Screw for dial: under some conditions these little screws have an annoying habit of unscrewing themselves as a result of vibrations. Don't take it personally if this happens to you. We suggest you tighten the screws on a regular basis—perhaps each time you calibrate the indicator—so that they won't fall out and jam up the works. It's a little bit like tightening those screws on your eyeglass frames, before they fall out—probably while you're on vacation somewhere. (The manufacturer solved this problem in new models made in 2014 by simply gluing these small dial screws in place. This can make it very hard to remove them during a repair.) Horseshoe Clips used on the old Interapid 310 and 311 series indicators can be purchased from Mr. Wayne Root who has manufactured a supply of these. They are available on E-Bay by clicking here. FYI: Ball Bearing tap size M4x0.35 Hair springs can be daunting so we've made a hair spring and gear assembly available. Just remove the old gear and hair spring, and replace with the new. See the parts list above. Up and down pressure on the contact point should be about even. This is the function of the return lever (drawing #9) and the shape of the spring. For ideal performance, the shape of this spring should mimic that of a brand new part. Often times, this spring gets bent out of shape when it is removed during a repair attempt.  
Part 123083 (left) for .0001" indicators, part 123084 (right) for .0005" indicators showing ideal spring shapes. Crystal replacement: Interapid crystals are not user replaceable. They require a crystal press for insertion. The crystals are flat or just slightly convex, slightly over-sized and must be inserted with a crystal press. The crystal press will make them dome-shaped and this is what keeps the crystals in place. You can opt to purchase the bezel with crystal already installed (see parts list above) so that you simply remove the old bezel and screw on the new bezel with the new crystal, or you can send us the indicator with instructions to replace the crystal only. The cost is $30. Removing the bezel: The bezel is threaded and unscrews. Hold the lower bezel plate steady with a small screw driver or pin, placed in one of the two holes, while you unscrew the bezel (see details below). Stem attachment: If the mounting stem is bent or broken you can replace it with a bit of care. When you remove the old stem, don't lose the other parts. Unscrew A (#18), remove B (#19), tap out the bushing E (#22), save the washer D (#21) which goes on the inside, then remove stem C (#20). Reassemble in reverse order. 
Be advised that we only sell the new style stem attachment. Old style stem attachments, pre-1965, are no longer available.
The old style, shown in the photo to the left, had an adjusting screw built into the stem and had a large diameter chrome pin running through the sides. It did not have the components shown in the drawing above. It will not be possible to install the new style stem into the old model bodies. 
Contact lever 110547 installed on the pivot. When replacing, be sure you do not install it backwards. The pivot and the contact point are not included when ordering this part.
How to tighten a loose bezel 
The bezel is screwed on as you have probably noticed.
Take a look under the rim and you'll see two holes. Insert a rod, a pin, a screw driver, something small into one of the holes. This will keep the plate from rotating while you turn the bezel and now you can tighten it again, by hand. If you have the small diameter bezel, there won't be any holes but there will be two slots (you can also see this slot in the enclosed photo). The slots serve the same purpose for the small diameter indicators (but not for the large diameter).
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