Why spring nuts?

Shakeproof spring nuts are one-piece, self-locking, multipurpose devices that prevent screws from loosening due to vibration. The use of spring nuts often eliminates the need for additional fasteners. And, because they allow faster and easier assembly, spring nuts can lower costs of manufacture. Their installation requires no special tools, equipment or skills.

How Spring Nuts Work

SpiraCone Impressions: The SpiraCone impression offers some significant advantages. The funnel lead enables easier starting even if the screw is misaligned. No cross-threading can occur. A greater choice of material thickness is available with SpiraCone nuts. In addition, this stronger form enables the SpiraCone to hold its shape better even when torqued to the extreme. The result is a higher unit clamping force. Because of its design, the spring nut, even if rusted can be easily loosened.

Twin prong Impressions
These spring nuts create both an inward-thread lock and an arched-spring lock. These two locking forces are exerted on the screw as it is torqued and prevent the screw from loosening.

The inward-thread lock is exerted by two arched prongs which, under torque,move inward to engage and lock on the screw thread root. The prongs are free-acting and compensate for screw thread tolerance variation.

The arched-spring lock is exerted by the compression of the arch in both the prongs and base as the screw is torqued. A strong upward motion is exerted against the screw threads.

Wide Range Panel Nuts
These fasteners allow panel thickness variations of as much as one eighth inch to be designed into a product. Wide Range Panel Nuts can accommodate thicknesses from light sheet metal to heavy fiber-board using just one type of fastener.This makes for economy in both stocking and availability.

Form Variations
Drawing accompanying headings for each section show the “A” form of the parts listed.

Variations are indicated by bullets in the Form listings and the drawings are on the inside of each section.

Spring Nuts General Information

Machine Screw Torque and Tensile Limits

SCREW
SIZE
STANDARD
MATERIAL
THICKNESS
RECOMMENDED
INSTALLATION
TORQUE
TENSILE
LOAD LIMIT
(LBS)
SPIRACONE APPLICATIONS
4-36 0.012 4 in-lbs 110
4-40 0.012 4 in-lbs 110
6-32 0.017 6 in-lbs 150
8-32 0.017 8 in-lbs 250
10-24 0.02 14 in-lbs 450
10-32 0.017 10 in-lbs 500
1/4-20 0.025 40 in-lbs 650
5/16-18 0.025 60 in-lbs 1200
TWIN PRONG APPLICATIONS
4-36 0.012 3 in-lbs 100
4-40 0.012 3 in-lbs 100
6-32 0.017 5 in-lbs 150
8-32 0.017 7 in-lbs 250
10-24 0.022 12 in-lbs 350
3/16-24 0.022 12 in-lbs 350
1/4-20 0.025 30 in-lbs 600
5/16-18 0.028 30 in-lbs 1000

Sheet Metal Screw Torque and Tensile Limits

SCREW SIZE THREADS PER INCH STANDARD
MATERIAL
THICKNESS
RECOMMENDED INSTALLATION TENSILE
LOAD LIMIT
TORQUE
(LBS)
SPIRACONE APPLICATIONS
4A 24 0.02 8 in-lbs 450
4B 24 0.02 8 in-lbs 450
6A 18 0.02 12 in-lbs 525
6B 20 0.02 12 in-lbs 525
8A 15 0.025 20 in-lbs 650
8B 18 0.025 20 in-lbs 650
10A 12 0.025 30 in-lbs 1000
10B 16 0.025 30 in-lbs 1000
14A 10 0.03 60 in-lbs 1400
1/4B 14 0.03 60 in-lbs 1400
5/16B 12 0.04 120 in-lbs 1800
TWIN PRONG APPLICATIONS
4A 24 0.022 9 in-lbs 300
4B 24 0.022 9 in-lbs 300
6A 18 0.025 11 in-lbs 400
6B 20 0.025 11 in-lbs 400
8A 15 0.028 17 in-lbs 600
8B 18 0.028 17 in-lbs 600
10A 12 0.031 31 in-lbs 800
10B 16 0.031 31 in-lbs 800
12A 11 0.034 34 in-lbs 900
12B 14 0.034 34 in-lbs 900
14A 10 0.037 48 in-lbs 1150
1/4B 14 0.037 48 in-lbs 1150
5/16B 12 0.044 16 ft-lbs 1200
3/8B 12 0.05 19 ft-lbs 2500

Acme Thread Bolt Torque and Tensile Limits

SCREW
SIZE
STANDARD
MATERIAL
THICKNESS
RECOMMENDED
INSTALLATION
TORQUE
TENSILE
LOAD LIMIT
(LBS)
SPIRACONE APPLICATIONS
5/16-10 .044 135 IN-LBS 2500
TWIN PRONG APPLICATIONS
5/16-10 .044 19 FT-LBS 2200

Clearance Hole — Flat Nuts Only

SCREW
SIZE
HOLE DIAMETER—
SPIRACONE
HOLE DIAMETER—
TWIN PRONG
4 9/64 1/8
6 11/64 1/8
8 13/64 3/16
10 1/4 7/32
12 9/32 1/4
14, 1/4 5/16 9/32
5/16 3/8 11/32

Self-retaining fasteners, such as U or J nuts may “snap” onto panel holes. The hole diameters listed will not, of course apply. Specific recommendations for each of these styles is listed for each part.

Finishes

Over 450 different finishes have been used on Spring Nuts in the past years. Virtually any finish may be supplied. The most popular, however, are as follows:

  • Mechanical Zinc is a standard finish.
  • Phosphate with oil or wax is also a standard finish.
  • Phosphate with two coats of paint. The paint protection available includes olive drab, bright green and black phenolics as well as aluminum.
  • Plain Oil

Our engineers have had experience with many corrosion problems and will be glad to help you choose.

Materials

Although spring nuts are usually made of heat treated steel, they can be made of any appropriate metal. Screw end protrusion Because more and more screws are being made with header points, chamfer points and gimlet points of various design, we recommend that a thread minimum of one whole pitch of full diameter protrude past the top of the spring nut, whether SpiraCone or Twin Prong design.

Spring Nut Form Variations

Flat Nut Forms

tf33-1

J And U Nut Forms

tf33-2

Push-On Nut Forms

tf33-3