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7. The vacuum gauge should read less than 150 mbar (Fig. 3). It should be in the green portion of the gauge.

Vacuum ValveExhaust FlapVacuum Gauge Image Removed
Image Added

                                      Figure 3

1. 1. If there is not a proper vacuum seal right away, try pressing lightly on the slides to help them seal and make sure the exhaust flap (Fig. 3) is clean.
   2. If that does not work, take off the slides and clean them and chuck face again.

8. Gently set the jig upright on the lapping plate in the forward arm.

9. The plate monitor can stay in place on the back arm.

10. Turn on the abrasive drum by overriding and make sure it is dripping properly.

11. Reset timer and set it to 10 to 20 minutes depending how hard the samples are.

1. 1. Samples that cut quickly on the PetroThin, lap for about 10 to 12 minutes for the first time.
   2. Samples that cut slowly on the PetroThin, lap for about 15 to 20 minutes for the first time.

12. Set the plate speed to 5 rpms.

13. When the plate is wet, press Start.

14. Increase the plate speed in small increments to 58 rpms.

15. The jig should start to spin after a couple minutes when all the samples begin to even out to the same thickness.

1. 1. Bungee cords can be added to the vacuum hose to assist the jig spin.
   2. Do not walk out of the lab when the LP 50 is running.
   3. If the samples are left on too long, the abrasive will "pluck" minerals out of the sample, leaving a hole.

16. When time is up, press Stop.

1. 1. It is best to bring the speed back down to 5 rpms after the lapping plate is stopped to help prevent starting it back up at a high speed.

17. Take the jig off the plate carefully.

18. Open vacuum valve and turn it off.

19. Place jig chuck face up in the sink.

20. Scrub the jig and slides gently with a soft brush to break the vacuum seal.

21. Clean the jig by scrubbing it down with warm water and a soft brush. Then, blow air through the jig and on the chuck face with the air gun.

22. Rinse the samples with warm water, and then

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wipe them with a kimwipe and isopropyl alcohol. Blow them dry with the air gun.

MEASURING SAMPLES

1. Hold the micrometer with your pinkie and ring finger through the "C" part of the micrometer. Your index finger and thumb will move the dial.
2. Clean the micrometer before use by placing a piece of paper in between the two bars and closing it gently (do not apply force). Pull the paper out and repeat.
   1. Gently close the micrometer all the way. It should read zero.
3. To measure the sample, place it in between the two bars and close them gently onto the slide where the sample sits.
   1. Take a measurement at the middle and sides to make sure that the sample is even all the way across.
4. On the micrometer, each tick mark is 10 um. The difference between the thickness you measure and the thickness of the slide is the thickness of the sample. For an example, if you measure 19 on the micrometer and the slide is 15, that mean the sample is 40 um.
   1. Soft samples should be about 45 to 50 um.
      1. If the sample is too thin, they will either not get a good polish before they reach their target thickness of 30 um, or, they will become too thin.
   2. Medium or hard samples should be about 40 um. This is the majority of samples.
   3. Very hard samples should be about 35 um.
      1. If the sample is too thick, it will take a very long time to polish down to the target thickness.
5. Write the thickness next to each sample on the sample tray.
6. If the samples are too thick, put them back on the lapping wheel for a couple more minutes.

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