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In this video, I will be explaining what is a universal bevel protractor and how to read one. This protractor is a precision gage used to check angles on parts which holds an accuracy up to 5 minutes using the vernier scale. This particular protector is made by Starrett, other manufacturers of these as well, styles and qualities will vary. Some also have a magnifying glass over the vernier scale for easier viewing. How to read the protractor with vernier scale will be towards the end of the video.
It’s able to rotate 360 degrees but is broken into 90 degree segments. It can read in both the clockwise and counterclockwise direction which I’ll show you in a moment.
First, we have the beam, also known as a base or stock which is a stationary piece used as the measuring edge. Sometimes you can also mount an acute angle attachment to the beam to measure acute angles. This means angles smaller than 90 degrees.
Next is the blade that rotates along with the protractor and can be adjusted.
Here is the protector, as mentioned earlier it rotates 360 degrees but is broken into 90 degree segments.
The lock for the protractor to keep everything in place.
Another lock for the blade to prevent it from moving.
A fine adjustment that needs to be pushed down to engage a gear so the protractor can move.
And finally, the vernier scale allowing us to achieve an accuracy within 5 minutes.
Now to show you the bevel protractor’s operations. If the blade lock is disengaged and as you can see the blade moves freely.
Rotate to lock and the blade is locked into place.
Next, disable the protractor lock and it rotates freely.
Tighten and then it’s locked into place.
Disengage the lock again.
Then push down the fine adjustment to engage the gear and twist to rotate the protractor.
Now to measure the bolt, demonstrating the protector can measure from either side of the beam. Ensure the blade is locked so it doesn’t have any movement, the object against the working edge and align the blade against the other surface.
Lock the protractor and take a reading. We have a reading of about 60 degrees and we are measuring in the counterclockwise direction. The degree numbers are increasing to the left. In order to calculate an over 90 degrees which we have, minus your reading from 180, this gives us 120 degrees. In a moment I’ll show you how to use the vernier scale.
Aligning the head of the bolt on the beam again, but this time on the other side. This time we are measuring in the clockwise direction, therefore, the numbers are increasing to the right. With a reading of 60 degrees, measuring an angle greater than 90 degrees, 180 minus 60 gives us a final measurement of 120 degrees.
Moving onto reading the vernier scale. Just setting the bevel protractor at a random reading, while this can be hard to see on camera due to the glare, I have taken photos for a better visual representation.
As you can see the numbers are increasing in the counterclockwise direction. Taking the first reading, using the 0 line on the vernier scale, which line does it pass on the protractor.
First, we have 30 degrees.
Considering we’re traveling in the counterclockwise direction, the vernier scale must go in the same direction.
Determine which line between the vernier scale and protector aligns best.
This would be 25 minutes.
The final measurement is 30 degrees and 25 minutes.
The next example, this time measuring in the clockwise direction. Again determine which line the 0 on the vernier scale passes on the protractor. This time it’s 76 degrees.
Which line does the protractor and vernier scale align with best? Being that we’re traveling in the clockwise direction, do the same with the vernier scale. We have 45 minutes.
76 degrees and 45 minutes is our final measurement.
And a third example. Traveling in the clockwise direction, the 0 line on the vernier passes 54 degrees.
Taking a reading from the right side of the vernier, we have a minute measurement of 50.
Leaving us a final measurement of 54 degrees and 50 minutes.
This concludes the rest of my video, if you have enjoyed it, please leave a comment below and throw a like my way. Don’t forget to subscribe for more metalworking videos, thanks for watching.