The Complete Guide to Clips
This guide to clips covers different types of electrical clips and a brief history of how our modern-day clips came to be. If you are looking for help in finding the exact clip you need, try our clip selector here.
If you are looking for a place to buy alligator clips, our authorized distributor list is here.
Ralph S. Mueller, known as the "Skipper of the Clipper," co-invented the Universal Test Clip in 1908 and founded Mueller Electric Co. to create and sell the device.
An alligator clip (also called a crocodile clip outside of the US) is a spring loaded metal clip that is used for making temporary electrical connections. The name comes from the resemblance to an alligator or crocodile’s jaws as the clip is sometimes serrated with little “teeth”. The clip functions similarly to a clothespin.
Alligator Clips can come in many different types of metal and colors. Different metals are sometimes more useful for particular applications, but sometimes it's also just a matter of aesthetics. Read our guide to finishes for help in selecting the right finish.
Some uses are:
Electrical connections: The main use of an alligator clip is for an electrical connection. The clip is attached to components and establishes a connection between the two. Because it’s a clip, it will stay put which frees up the user’s hands.
Laboratory: alligator clips are a cheap easy way to assemble or alter experimental circuits. They are typically used to connect two wires or to connect one wire to the anode or cathode of a device. They are also useful in educational laboratory settings, often used with batteries, lightbulbs, and other devices.
Dentistry: Alligator clips are often used in dental offices on a cord to attach a bib.
Crafts: Alligator clips are used in many hobby and craft activities, including holding items together for soldering or gluing, or making different things out of the clip itself.
ID badges: Alligator clips are often utilized for holding ID badges for conventions and conferences. The clips are on the ends of a lanyard worn around the neck or attached to a front pocket with the clips grabbing onto the badge.
Plier Style Clips
Plier style alligator clips are most commonly used in the automotive industry for battery chargers and jumper cables as well as for welding applications. They come in a variety of sizes and styles and are often insulated for safety and comfort.
A Kelvin or Kelvinized clip is a special plier style clip. The jaws of a Kelvin clip are insulated from each other, allowing 2 isolated wires to connect to a single test point. This is also called Kelvin sensing or four terminal (4T) sensing. This type of connection helps to measure very low resistances and makes a more accurate measurement than traditional testing with just 1 wire (2 terminals).
Center Spring Clip
These versatile clips are the grandfather design of all modern clips and are the clip design that preceded modern-day alligator clips. While they fall into what is now considered the the alligator clip family, they are referred to as Center Squeeze Clips, Center Spring Clips. These clips invented by Ralph Mueller in 1908 paved the way for innovation in the world of electrical connections and many other clip designs.
These are used for a range of industries including automotive analyzers, meter testing equipment, battery testing, welding, and earthing, bonding, and grounding applications.
Center Spring Clips use compression springs which are more durable and last longer than the torsion springs used in the alligator, plier, and telecom clips.
Fun Fact: The original name for a center spring clip was a “universal test clip”
Hybrid Clips (EZ-Squeeze)
Is it a Center Spring or is it a Plier Style? It's both!
The EZ-Squeeze (Easy Squeeze) is a variation on a Center Spring clip but it squeezes like pliers. As its name suggests, the EZ-Squeeze is easier to open because it uses 75% less pressure to open as a Center Spring clip and it retains the same clamping pressure. The benefits of this clip is that it can replace a Center Spring clip and anyone can open it. It reduces hand fatigue and is favored by people with weak hand strength or arthritis. This is a very new style of clip that is patent pending.
Telecom Clips (Bed Of Nails)
This variation of an alligator clip has piercing spikes in the teeth to connect to both bare and insulated wires. The benefit is that they can be used on insulated wires without having to strip the insulation off, so they can connect anywhere along the wire. These type of clips are used mainly by the telephone industry as well as by anyone needing to take a measurement without stripping the wire insulation. Telecom clips are also called Popper clips.
Insulators, also called a “shroud” or "boot" are coverings to prevent accidental short-circuits. They slip onto a clip and prevent it from touching other metals. The very first insulators were made from rubber nipples to nurse baby lambs.
What we call an Alligator clip in the United States is a Crocodile Clip to people in Europe and other areas of the world.
For the most part, you can assume that anyone using the term crocodile clip is referring to an alligator clip.
In the US, we have one type of clip that is referred to as a crocodile clip - which is still a type of center spring alligator clip. This causes a lot of confusion.
To clarify, There does not seem to be any consistent differentiation between the two terms. Alligator clips and Crocodile clips are the same thing, and using either term is correct, and most people will know what you are talking about if you use either term.
"Throughout the years, the ever increasing applications of electricity have created new human needs, which involved testing devices. We have sensed these needs and where necessary have offered additional types of clips to meet them.... One of our slogans is literally true: 'Wherever electric current flows you will find Mueller clips serving mankind.' Of one thing you can be pretty sure - the final testing of an electric device or peice of apparatus at a factory and the repairing and testing of it in the field involves the use of clips."
- Ralph Mueller The Skipper of the Clipper 1957
Some of the first clip designs. The very first model was handmade as were the next two. Dies were utilized to mass produce the next design in 1910. Note the first insulator made in 1910 with a rubber nursing nipple originally made for baby lambs.
An Ad from 1934 featuring a letter from a farmer who found a new use for the clips. The drawing is by Hal Donahey, a famous cartoonist at the time.
"Farmer Schumacher of Menominee Falls, Wisconsin writes us: - "In regard of your letter that come to me about them clips. Thay are fine and we here on the farm dont wont to be with out them all so the neighbors that got some, but now Ill tell you how we here used them. Put your clips on a little rope about 5 ft long that is longer if the barn is higher. Have a ring on end of rope. Then put a wire from one end of barn to other. Slide your ring of wire as you go along milking from cow to cow. it is better if you have two or more clips then the cow near you can't hurt you eather. We here take clips off after milking is done. But I guess you just as well let them on. Hoping you can unstand what I mean how we here use the clips."
"Is your cow contented? Does she point you out in a crowd with pride? If not, why not use a Universal Clip to hold her tail while milking, so that when the other girls are around she won't have to lower her head and blush guiltily whenever cow-tail holding devices are under discussion."
"Who's afraid of the big bad cow
With a clip aholdin' her tail?"
The D.N.C. (Dental Napkin Clip)
Mueller was constantly demonstrating more uses for clips that stretched beyond just electrical uses. This idea was published in "The Clipper," a Mueller company publication on May 15th 1934. Note the style of clip is a center spring clip - a different design than the alligator clip that is used in dental offices today. That style of clip as we now know it would not be invented until much later.