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Indicator Crystal Installation Reference Page

The crystals (clear plastic lens) for test indicators, dial indicators and calipers are typically larger than the bezel for which they are designed.

New crystals are also flat. They become domed once they are inserted, under pressure. An old crystal will appear domed because, after a long time, it will take on this shape. Unfortunately, at this point it will also fall out easily.

The crystals have a beveled edge which will fit into the groove on the upper part of the bezel, but must be inserted in a concave (domed) manner so that the crystal will remain in place under pressure, and so that the plastic clears the movable dial hand. You will need to order a crystal that is at least 1 mm larger in diameter than the bezel requires.


The flat crystal has to be larger than the inside diameter of the bezel (where the crystal will fit).

A crystal press is usually required to give the plastic lens its concave shape. (Bestest indicators and B&S calipers are exceptions.) Place the crystal and bezel in the press, in the correct orientation (take into consideration the beveled edge: the smaller surface will become the upper surface) and while the press is bending the plastic, gently snap the bezel into place. Release the press and the crystal will be firmly seated and have the correct curvature.

The press can not be used with crystals made of glass, which will shatter under pressure.

Hint: Use a bottom cup the same size or one size smaller than the diameter of the crystal.

Glue or cement is never used to hold the crystal in place. Some manufacturers may use a thin bead of silicon to create a waterproof seal. This is a tricky maneuver and should only be attempted with caution.

While home-made presses can be improvised, for frequent use and reliable results we suggest ordering the portable Crystal Press #7000 shown above. It allows for easy crystal replacement on all size test indicators (except for BesTest and TesaTast) and AGD series 1 and 2 dial indicators (Federal indicators excepted), and certain dial calipers. Before buying the press, read the instructions below to make sure a press will work with your indicators or calipers.


Crystal Press shown with various inserts (included) The photographer, not knowing different, mounted the lower cup incorrectly. It should be the other way around. Refer to the video below.

This hand operated press designed for use with Mitutoyo indicators, will allow you to insert crystals into bezels on test indicators, dial calipers and dial indicators up to 2-1/4" diameter. Comes with 8 different inserts as shown above. It can also be used for other brands of indicators including Interapid, Compac and Starrett. It is not suitable for Bestest indicators, Brown & Sharpe calipers or Federal dial indicators. Make sure that this press will work for the gages you have by reading the instructions printed below.

  • Mitutoyo Crystal press no. 7000 may be available from a local Mitutoyo dealer. (We cannot supply this tool, unfortunately.)
Why didn't we think of this before?

Wouldn't it be easier to just buy a new bezel with a crystal already installed? If you don't have a crystal press, it's the way to go.

Crystal Size Chart

Even though the manufacturer's name may be listed next to a particular crystal in the ordering chart below, it does not mean that every indicator or caliper made by that manufacturer can use that crystal. Be sure to measure the inside diameter of the bezel. (Read instructions above carefully)

  • Important: Select sizes are now available for purchase.

Note: this is the maximum diameter (±0.1 mm) of the plastic crystal when flat. After the crystal is installed, it will be domed. If you measure an old crystal, which is already domed, take this into consideration.

Diameter Suitable for (read instructions below carefully)
25.1 mm Alina, Compac (small dial models) IPW25.1 @ $6.85
26.7 mm Standard Gage, Mitutoyo IPW26.7 @ $6.85
27.9 mm BesTest (old models), Girod, Puppitast, TesaTast IPW27.9 @ $6.85
28.6 mm MarTest, China, Interapid, Federal "A", B&S Group O IPW28.6 @ $6.50
30.8 mm Mitutoyo "Pocket" style, Starrett models made in China IPW30.8 @ $6.50
34.7 mm Mitutoyo, Teclock IPW34.7 @ $6.50
35.7 mm (special .032" thickness) Brown & Sharpe, TESA, Etalon, Compac
36.6 mm Starrett model 196, Interapid IPW36.6 @ $6.50
36.8 mm Starrett IPW36.8 @ $6.50
37.8 mm Girodtast, Tesatast, Mitutoyo, B&S, Starrett IPW37.8 @ $6.50
39.0 mm Alina, Puppitast, MarTest, Compac, Boice IPW39.0 @ $6.50
40.0 mm Starrett IPW40.0 @ $7.50
42.0 mm Mitutoyo IPW42.0 @ $7.50
52.1 mm Peacock, Intertest
52.1 mm (special) Compac dial bore gage (old style)
53.2 mm Boice, Starrett, Mahr-Federal
53.8 mm CDI, Mitutoyo, S-T, Standard, Starrett, Teclock

Companion Reference Guide for Test Indicators
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