Polski 
- 98% satisfied customers
- 72h delivery
- 30 dni na zwrot
Description
THREAD1 1/4"-12 UNF
TOLERANCE2A
STANDARDASME B1.1
MATERIALTool steel
UNF 1.1/4-12 thread ring gauge — GO and NO-GO set
Two ring gauges for external inch threads
| TECHNICAL DATA | |
|---|---|
| Thread type | Unified inch fine thread UNF |
| Thread size | 1.1/4-12 |
| Threads per inch | 12 TPI |
| Thread pitch | 2.117 mm |
| Nominal diameter | 31.750 mm |
| Tolerance class | 2A |
| Pitch diameter d2 | 30.173 – 30.330 mm |
| Gauge type | Set: GO ring + NO-GO ring |
| Material | Tool steel, hardened |
| Hardness | 58-62 HRC |
| Standard | ASME B1.1 / ASME B1.2 |
| Manufacturer | Varel |
T
GO ring gauge — screwed on by hand along the full bolt thread.
Z
NO-GO ring with a groove in the knurled surface — stops after no more than 3 turns.
The 1 1/4-12 UNF-2A engraving on the face of both ring gauges indicates the size and tolerance class of the bolt being inspected.
UNF 1.1/4-12 thread ring gauge checks an external thread — on a bolt, stud, or threaded shaft. The GO ring gauge must screw on by hand over the full thread length, while the NO-GO ring gauge may advance no more than three full turns per ASME B1.2. The metric standard ISO 1502 permits two threads and does not apply here.
This size is a typical end thread on hydraulic cylinder piston rods approximately one inch in diameter, as well as the thread used on clevises and ball joints in cylinders built to NFPA standards. This component is screwed together and taken apart every time the cylinder is rebuilt.
GO/NO-GO inspection: GO and NO-GO ring gauges
Thread acceptance criterion per ASME B1.2
1
The GO ring gauge is threaded by hand, without force, over the full thread of the 1 1/4-12 UNF bolt.
2
The NO-GO ring stops after no more than 3 full turns, without forcing.
3
The GO ring passed and the NO-GO ring stopped — the bolt meets class 2A.
Thread inspection in 3 steps
1 GO ring (GO gauge)
Screwed on by hand — passes over the full length
2 NO-GO ring (NO-GO gauge)
Screwed on by hand — no more than 3 full turns
✓ Acceptable thread
Class 2A confirmed
Both conditions must be met simultaneously. At a pitch of 2.117 mm, the three permitted turns of the NO-GO ring gauge give 6.351 mm of engagement.
GO ring (GO gauge)
Represents the maximum material condition — the largest permissible pitch diameter of 30.330 mm. Checks thread form, pitch, and diameter simultaneously, because an error in any of these increases the functional thread diameter.
NO-GO ring (NO-GO gauge)
Represents the least material condition — the smallest permissible pitch diameter of 30.173 mm. Detects an undersized thread that will assemble easily but will not maintain tension. The body may be stamped LO.
✓ Thread acceptable — GO screws onto the full thread, NO-GO stops.
✗ Thread oversized — GO does not screw onto the bolt.
✗ Thread undersized — the NO-GO ring screws on more than 3 turns.
Threads commonly confused with this one
The decisive measurement
The entire family from one inch to one and a half inches has the same pitch 2.117 mm and differs only in diameter. Measurement distinguishes them: 31.750 mm is 1 1/4 inches, 28.575 mm is 1 1/8, and 34.925 mm is 1 3/8. A thread pitch gauge does not help with this family.
The pitch is derived from the designation: 12 threads per inch means 25.4 divided by 12, or 2.117 mm. The basic pitch diameter is 31.750 − 0.6495 × 2.117 = 30.375 mm. Class 2A ring gauges check it within the range 30.173 – 30.330 mm, below the basic value by an allowance of 0.046 mm.
Classes 1A, 2A, and 3A for size 1.1/4-12
Why this set is class 2A
Comparison of external thread classes
The basic pitch diameter for this thread is 30.375 mm. Classes 1A and 2A have an allowance of 0.046 mm, so their upper limit lies below the basic value. Class 3A has no allowance.
| Class | Allowance [mm] | d2 permissible [mm] | Tolerance zone | Application | Status |
|---|---|---|---|---|---|
| 1A | 0.046 | 30.096 – 30.330 mm | 0.234 mm | Field assembly, threads exposed to impact damage | |
| 2A | 0.046 | 30.173 – 30.330 mm | 0.157 mm | Commercial standard — bolts and threaded studs | THIS PRODUCT |
| 3A | 0.000 | 30.259 – 30.376 mm | 0.117 mm | Aviation, precision engineering |
Class 2A is the commercial standard — it covers the vast majority of inch bolts and mates with class 1B, 2B, and 3B internal threads. Class 3A is used where tightening torque must be repeatable from part to part.
▲
Piston rod thread wear starts at the first few threads
The piston rod end transmits the full cylinder force in the push-pull cycle, so its thread is subjected to fatigue loading rather than clamping force. Elongation starts at the transition from the thread to the shank and remains invisible to the naked eye for a long time. The NO-GO ring gauge detects this earlier than visual inspection — and before the end breaks off under load.
Inspection scope and storage
What the gauge confirms and what it cannot measure
INCLUDED IN THE SET:
| ▸ | GO (pass) ring gauge UNF 1.1/4-12 2A |
| ▸ | NO-GO (reject) ring gauge UNF 1.1/4-12 2A |
| ▸ | NO-GO ring marked with a groove or dot |
WHAT IT CANNOT MEASURE:
| ▸ | Thread major diameter — for 2A, this is 31.415 – 31.704 mm |
| ▸ | Stud straightness and runout |
| ▸ | Thread flank roughness |
Frequently asked questions
Yes, this is one of the typical threads used on piston rod ends and clevises in NFPA-standard cylinders with a rod diameter of about one inch. This size is not used for hydraulic connections — ORB and JIC systems omit it.
By diameter alone, because the pitch is identical for all of them at 2.117 mm. Measurement with a caliper is decisive: 1 1/8 inches is 28.575 mm, 1 1/4 is 31.750 mm, and 1 3/8 is 34.925 mm. A thread pitch gauge will show twelve threads per inch for each.
No. The GO ring gauge only confirms that the thread is not oversized — it will also screw onto an undersized thread that is below the lower tolerance limit. Only the NO-GO ring gauge checks the other limit. Inspection with a single ring gauge leaves half the tolerance unchecked.
Ring gauges are verified with setting gauges — plugs made to tighter tolerances in class W. The standard specifies neither a time interval nor a number of measurements: the frequency is set by the user's quality system, because wear depends on the intensity of use and operating conditions.
Product accessories
Reviews
No customer reviews for the moment.
Shipping
All orders are delivered by courier company GLS. For orders exceeding 369 PLN gross shipping is FREE
| Courier GLS | Przelew24 / Prepayment | 14,76 zł gross | Delivery time 1 working day |
| Courier GLS | Cash on delivery | 17,26 zł gross | Lead time 1 working day |
Recommended for you
This website uses its own and third-party cookies to improve our services and show you advertising related to your preferences by analyzing your browsing habits. To give your consent to its use, press the Accept button.
Cookie preferences
Functional cookiesTechnical
Functional cookies are strictly necessary to provide the services of the shop, as well as for its proper functioning, so it is not possible to refuse their use. They allow the user to browse through our website and use the different options or services that exist on it.
Advertising Cookies
These are cookies that collect information about the advertisements shown to users of the website. They can be anonymous, if they only collect information about the advertising spaces shown without identifying the user, or personalised, if they collect personal information about the user of the shop by a third party, for the personalisation of these advertising spaces.
Analytics cookies
Collect information about the user's browsing experience in the shop, usually anonymously, although sometimes they also allow the user to be uniquely and unequivocally identified in order to obtain reports on the user's interests in the products or services offered by the shop.