View Full Version : Electrical Plugs & Connectors: Why So Stiff to Join Together

11-17-2014, 07:07 PM
A recent stint at building some new extension cords from
SOOW cable with Leviton plugs and connectors at each
end renews a question - why do today's plugs and connectors
take so much more effort to join and separate than in the

For these kind of cables, I use Leviton plugs & connectors
now. However, others I have tried are just as stiff.

Has there been a design change in the standard with a view
to reducing the likelyhood of cables disconnecting? I have
long just tied the two joining ends together into a loop.


Mike Folks
11-17-2014, 08:12 PM
Are they US, or China made? I've got some plugs and receptacles at home do not mate well. I suspect manufacturing tolerances have caused this problem. I remember long ago of buying electrical parts that fit and worked, but now in todays economy, cheap is the word.

11-17-2014, 09:00 PM
I'm hearing you.:) I cant answer your question but I can commiserate.
Here in Australia we have a different system to the USA for domsetic electricity. You may or may not be aware of that, but our domestic system is 240V 50hz. Our plugs and sockets are 2 conductors (active and neutral) which are at an angle to each other and a vertical earth pin. The problem I am finding as I get older (and Arthritus in my hands gets worse), particularly with extention power boards, is that the plugs on a lot of appliances, appear to have been designed for someone with the manual dexterity of a brain surgeon and the finger strength of King Kong. Some of the plugs are extremly difficult to get a grip on to remove them from the socket. Some of the power boards are also very tight in the sockets and when you combine the two it can be quite frustrating.(not to mention painful)
Obviously the people who design this stuff have never actually had to use it. Some of the plugs have a loop on the back to allow a finger to be put in to help remove the plug. Great idea- if you have small fingers. Not so good if you have knuckles swollen with Arthritus. ( I dont like this getting old - and I'm only 56.:rolleyes:
all the best

Ohio Mike
11-17-2014, 09:08 PM
Maybe you're just used to the old ones that are wore out?

11-17-2014, 09:41 PM
Maybe you're just buying quality now? SPEC grade is firmer to insert, and stays that way for the lifetime of the product. The dirt cheap plug and receptacles are all over the place...and get really sloppy over time. The worst are the molded plug ends on cheap cords - I chop those off and put on Hubble (or similar) plugs and receptacles..

11-17-2014, 10:03 PM
Thanks for the heads up Eddy, I'll make a point of looking for those hard to undo plugs and receptacles.
I'm tired of having to loop everything together in order to use it. Except for some of the better quality new cables that I've bought lately all of my old ones simply fall apart at the mere suggestion of movement somewhere in the cord.
Leviton plug and receptacles, here I come.:)

Mr Fixit
11-17-2014, 11:04 PM
lakeside53, Has it right.
SPEC GRADE or HOSPITAL GRADE have 2 flats on the inside that wipe the prong you are inserting, so it takes more force to install. That is why you are finding leviton to be hard to use they produce SPEC GRADE and better. I would also suggest Pass & saymour, Hubbell, as good choices for replacement parts. Spent a few years in the field installing and working with these products not associated with or do I sell the items mentioned.

Mr fixit for the family
Chris :)

Bob Ford
11-17-2014, 11:05 PM
A little bit of graphite will help and it conducts electricity. The poor fitting ones usually have the area around the neutral melting first. Nice fire hazard. As cords are abused and overloaded the plugs get loose causing voltage drop which raises the current which causes the plugs to get worse. This also gives the tools on the end of the cord a hard time.


The Artful Bodger
11-18-2014, 12:07 AM
Where does Ohm's law get a look in on this?

Graphite is a very good conductor and I shudder at the thought of it mixed up in typical plugs and sockets on extension cords.

Bob Ford
11-18-2014, 12:23 AM
The key word was a LITTLE bit. Like very light dusting on the prongs.


11-18-2014, 12:28 AM
Hubbell used to be my device of choice for everything. I still use
their Twist-Locks for 220V/1PH plugs, connectors and receptacles.

I liked working with their "Valise" series of 2Pole, 3Wire, 5-15P 15A
125V straight blade devices. Compared with what I was used to, the
Valise assembled really nicely, worked well and looked professional.
However, while the hard nylon bodies are really tough in moderate
conditions, they tend toward brittleness in the extreme cold here.
So they can be intolerant towards being dropped. They don't break
completely, but they crack and chip on me.

Strangely, PVC-bodied devices seemed to survive better. Initially I
was buying no-name units from my wholesaler that were superficial
look-alikes to the Leviton 515PV and cost a bit less.

http://www.leviton.com/OA_HTML/ibcGetAttachment.jsp?cItemId=SEJdmLgAdo4XXkxryQXJW A&label=IBE&appName=IBE&sitex=10251:22372:US

Choosing those proved to be a mistake in terms of time and money.
I removed the ones I'd installed and threw out the ones I hadn't
used yet. The wholesaler was a good outfit - I don't know how
they came to be carrying that product, but I am glad I faced facts
and dumped mine before I experienced a bigger problem.

The Leviton 515PV have been accurately molded and are standing
up well, they are just a nuisance to connect/disconnect. The
Hubbells were never like this, yet it is a common difficulty now
with ready-made extension cords, surge protectors and so on.
Hence the question about whether standards have changed.

The 515PV plug and connector have some size to get a grip on.
It has been a while since I lived next to Lygon St. and I can't
quite picture the hardware common in Oz, but I can appreciate
bollie7 remarks about difficulties people with infirmities such as
arthritis face.

Thanks for the comments.


11-18-2014, 12:51 AM
... from my wholesaler that were superficial look-alikes
to the Leviton 515PV and cost a bit less.Correction. The no-names were similar to Cooper plugs. The Coopers
are 'ok', but I have settled on the Levitons.

Here's a tip: if you look inside a no-name plug and see "ERIW LUSNI"
molded into the inside rim of the male portion of the plug that carries
the blades and terminals, put it back on the shelf and look elsewhere.

When you notice what a quality plug has molded there, you'll understand.


11-18-2014, 02:45 AM
You can get silver-bearing or copper-bearing conductive grease that may help, but you must be careful to use only a little. Actually, ordinary grease or Vaseline can be used, and if the connection is tight, the many rough "points" on the mating surfaces displace the grease and make contact. You can also brighten up the plug prongs with Scotch-Brite to get better conductivity, as the copper oxide (or sulphide) that forms is a poor conductor. You can also apply a light coating of silver plating which greatly enhances the connection, and the black oxidation on silver is a much better conductor than that on bare copper (or brass). Another good compound to apply is No-Al-Ox (http://www.homedepot.com/p/Ideal-NOALOX-4-oz-Anti-Oxidant-Compound-30-026/202276208), which is mostly for aluminum but I think also protects copper from oxidation. If you really want the best, try gold plating, but silver is actually a much better conductor and cheaper and easier to apply.

Look at http://cool-amp.com/.

11-18-2014, 03:08 AM
I use grease but non conductive silicon plumbers grease, cheap and the dielectric is only a small bit less than the electrical grade, which Dow Corning make, they also badge it as vacuum grease but that's a bit thick

11-18-2014, 08:15 AM
On the sticky plugs that are on our trucks, outside, in the elements I always use dielectric grease on the plugs and never any trouble since.

In the shop I have the opposite problem of the plugs coming apart, falling out of the wall outlet, ect.

11-18-2014, 08:53 AM
I agree on the use of silicone grease. I have used a lot of it through out my career. Automotive uses it in there sockets also.

There are 2 reasons I can speculate why the plugs are so tight on quality unit. 1) The harder they go it, the harder they come apart. You can drag the cord around and your tool won't come unplugged. On cheap cords you have to tie a knot in them to prevent that. 2) A loose connection will generate heat causing the plug burn out or at worst start a fire. Unfortunately, the older we get the more we notice it. Just like our eye sight. Don't get me started on gas pump display screens :).

Bob Ford
11-18-2014, 09:26 AM
Guys the use of dielectric grease is helping the problem. You do not want to insulate the connections. You want a good connection in the cord ends so as to not build up heat. A light dusting of graphite on the male plug will help. Any sanding or otherwise remove the plating of the contacts greatly shortens the connections life. Cord caps that fall apart are at the end of their service life. In use they will feel hotter that the cord. When changed the insulation will be hard. Trim back the cord to get good insulation on the wires.


11-18-2014, 12:06 PM
In regards to the use of various lubricants, I would like to ask if the use of spray silicon is bad? I have used it for years and it helps, but I wondered if there was a down side to it.


11-18-2014, 12:25 PM
Guys the use of dielectric grease is helping the problem.

The problem isn't bad conduction, it's difficult insertion. I've never had a problem using dielectric grease on an electrical connection.

That, and I despise the messiness of graphite powder!

Bob Ford
11-18-2014, 01:44 PM

Grease that inhibits the flow of electricity is called dielectric. It is a insulator. You can have a good electrical connection or a loose electrical connection, but not both. If you want easy plugin's get cheap cords and caps. If you want safe and full power buy quality parts. When parts wear replace them.


11-18-2014, 03:45 PM
I'm betting graphite is a bad idea. I've done a lot of research on contact resistance and wear in my job. Particles of graphite will separate the contacts, and will provide resistive paths through the graphite. Resistive=heat generation=burning. Most contacts that are designed for high switch count lifecycles are lubricated. The lubrication medium itself is usually a dielectric. Contact pressure should squeeze out the lubricant and allow electrical contact. Therefore the proper film strength is required of the lubricant, as well as the proper amount applied. In my work the lubricant is applied as a vapor deposition under controlled conditions. By the way, consistent with common sense, greater contact pressure=reduced contact resistance, which is why higher quality or higher power plugs are harder to mate. Contacts as seen on a microscopic scale don't really have much actual contact surface.

11-18-2014, 03:57 PM
I looked up the lube we use and it's in the class of polyalphaolefin synthetic lubricants. They are good dielectrics.

11-18-2014, 04:24 PM
Use of dialectic grease on electrical connection is standard practice. Dow compond 4 or compond 11 are good examples. Any good switch you buy will be greased. I used grease on high frequency very low voltage transducer with no detrimental affect to there operation. The purpose of the grease is to lubercate moveable parts, prevent oxidation/corrosion and displace water. Grease is not considered any insulator, it just does not conduct electricity. When you slide the plugs together the grease is wiped off allowing for conduction of electricity.

11-18-2014, 04:42 PM
If anyone's interested in the science of electrical contacts, this is one of the best documents I've seen: http://www.te.com/documentation/whitepapers/pdf/p154-74.pdf

11-18-2014, 05:24 PM
I stick the end of automotive connectors on the end of the dielectric grease tube and fill the connector before inserting the wire and crimping them. I have done the same for the 110v sockets I have trouble with sticking (mostly on our trucks out in the elements) and it works wonders and never a contact problem because of it.

Works great for me, Imma keep doin it.

11-18-2014, 10:18 PM
That was an excellent artical. Thanks for posting it.

11-19-2014, 08:48 AM
Guys the use of dielectric grease is helping the problem. You do not want to insulate the connections. You want a good connection in the cord ends so as to not build up heat. A light dusting of graphite on the male plug will help. Any sanding or otherwise remove the plating of the contacts greatly shortens the connections life. Cord caps that fall apart are at the end of their service life. In use they will feel hotter that the cord. When changed the insulation will be hard. Trim back the cord to get good insulation on the wires.


No, no, no!!! You don't want to put any conductive grease or powder in a plug. It's a recipe for disaster. You want a dielectric grease. It's the industry standard. If you want to get fancy use a grease that has antioxidant properties.

Bob Ford
11-19-2014, 09:27 AM

I use nothing in or on cord connections. Grease attracts dirt or grit which makes the problem worse. As I said earlier if you want easy fitting cord caps buy cheap and undersize. If you want safe use the correct size cap and wire for the job. Dielectric grease on high voltage switch gear in a non dusty environment is a good idea, but on cord caps that are always in crud suggest you have spares you will need them.


Bob Ford
11-19-2014, 09:56 AM
This is how you should apply graphite to male cord caps. Dip your finger tip in graphite. Shake off any loose graphite. Run your finger tip down each side of the male prong. You should see a slight color change. Never any clumps of graphite. This amount will not track at voltages of less than 300 v.

Those that use grease or oil of any kind will in short order have a fine grinding compound which will smooth the parts and quickly wear them out.

The best option is add nothing that is how they were designed to work. Cords used outside are dragged
in dirt, water, and manner of crud. Even in a shop there is gritty dust. Take care of your cords and maintain them so you do not get electrocuted.