Interapid Test Indicator Spare Parts

Movement Parts

Caution: these parts are for recent model numbers starting with 312 or 312B. They will not fit older 311 and 310 models. (Drawing courtesy of the manufacturer.)

What are the most frequently used repair parts for Interapid test indicators?

We have been asked this question by start-up repair shops and in-house repair departments. Here are the most frequently used parts which should be in their inventory:

• crystal
• contact point
• mounting stem 111317
• ball bearing spanner nut 123073
• pivot 105925
• movement screw 105908
• hair spring (both .0005" and .0001")
• rack lever for .0005" models
• dial screw
• ball bearing

Among the most sought-after Interapid parts are the two movement fastening screws 105908 (item 23 on the list).

Dials: Up until recently, these dials were made of metal. Nice sturdy things, cleanly printed. New models (since 2014) have replaced these with a bright white plastic dial, still nicely printed. They are a bit thinner. But be careful: cleaning solvents may affect the plastic. Naphtha does not dissolve the plastic, but it will cause the plastic to warp if you don't dry it off promptly. Better to use a water-based cleaner if you need to soak the dials.

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. We suggest NOT trying to remove them if the movement does not need to be disassembled.)

Horseshoe Clips used on the old Interapid 310 and 311 series indicators are no longer available.

FYI: Ball Bearing tap size M4x0.35

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. Refer to our repair manual for illustrations.

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 $37.

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 #18, remove #19, tap out the bushing #22, save the washer#21 (which goes on the inside), then remove stem 111317. Reassemble in reverse order. Take a look at this short video to see how it's done.