the dust with oil. The molten metal should be poured upto a level of less than the radius of internal thread for easy removal. After solidification we have to remove the metal by lifting it up and then we should go for the measurements.
Another approximation method is preparing the cast of the internal thread profile and following the same procedure as for the external threads. For preparing the cast of the internal thread, the nut is fixed in between two wooden blocks with certain gap. Through this gap molten form of metal like wax or sulphur is poured into the nut. Before pouring the molten metal, the internal thread profile should be properly cleaned and brushed from all the dust with oil. The molten metal should be poured upto a level of less than the radius of internal thread for easy removal. After solidification we have to remove the metal by lifting it up and then we should go for the measurements.
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