Interapid M1.7 Contact Points

contact point length illustrated

Usable, exposed catalog length is the amount of protrusion (L) as shown in the sketch. The actual length is about 2 mm longer.


How are they measured? From the shoulder (not including the thread) to the center of the ball. Contact point
thread size is M1.7 x 0.35 Those are the measurements given below.

Why do many catalogs have different lengths from those listed below? The Interapid carbide point lengths shown in the catalogs are the length of protrusion from the front of the indicator. A useful figure in some circumstances but not particularly helpful if you have a handful of contact points and you need to sort them out. We have also listed the actual length of the point from the
shoulder to the center of the ball as a reference.

Ball diameter is .080" (2 mm) on new Interapid indicators. Carbide is standard with these models.

Most significantly, for accurate readings, Interapid contact points must be at an angle of about 12-15 degrees from the work surface. This is more critical with .0001" indicators where errors can quickly add up.
Catalog length = .650"
Actual length = .687"
  • 312B-1
  • 312B-2
  • 312B-3
  • 312B-4
  • 312B-20
  • 312B-1v
  • 312B-2v
  • 312B-3v
  • 312B-20v
Ball Ø Actual Mfg equivalent Our Part Number US$
carbide .015" .687" 74.116284 MTC39-02 $29.50
carbide .031" .687" 74.105998 MTC39-03 $24.50
carbide .060" .687" 74.105997 MTC39-04 $24.50
carbide .080" .687" 74.105996 MTC39-05 $24.50
Nylon .060" .687" none MTC39-19 $35.50
Teflon .060" .687" none MTC39-16 $35.50
Teflon .080" .687" none MTC39-17 $35.50
ruby .040" .687" none MTC39-13 $35.50
ruby .080" .687" none MTC39-14 $35.50
Catalog length = 2.675"
Actual length = 2.750"
  • 312B-15
  • 312B-15v
Ball Ø Actual Mfg equivalent Our Part Number US$
carbide .015" 2.750" none MTC40-33 $29.50
carbide .031" 2.750" 74.111910 MTC40-34 $29.50
carbide .080" 2.750" 74.111913 MTC40-35 $29.50
carbide .100" 2.750" 74.111912 MTC40-36 $29.50
carbide .080" 5.5" none MTC39-55 info
Catalog length = 16.5 mm
Actual length = 18.5 mm
  • 312-1
  • 312-2
  • 312-1v
  • 312-2v
Ball Ø Actual Mfg equivalent Our Part Number US$
carbide 2.0 mm 18.5 mm 74.105993 MTC40-05 $24.50
carbide 1.5 mm 18.5 mm 74.105994 MTC40-04 $24.50
carbide 0.8 mm 18.5 mm 74.105995 MTC40-03 $24.50
Catalog length = 15.2 mm
Actual length = 17.2 mm
  • 312-3
  • 312-4
Ball Ø Actual Mfg equivalent Our Part Number US$
carbide 2.0 mm 17.2 mm 74.110482 MTC40-15 $24.50
carbide 1.5 mm 17.2 mm 74.110491 MTC40-14 $24.50
carbide 0.8 mm 17.2 mm 74.110507 MTC40-13 $24.50
Teflon 2.0 mm 17.2 mm none MTC40-17 $38.50
contact point length illustrated
Double length

You can use these double length points on any of the models listed. The readings on the dial will be doubled as a result. The graduations on the .0005" indicator will therefore equal .001" and the graduations on the .0001" indicator will equal .0002". This only works if the contact point is exactly twice the length of the standard point.

  • 312B-1
  • 312B-2
  • 312B-3
  • 312B-4
  • 312B-20
  • 312B-1v
  • 312B-2v
  • 312B-3v
  • 312B-20v
Ball Ø Actual Mfg equivalent Our Part Number US$
carbide .030" 1.450" 74.106363 MTC39-33 $32.50
carbide .060" 1.450" none MTC39-34 $32.50
carbide .080" 1.450" 74.106361 MTC39-35 $32.50
carbide .120" 1.450" none MTC39-37 $32.50
Indexable bent contact point

The Indexable bent contact point is designed for use with Interapid test indicators and the photograph gives you an idea of its use.

Any notion of taking direct readings goes right out the window, however. This contortion means that you can only use your indicator for the purpose it was designed: comparison work. If you're not sure whether it'll work for you or not, buy just one piece to test it. We make no guarantees.

Ball diameters are limited and they're only available in carbide.

contact point length illustrated

Dimension A and B are approximate.

A B Carbide Ø Mfg equivalent Our Part Number US$
.6875" .3" .031" none MTC41-01 $44.00
.6875" .3" .060" none MTC41-02 $44.00
1.45" .3" .031" none MTC41-03 $44.00
1.45" .3" .060" none MTC41-04 $44.00

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