Compac Dial Bore Gages
"The most expensive—and hardest to obtain—dial bore gages in the world"


Compac model IA2A-IAP555A shown above, along with 2 of the contacts and extensions.

Swiss made Compac dial bore gages are among the finest measuring tools available. Years ago, they were also manufactured with the name Interapid, Alina and SPI. Except for the dial face, these were identical in every way. Old models (pre-1970) varied slightly from the new models but all parts of the measuring head, including contacts and extensions are interchangeable. The dial indicator has changed substantially and parts for the old indicator may no longer be available.

Replacement contact plugs and extensions are sometimes available from Long Island Indicator Service. An optional depth stop can be used to insure reading at a consistent depth.


Compac dial bore gauge complete set


Only complete sets of bore gages are available. And only by special order. You will no longer be able to buy the measuring head and the indicator separately as you could in the past.

With the complete set you will also receive the wooden box and all the necessary contacts and extensions for that model. Specially designed dial indicators are included. (It will not be possible to use any other kind or brand of indicator with this measuring head.)

It should be pointed out that all metric models are discontinued.

All Compac bore gages are considered a special order by the manufacturer. It will be necessary to verify pricing and delivery on a case-by-case basis. You may have to allow 4 to 5 months for delivery in some cases. Although the manufacturer had announced that these were discontinued, they have had a change of mind, probably because there is still a small demand for them. We consider this very good news.

Spare parts are either in short supply or unavailable. Repairs may not be possible on new or old gages.

Important: unless you have a very good reason for using Compac bore gages and are willing to pay the price and wait the wait, we strongly urge you to consider buying a Mitutoyo or Dorsey Metrology gage instead.


Measuring head

Dial indicator resolution

Compac model number


Order no.

(made to order)

2018 Price US$
request verification












8 months







8 months

on request






8 months







8 months













8 months

on request


Prices change often and not usually for the better. The price listed is a current estimate which needs verification. Please email us for information.

It is not possible to place orders online. Please contact us for ordering instructions. Keep in mind that these will be made to order and require a minimum of 20 weeks for delivery. Delivery can take longer from past experience. Pricing needs to be verified for each order. Compac bore gages are made to order and once delivered, can not be returned (unless defective). We will require a 50% deposit which is only refundable if the manufacturer cancels the order.


Small bore replacement heads


The smallest bore gage (.16-.26") consists of 6 small measuring heads. These can also be bought individually, without a box, indicator or accessories. All you need is an indicator (IAP365A or IAP367A) as shown above. Metric models are also available. Wooden box #042399 is separately available to store all these measuring heads.

Only two pieces of #044065 remain in stock. They are no longer being manufactured.


Measuring head only

Part no.

Order no.


Liquidation Price






Measuring depth


  • .150"-.270" gage minimum: .020" maximum: 1.625"
  • .270"-.510" gage minimum: .120" maximum: 2.375"
  • .500"-1.00" gage minimum: .200" maximum: 3.500"
  • .800"-2.00" gage minimum: .320" maximum: 4.750"
  • 2-6" and 2-12" gages minimum: .360" maximum: 8.750"

Longer depth extensions are not available.


Repairs and spare parts


If you already own one of these bore gages, you know that they were the very best available. Take extra good care of them! (They don't make 'em like they used to.) Spare parts are now in short supply and, in some cases, no longer available. Repairs on new or old gages may no longer be possible.

Spare parts for Compac bore gages are no longer available from us. The parts lists shown elsewhere on this site are intended for reference purposes only.


Regular indicator vs. bore gage indicator


The Compac and Interapid bore gage indicator and the regular dial indicators may have the same model number, but there are some internal differences, as well as the obviously different case. The letters IAP identify the indicator designed for use with the dial bore gages. For example: IAP555A is the bore gage indicator, while 555A is the standard dial indicator. This distinction must not be overlooked when ordering parts.


Important calibration information


Compac and Interapid bore gages measure by comparison and therefore must be calibrated before use by means of one of the following:

  • reference ring gage
  • fork for slip gages
  • masterpiece
  • gap gage
  • micrometer

To calibrate the bore gage, proceed as follows:

  • Push the button in order to withdraw the movable contact and insert the measuring probes into the reference gage.
  • Seek the return point by oscillating the probe.
  • Turn the dial until the return point of the hand corresponds to the actual dimension of the ring gage.
  • Fasten bezel clamp screw.
  • Set the tolerance markers.
  • The instrument is ready for use.


Measuring Accuracy


The manufacturer does not supply any specifications for the accuracy of the bore measuring head because this gage is only used as a comparator; however, the dial indicators used in conjunction with the measuring head have the following accuracy:

IAP365A indicators:

.0001" accuracy

IAP367A indicators:

.0001" accuracy

IAP555A indicators:

.0001" accuracy

IAP365 indicators:

0,002 mm accuracy

IAP367 indicators:

0,002 mm accuracy

IAP555 indicators:

0,002 mm accuracy

IAP556 indicators:

0,002 mm accuracy


The bore gage indicator alone will have the same allowable total deviation (fges) as the corresponding dial indicators:

365A indicators:

fges = .00020"

367A indicators:

fges = .00020"

555A indicators:

fges = .00055"

365 indicators:

fges = 5 microns

367 indicators:

fges = 5 microns

555 indicators:

fges = 14 microns

556 indicators:

fges = 14 microns

How does it measure up?


And finally, how does the Compac dial bore gage compare to the competition? Take a look at page 8 and judge for yourself.




Q: I need the 2-6" dial bore gage but you say that only the 2-12" is available. I guess that will work, right?

  • The 2-12" dial bore gage is perfectly suited to measure from 2-6". Only three attachments make the difference between the two and you won't need to use the attachments if you are not measuring to 12-inches. (And, no, you can not buy the gage without the attachments. That would be too simple and logical.)

Q: I bought a measuring head a while back for a Compac .50 to 1.00 bore gage. I have been avoiding using it because I have to rock it pretty far to get the indicator to move. It seems like it has a flat or not enough of a crown on the contact. Is this something you can fix or do you have another carbide contact in stock to replace?

  • The gaging plunger (the movable contact) is not easy to install. If that is the worn part, then you should send it to us. We have replacements for the interchangeable contacts.



BesTest and TesaTast Indicator Repair Manual … page 177
Starrett 711 Last Word Indicator Repair Manual … page 199
Interapid Indicator Repair Manual … page 208
Compac Test Indicator Repair Manual … page 194
Mitutoyo Test Indicator Repair Manual … page 102

New! Companion Reference Guide for Test Indicators … page 178

Long Island Indicator Service Inc
14 Sarah Drive
Hauppauge NY 11788 — USA

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This page's most recent revision: 19 October 2019
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Long Island Indicator Service Inc

Precision Tool Repairs, Sales & Spare Parts