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Long Island Indicator Service


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Interapid Test Indicator Spare Parts


These parts are for recent Interapid test indicators whose model numbers begin with 312 and 312B. You will not be able to use these parts on the old 311 and 310 models. The drawings above are for the .0001" horizontal models. The parts for the .0005" indicator and the vertical models may have a slightly different appearance. Order parts for all models from the list below.

Test indicators with .001" graduations such as model 312B-20 and 312B-20V will take the same parts as the .0005" indicators. Brown & Sharpe model 7025-4 is the same as Interapid 312B-1.

Model 312B-15 and 312B-15V will take the same movement parts as the other .0001" models. The return lever is different and unique. Check the parts list carefully if ordering for these.

Select parts are available from us, as shown below. If you need other parts, please contact the manufacturer for assistance. A few rarely used parts are not included in this online list.

For additional parts and drawings, please refer to our Interapid Indicator Repair Manual

Drawing No. Description Order No. Price (US$)
0 plastic storage box (not suitable for 312B-15 or 312B-15V) 111473 29.80
1 body only for 312B-1, B-2, B-20 111360 139.00
1 body only 312B-3, B-4, B-15 (allow 4-6 weeks) 111361 139.00
3 outer dial 0-4-0 (1.5" diameter) .0001" 026423 17.40
3 outer dial 0-15-0 (1" diameter) .001" 026428
3 outer dial 0-15-0 (1" diameter) .0005" 026426
3 outer dial 0-15-0 (1.5" diameter) .0005" 026422 17.40
4 screw for dial (see note below) caution: very small 105912 19.00
5 hand, revolution counter 108205 21.00
6 hand for 1" dial 108045 23.00
6 hand for 1.5" dial 108046 25.00
7 contact point lever .0001” (see notes) 110547 32.00
7 contact point lever .0005” (see notes) 110614 22.50
8 rack lever .0001” (and -15, -15V models) 110518 25.00
8 rack lever .0005” 110610 35.00
9 return lever .0001” 123083 24.00
9 return lever .0005” 123084 23.50
9 return lever for 312B-15 and 312B-15V 123101 26.50
10 ball bearing with spanner nut 109941 19.60
11 spanner nut only 123073 11.90
12 contact points see page 21
13 pivot 105925 29.00
14 screw for dovetail 106289 2.95
15 dovetail large 106288 20.50
16 dovetail short 106287 19.20
17 screw, travel limit 111326
18 stem attachment screw — see notes below 111318 4.50
19 stem attachment nylon — see notes below 111319 3.80
20 stem attachment ø 4 mm — see notes below 111317 32.50
21 stem attachment washer — see notes below 106034 3.20
22 stem attachment bushing — see notes below 110666 13.60
23 movement fastening screw (one piece) see notes below 105908 8.50
24 bezel with crystal installed (1” diameter) for models ending -2 -20 -4 -2V -20V 123079 32.00
24 bezel with crystal installed (1.5” diameter) for models ending -1 -3 -15 -1V -3V -15V 123080 35.00
25 crystal only for small bezel size 1” (plastic ø 28.6 mm) for models ending -2 -20 -4 -2V -20V 105967 16.00
25 crystal only for large bezel size 1.5” (plastic ø 36.6 mm) for models ending -1 -3 -15 -1V -3V -15V 105968 19.00
27 extension ring for large bezel 110300
28 complete movement for B-1, B-2, B-20, B-1V, B-20V, B-2V 111904 155.00
28 complete movement for B-3, B-4, B-3V 111905 155.00
29 contact point wrench 18.60307 9.40

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.)

Drawing No. Description Order No. Price (US$)
30 dial inserts (refer to Interapid Repair Manual for details)
31 center pinion for 312-1, 312-2, 312-1V, 312-2V, 312B-1, 312B-2, 312B-20, B-1V, B-2V, B-20V 123089 16.00
31 center pinion for 312-3, 312-4, 312B-3, 312B-4 and 312B-3V, 312B-15, 312B-15V 123097 16.20
32 bearing .0005” bottom 123088
32 jewel .0001” bottom 123096
33 hair spring gear .0005” 123091 16.00
33 hair spring gear .0001” (and 312B-15, 312B-15V) 123099 15.80
34 bezel friction spring 123082 14.90
35 lower movement plate for .0005" and .001" models 123086 59.00
35 lower movement plate for .0001" and 312B-15 and 312B-15V 123094
36 bearing .0005” top 123090
36 jewel .0001” top 123098
37 peg for hair spring 123078
38 upper movement plate screw 123076 5.20
40 crown gear for 312-1, 312-2, 312-1V, 312-2V, 312B-1, B-2, B-20, B-1V, B-2V, B-20V 123087 31.00
40 crown gear for 312-3, 312-4, 312B-3, 312B-4, 312B-3V, 312B-15, 312B-15V 123095 25.50
41 mounting ring with threads (bezel attaching inner ring) 123081 15.80
42 hair spring .0005” 123092 31.00
42 hair spring .0001” 123100 36.00
42 hair spring specifically for 312B-15 and 312B-15v 123242 58.00
43 screw for crown gear bearing 123075 11.90
44 crown gear bearing 123074 18.20

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
Stacks Image 784

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.


Caution if buying from Amazon: their product images sometimes do not match the product description. Read carefully!

Companion Reference Guide for Test Indicators
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