ASME UN screw thread calculator to calculate imperial unified screw thread basic major, minor, pitch diameters and thread tolerance for the external
(bolt) and internal (nut) inch threads according to ASME B1.1 standard.
- Standard series of UNC, UNF, UNEF, UN-4, UN-6, UN-8, UN-12, UN-16, UN-20, UN-28 and UN-32.
- Tolerance classes of 1A, 2A and 3A for bolts and 1B, 2B and 3B for nuts
Tolerance class 2A and class 2B are selected classes for commercial external
and internal threads per ASME B1.1. The user shall use class 2A for bolts and 2B for nuts unless there is a specific requirement to use other tolerance classes.
Dimensions given by this calculator are at 68 °F.
UN Unified Screw Thread Calculator:
Note : * 2A is normally selected for commercial external (bolt) threads. Use
this tolerance class for commercial external (bolt) threads.
Note : ** 2B is normally selected for commercial internal (nut) threads. Use
this tolerance class for commercial internal (nut) threads.
|
RESULTS |
|
Parameter |
Value |
|
Nominal Size |
-- |
---
|
--- |
|
Threads per inch |
-- |
---
|
|
Tolerance Class for External Thread |
-- |
---
|
|
Tolerance Class for Internal Thread |
-- |
---
|
|
Series Designation |
-- |
---
|
|
LIMITS OF SIZES FOR EXTERNAL THREADS (BOLTS) |
|
Allowance |
es |
---
|
inch |
|
Maximum Major Diameter |
dmax |
---
|
|
Minimum Major Diameter |
dmin |
---
|
|
Maximum Pitch Diameter |
d2max |
---
|
|
Minimum Pitch Diameter |
d2min |
---
|
| Maximum Minor Diameter |
d1max |
---
|
|
UNR Maximum Minor Diameter |
d3max |
---
|
|
Thread Callout |
---
|
|
LIMITS OF SIZES FOR INTERNAL THREADS (NUTS) |
|
Minimum Major Diameter |
Dmin |
---
|
inch |
|
Maximum Pitch Diameter |
D2max |
---
|
|
Minimum Pitch Diameter |
D2min |
---
|
|
Maximum Minor Diameter |
D1max |
---
|
|
Minimum Minor Diameter |
D1min |
---
|
| Thread Callout |
---
|
|
BASIC DIMENSIONS |
|
Basic Major Diameter |
d , D |
---
|
inch |
|
Basic Pitch Diameter |
d2 , D2 |
---
|
|
Basic Minor Diameter |
d1 , D 1 |
---
|
UNR Reference Minor Diameter
for External threads |
d3 |
---
|
|
Fundamental Triangle Height |
H |
---
|
|
Lead Angle at Basic Pitch Dia. |
λ |
---
|
--- |
Note-1: ASME B1.1-2003 specifies limits of size that pertain whether threads are
coated or uncoated. Only in Class 2A threads is the allowance available to
accommodate coatings. Thus, in all classes of internal threads and in all
Classes 1A and 3A external threads, limits of size must be adjusted before
plating to provide suitable provision for the desired coating.
Note-2: Unless otherwise specified, size limits for standard external thread
Class 2A apply prior to coating. The external thread allowance may thus be used
to accommodate the coating thickness on coated parts, provided that the maximum coating thickness is no more than one-fourth of the allowance.
Note 3: The minimum diameters of Class 1B, 2B and 3B threads, whether or not
plated or coated, are basic and give no allowance or clearance for assembly at maximum-material
limits.