Multi-Ball Thread Location Gage Logo   
Welcome to our FAQ (frequently asked questions) page.

This list is a just a few of the questions we get asked about the Multi-Ball location gage.  If you have other questions, give us a call at 317-899-0899 or send e-mail to  

How is Multi-Ball different from other gages?

  • Multi-Ball utilizes a patented design that centers a pin inside a pattern of balls (Fig. 1).  This simple concept aligns the pin with the thread axis.  No other product has this system.

  • Multi-Ball's centering action is mechanically activated and controlled by the user. The balls can be positioned anywhere along the thread.   No other product offers this level of control.

  • Multi-Ball is a precision assembly with radially moving balls. Other designs are one piece and have no moving parts.

  • Multi-Ball is designed to use two point axis definition.  Other designs discourage this tolerance saving technique.

  • Multi-Ball contacts only the workpiece thread flanks.  Other gages rely on other workpiece features which can induce errors.

Basic Multi-Ball Concept
Fig 1
(Simplified Illustration)

return to top

How is ball contact different from the plug gages?

Regardless of the brand or design, plug type thread location gages are essentially "Go" plugs.  The flank surface of these plugs can only contact the high points in the hole.  These high points are always unknown because they vary from hole to hole and may not even be functional thread features.  As a result, it is  impossible for the plug to distinguish between a burr, foreign material, or the desired thread form.


With ball contact, the point of contact on both the flanks as well as the axial location is known.  The advantage of this is that you are assured the gage is always locating on the functional surface of the thread and not on some other feature or deformation that would induce errors into the X-Y position data.

return to top

Why should I consider using Multi-Ball location gages?

Because you want more tolerance.  Gage and inspection process uncertainties rob you of significant amounts of tolerance that should be applied to manufacturing.  Less usable tolerance makes manufacturing more costly.

Multi-Ball location gages allow you to use the maximum amount of the stated tolerance by reducing gage and process uncertainty in two ways:

  1. The centering action of Multi-Ball reduces gage alignment errors.

  2. The Multi-Ball design allows the use of two point axis definition.  This eliminates the errors inherent to single point axis definition.

return to top

Why do Multi-Ball gages have a long pin surface?

Multi-Ball thread location gages have a pin that increases in length and diameter as the thread size increases.  This provides a surface sufficient for defining two points on opposite ends of the pin.  The farther apart the two points are from each other the less any error is multiplied when the points are connected to define an axis.  This longer length allows the two point axis definition method to be used.  Shorter pin lengths on other gages are primarily used with the single point axis definition method.

return to top

When threaded holes are specified in a manner similar to the illustration above, the thread axis is permitted to be at an angle to the primary datum -A- as long as the axis is within the .010 diameter X .50 long tolerance zone. 

The single point axis definition method ignores the true orientation of the thread axis and projects an assumed axis perpendicular to the primary datum.  When this method is used with inaccurate thread location gages, errors accumulate dramatically and the resulting data becomes in doubt.

Essentially, the single point axis definition method is inspecting the thread location to a flat two dimensional "circular tolerance zone" not a "cylindrical tolerance zone" as specified.

Fig. 3

The two point axis definition method makes no assumptions about the thread axis orientation.  Instead, this method identifies the thread axis orientation.

Once the axis orientation is defined, it is simple to determine if the axis is within the three dimensional "cylindrical tolerance zone".

Fig. 4

return to top

Home ] How Is It Used ] Usage Instructions ] Custom Micrometers ] Custom Location Gages ] Contact Us ] [ Location Gage FAQ ] Press Release ]