HEX SERRATED FLANGE LOCKING SCREWS
Earnest Machine Products line of Hex Serrated Flange Screws are designed to provide excellent resistance to loosening along with high toughness.
The Serrated Flange Screws in sizes 1/4” and larger are made to the dimensions specified in the Industrial Fasteners Institute standard IFI 111 with the addition of locking serrations under the flange. The machine screws sizes (#6 to #12) are made to the same proportionality as specified in IFI (see dimensions on page 2)
The physical properties of the screws are designed to be equivalent to the strength requirements for a grade 5 cap screw (120,000 psi tensile strength) with the addition of a case hardened surface treatment. The case hardened surface adds strength and toughness to the locking serrations providing resistance to rounding off and ensures that they bite into the surface they are being installed on. The “120M” head marking (on sizes 1/4 and larger) designates that the product has a tensile strength of 120,000 psi (equivalent to Grade 5).
The combination of the high surface hardness along with the design of the locking serrations on the face of the flange ensures that the head of the screw "locks" onto the material being clamped to provide excellent resistance to loosening do to vibration.
The design of the locking serrations ensures:
Minimum resistance to rotation is encountered during the assembly of the screws (in the clockwise direction). This ensures that sufficient clamp forces are developed when the screws are tightened to Grade 5 torque levels.
When forces are encountered that try to loosen the screw, the serrations bite into the material being clamped to maximize the resistance to rotation (in the counterclockwise direction).
Material and Heat Treatment:
Manufactured from carbon steel that has been case hardened to a depth of .003? to .012? with a:
Surface Hardness - R15N 79/86
Core Hardness - Rc 25/34.
Ultimate Tensile Strength - 120,000 psi min (equivalent to Grade 5)
Surface Finish:
The screws are plated with Zinc and Clear Chromate to provide excellent corrosion resistance and uniform torque tension performance. The screws are "baked out" after plating to for hydrogen embrittlement relief.
| Size |
Flange Dia. |
Head Thickness |
Width Across Flats |
| |
Max |
Max |
|
| #6 – 32 |
.266 |
.157 |
3/16 |
| #8 – 32 |
.355 |
.186 |
1/4 |
| # 10 – 24 & 32 |
.460 |
.210 |
5/16 |
| #12 - 24 |
.520 |
.240 |
5/16 |
| 1/4 – 20 |
.565 |
.280 |
3/8 |
| 5/16 – 18 |
.680 |
.320 |
1/2 |
| 3/8 – 16 |
.810 |
.390 |
9/16 |
| 7/16 – 14 |
.930 |
.460 |
11/16 |
| 1/2 – 13 |
1.070 |
.510 |
3/4 |
| 5/8 – 11 |
1.330 |
.620 |
15/16 |
| 3/4 – 10 |
1.590 |
.730 |
1 1/8 |
Thread Length:
Machine screw sizes are threaded to head up to 1” length.
For fractional sizes, the second column in the chart below lists the lengths that will be
threaded to the head. For longer lengths the minimum guaranteed thread length will be 2 x dia + 1/4” to a maximum thread length of 2”
| Diameter |
Lengths that are
Threaded to Head |
Min Thread Length for
Lengths longer than listed in previous column |
| 1/4 |
1 1/4 |
3/4” |
| 5/16 |
1 3/8 |
7/8” |
| 3/8 |
1 1/2 |
1” |
| 7/16 |
1 3/4 |
1 1/8” |
| 1/2 |
1 7/8 |
1 1/4” |