Engineering – More than Nuts and Bolts… The Lifetime of a Stabiltec Product (part 2)

Engineering – More than Nuts and Bolts… The Lifetime of a Stabiltec Product (part 2)

Hey guys sorry I haven’t been on here in a while, working overtime is taking its toll on me, since I am used to sitting at a desk 5 days a week…

The last post mentioned a tool commonly referred to as “knuckles”, and this post will serve to show you the lifetime of one of them. At Stabiltec Houston we repair knuckles made by us and by other manufacturers. And let me tell you, it’s a workout.

(These are solid steel by the way… and when we work on them they’re normally several hundred degrees Fahrenheit, you can imagine how fun it is moving them around)

Here is part of a blueprint for a fairly simple transmission, which features a “driver” on either end, a long double ended piece, or a “driven” in the middle. There are a myriad of different designs that make up the several-mile long drill string that goes down-hole, and specifications are different by customer. This specific blueprint is for Halliburton, one of the top three drilling firms in the world.

knuckle diagram.png

Now that you know what they look like, here is how we receive them for repair in Houston…

Restoring knuckles back to excellent condition requires lots of heating, welding, grinding, followed by more heating, welding, and… you guessed it… grinding.

The wear is due to high-torque rotation.
This knuckle gauge gives an idea of where the knuckle should be, telling us how much we need to build up.


Step One – Preheating

Knuckles are heated in a large oven…
Before the first procedure, tools have to be heated to at least 650 degrees Fahrenheit, as checked with this marker


Step Two – “Migging”


Using a knuckle gauge as a guide (shown in the first picture), we weld up the walls of the worn blade, forming a sort of horseshoe shape, and create a lip on the top of the knuckle. This serves as a housing for the hard metal to be welded onto.


 Step 3 – First Grind / Gauging

This step is pretty tedious, too much pressure on the hand grinder and you can miss the gauge, causing you to have to build up a wall again.
After the walls are aligned to the gauge size they are ready to be outfitted with hard metal.


Step 4: Preheat II

Knuckles are reheated either in the oven, or if they are too large like this one, individually.
For this preheat, knuckles need to reach a minimum temperature of 450 degrees Fahrenheit


Step 5: “Stoody” / Clean Up

Hard metal is welded on, filling the hollow we made earlier, in the form of a special tungsten-carbide infused wire.


After about twenty minutes of careful grinding, HAZZAH!


Step 6: Dry Moly and Stencil

After polishing up the tool, we spray them down with dry moly, which acts as a solid lubricant, and protects the knuckles during the delivery process.



This is one of the tasks that I perform at work, depending on my assignment, and can perform this task from start to finish. Learning how to do each step with precision and efficiency forces me to pay attention to the details and not take any shortcuts. Starting off, I had immense trouble executing the first grind (gauging). I would become frustrated after having to weld up a wall three or four times, but would receive great advice from my co-workers. I can now knock at knuckles just as quick and just as pretty as any other guy in the shop. (Sometimes prettier, I’m a perfectionist with this kind of stuff)

Overall, my experience with knuckle repair has taught me how to maximize efficiency, which is by doing it right the first time. However, my learning experience has taught me how important it is to make mistakes as well.

I will expand on the importance of making mistakes in my next post, and just a heads up, it involves me getting yelled at by Joe, my supervisor, and causing a train wreck of a work-week for the guys at the shop. JUICY STUFF – Stay tuned…


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