Sadly, all Compac test indicators were discontinued in 2020. Since we still repair indicators that were bought in the 1960s there is every reason to believe they will remain in the connoisseur’s tool box for years to come.
Compac models are designed to permit a true reading when the angle between the stylus and the reference surface is 0° (i.e.., 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 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 certificate, please specify at time of ordering. We will provide these certificates for an additional charge (series 210, 220 and 230 indicators shown on this page only).
While Compac test indicators are accurate ± 1 graduation when used as a comparator, they have total allowable deviations over their entire range as follows:
All spare parts are available and, with experience since 1959, repairs can effectively be made on any of these indicators.
Because we are an authorizer repair shop, we can also take care of any warranty issues which might arise. When making repairs, 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 indicator that's as good as new and one you can rely on. For details, including repair costs, see page 30.
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.
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 (i.e., 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 our separate contact points list.
Q: I just tested a Compac 215GA. The movement through range is good, but the hysteresis in both directions (up or down) is .0003” or .0004”. Can you tell me what I should suspect is causing this huge error in hysteresis? I seem to have similar trouble with this indicator every calibration.
Q: I have a Compac 224GA for which adjusting the contact point angle seems awfully stiff. I am afraid of breaking the contact point off at its thread. I don’t see a screw for adjustment of that aspect. Is there an adjustment? Lubrication of the “brake claw” that appears to grip the contact pivot?
Q: After testing the .0001 test indicators we believe that the double swipe .0001 indicators just don’t read as true as the single revolution BesTest, for instance. Have you noticed similar results?
Q: I am interested in the Compac 213GLA test indicator. Your website said that some have had dials that were not printed very well, though, but also that Compac was your indicator of choice for 4 decades. Are the dials back up to snuff?
Q: What is the best way to preserve the dovetails in the long run on something like the Compac, with integral, non-hardened dovetails?
Q: I want a quality dial test indicator where the dial hand always moves clockwise whether the point is pressed from either direction and no "reversing lever" to worry about. I also prefer .0005" graduations, 1.5" dial, and .060" movement or close to it. I was under the impression the Compac worked in this manner, but I was just told they work just like my interapid.
For answers to these and many more questions please take a look at our new publication: Reference Guide for Test Indicators
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