Solderless Electrical Connector

3,156

16

60

About: I miss the days when magazines like Popular Mechanics had all sorts of DIY projects for making and repairing just about everything. I am enjoying posting things I have learned and done since I got my first ...

Many years ago when I was helping my father in his small electrical wiring business we often used what we called SE connectors. I suspect SE meant "solderless electrical" connectors. I cannot find them anywhere, but I have occasional temporary need for one or two. So, I made my own from steel. Those I remember were solid copper.

Materials

  • 18 gauge sheet steel
  • 10-24 screw (or M5 coarse thread)
  • 10-24 nut (or M5 coarse thread)
  • Motor oil

Tools

  • Saw or shears
  • Hammer
  • Pliers
  • Vise
  • MIG welder
  • Grinder
  • 10-24 tap and tap wrench

The photo shows my SE connector in use. It nicely accommodates #10 wire or smaller. I want to connect wires together temporarily for testing wire pathways through walls with an Ohmmeter.

Teacher Notes

Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.

Step 1: Cut the Steel

I cut 18 gauge sheet steel to about 1/2 inch wide and 1 1/4 inches long.

Step 2: Bend the Steel

I found a piece of scrap steel almost identical in thickness to the diameter of the #10 screw I am using, which is about 3/16 inch. The first photo shows beginning to bend the steel into a "U" shape. The second photo shows my finished product. Ideally, the ends are equal. In practice that takes some attention and work to achieve. A quicker and easier way is to cut the steel longer than 1 1/4 inches and trim away any uneven ends with a saw or grinder.

Step 3: Prepare to Weld

The first photo shows the two pieces ready to weld together. In the second photo I have lifted the "U" shaped piece a little with six layers of masking tape. This is so the screw is more centered in the opening and less likely to bind on the internal sides of the "U" piece. I used a light tension spring clamp to hold the "U" shaped piece in place. The spring clamp also insures a ground connection for better welding. I will run a weld bead where the nut meets the 18 gauge steel. I left the screw in the nut for welding because I do not want to burn up the nut. The screw helps spread out the heat and protect the nut. I set the welder for 18 gauge steel. Even though the nut is thicker, it does not have much mass. The nut turned red hot, even though I kept welding time short.

Step 4: Chase Threads

I chased the treads with a tap in case the screw shifted during welding and in case the nut distorted from the heat. Notice the weld bead where the nut joins to the flat steel. Add a drop of motor oil to the threads for smooth action.

Step 5: Real World Use

When my father and I used SE connectors many years ago, we used them to join wires together. Then we taped the connectors and folded them into junction boxes. Wire nuts were just coming into widespread use at the time and may be what made SE connectors extinct.

The photo shows a real world use I have for my steel SE connectors. A friend has two three-way switches together with one 4-way switch in his shop. From the day he moved into this shop, the 3-way switches have never worked correctly. I unspooled about 80 feet of single strand plastic covered wire across the floor from one 3-way switch to the 4-way switch at the other end of the building. I used my SE connector to connect one of the travelers to the wire on the floor. At the other end I used an Ohmmeter to determine if there is continuity between the wire under test on both ends. I discovered the traveler is broken or not connected somewhere in the walls or ceiling. All other wires related to those switches show good connections and good continuity. Now we know what the problem is. We just do not know exactly where it is, yet.

Be the First to Share

    Recommendations

    • Instrument Contest

      Instrument Contest
    • Make it Glow Contest

      Make it Glow Contest
    • STEM Contest

      STEM Contest

    60 Discussions

    0
    None
    tcompton

    4 weeks ago on Introduction

    The picture you posted looks very much like a ground rod clamp, sometimes called acorn clamp which is way too big for your application, but there are other readily available alternatives. You mentioned wire nuts which is my first thought, but you might also consider a split bolt connector. They come in a wide range of sizes, will accommodate more than 2 conductors, and within reason more than one gauge.

    The term SE connector sounds vaguely familiar (maybe service entrance?), but that would, in my experience refer to a mechanical restraint for the entire cable, not a splice device for individual conductors.

    While your solution looks like a perfectly viable device, I’d be more inclined to take a trip to your local electrical supply house. Waaaay less work! :-)

    1 reply
    0
    None
    Phil Btcompton

    Reply 4 weeks ago

    Several people have made comments virtually identical to yours. Yes, a ground rod clamp is very similar, although huge by comparison. I am familiar with splitbiolts. This fits more neatly in closer quarters and can be attached for my needs with a screwdriver and my fingers. A splitbolt requires two wrenches or a wrench and a hefty pliers. As I mentioned to someone else, a wire nut would require me to remove a copper wire from the screw on a switch, straighten it, attach the wire nut, then remove the wire nut and bend a new loop for the terminal screw so I can attach it to the switch again. I knew exactly what I wanted and needed, and I made exactly that. Remember, this is designed for a test that lasts minutes. The only electrical power involved in the test is the equivalent of two or three AA batteries.

    2
    None
    IrvM1

    6 weeks ago

    Please, please change the photo to show the clamp used for some safe purpose.
    Although you say it's for temporary testing, it's not safe even for that, and remember,
    people on the internet lack reading comprehension. They won't register the warnings, just follow the picture.

    3 replies
    0
    None
    Phil BIrvM1

    Reply 6 weeks ago

    Please tell me exactly what is unsafe about this connector? It is an exact replica of the copper SE connectors that were in wide use at the time wire nuts came into broader use, except that this one is made from steel. Those copper SE connectors were UL approved. Thank you for recognizing I said I am using this for a temporary connection on a circuit powered by the batteries in an Ohmmeter.

    0
    None
    Cekpi7Phil B

    Reply 5 weeks ago

    Only thing i can think of is isolation, these are not isolated at all and i wouldn't put these nowhere anything that's over 50V. Not to mention they can easily short other terminal, for example if one of these was on positive terminal and casing (or car chassis) was ground, one wrong move and this will be glowing red.
    They can be useful in some cases though.

    0
    None
    Phil BCekpi7

    Reply 5 weeks ago

    By “isolated” did you perhaps mean “insulated?” A splitbolt connector is not insulated initially, but is before everything is closed up. As I said, my intention for this is a temporary test lasting a few minutes and done at the voltage of two or three AA batteries. The original UL approved version looked exactly like mine, except that it was all copper. Everyone covered them appropriately with electrical tape, unless, perhaps, the connector was used on bare ground wires.

    0
    None
    Pete Buxton

    5 weeks ago

    Thanks for showing how you solved your problem.Your design looks practical and easy to make for the purpose you stated. Many people enjoy DIY rather than just buying a part, especially if they have the materials and tools and they live in a remote location. I'm glad that people share things that worked for them so others can use that information directly or modify it to suit their purpose and share too. Most DIY people understand what is safe to do using logic and experience. Must there be stern comments and safety warnings for the use of a screw and nut? If someone is ignorant of known dangers and wants to learn the hard way, I think it's their choice and destiny.

    3 replies
    0
    None
    Phil BPete Buxton

    Reply 5 weeks ago

    Thank you. My Instructable did not show a new design I developed, but my copy of an old connector design no longer available anyplace I can find. I simply replicated it with what I have and can do. There is no danger someone will use a quantity of these in household wiring because time and effort to make even one is too much. Wire nuts are much less expensive. But, for what I needed to do, this connector serves better than anything else I know. This is not the first time someone told me something I use safely is dangerous and should not be presented in the field of ideas.

    0
    None
    Pete BuxtonPhil B

    Reply 5 weeks ago

    I'm with you. Your design could be used to temporarily connect and extend rods and/or wire sections that don't even carry electricity. Those safety inspectors who complained should lurk in the electrical section of Lowe's to warn people what they can and can't do with parts they are buying.

    0
    None
    Phil BPete Buxton

    Reply 5 weeks ago

    A few years ago I knew a guy who had worked as a plant electrician. He and some others were on a tour in Hungary, if I remember correctly. They were watching a local electrician wrestling a cable probably about 4/0 into a lug. It was not going. He pulled out a side cutter pliers and snipped off a couple of strands so it would fit. The electrician grinned sheepishly at the American visitors. They smiled knowingly back at him. They had all been there and done that. You are right. This connector I replicated could be used for various non-electrical things. Depending on the need, steel thicker than 18 gauge could be used if more strength was needed.

    0
    None
    LarryF29

    5 weeks ago

    I understand why he did this , he was thinking back when he worked with his dad, great story.
    Not to say anything here but there are many types of compression type clamps for electrical out there so you would not have to reinvent the wheel here. You could consider using a ground rod clamp to obtain the same thing as what he welded together. Also just use the ground clamps usually found in Lowe’s or found on equipment. If you don’t want the ear with the hole , just snip it off.

    CA5004A0-DA65-419E-AEF2-21D889204395.pngFB2F6917-7B66-42FE-A4D4-8D8232A36F9B.png
    1 reply
    0
    None
    Phil BLarryF29

    Reply 5 weeks ago

    For my need on this project a ground rod clamp is far too huge. The other lug is much closer. Someone else suggested that, too, but the mounting tang gets in the way and runs the risk of making contact with something that compromises the test I needed to make. Yes, I could cut it off. You have probably never seen the SE connectors I remember and tried to replicate. That is what I wanted and needed, not something else. The SE connectors I remember came in different sizes. The smallest would hold probably three stripped 14 gauge wires at maximum. The size for 12 gauge wire would hold three or four of those at maximum. The size for 10 gauge wires probably held a maximum of three bare wires. My need is for something I can assemble for a short test at 4.5 volts DC and then easily dismantle. A crimp connector is not an option.

    2
    None
    GUlNNESS

    6 weeks ago

    I was also shocked - NOT insulated, Surely cant be up to code!
    I have read a lot of replies as well as Phil B.
    I then took the time to re-read
    This is great in the examples he has mentioned
    A 'standard' choc block cannot hold thick wires
    The wires may be too short to twist together
    It is temporary
    It is NOT mains
    It is something HE wanted to do to relive a memory with his father
    It is some HE wanted to share
    Why do people want to be the Hi Viz / Safety hat / Steel Boots / Wire mesh jacket / safety googles / Kevlar trousers / ear defenders brigade for ... changing a light bulb
    People who criticise and do not give can be likened to parasites
    Phil B. carry on and good on you for doing what you want to do
    People who 'die' from being idiots are not my problem
    Thank you for reading

    1 reply
    2
    None
    Phil BGUlNNESS

    Reply 6 weeks ago

    Thank you. As concerns a lack of insulation, split bolts are not insulated initially, but are when the job is done. With the original version of these connectors and with split bolts we covered them quite well with rubber tape and then covered that with cloth friction tape or with plastic electrical tape.

    2
    None
    gsimon75

    6 weeks ago

    To begin with, iron-copper joints are not that good idea. Whatever moisture they get from the air, they'll corrode quickly: https://en.wikipedia.org/wiki/Galvanic_corrosion

    Furthermore, one wire rarely makes a circuit, so wherever you need one cable joint, you'll need at least one other. And where you have two separate wires, you need insulation.

    Preferably such that
    - doesn't deteriorate in a few years
    - doesn't take up air moisture and starts transconducting
    - isn't eaten up by insects
    - doesn't loosen up from the thermal expansion/contraction (wires do heat up from the current, even if just a bit)

    Practically this means either cast or crimped plastic, or heatshrink tubing. How do you intend to insulate two or more of these ... things in a crowded wall-mounted cabling box?

    Sorry to say, but this is a reinvention of the terminal strips, only in an outright dangerous way, for a remarkable amount of effort, with no known 'absolute maximum' ratings.

    Sure, if we're trying to power up the last radio transmitter of the continent in a zombie apocalypse situation, these are indeed better than just twist the wires together (but still don't forget to mash some chewing gum around it!) :D ...

    As in all the other, real-life situations, *please* throw these contraptions back to the drawer, go to the nearest electrician shop, buy some terminal strips, and care to choose one rated for the ampage to
    be transmitted, conforming to the local electrical legal rules.

    2 replies
    2
    None
    Phil Bgsimon75

    Reply 6 weeks ago

    What many call wire nuts I always called Scotchloks. I always preferred those made by Scotch. What are they but a steel spring covered with a plastic insulator? Some are even bare without any insulation. They provide an iron/copper joint. Perhaps the spring is coated, but there is a lot of abrasion while twisting them into place on a cluster of copper wires and that pretty well removes any coating. They have been in use for decades, but I have never seen or heard of any rusting or failing because of rust. Did you notice I said I needed this for a temporary connection so I could make a low voltage DC test? Your comments assume this is a line voltage permanent connector.

    1
    None
    gsimon75Phil B

    Reply 6 weeks ago

    Well, Sir, everyone chooses the tools he finds most convenient, so in this case I can't add any more than I wish you good luck and take care!

    2
    None
    RadGumbo

    6 weeks ago

    As an electrical professional, I was horrified to read your instructable as there are a host of issues that could lead to loss of life and/or property. To start the device you constructed is not UL listed nor follows any known NEC guidelines for such devices. The hardware you employed lacks enough thread through the nut to insure integrity of the joint. Vibration over time will loosen joints. A majority of structure fires due to electrical faults are related to loose joints. For the purposes of the "real world" example you referenced, a properly sized wire nut is the preferred remedy, and meets NEC code. Additionally, other products such as insulated terminal blocks (i.e. Polaris Taps) come in a number of sizes and are tested and certified for their use in these applications and represent a proper and safe method for addressing similar electrical issues. Your instructable WILL put people at considerable risk, and I would recommend you remove it. The electrical code is constantly being updated as more experience uncovers additional issues, and what was legal under the code twenty or more years ago may not be legal today. The Code exists because it saves lives...everyday.
    1 reply
    1
    None
    Phil BRadGumbo

    Reply 6 weeks ago

    What I made has more steel thread than the threaded copper on the connectors I remember, and those were UL approved. Did you notice this is not a permanent connector, but only temporary for a low voltage DC test? Your comments assume this was made for a permanent line voltage connection.

    1
    None
    GlenFf

    6 weeks ago

    Hi Phil B,
    You have written a very nice and concise little Instructable here. And crystal clear close up photos too - sweet!
    I acknowledge that you have clearly stated that this is intended for ***temporary use*** -
    "The photo shows my SE connector in use. It nicely accommodates #10 wire or smaller. ***I want to connect wires together temporarily for testing wire pathways through walls with an Ohmmeter.***"
    May I suggest that you move this paragraph up to the very top of your Instructable, instead of after the Materials and Tools lists as it is presently positioned. I missed this paragraph the first time I read it. (I agree with Tedwards and GlenGH that the instructable has the potential for unsafe outcomes if readers try to use this for permanent connections.)
    I would also like to offer an alternate construction method, one that does not require any welding, and would make mass production easier. I hope I can adequately describe my idea in words, without pictures.
    My suggestion is to use steel or copper circular pipe for the crimp cage, probably about 1/2 inch (~12 mm) diameter. Drill a hole/holes along the top of the pipe, approx 3/16 or 1/4 (~5 to ~6 mm) holes, just larger than the diameter of your #10 screw shaft (incl. thread). Now the #10 screw can be inserted freely into the hole. The #10 nut can be placed inside the pipe. Once the nut is threaded over the screw, the nut is "held captive" by the wall of the pipe.
    The pipe can be drilled with as many holes as you require SE connectors. I imagine the holes would be spaced about 1/2 inch (~12 mm) apart. Then just cut the pipe midway between each hole to produce the cages. Once cut, the cages could have nuts and screws inserted and assembled, and then cages can be crimped or "squashed" on the sides to produce a nice oval shape, as desired.