External Variable Gages
TRI-ROLL External Thread Gage
This gage is ideally suited to thread measuring applications where the gage is to be dedicated to only one thread size or is used to measure a narrow range of sizes. This gage comes in a number of different frame sizes providing a total measurement range of #0-80 (M1.6) through 3⅜” (M85). Each frame size will cover 2 to 4 standard thread diameters in both inch and metric sizes. For example, the #4 frame size covers #10, #12, l/4″ and 5/16″ sizes. This design is best suited to manufacturing applications.
The TRI-ROLL Gage is a three roll, 120 degree contact position design. The following gaging roll types are available:
| Thread Characteristic | Roll Type | ANSI/ASME # |
| Functional Diameter (UNR) | 3 | 4.3 |
| Functional Diameter (UNJ) | 3″J” | 4.3 Modified |
| Pitch Diameter (cone & vee) | 4 | 4.5 |
| Minor Diameter | Minor | 5.2 |
| Lead & Flank Angle | Differential | 4.8 |
| Runout (P.D. to major) | Runout | 4.7 |
A different set of gaging rolls is required for each thread size to be measured.
TRI-ROLL Gages are set with Gage Class “W” single end, full form, threaded setting plugs. Users having ring gage setting plugs can use them if only the full formed section is used. For the greatest measuring accuracy always set the TRI-ROLL Gage using the calibrated size of the setting plug instead of the nominal size marked on its handle.
The result of a long form Gage Repeatability and Reproducibility Study of the TRI-ROLL Gage was 15% with functional diameter gaging rolls and 20% with pitch diameter gaging rolls.| Inch | Metric | Single Frame Unit* |
| #0 thru #1 | M1 | TRU-100E |
| #2 thru #3 | M2 thru 2.5 | TRU-101E |
| #4 thru #8 | M3 thru M4 | TRU-102E |
| #10 thru 5/16 | M5 thru M6 | TRU-103E |
| 3/8 thru 1/2 | M8 thru M12 | TRU-104E |
| 9/16 thru 3/4 | M14 thru M16 | TRU-105E |
| 7/8 thru 1-1/8 | M20 thru M24 | TRU-106E |
| 1-1/4 thru 1-1/2 | M30 thru M38 | TRU-107E |
| 1-5/8 thru 1-7/8 | M39 thru M47 | TRU-108E |
| 2 thru 2-1/4 | M48 thru M56 | TRU-109E |
*NOTE: Double Frame Unit, TRU-2XX, Triple Frame Unit, TRU-3XX
X-180 Segment External Thread Gage
The X-180 Gage is of the two-segment, 180 degree contact design. The single frame size covers #2 (M2) through 3/4″ (M 18).
This design can be used to measure functional diameter in all specifications and 180 degree circularity in ANSI/ASME System 23 and SAE AS8879 “Safety Critical” inspection. A different set of gaging segments is required to measure each thread size. The X-180 Gage can be changed from one size to another in less than one minute.
The use of the three roll or two segment gage design to measure functional diameter is optional in ANSI/ASME, SAE AS8879.
The result of a long form Gage Repeatability and Reproducibility Study for the X-180 Gage was 11 % for measuring functional diameter.
X-120 Adjustable Tri-Roll Thread Gage
The X-120 Gage is the same basic design as the TRI-ROLL Gage, having three rolls which contact the thread at 120 degrees apart. The differences are that the X-120 gage is much more widely adjustable and fewer gaging rolls are required because only one set of rolls is needed for each TPI (threads per inch). There are two gage frame sizes; small, #4 (M3) through 1″ (M24) and large, 1-1/8″ (M30) through 2″ (M50).
The thread size can be changed in less than three minutes by simply loosening four screws, adjusting the gaging roll axis pin position with a screw diameter template, retightening the four screws, attaching the gaging rolls, and setting the gage with the threaded setting master.
The X-120 Gage is best suited for use in incoming and final inspection. The following gaging rolls are available:
| Thread Characteristic | ANSI/ASME # |
| Functional Diameter | 4.3 |
| Pitch Diameter (cone & vee) | 4.5 |
| “VARIMINOR” (minor diameters 32 TPI & less) | 5.2 Variable |
The “X-120” Gage is set with a Class “W”, single end, threaded plug gage.
The result of a long form Gage Repeatability and Reproducibility Study for the X-120 Gage was 17% with functional diameter gaging rolls and 25% with pitch diameter gaging rolls.
