Disassembly of Interapids
To get at the internals the dial assy needs to be removed, removing the side screws is not recommended, the adjustment on those screws is critical to the proper functioning of the indicator.
To start: the bezel / crystal assy unscrews counter clockwise, you use a small screw driver or the like to hold the bottom base and unscrew bezel by hand placing the driver so the edge rests against the ind body as a positive stop allowing you to put some torque on the bezel. there are notches in the lower plate to facilitate this, after bezel is off the 2 screws under dial assy will allow removal of base plate, as someone suggested tape will hold the zero position, but it's no big deal to reset.
Resetting Backlash spring:
Holding the assy in your left hand put the tip of your right index finger on the crown gear and roll forward (towards your left hand) depending on finger length watch the dial till both hands are zeroed, (hand should be moving counter-clockwise with the small hand to the right for reference) normally you will go around past zero at least twice for the proper backlash spring tension, The test is weather you have equal pressure when depressing contact point in both directions, it should be very close.
Hand removal:
If cleaning the dial assy the hands and dials need to be removed and very carefully I should point out, the pinion is very thin and easily broken if not done properly with 2 hand priers and equal pressure . Wiha sells chip removers that work very well for the large hand (#26810 $6.10-Digikey). The small hand is removed by first taking the dial screws off and placing an exacto blade under dial adjacent to the hand and twist blade handle to lift up on dial and it will pop off, hold a finger over hand so as not to send it flying. The Exacto is also useful in removing the screws as they are really tiny even with the smallest Precision driver.
Cleaning:
Cleaning should be done in an ultrasonic cleaner in a jar with denatured alcohol, being careful not to leave it in for too long as the paint is easily removed, you can also dip into alcohol and then blow out with compressed air, when cleaning the dial assy use very light air pressure and the hand temporarily installed and held so as not to damage hair spring (high pressure air will blow the spring out making further repairs necessary. Once cleaned lubrication is necessary.
Lubrication, dial assy:
Spraying some Wd 40 on a block or any hard surface and dipping the tip of exacto to place "minute!" amounts of oil on each bearing/jewel top and bottom, the lower center pinion (large hand) bearing is above the crown gear and also needs lubrication its a little hard to get to but the tip of the blade can reach it.
Lubrication, main body:
Lubing the body bearings is done in the same manner, you can put excess in and blow out with compressed air. If the bearings are out apply a lot of WD40 into the ball bearing assy with a small diameter test indicator contact point mounted in a hand drill press against the roller cage and spin at a fairly high speed then reverse, rinse with fresh WD and repeat, blow out the bearing with compressed air and that will be sufficiant.
Bearing adjustment:
Adjustment of the bearings is critical,the sector gear must fall freely when raised to the middle position under its own weight, in addition to having next to none side to side play, the same goes for the lifting mechanism (side play) of the contact point assy, that's why I say to leave these bearings alone. But if they have been touched, leave one side locked and snug and tighten the opposite side then. back off just enough to allow movement,remember tightening the locknuts will also tighten the bearings so you need to loosen enough to allow free movement after tightening, you can check play with tweezers inside the body assy.In addition the gear sector and cam assy inside the body need some clearance from each other, not a lot just not touching.
Re-assembly:
When re-installing the dial assy, wind as described above and hold indicator hand with your finger at the 12 O'clock position, then you must lift the sector to the middle position by depressing the contact point from above, it requires very little pressure to get it in that position, and you will feel a positive stop before cam lifts it to the upper position , you will know when done correctly if you depress point in both directions and you have equal range and it returns to zero. A few tenths of inequality is acceptable being it's past the workable range of the indicator.
If the hands have been removed the starting point for setting backlash tension is around a finger length, that is rolling the crown gear from finger tip to the second knuckle around 2" the hand should be going counter-clockwise, holding position with the small hand to the right, the small hand does not need to be installed now just for reference.
After assy check for equal pressure top and bottom and adjust backlash accordingly SLIGHTLY more or less depending on the situation.This can be checked without installing the screws that hold the dial assy on, just hold it in place and test.
Checking accuracy:
Because of the way interapids are made and the shape of them,the proper way to check accuracy is with the contact point adjusted parallel to the bezel assy, normally I hold it up to a window with blinds on it and use the slats as a reference holding the body so that the bezel is horizontal and bend the point accordingly.
Any questions feel free to shoot me an email