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
4-360.0124 in-lbs110
4-400.0124 in-lbs110
6-320.0176 in-lbs150
8-320.0178 in-lbs250
10-240.0214 in-lbs450
10-320.01710 in-lbs500
1/4-200.02540 in-lbs650
5/16-180.02560 in-lbs1200
TWIN PRONG APPLICATIONS
4-360.0123 in-lbs100
4-400.0123 in-lbs100
6-320.0175 in-lbs150
8-320.0177 in-lbs250
10-240.02212 in-lbs350
3/16-240.02212 in-lbs350
1/4-200.02530 in-lbs600
5/16-180.02830 in-lbs1000

Sheet Metal Screw Torque and Tensile Limits

SCREW SIZETHREADS PER INCHSTANDARD
MATERIAL
THICKNESS
RECOMMENDED INSTALLATIONTENSILE
LOAD LIMIT
TORQUE
(LBS)
SPIRACONE APPLICATIONS
4A240.028 in-lbs450
4B240.028 in-lbs450
6A180.0212 in-lbs525
6B200.0212 in-lbs525
8A150.02520 in-lbs650
8B180.02520 in-lbs650
10A120.02530 in-lbs1000
10B160.02530 in-lbs1000
14A100.0360 in-lbs1400
1/4B140.0360 in-lbs1400
5/16B120.04120 in-lbs1800
TWIN PRONG APPLICATIONS
4A240.0229 in-lbs300
4B240.0229 in-lbs300
6A180.02511 in-lbs400
6B200.02511 in-lbs400
8A150.02817 in-lbs600
8B180.02817 in-lbs600
10A120.03131 in-lbs800
10B160.03131 in-lbs800
12A110.03434 in-lbs900
12B140.03434 in-lbs900
14A100.03748 in-lbs1150
1/4B140.03748 in-lbs1150
5/16B120.04416 ft-lbs1200
3/8B120.0519 ft-lbs2500

Acme Thread Bolt Torque and Tensile Limits

SCREW
SIZE
STANDARD
MATERIAL
THICKNESS
RECOMMENDED
INSTALLATION
TORQUE
TENSILE
LOAD LIMIT
(LBS)
SPIRACONE APPLICATIONS
5/16-10.044135 IN-LBS2500
TWIN PRONG APPLICATIONS
5/16-10.04419 FT-LBS2200

Clearance Hole — Flat Nuts Only

SCREW
SIZE
HOLE DIAMETER—
SPIRACONE
HOLE DIAMETER—
TWIN PRONG
49/641/8
611/641/8
813/643/16
101/47/32
129/321/4
14, 1/45/169/32
5/163/811/32

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