Home > EMF Rod End FAQ
Frequently Asked Questions 


 Q: Where did the Heim Joint come from? A: The Rod End was an amazing new component found on the high-tech control systems of a captured German fighter plane, shot down by the British, early in World War II. H.G. Heim Company was given an exclusive patent to manufacture the joints in North America. After the patent ran out, the name "Heim" stuck as a slang term. 

Q: Where are Heim Joints used and why? A: Heim Joints (Rod Ends) are used throughout the world. They offer easy mounting and adjustment of linkages and control rods. They are used in many different applications such as boats, doctor offices, fighter planes, the space shuttle and most importantly, monster trucks. Heim Joints are often one of the most overlooked necessities in a good build. In a truck world full of massive motors, unbreakable axles, huge tires, long travel nitrogen shocks, drop boxes and built transmissions, who cares about a Heim, right? The truth is, without the Heim you would be stuck on leaf springs, slowly driving over cars, not launching over bus stacks. The Heim is what allows all the crazy travel. If you break a Heim, it can break drive shafts, transmissions, bend shocks and cost you a heap of money. With all that being said there are so many things that are questionable. This article isn't going to regurgitate numbers and abbreviations that can be found on the net. It's just answering simple questions that have been asked time and time again but are never really answered. 

Q:  What is Liquid Nitriding?   A:  Liquid Nitriding, also known as Salt Bath Nitriding is a thermochemical diffusion process whereby nitrogen and carbon are simultaneously introduced into the surface of ferrous metals to develop or enhance particular engineering properties and thus increase performance.  The process is carried out at a subcritical temperature, typically 1050F, in a molten salt bath composed of a mixture of cynates and carbonates of Sodium & Potassium.  This proprietary sale is known commercially as "Scuff-Rite" and conforms to ASM 2753.

Salt Bath Nitriding improves wear resistance, lubricity, fatigue strength and corrosion resistance as a result of the presence of an iron nitride compound(s) formed at the surface, in addition to a zone of diffused nitrogen in a solid solution with the base material subjacent to the compound layer.  Both of these zones are metallurgically discernable, each providing specific engineering properties.

Improvement in Fatigue Strength with Chrome Alloy Steels (used on all of our joints) - 20-30%.

If you would like more information please feel free to contact us and we can send you a PDF about the process.


Q: What exactly do you mean by "Load Ratings"? 


A: (1) Axial Load - This is the force or load a joint can handle sideways. This is important when you are bouncing your rig off the side of the mud pits, have a hard side landing or a single shear application. This 1 ¼ " joint was put in a 250 ton press and the centre popped out of the body at 2000 lbs. (2) Radial Load - This is the force a Heim can take before it tears apart. Tensile is the point of failure. Yield is the point in which it deforms. It is important to use the yield numbers as a safety factor, since this is the point the joint becomes junk. (3) You can see the race and ball assembly poking out the side of the body. This is rare and the press test was a bit over the top. However, there are joints that can handle 25,000 lbs + in the same test. An average radial load rating for a 1 1/4" joint is around 40,000 lbs reaching up to 75,000 lbs. New hybrid joints have reached up to 130-140,000 lbs. At this point, the bolt holding the joint to the mount becomes the weak point. 


Q: How do I know how much thread engagement I need? 


 (4) Thread Engagement - The strongest joint in the world is no good if it isn't threaded correctly. Standard practice is 1.5 times the depth of the diameter of the shank. For example, if the threaded shank of the joint is 1 ¼", you need a minimum of 1 7/8 " threaded into your link. A higher-end joint made from chromoly will allow a thread depth of 1 times the diameter. There is zero, minimum, mid and full engagement. The goal is midway engagement, allowing maximum adjustment in and out. Since the shank is only as strong as 1.5 times its diameter, 100 percent engagement isn't necessary, nor is it stronger. 

Q: I've tried welding my tube insert in and now the joint doesn't fit! How do I properly weld in a tube insert? A: Be gentle. You don't have to pour the heat to it .The first thing welders do is turn the heat up for penetration. This is not a pipeline, a D-10 cat nor a lifting lug. It's a suspension joint that ultimately connects to a 1/8 thick piece of frame. It's normally 1018 cold roll so it welds nice. A ¼ inch chamfer and single pass all the way around the tube works well. On average a single weld 1 inch long can hold up to 60 000 pounds. Do not weld it with the joint stem in the insert. It doesn't prevent distortion. Do not thread the stem in until it's cold. Let it cool naturally. No dunking it in water. Once it's welded and cool, apply anti seize and thread the stem in gently. If it jams do not force it. Stop, back it out a half turn and try again. If it becomes jammed again DO NOT FORCE IT. Take a hammer and tap the end of the joint. Proceed with the clockwise/counter clockwise motion smacking the end with the hammer as you turn. Any further issues call someone that's more patient than you to do it. If the joint becomes so jammed that it cannot be removed simply zip disc the insert. Cut in until you see the tip of the threads, take a chisel and separate the grind slot. Proceed to turn the rod out. It's way cheaper replacing the insert than the joint. 

Q: What sizes of joints are there? 


 A: (5) Joint Sizes - When it comes to sizes, generally the shank size matches the hole size. In the past, the joints were intended for more of a push/pull application with slight misalignment. This worked great, the stud and fastening bolt were equal in strength. Today there is a call for greater misalignment and the constant, heavy side-impact delivered to a trucks link create a need for a shank 60% larger than the bolt . In Image 5, the smallest Heim Joint is a 1 ¼" x 1" standard rod end . The other joints range from 1 ¼" up to 2" all with high misalignment balls. Unlike the standard rod end, the other joints through-holes are 60% the size of the stems. This allows for maximum strength with a deflection of 25 degrees. These are the newer hybrids. The two center ones are missing the balls. These types of joints have interchangeable internals. 

Q: What does TPI Mean? A: TPI stands for "Threads Per Inch. Threads on a joint are fairly standard. ANSI Class 2B. The most common sizes are ¾" 16 TPI, 7/8" 14 TPI, 1" 14 TPI and 1 ¼" 12 TPI. When you're trying to order a tap or jam nut and someone asks the thread pitch this is what they are talking about. 

Q: How do I know where to place my mounts or how wide of a Heim Joint I need to fit inside my existing mounts? 


A: (6 ) Mounting Width - When the shank of a joint snaps clean in two, it is often shrugged off as poor quality of steel or casting. If you look deeper, the cause of a clean break becomes clear. If a mount is allowed to come in contact with the body of a joint, it will bend it. As it twists the body sideways, all the force is placed at the top of the threads. This area is a stress point and it will snap a joint in the blink of an eye. When placing your mounts, make sure there is enough clearance between the mount and the joint at full misalignment. In figure 6, the red arrows indicate trace marks where the mount dug into the top and bottom on opposing sides. The mount on the top left indicates ones that are too close together and mounts on the top right are just right. Any tighter is too tight and any wider, the bolt will bend too easily. 

Q: What are Misalignment spacers and what are they used for? 


 A: (7) Misalignment Spacers - These are used for more misalignment than the manufactured joint will allow. It does this by decreasing the size of the bolt hole in the ball. What the spacer does is take the ball and continue its radius. The same misalignment is achieved with a ball that already has a smaller hole. (ie: if a joint has a 1" bolt hole and you use "high misalignment" spacers, they will reduce the hole size to ¾", ½" etc. By using the smaller bolt, it gives you more misalignment because of the extra clearance between edge of the bolt and the lip of the race. The down side to the spacer is that it has a seam, which allows dirt and grit to be carried into the race while high misalignment is being achieved. A ball with the spacers machined right on is another option to eliminate this problem and to sometimes achieve even better deflection rates. 

Q: How do you know when to use right and left joints? A: The whole point behind the cash spent on Heim Joints, threaded links and mount tabs is adjustability. A suspension link is a turnbuckle. Using left and right-hand threads allows you to increase or decrease the length of your link simply by turning it clockwise or counter clockwise. I've heard 100 reasons why guys want to run all right-handed joints. The only one that makes sense is less spare parts. Really, if you had to choose between setting your pinion angle by the simple twist of a link or spending hours unbolting and re-bolting your suspension just to save a few bucks, wouldn't you choose to run left and right joints? 

Q: Do I really need to use a Jam Nut? What is their purpose? A: Jam Nuts - If you don't use these you're wrecking your joint and link. The jam nuts job is to stretch the shank, pulling both the Inner diameter and outer diameter threads into each other and eliminating all movement and slop. All too often you'll see a rig missing these. It's a ticking time bomb. Some people will weld their jam nuts so they won't come loose. This defeats the purpose of the jam nut pressing the threads together. It will create interference but it won't be stretching the threads as required. As well you should use proper jam nuts. The machined face allows better surface contact helping the nut lock. 



Sneak peak of a Billet 4140 Chromoly joint going from raw material to a finished body. 



Above all else, have fun building and remember.... when in doubt, Go Big!