How to Measure Gems With Calipers

Determine the size of gemstones using calipers.

Jewelry design and manufacturing requires a knowledge of gem size. In order to measure gems, you will require a special tool called calipers. Calipers can be manual or digital but, in either case, the directions for usage are the same. You are able to measure both the outside and inside of a gem. The outside measurement will provide you with a length and width value while the inside measurement can give you the size of the center hole in the gem.

Things You'll Need

• Microfiber cloth
• Calipers

Instructions

Outside Measurement

1. Wipe the jaws of the calipers to remove any dust or dirt. Your calipers have two sets of two jaws, or metal extensions, that are used for measuring. There is one small set on the top and one large set on the bottom. The small set is used for inside measurement while the large set is used for outside measurement. The jaws operate in the exact same fashion. One of the jaws is fixed while the other slides. Residue on the jaws can distort your readings so clean them thoroughly before measuring.

2. Close the jaws of the caliper by pressing on the bump of the sliding piece and pushing together. Make sure the reading is 0 when the jaws are closed to ensure the calipers are in good working order.

3. Slide the jaws open and hold your gem between the two jaws.

4. Slide the jaws closed on the gem by pushing the sliding piece toward the gem until it touches and holds the gem in place.

5. Read the measurement. If you are using a manual caliper, you will read the measurement as you would on a ruler. There will be notches and numbers that indicate the size of your gem. If you are using a digital caliper, the display screen will show your size.

Inside Measurement

1. Follow Steps 1 and 2 of "Outside Measurement" to ensure your calipers are clean and working properly. The inside measurement jaws are on the top of the caliper.

2. Slide the jaws closed and hold your gem at the tips of the jaws. Since you are measuring an interior space, such as a hole in the center of the gem, you will need to start with the calipers closed.

3. Slide the jaws apart until they are tight against the opening that your are measuring.

4. Read the measurement in the same manner as outlined in Step 5 of "Outside Measurement".

Tips & Warnings

• Always keep the gem straight inside of the calipers to get an accurate reading.

References

• Little Machine Shop: Using Calipers
• Archaelogica: Using Calipers