Improving a Welder Ground Clamp

These stamped steel ground clamps are standard from the factory on many welders.  They work pretty well, but performance degrades in time.  I could buy a nice brass ground clamp, but would rather just improve the contact and current path on this clamp.  

Step 1: Fit a Piece of Aluminum Bar Stock

I decided to fit some aluminum bar stock inside one half of the stamped steel spring clamp.  My bar stock is 1/8 inch x 3/4 inch.  The space inside the stamped steel clamp handle is about 9/16 inch.  I used a hacksaw to trim off the excess. 

Step 2: Drill a Hole in the Aluminum

Drill a hole through the piece of aluminum for the cable bolt.

Step 3: Cut and Bend the Aluminum Piece

In this photo I have drilled out and removed the rivet that holds the clamp together, removed the plastic handle grip, loosened the bolt, removed the cable, cut the piece of aluminum to length, and bent it to fit the contours of the stamped piece of steel.

Step 4: Build Up the Thickness

I cut a second piece of aluminum to thicken it inside the jaws so it can clamp directly against the steel I am welding.

Step 5: Drill for a Brass Screw

I drilled through both pieces of aluminum at the jaw and the steel of the jaw, used a countersink to prepare the aluminum for a bevel head brass screw, inserted the screw and fastened it with a brass nut.  I cut the brass screw end nearly flush with the nut and peened it with a hammer to keep it from coming loose in the future.

Step 6: Inserting the Spring

The spring is quite strong.  I did not want to wrestle it back into the handle halves while trying to insert a screw to replace the rivet.  I decided to squeeze the spring in my vise and tie it in its squeezed position with some sturdy wire. 

Step 7: Assembling the Two Halves of the Clamp

Line up the holes in the two halves of the clamp.  Slide the spring into the clamp and insert a screw to replace the rivet so that the screw also passes through the spring.  Put a locking nut onto the end of the screw.  Make certain one of the plastic handle grips is already on the ground cable.  Bolt the cable to the clamp.  The bolt now passes through both the steel handle and the hole you drilled in the aluminum.

Step 8: Finish Reassembly

Cut the wire retainer on the clamp spring.  Remove the wire with a pair of pliers. Slide the plastic grips onto the spring clamp. 

Step 9: Grind Away Steel on the Improved Jaw

Grind away raised portions on the jaw to which aluminum has been added.  Here you see I have ground away some of the steel.  I may yet grind away the remaining peaks. 

Step 10: Getting the Maximum Contact Area

In the photo you can see I did grind away the remaining peaks on the improved side of the clamp (bottom half in the photo).  I also filed the screwhead so it does not rise above the aluminum in the jaw at all.  And, I have inserted a piece of scrap steel between the jaw and the piece to which the clamp is attached.  This makes a pressure point in the middle of the clamp jaw's length that pulls the flat aluminum added to the jaw firmly against the work piece for a broad area of electrical contact.  If one were welding on a round tube, it would perform the same function without an added piece of scrap.

The performance of any welder improves with a better ground clamp.  This ground clamp now has more surface area to make contact with the work, and it will not rust.  If an oxide forms on the aluminum, I can use a file or a little sandpaper to restore a clean finish.

Comments

[charles543]

I am an electrician. I have never heard of aluminum as a contact surface. I have heard of brass. If there is any rust or dirt, a flat surface will not bite in. A pointy surface will.

[rfrench6]

most all power transmission lines are aluminum. they are less conductive than copper, but lighter over long distances, and cheaper, of course.

[Phil B]

Thank you for your comment. Aluminum is an excellent conductor. As you know, there was a period of time when aluminum wire was used in place of copper for household wiring, until it was realized screws at terminal points with aluminum wire tended to work loose, generate extra heat, and cause fires. Cables from a distribution transformer to a meter mast are still often aluminum tri-plex cable, and have been for more than 50 years.

While a pointy surface may dig in better than a flat surface, a pointy surface also has less contact area than a flat surface. I used this ground clamp modification almost seven years and never sensed reduced conductivity. I did have a factory issue steel stamped battery charger clamp on a 230 volt AC stick welder. The welder's performance increased in a noticeable way when I replaced that clamp with a commercial cast bronze clamp. That experience led me to this modification.

I would say part of the equation is also a surface on the piece to be welded that is clean and free of contaminants, although there have been times when I did not clean the surface on the work piece before applying the ground clamp for a weld. I have also tightly applied a Vise-Grip pliers to an irregular work piece and attached the ground clamp to the Vise-Grips. That works very well, especially where there is a painted surface on the work piece and I do not want to burn it any more than necessary.

In place of aluminum bar, a person could also flatten some copper tubing used in plumbing. But, the aluminum has worked very well.

[charles543]

to Phil B:

Car batteries can deliver 400A or more. I like 4 batteries. The arc is easier to start, and is much more stable. I don't have 4 car batteries, and it would be way too expensive to buy them. I saw a video on youtube where a guy was using 4 5 amperehour batteries out of uninterruptible computer power supplies. I found 4 9 amperehour batteries on ebay for $50.00 and a 48V charger for $9.95. With cheap jumper cables for leads I was burning up 3/32 rods. Now I am using #14 wire leads 10' long for leads. They seem to work pretty well. I want to get some steel band to come off the positive end of my battery, so I can clamp onto the band at different places to get different currents. I figure I can get about 7 minutes of arc at 100A.

[Phil B]

I have read about joining car batteries in series for an improvised welder, but usually for a quick emergency repair to an off-road vehicle.

[laxap]

I am intending to start welding, and am surprised when seeing how small the contact surface offered by standard unmodified clamps is. So I find your article very relevant.

What about simply winding some fairly thick copper wire around each half of the clamp? or some desoldering braid?

[Phil B]

Those things should help quite a lot. Much may depend on the size and shape of what you need to grab with your ground clamp. That is, making the ground clamp hold on small items may be different from making it hold on large items. Of course, another option is to go to a welding supply store and buy a really good commercial ground clamp. What I did here has worked out very well. Thank you for looking and for commenting.

[kill-a-watt]

This could be useful for the many people like 4x4ers who weld in the field with batteries and jumper cables.

http://www.youtube.com/watch?v=8tHJ0NSjZnM

(not my vid)

[Phil B]

Here is a car battery welding demonstration that runs about 9 minutes. I am surprised he is able to get enough power to weld with 1/8" #6011 rod on pretty thick material.

[kill-a-watt]

it actually works OK, but the current is too high and the arc is hard to keep going. I was able to weld maybe 1-2" before I lost the arc. I used rods from 1/16 to 1/8 just fine though.

Tim Anderson here: https://www.instructables.com/id/Golfcart--Welder/step6/Arc-Stabilizer-and-Stinger/ talks about making an inductor to stabilize the arc. Unfortunatly, every microwave I've taken apart for the inductor has used a tiny iron core instead of the hefty ones they used to use. I think I need an older one.

(One of the microwaves came with a surprise! Cockroaches! Make sure you do your initial disassembly of the "curb shopped" microwave outside!)

I think if someone could come up with a sub-$50 box that included the inductor and added in a device that imposed a high frequency high voltage "arc starter" (to avoid the "scratch start"), they might have a winner. However, I'd guess the liability insurance would make this impossible to hit my price point. Everyone always says that welding with batteries is "for emergency use only"

Oh and I want to tell you that I made a quickie welding mask for my brother to watch me weld. I bought a $3 #10 lens and made the rest out of some clear packaging plastic (to protect the lens from splatter), duct tape, and a beer flat. Worked great! I'll have to make a slightly better one following your instructions later.

[Phil B]

Thank you for your response.  Years ago Popular Mechanics and Popular Science magazines had plans for home-built welders.  The PM version ran on 230 volts and used the steel core from a step down transformer salvaged from the local electrical power utility.  That was before oil loaded with PCB's was used to cool them.  The windings were #12 plastic covered household wire laid parallel in multiple strands to gain the current carrying capacity required.  Welding current settings were by plugging into different sockets connected to taps on the secondary windings.  The PS version used a surplus WW II aircraft generator powered by a 5 HP gasoline engine.  Both had an arc stabilizer made from a brick of steel laminations wound with multiple turns of wire.  One of them allowed the core to move in and out of the coil for adjustment of the stabilization.  The library at a local college has both magazines complete back to the initial issues.  I had seen both before, but found them again with the Reader's Guide to Periodical Literature.  They may even be on-line by now.  I am glad to know the guest welding hood worked out for you.  UV protection is important, and I am planning to paint mine black.  Between the cardboard and the paint, there should be pretty good protection.  Thanks for letting me know.

[Phil B]

I found the welder plans I remember.  They are from the November 1965 Popular Science Magazine, p. 142f.  You can view the article on-line here.  It probably will not take you to the exact correct page.  Click on "Contents" in the menu bar at the top.  Scroll down a little and click on "142 Make Your Own Arc Welder."  That will take you to the correct page.

[kill-a-watt]

Here's the plans for the one that took a war-surplus Delco Remy P-l aircraft generator:

http://www.vintageprojects.com/metal-welding/auto-arc-welder.html

[Phil B]

I think the generator welder and stabilizer in your link is very, very close electrically to the plans I saw, but they were mounted on a wheeled cart the home builder makes to carry the generator and the gasoline engine, not inside the engine compartment of an automobile. Whereas the output on the Vintage Projects welder varies according to engine RPM, the plans I saw were limited to around 75 amps of welding current, probably because the 5 HP engine cannot manage more spin on the generator. Thank you for locating this link.

[kill-a-watt]

I figured it out. You need to use the "rich editor", and then get the "embed" code from the webpage of the video (in youtube, that's currently below the video, shown by pressing the "embed" button.) Paste the entire code into the Instructables window.

Also, this Instructable: https://www.instructables.com/id/How-to-embed-a-video-into-Instructables/ is deprecated.

[kill-a-watt]

Well that didn't work. I guess they rolled back features. Reminds me of Adobe.

[Phil B]

I remember reading about some 4 x 4 fans who had to stop and weld a cracked suspension part one of the vehicles. They connected several of the auto batteries in series and had the repair done in a short time. Since the ground clamp shown is pretty much identical to those found on automotive jumper cables, this adaptation could be useful to boost current carrying capacity, especially on a set of cables starting to show signs of wear and tear. Thanks for your comments. I am sorry your video link did not work out, but I think I get the idea.

[rimar2000]

Phil, I always wondered why the ground clamp is so weak, whether to deal with so many amperes. Now I see you have a response!

I think I will do that you suggest.

Tomorrow I will take five days of rest at Piriapolis, Uruguay. I will miss my workshop...

[blkhawk]

Have a good time in your trip! Please bring me coins and bills because I love to collect money from all over the world! :)

[rimar2000]

I collect US dollars, I have a big trunk totally full of them. Some time ago I had to throw away a lot of Kg of dollars because they were rusty, all green!