I used to think that the saving part of the job was the boring part. The little sacrificial adapter between the rig and the first drill rod. You know the one. No one is excited about them. Nobody posts pictures of them. They are the screen protector on your phone, cheap, boring and only seen when something goes wrong.

Then I spent a week on a jobsite watching a customer scrap drill rods due to a sub that should have been changed months ago. That was my ‘oh no’ moment. And I’ve been bugging people about it ever since.

If you’ve ever pointed the finger at your drill rods for failure, give me five minutes. This one’s worth it.

Quick clarification:

when I say bent sub I’m not talking about the intentional bent sub you run with a mud motor for steering. That one is supposed to be curved. I’m talking about a sub that’s been tweaked, bent or worn out of spec – usually a saver sub or adapter in that first connection. The one that is supposed to take the abuse so your drill rod doesn’t have to.

Here’s the deal A saver sub is the gatekeeper. It’s the part that surrenders. It’s designed to be worn so your rig spindle and your drill rod threads don’t have to. But when it’s bent or broken, it no longer protects and begins to attack.

A used saver sub generally shows that the threads are worn, the shoulders are rounded, and the connection is not making a tight seat. You can still wind it on. That’s the problem. It feels nice. But it is not alright. Now the torque is carried by the threads instead of the shoulder. The joint bends. Hit the pin or box of the first drill rod. You see shiny, galling shoulders, flattened thread crests, heat, maybe even cracks at the root of the thread.

And that first bar?

It doesn’t stay on the rig all the time. Back it goes on the shelf. Next job, it’s rod number 37 in the string. Its torn threads gnaw at the rod beside it. Then that rod goes back in the rack. You got two questionable rods now. Then four. Then you’re looking at a rack of “maybe” rods, trying to figure out which ones are good.

There’s the part nobody knows about. A bad sub hurts more than one rod. It will ruin your whole supply of drill rods.

A bent sub is more direct still. Runout in a bent condition. It pushes and pulls on the first rod with each rotation. That’s cyclic flexure. Fatigue of drill rod is real. The cracks start at the root of the threads. You can’t see them. Then one day, bang, rod fails downhole. And all eyes are on the stick. But the rod was a victim. The criminal was the sub.

One time I had a customer call me pretty hot. “Your drill rods are no good,” he said. I drove away. First rod had stripped threads. Saver sub had a bend showing. “It is alright, it’s still threading on,” he said. I asked him to turn it. The wobble was evident from ten feet. ‘We introduced a new saver sub. The rod failures ceased. Already he’d thrown 15 rods away. Fifteen. That’s when I knew a bad sub doesn’t cost you a sub. It taxes your whole stock.

you don’t keep drill rods in perfect order. You take what’s on the rack. A rod that is damaged is a damage vector. It breaks another rod. And then another. Soon you can’t separate the good from the junk. You either run them and pray, or you junk good rods because you can’t trust them. Both are expensive options. And time off? Downtime is more expensive than anything.

So what do you do exactly?

Check your sub saver. Every time shift. Turn her. Replace if wobbly. Check out the threads. Replace if they are sharp, flattened, galled, or the shoulder is rounded. Keep an extra one on the truck. Use the proper thread compound. To specification. Make up. And please, stop using “it still threads on” as a quality metric. That’s like saying a tire is good because it still holds air sitting on the rim.

If you’ve had a bad sub check your first 3-5 rods. Mark them up. Separate the suspect ones. Don’t just put them back on the rack and hope for the best. Not sure. Send me some pics of the sub and the first rod threads. Let me tell you what I see.

The Saver sub costs a few hundred dollars. A drill rod is four numbers. A rack is six figures. Downtime is what you call it, usually a very bad day. So why take the risk?

Your inventory of drill rods is a system. The sub is the gate goalkeeper. A bad link is a bent or worn sub. Fix the cheap bit first. If you’re experiencing rod failures, don’t just blame the rods. Check the sub.

I’d rather keep you with the rods you’ve got than sell you new ones. But I’m here if you want new ones too.