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Centralizing ACME Screw Threads

3-Gage and 4-Gage Centralizing ACME Screw Thread Plug Gages

The screw thread form for Centralizing Acme screw threads has a limited clearance at the major diameter of both the internal and external threads. This limited clearance makes the major diameter of the Centralizing ACME Screw Thread a critical dimension and one that needs to be monitored. If the Centralizing ACME Screw Thread is manufactured without regard to the major diameter, in all likelihood it will fail in the field because it will not meet the original engineer's design criteria.

External Centralizing ACME Screw Thread Major Diameter
Monitoring the External Centralizing ACME Screw Thread Major Diameter is easily done with a micrometer, or in more critical applications, a set of GO/NOGO Plain Cylindrical Ring Gages.

Internal Centralizing ACME Screw Thread Major Diameter
Monitoring the Internal Centralizing ACME Screw Thread Major Diameter is trickier. The internal major diameter cannot be easily measured by direct measurement so special tools are required. Before you ask; the standard GO/NOGO Screw Thread Work Plug Gauges do not do this job. The gage design for standard GO work plug thread gauge only looks at the major diameter to assure that it does not violate the maximum material condition. The standard NOGO work plug screw thread plug gage major diameter is designed to be only a clearance dimension. In-depth discussion on major and minor diameters of parts and gauges.

To monitor the internal Centralizing ACME screw thread major diameter, additional gage member(s) are required.

3-Gage System
The system currently specified in ANSI/ASME B1.5 is the 3-gauge system. The 3-gage system adds a third gauge, the NOGO Major Diameter Check Gage, to evaluate the major diameter for the minimum material condition.

The gages in the 3-gauge system are:
  1. The standard GO Work Plug Gage which checks the internal Centralizing ACME Screw Thread to assure that the Centralizing ACME Screw Thread does not violate the maximum material condition.
  2. The standard NOGO Work Plug Gauge checks the internal Centralizing ACME Screw Thread to assure that the Pitch Diameter has not become too large.
  3. The NOGO Major Diameter Plug Gage checks the Centralizing ACME Screw Thread to assure that the Major Diameter has not been made too big.

4-Gauge System
An alternate combination of Centralizing ACME Screw Thread Gages is the 4-gauge system. The 4-gage system is not listed in ANSI/ASME B1.5, but is suggested by some gauge makers because it looks more closely at the critical thread features. The two areas of focus are the pitch diameter and the major diameter. This 4-Gage System consists of GO/NOGO Pitch Diameter Plug Gauges in conjunction with the GO/NOGO Major Diameter Plug Gages.

The gages in the 4-gauge system are:

  1. The GO Pitch Diameter Plug Gage checks the internal Centralizing ACME Screw Thread to assure that it does not violate the maximum material condition for all attributes other than the major diameter. It is made identical to the standard GO Work Plug Gauge except that it has a reduced major diameter so that the GO pitch diameter gage member does not even see the internal major diameter.
  2. The standard NOGO Work Plug Gauge checks the internal Centralizing ACME Screw Thread to assure that the Pitch Diameter has not become too large.
  3. The GO Major Diameter Plug Gage checks the Centralizing ACME Screw Thread to assure that the major diameter is not too small. The GO major diameter plug gauge is designed to clear all other aspects of the Centralizing ACME Screw Thread and look only at the Major Diameter to evaluate it at the maximum material condition.
  4. The NOGO Major Diameter Plug Gage checks the Centralizing ACME Screw Thread to assure that the Major Diameter has not gotten too big. The NOGO major diameter plug gauge is designed to clear all other aspects of the Centralizing ACME Screw Thread and only check the Major Diameter for an oversize condition.

There are a few "brave souls" who try to make an internal Centralizing ACME Screw Thread without the special Major Diameter Plug Gage(s), monitoring only the wear on their cutting tool. If you are reading this page, I am sure that you are not one of them.

If the Centralizing ACME Screw Threads require measurement by a variable thread measurement system, special fingers can be made to monitor the major diameter.

For more information click the links below.
General Purpose ACME Screw Thread Profile
General Purpose Screw Thread Data
Centralizing ACME
Centralizing ACME 3-Gage System VS. 4-Gage System
Stub ACME

Disclaimer:
This data is provided for general information only. The intention is to provide accurate information; regardless; errors may exist in the supplied information. If accuracy is critical, base your final decisions on the data provided in the root document: ANSI/ASME B1.5; which is a copyrighted document. To purchase a copy visit an Authorized Reseller.

Comments:
Original Posting: 10/21/2009
Last Revision: 4/17/2013
Error corrections in, or comments about, the above data can be sent to: gageguy@gagecrib.com

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