Diameter of a Cylinder
- Measure multiple places on the cylinder
- Measure at the 3 locations on the cylinder which would be cut if you were cutting the cylinder into fourths.
- Should the part be less than 0.5", measure in the 2 locations that would divide the cylinder into thirds.
- Measurements should be taken from the head of the part down (non differentiated parts such as pins have no control on initial side)
- If all three measurements are within a 1/10-of-the-dimension-tolerance range (ex. for a dimension with a 0.005 tolerance, 3 recorded measurements on the same part are within 0.005 of each other), record the last measurement
- If all three measurements are outside this range, record the last measurement, write a note
- If this happens 3 or more times during an inspection, perform a capability index analysis on the difference between the upper and lower measurement for 30 parts.
Length of a Cylinder
- If the cylinder is less than 6" it can be measured with a caliper, if it is greater than 12" it must be measured with the CMM. Between here is at the discretion of the quality inspector and must be recorded in the Gage Review
- Place the part long-ways in the measuring teeth of the caliper
- Turn the part 90 degrees to measure again
- If both measurements are within a 1/10-of-the-dimension-tolerance range (ex. for a dimension with a 0.005 tolerance, 3 recorded measurements on the same part are within 0.005 of each other), record the last measurement
- If both measurements are outside this range, record the last measurement, write a note
- If this happens 3 or more times during an inspection, perform a capability index analysis on the perpendicularity of the head to the cylinder (using the cylinder as a datum) for 30 parts.
- Obtain a threaded bolt at least 5x larger than the expected thread depth
- Make sure bolt is threaded all the way to both sides
- Screw bolt in until stops
- Measure head height to threaded surface
- Thread depth = Total Bolt Length - Measured Bolt Length
Inside Diameter of a Rubber O-Ring
- Cut the o-ring so that it may be straightened
- Lay the rubber the groove of the ruler and line up with the edge
- Lightly lay the rubber in the groove without stretching
- Once straight, mark it final point or leave in if it remains straight
- Use the calipers to measure from the start of the ruler to where the o-ring (now cut into a line) ends
- Take the length and divide by 3.142
- Subtract out the width of the rubber itself
- This is the inside diameter of the o-ring
- Hit crosshairs at two points on the shaft side of the part
- Hit crosshairs at two points on the base side of the part
- Obtain angle from the read-out
- Hit crosshairs at the exact intersection of the shaft and the chamfer
- Hit crosshairs at the exact intersection of the base and the chamfer
- Read off only the axis that is stated should be measured from the print
- If the print measures length of chamfer from starting to base, then only the axis which runs the length of the part is recorded.
- The part is setup with a profile view on the optical comparator
- Three different points are hit with the crosshairs, between the edge nearest the under-side of the head and the apex of the head. These three different positions should be as equally spaced as possible, cutting the quarter circle into fourths.
- Record the measurement radius
- Do the same for the other side of the head
- If the differentiation is off by more than 1/10 of the dimension tolerance, make a note.
- Should this occur on more than 3 parts during the sample, a capability analysis must be done.
- The preferred method is to use the head of the part to create a virtual sphere on the CMM [However, size may prohibit this]
- This spherical feature should be extracted using spiral techniques rather than point techniques.
Drive & Drill Depth
When drive depth differs from drill depth, the most accurate measurement method entails using a cross-sectioned part. Using a pin when measuring drive depth can lead to a deeper reading with the hole. Likewise, using a pin with a conical drilled hole can lead to a reading which is too shallow for drill depth.
These inspection instructions may be followed when measuring an internal drive depth:
- Choose a gauge pin that fits the internal circumcircle of the drive
- Place the pin upright on the optical comparator and focus the comparator on the top tip of the pin
- Place the crosshairs at the tip of the pin
- Zero out the comparator
- Place the part, drive down, on the top of the erected pin.
- Move the crosshairs down to the top-most visible part of the pin (as per step 5, the part should now be covering the tip of the pin).
- This is the reading for the drive depth.
- Goto http://www.trianglecalculator.net/
- Enter the drill angle into the "A" angle
- Enter the pin diameter into "a" side length
- Take the result of [180-"A"]/2 and place in for degree "C"
- Look at the Height calculation to the right (not the side length of "b" or "c")
- Add the result of step 5 to the Drive depth obtained in part 1.
- Room temperature must be between 70 and 75 degrees F
- Get Base formula (Blue)
- Get Catalyst formula (Yellow)
- Place equal quantities on a paper pad and mix together with a flat knife. Keep turning over until green
- For larger cavities: Scoop it into the cavity containing internal measurements
- For smaller cavities: Insert mixture into a plastic syringe. Place a push rod in the syringe and inject into smaller cavity
- Wait for 15 - 17 minutes
- Remove rubber and use for measurements