Compac Test Indicator
Single Revolution Series 240 - Inch models
Horizontal Style

Compac model 244GA with large, easy to read dial is shown above, with box and two stem attachments (4 mm and 8 mm). The large hand moves smoothly once around the easy to read dial.

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Graduations

Total
range

Compac no.

Dial Ø

Contact point length

Order No.

List

Sale price

.0005"

.030"

244A

1.06"

.68"

27742

129.00

109.00

.0005"

.030"

244GA

1.58"

.68"

27743

136.00

119.00

.0005"

.020"

244LA

1.06"

1.80"

27745

177.00

139.00

.0005"

.020"

244GLA

1.58"

1.80"

27744

190.00

149.00

.0001"

.008"

245A

1.06"

.72"

27747

142.00

119.00

.0001"

.008"

245GA

1.58"

.72"

27749

154.00

129.00

.00005"

.008"

20-055-0

1.58"

.72"

20-055-0

187.00

179.00

A schematic drawing is available showing indicator dimensions. Two stem attachments T4 (5/32" equivalent to 4 mm) and T8 (8mm) are included. For tolerances see below. Model 20-055-0 has the same tolerances and specifications as model 245GA

Metric models can be found on page 108.

Free crystal replacement

Crystals get scratched, discolor or crack for one reason or another, but here's good news: if you bought the Compac test indicator from us, we'll give you a coupon good for a one time crystal replacement. Here are the details:

• It's a Compac test indicator
• You bought it from Long Island Indicator Service and can prove it
• We'll replace the crystal one time
• For as long as you own the gage
• At no cost except shipping and handling

Black dial - yellow dial - white dial

Compac model 244BF and other black dial models have been discontinued. It had a black dial and orange hand like the more popular Bestest indicators. Long Island Indicator has replacement dials and hands for some of these models, and because all other parts are identical to the standard white dial models these indicators will remain serviceable for years to come.

Yellow dials are the standard for metric gages in the USA. While most new metric Compac indicators are shipped with white dials, yellow dials can be purchased and installed.

Important calibration information

Compac models are designed to permit a true reading when the angle between the stylus and the reference surface is 0° (ie., they are parallel).

Since the dial test indicator is used as a comparator, the angle can usually be set to remain at 0° for all comparisons. However, when the indicator is run through its range while attempting direct readings or for calibration, this angle will of necessity change, introducing the cosine error.

In the rare cases when measurement is required with the stylus at an angle other than 0° with respect to the reference surface the readings should be corrected. Refer to calibration instructions on gage 7 for details.

All new Compac test indicators come with a calibration certificate from the manufacturer, but they are not NIST traceable. If you need an NIST calibration cert, please specify at time of ordering. We will provide these certs free of charge for Series 240 (see details above).

While Compac test indicators are accurate ± 1 graduation when used as a comparator, they have total allowable deviations over their entire range as follows:

Model

total range

dial configuration

total deviation

hysteresis

repeatability

measuring force

244A/244GA

.030"

0-15-0

.0005"

.00015"

.0001"

0.25N

244LA/244GLA

.020"

0-10-0

.0005"

.00015"

.00015"

0.10N

245A/245GA

.008"

0-4-0

.00015"

.00015"

.00006"

0.25N

Source: Tesa SA, July 2005

Contact point length

It is imperative that the correct length of contact point be used with dial test indicators. Test indicators rely on leverage ratios to amplify the readings. Changing the length of the contact point will alter the ratio and result in incorrect readings. The common problem of incremental errors (ie, the readings gradually get worse from one revolution to the next) is most likely due to the installation of the wrong length point.

Most manufacturers specify the proper point length in their catalogs. It is not always clear, however, how the over-all length of the point is measured.

Compac contact points should be measured from the center of the carbide ball to the far end of the threads.

Some end-users purposely install extra-long contact points because their application requires it. If the contact point is exactly twice the length, then the readings on the dial will be doubled. Most .0001" Compac indicators can be fitted with a long point which will make the graduations read .0002"

Most manufacturers make indicators designed for use with long contact points. Compac test indicators have the letter designation "L" as a component of their model numbers.

Contact points can have a variety of ball diameters typically ranging from .015" to .120" and are available in carbide or ruby (special order). It is highly recommended that contact points fitted with carbide balls be used, especially for .0001" indicators. The size of the ball diameter has no effect on the indicator's accuracy.

To find the ordering number for contact points refer to the contact points list shown on page 21.

Compac Repair Service

All parts are available and with 40 years of experience repairs can effectively be made on any of these indicators.

It's our policy to replace any damaged or worn parts necessary for the full function of the indicator. This way you'll be sure to get an instrument that's as good as new and one you can rely on. If you use a credit card for payment, turn-around is less than one week. For full details regarding repairs of Compac as well as other brands of indicators, please refer to page 30.

Also, if you buy the indicator from us, you'll get a coupon good for one free crystal replacement when it gets damaged - for whatever reason.

Plus, if you request it, we'll provide you with a short-form certificate of calibration free with every indicator repair. After all, when your instrument comes back, you need to know that it's accurate.

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This page's most recent revision: 31 January 2008
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