Long Island Indicator Service

Blake Co-Ax Indicator

The original center locating indicator (made in U.S.A.) providing a unique approach to quick, accurate centering in boring and milling set-ups

Blake Co-Ax Indicator photo taken by Long Island Indicator Service

This is the
genuine Blake Co-Axial indicator made in USA since 1959. (Chinese CoAx imitations are sold by major catalog companies under "brand" names such as Fowler, SPI and Phase II and we strongly urge customers to think twice before investing in one of those.)

At Long Island Indicator Service we are always prepared to service what we sell. If your Co-Ax indicator ever malfunctions simply return it to us for a free repair evaluation. We've got lots of experience and plenty of parts for a truly professional repair. You can buy this gage with the confidence that it will be functional for many years to come.

complete set includes the indicator, internal feeler #851, external feeler #852 (shown in photo), restraining arm and box.


  • Feeler ball diameter: 1/8 inch
  • Measuring range: 1/4 inch axis offset
  • Capacity: 5/32 to 4.25 inches internal; 0 to 4.25" external. Optional feelers extend these capacities to 12 inches. See accessories list below.
  • Speed: spindle rotation up to 800 rpm
  • Locating accuracy: .0002" of true center
  • Initial positioning: within 7/16 inch diameter of true location
  • Graduations: .0005" or 0,01mm
  • The entire gage will just fit into a 2.2" diameter cylindrical space
  • Overall length of gage, without the feeler is roughly 5.2", with the shortest (standard) feeler installed, the overall length is about 6-3/4 inches. When the upper shaft is inserted into a chuck, the overall length is about 5-3/4 inches.
  • The spindle diameter is 3/8" on the inch model, 10 mm on the metric model.

The indicator dial remains stationary while the machine spindle rotates, leaving the operator with both hands free to accurately position the machine table in the X-Y axis while conveniently observing the needle deflection.

The Co-Ax indicator operates at any angle from horizontal to vertical without any change, and from internal to external diameter by simply changing the feeler." *- (SPI catalog)

The Co-Ax indicator will read accurately even if the machine spindle "wobbles."

Spare Parts

  • Straight feeler (standard included): used for inside diameters (ID) up to approximately 4.25 inches.
  • Curved feeler (shown in photo, standard included): used for outside diameters (OD) up to approximately 4.25 inches as well as inside diameters larger than approximately one inch.
  • Center point feeler : this optional accessory is for use on center punch marks. The spring loaded point should be depressed into its housing 1/32 to 1/16 inch.


"Under normal conditions, the Co-Ax indicator should require no servicing and only the consideration in use and handling due any precision instrument. Allowance for familiarization should be made when it is first being used." — (manufacturer's instructions)

Serial Numbers:

The manufacturer clearly warns: do not engrave names or serial numbers on the body of the Co-Ax indicator. This often damages the instrument and will certainly void any warranty. We need to point out that every new Co-Ax indicator comes with a hand etched serial number at the base of the shaft. This manufacturer serial number does not void the warranty, rest assured. Use this number for ISO purposes or to keep track of your inventory. The other option is to affix an ID sticker to the indicator.

If the shaft becomes bent and needs to be replaced by a repair shop, your indicator will get a new serial number. If this happens, you will have to update your records accordingly.

Repair Service:

Each Co-Ax indicator has been run-in under actual operating conditions by the manufacturer and thoroughly checked out for accuracy and freedom from defects before it is approved for packaging, and is fully guaranteed against defective workmanship and materials.

Important: we can only repair the genuine Blake Co-Ax indicator. Please do not send us anything made in China.

When returning the Co-Ax indicator for service or repair, please indicate whether or not the restraining arm or feelers missing from the package are to be replaced. Also, briefly explain the reason for the return.

This is an original made-in-USA Blake co-ax indicator, but beware of Copy Cats!

Inexpensive versions of the Co-Axial indicator are made in China. Just like the "Rolex" watches you can buy for $30 from any street vendor at Downtown, Any City, USA, they're outright frauds. The made-in-China Co-Axial indicator is of fair quality but a shameful copy. All we can do is strongly urge you to purchase the genuine article—made in the USA—shown on this page.

Co-Ax use:

The Co-Ax indicator is designed primarily as a precision centering instrument for locating a workpiece on a **horizontal** or **vertical** machine tool while the spindle rotates under power.

The Co-Ax indicator is equally useful for positioning work in the situation where it may be desirable to turn the machine spindle by hand. When turning the spindle by hand, the direction and distance of location error may be determined thus:

  • Direction is indicated by the radial position of the feeler when the indicator hand is at its high reading.
  • Distance is indicated by the total travel of the indicator hand through one full revolution of the machine spindle.
What is the smallest hole that can be centered?

The standard feeler has a 1/8" ball at the end. However, we have specially made feelers with a 1/16" ball which can be found on [page 110](http://www.longislandindicator.com/p110.html). The smallest hole, in theory, would be 1/16" if you use this feeler.

You are welcome to grind down the standard feeler so that you can work with smaller holes. The ball doesn't have to be round since only one spot touches the surface as you rotate the gage. Another solution, and perhaps a better one, is to put a pin into the hole, and then center it from the outside using the OD feelers.

Additionally, we have the following statement from the manufacturer:

"The Blake Co-Ax indicator is a centering device. It requires a reading of both sides of the bore (or boss), in each axis, to arrive at center. Its sole function is to find center. It is never to be used as a measuring instrument.

You can not certify the Co-Ax on a surface plate. It must be put in the spindle of the machine in which it would normally be used and indicate a precision ring or plug. Then remove it and use a .0001" indicator to check that you are on center.

The Co-Ax indicator is made to be used under power. When checking the Co-Ax position with a test indicator the spindle should be rotated manually for both indicators due to the fact that spindle torque under power on some machines will give a different reading for center."

Set up and use:

The manufacturer provides the following guidelines:

  1. Pre-position the work piece to within the indicator's travel range.
  2. Place the appropriate feeler in the indicator rocker bracket and secure it with the thumb screw. Position the rocker bracket on the rocker friction joint such that the small indicator hand is centrally located on its graduation scale when the feeler is in operational contact with the work piece.
  3. Start the machine spindle. Caution: check for interference before turning on the power. The speed should not exceed 700 to 800 rpm at any time.
  4. Move the machine table along the axis of one positioning screw to a point where the indicator hand travel range has diminished to its lowest distance, thus indicating that the work center is centered in the spindle plane in the one direction.
  5. Move the machine table along the axis of the other positioning screw until the indicator hand travel range diminishes to zero, thus indicating that the work piece center is in axial alignment with the machine spindle.

Note: the Co-Ax indicator is fitted and tested for operation at or above 58°F. Bearing stiffness may be present at lower temperatures.

The dial graduation is divided such that each division represents .0005" (0,01mm) of axis offset (deviation from true location) when the feeler is tracing a diameter of two inches. This will vary slightly with feeler angle.

Q&A about the Blake Co-Ax indicator

Q: I have a co-ax indicator that was dropped. I would like to send it to you for repair. I do not know the manufacturer. The dial says, 6 jewels and 0.0005 axis offset. That's all.

  • Genuine Made-in-America co-ax gages will have the Blake name on the dial. All others are made in China. We can only repair the genuine article.
Q: I have to indicate a 10-inch diameter. Which length point should I order?

  • The five inch long contact point is designed to center a diameter of 10 inches.

Is it time to take a break?

The "other" Swiss indicator still made in Switzerland.

Long Island Indicator Service
Long Island Indicator Service was founded in 1960. We provide professional repair service for precision measuring tools and gages with an emphasis on Swiss made test indicators, dial indicators, dial calipers and micrometers. We are pleased to be a recognized service partner for Brown & Sharpe.

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