Threads and gears
Thread limit gaugesThread limit gauge (GO/NOT GO thread plug & ring gauge)
Also called: thread gauge, limit thread gauge, thread plug gauge, thread ring gauge, GP/NP (WP/IP)
≡Standards, measuring range and accuracy
- Standard
- JIS B 0251:2008 Limit gauges for metric screw threads
- ISO 1502:1996 ISO general-purpose metric screw threads — Gauges and gauging
- Measuring range
- —Not confirmed in public sources
- Resolution / graduation
- Description No graduations; it gives an overall pass/fail judgment centered on the pitch diameter
- Accuracy (instrument error / maximum permissible error)
- —Not confirmed in public sources
▦Types
Thread limit gauges (GO and NO-GO as a pair)
[3]1 source, for reference
Standard thread gauge (a plug and ring made to the basic thread profile, as a pair)
[3]1 source, for reference
Pipe thread gauges (parallel and taper. For taper gauges, pass if the end of the workpiece lies within the range of the notch on the end face (one step for PT, two steps for R))
[3]1 source, for reference
ISO grade gauge system and the conventional class 1–3 gauge system. In the class 1–3 system the NO-GO side distinguishes working (WP, WR) from inspection (IP, IR) gauges, which the ISO system does not
[3]1 source, for reference
◎Part names and functions
| # | Name | English | Function |
|---|---|---|---|
| 1 | GO thread plug gauge GP / NO-GO thread plug gauge NP (working WP, inspection IP) | GP / NP (WP, IP) | For internal threads.[3] |
| 2 | GO thread ring gauge GR / NO-GO thread ring gauge NR (WR, IR) | GR / NR (WR, IR) | For external threads.[3] |
| 3 | Setting plugs (GF, NF; wear check GW, NW) | Check plugs | Checks the ring gauges.[3] |
| 4 | Handle | Handle | May loosen over a long time; take care not to drop large gauges.[3] |
◷How to read the scale
✋Usage steps
- Clean the gauge and workpiece and check for rust, scratches and burrs[3]
- Apply lubricating oil to the gauge and brush chips and dust off the workpiece[3]
- Check the GO end first, then the NO-GO end[3]
- Screw in a plug gauge with about the force of holding a pencil (in practice slightly more). Do not clench the handle in your palm to screw it in (except for large ones)[3]
- For a ring gauge, hold the gauge fixed and screw the workpiece in by hand to avoid extra torque[3]
- Do not screw a pipe taper thread gauge in abruptly to the end (it goes in with a shock and can stick)[3]
Printed from Kezuriba (kezuriba.net/en/gauges/thread-limit-gauge/)
!Common measurement mistakes and countermeasures
Using a gauge as a substitute for a nut, bolt, tap or die
WhyLoss of accuracy and breakage. The gauge can no longer be guaranteed
CountermeasureDo not use it for anything other than inspection[3]
Using a class 2 thread gauge for ISO 6H/6g
WhyLimit sizes and tolerance positions are not necessarily the same
CountermeasureAs a rule, do not repurpose gauges[3]
✓Care, storage, inspection and calibration
Care and storage
- Do not store them fitted together. Rust-proof them and store in a place with little humidity and temperature change[3]
Inspection and calibration
- Check ring gauges with the wear check plugs and setting plugs, and inspect periodically. Do not use beyond the wear limit[3]
The pitch diameter of a thread can also be measured with a micrometer by the three-wire method (Mitutoyo E11003: for metric/unified 60°, E = M − 3d + 0.866025P, best wire diameter 0.577P). It can be linked to Kezuriba's thread pages.
⇄Related instruments
📚Sources
Content without a mark is what agreed across two or more sources from different publishers. Procedures and cautions are summarized in Kezuriba's own words based on the sources, and the diagrams were drawn by Kezuriba. Accuracy values are manufacturers' published figures, not values from JIS tables.