Technical Info
Key Highlights of SAE JS34 Specification for Lubricant Fittings

This specification is the most important and common standard for grease fittings. Many of the fittings we sell meet this standard. These considerations are important because the cost of a grease fitting is minimal in comparison to the equipment it is installed on. If a fitting fails, liability can be substantial. Please consider this information when reviewing your grease fitting needs. There are many unhardened and poorly manufactured fittings in the market. You get what you pay for.
  • Material and Manufacture: SAE JS34 requires that grease fittings be case hardened 0.13 to 0.23 mm deep, with a minimum hardness of 83 Rockwell on the 15N scale.
  • Dimensions and Tolerances: Unless specified, the tolerances on all dimensions are to be +/- 0.3 mm.
  • Check Valves: Fittings should be equipped with check valves.
  • Springs:Although not specified, the springs used inside the fittings need to be tempered. One common failure occurs when a spring breaks or distorts and the ball check then will not retract. Grease will leak out at the end.
  • Pipe Threads: Pipe threads shall conform with the detail in SAE J476 (copies available).
  • Finish: The fittings must be plated with a suitable material that passes a salt spray test in accordance with ASTM B 117 (72 hours to red rust). Efforts must be taken to prevent hydrogen embrittlement during plating.

FITTING MEASUREMENTS
To help you speed up detailing and specifying, virtually all fittings are illustrated with the complete dimensional data indicated... ready for transfer to your blueprints.

DRILLING AND TAPPING
For Threaded Fittings
Fitting Thread Size
Tap Drill Selection for Standard Thread Fittings
Drill Size Selection for Spin Drive Fittings
1/4" 28
#3 (for soft metal use #5)
"A" - .234" dia.*
5/16" -32
9/32" (for soft metal use "J")
-
1/8" Pipe
11/32" (for soft metal use "R")
3/8" - .375" dia.*
1/4" Pipe
7/16"
-

* Drill sizes given are nominal and may vary with different types of material. For maximum effectiveness, test applications should be conducted considering the type of material into which the fitting is to be installed (steel, brass, aluminum, etc.). Production tolerances of hole must be taken in consideration when conducting test.

HOW TO DETERMINE
PIPE THREAD SIZES

Male Threads - Measure outside diameter of large portion of thread at "A"; find figure nearest this dimension in column I of chart; and directly opposite in column II is ther nominal pipe (or pipe thread) size.
Female Threads - Measure outside diameter of thread at "B"; find figure nearest this dimension in column I of chart; and directly opposite in column II is the nominal pipe (or pipe thread) size.
I
Outside diameter

II
Nominal
size
(P.T.)
inch

Normal
engagement
for tight joint
(dimen "C")
inch
Number
of
threads
per
inch
Approx.
(fraction)
inch
Actual
(decimal)
inch
13/32
35/64
43/64
27/32
1-3/64
1-5/16
1-21/32
1-29/32
2-3/8
.405
.540
.675
.840
1.050
1.315
1.660
1.900
2.375
1/8
1/4
3/8
1/2
3/4
1
1-1/4
1-1/2
2
1/4
3/8
3/8
1/2
9/16
11/16
11/16
11/16
3/4
27
18
18
14
14
11-1/2
11-1/2
11-1/2
11-1/2
ACTUAL SIZE OF PIPE THREAD AT SMALL END
AS Fittings MS Fittings NAS Fittings Assortment BACF Grease Fittings Brass British BSF British BSP British BSPP British BSPT Buttonhead Grease Fittings Drive Grease Fittings Grease Fittings Feedline Flush Grease Fittings Hydraulic Grease Fittings Junction Block Leakproof Metric Grease Fittings Monel Grease Fittings Pin Type Grease Fittings Relief Grease Fittings Rivet Grease Fittings Safety Vents Self Threading Grease Fittings Shut-off Special Thread Stainless Accessories Extensions Metric-English Adapters Elbows 45° - 90° Plugs Bushings Lock Nut Male to Female Adapters Male to Male Adapters Female to Female Adapters Couplers Grease Guns Swivels Hoses Plastic Caps Tools