Sealing and Strain Relief at the Enclosure Wall
A cord grip does two jobs at the point where a flexible cable enters a box or a piece of equipment. It grips the cable jacket so any pull on the cord is taken by the fitting rather than by the terminals inside, and it closes the opening around the cable so the enclosure keeps whatever rating it was built to. Get the size wrong and it does neither.
Hub Size and Cable Range Are Two Different Numbers
This is the detail that causes most wrong orders in the category. The hub size, 3/8 inch through 1 inch here, describes the threaded knockout the fitting screws into. It says nothing about what cable fits through it. Each grip also carries a cable outside-diameter range, and the cable has to fall inside that range for the grip to seal and hold.
That is why a single 1 inch hub size appears across several part numbers on this page with different ranges behind it. Measure the actual outside diameter of the cable jacket with calipers, then pick the grip whose range brackets that measurement, then confirm the hub matches the knockout. A cable at the very bottom of a range will pull through under load, and one above the top of the range will not let the grip close. The enclosure on the other side of that hole has its own sizing rules, covered in Lumera's junction boxes and enclosures collection.
Nylon or Steel
Nylon grips are lighter, cost less, and will not corrode, which makes them a sensible default for indoor work, damp locations, and anywhere road salt, fertilizer, or cleaning chemicals are in the air. They also insulate, so they will not carry a fault current the way a metal fitting can.
Steel grips take mechanical abuse better and hold up where a fitting might get struck, walked on, or dragged against. They are the usual choice on equipment, machine enclosures, and industrial installations. A steel fitting in a wet or chemically aggressive location needs the right finish to avoid corroding at the threads, which is where nylon often wins outright. For exterior work the box, the cover, and the entry fitting all have to be rated as a set, which Lumera's weatherproof boxes collection groups together.
Straight or Angled Body
Body shape follows how the cable approaches the enclosure. A straight grip is the standard, taking the cable in line with the knockout. A 45 or 90 degree grip turns the cable as it enters, which matters when clearance behind the enclosure is tight or when the cable would otherwise leave with a sharp bend right at the fitting. Bending a cable hard against the face of a straight grip defeats the strain relief and eventually damages the jacket at that point, so where the run has to turn, turn it at the fitting rather than just past it.
Cord Grip, Connector, or Cable Gland
The terms overlap in daily use and the distinction is worth knowing. A cord grip and a cable gland are effectively the same product: a fitting that clamps a flexible cable jacket and seals the entry. A conduit connector, by contrast, terminates a raceway rather than a cable and has no gripping mechanism for a jacket at all.
Using a conduit connector where a cord grip belongs leaves the cable free to pull, and using a cord grip on conduit gives no proper raceway termination. Lumera's electrical fittings collection covers the raceway side of that split.
Where a conduit enters a box and the concern is protecting the conductors against the cut end of the raceway rather than gripping a cable, the correct part is a bushing. Lumera's conduit and grounding bushings collection covers those.
Keeping the Enclosure Rating Intact
An enclosure only holds its rating if every opening in it is closed to the same standard. Putting a non-rated grip into a NEMA 4X box gives you a NEMA 4X box with an unsealed hole in it, which is not a rated enclosure at all. Where the box has to keep out rain, hose spray, or dust, the fitting has to be rated for that too, along with a sealing washer or gasket where the manufacturer specifies one.
The rating on the box is only meaningful when every opening in it is closed to the same standard.
Where Cord Grips Are Actually Required
Flexible cord entering any enclosure needs strain relief, and there are a handful of places this comes up constantly: portable and semi-permanent equipment, motors and pumps, machine control panels, sign and display cabinets, and pendant-hung fixtures where the cable carries some of the weight. In each case the cable is subject to pull, vibration, or movement that a terminal screw was never meant to resist.
The general rule worth remembering is that flexible cord is not a substitute for permanent wiring, so if a cord grip is being used to bring a cord into a box in place of a proper raceway run, the installation itself may be the problem rather than the fitting. A permanent connection belongs in a proper enclosure fed by raceway instead.
Installation
Tighten the sealing nut enough to grip the jacket firmly without crushing it, since an over-tightened grip deforms the insulation underneath and creates the failure it was installed to prevent. Leave a small amount of slack inside the enclosure so the conductors are not under tension at the terminals. On any outdoor installation, orient the entry so water runs away from the fitting rather than into it, and use the gasket or sealing ring the manufacturer supplies rather than substituting sealant. Anything connecting to building wiring should be installed by a licensed electrician, and the enclosure the fitting lands on should carry a rating that matches, which Lumera's NEMA enclosures collection covers.
Cord Grip and Cable Gland FAQs
How do I pick the right size cord grip?
Two measurements matter, not one. The hub size, such as 1/2 inch or 1 inch, has to match the threaded knockout in the enclosure. Separately, the grip has a cable outside-diameter range, and your cable jacket has to fall inside it. Measure the jacket with calipers before ordering, because several grips share one hub size with different cable ranges.
What is the difference between a cord grip and a conduit connector?
A cord grip clamps a flexible cable jacket and seals the opening around it. A conduit connector terminates a raceway and has no mechanism for gripping a jacket. Using a conduit connector where a cord grip belongs leaves the cable free to pull on the terminals inside.
Should I use nylon or steel?
Nylon costs less, will not corrode, and insulates, which makes it a good default for indoor, damp, and chemically aggressive locations. Steel handles physical abuse better and suits equipment, machine enclosures, and industrial work. In wet or corrosive areas, nylon often outlasts steel at the threads.
Will a cord grip keep my enclosure watertight?
Only if the grip itself is rated for the same conditions and installed with any gasket the manufacturer specifies. An enclosure keeps its rating only when every opening is closed to that same standard, so a non-rated fitting in a rated box means the box is no longer rated.
When do I need an angled cord grip?
When clearance behind the enclosure is tight, or when a straight fitting would force the cable into a sharp bend right at the entry point. Bending a cable hard against the face of a straight grip defeats the strain relief and damages the jacket over time, so turn the cable at the fitting instead.
