PAGE 233 — CRYSTALS

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Long Island Indicator Service

PROFESSIONAL REPAIRS & SALES IN THE U.S.A. SINCE 1959

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Roy Meyer and team


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.

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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.

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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.)

Companion Reference Guide for Test Indicators
$15.00 Now available at Amazon.com

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: We do not sell individual crystals at this time. This page is for reference only.

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 (unless otherwise noted)
25.1 mm Alina, Compac (small dial models)
26.7 mm Standard Gage, Mitutoyo
27.9 mm BesTest (old models), Girod, Puppitast, TesaTast
28.6 mm MarTest, China, Interapid, Federal "A", B&S Group O
30.8 mm Mitutoyo "Pocket" style, Starrett models made in China
34.7 mm Mitutoyo, Teclock
35.7 mm (special .032" thickness) Brown & Sharpe, TESA, Etalon, Compac
36.6 mm Starrett model 196, Interapid
36.8 mm Starrett
37.8 mm Girodtast, Tesatast, Mitutoyo, B&S, Starrett
39.0 mm Alina, Puppitast, MarTest, Compac, Boice
40.0 mm Starrett
42.0 mm Mitutoyo
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

Some people are successful in polishing scratches and foggy areas out of their plastic crystals. This is not a method we use nor can we guarantee that it will give you the best results. However, it might be the perfect alternative to buying new parts and a crystal press.

Companion Reference Guide for Test Indicators
$15.00 Now available at Amazon.com

Disclosure: some of the links on this website may direct you to Amazon. Any purchases you make from those links will result in a commission for us. That commission helps to pay for the construction and upkeep of this web site. We are grateful for any purchases you make through those links.

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