Drill Rod & Drill Head Selection: An Admin Buyer’s 5-Step Checklist

Who This Checklist Is For

If you're responsible for ordering 5mm drill rod, steel drill pipe, or DTH drill rod—and you report to both the operations manager and finance—then this is for you.

I'm the office administrator for a 120-person drilling services company. I manage all consumables and tooling orders—roughly $85,000 annually across 9 vendors. In Q1 2024, we spent about $12,000 just on drill rods and bits across 3 projects.

This checklist covers the 5 steps I now follow to avoid the costly mismatches I made in 2022 and 2023. Use it when you're sourcing for a new project or switching suppliers. It works whether you're ordering core bits, DTH rods, or combination strings.

5 Steps to Get Drill Rod & Head Selection Right

Step 1: Match Your Rod to Your Machine and Material—Not Just the Price

A 5mm drill rod and a 40mm core bit don't automatically play nice. I've learned this the hard way.

Before you email three drill pipe companies for quotes, you need to confirm three things:

• Rod diameter vs. bit shank—a 5mm rod usually goes with small core bits (like a 40mm core bit). But some steel drill pipe has compatibility limits. Check the spec sheet.
• Material hardness—if you're in limestone vs. granite, the rod material matters. For hard rock, a DTH drill rod with a hardened shank might be necessary.
• Thread type—tapered vs. reverse circulation. If you get this wrong, nothing fits.

I still kick myself for the time in early 2023 when I ordered 50 units of steel drill pipe based on the lowest per-foot price. The threads didn't match our existing collars. We had to store them for 8 weeks while the supplier sent replacement ends. That cost us $900 in idle labor.

Step 2: Vet Your Drill Pipe Companies—Don't Just Check Their Minimum Order Quantity

Here's the thing: a lot of drill pipe companies offer great prices on 5mm drill rod. But not all of them stock DTH drill rod in the same steel grade.

When vetting suppliers, I ask three questions now:

• Do you carry steel drill pipe in 5mm and 40mm thread standard for core bits?
• What's your lead time for DTH drill rod in 4m lengths?
• Do you provide material certificates (EN 10204 type 3.1 or equivalent)?

Oh, and I always ask for a reference in the same application. If they can't provide one, we move on. That $200 savings from a new vendor turned into a $1,500 problem when the rod failed mid-project and we couldn't get a replacement within 48 hours.

Step 3: Select the Right Drill Head Types for Your Rod Configuration

There are several drill head types, and choosing the wrong one means wasted rod life or poor penetration.

If you're using a 5mm drill rod, typical drill head types include:

• Cross bits—general purpose, longer life in abrasive rock.
• Button bits—faster penetration in softer materials, but wear faster in granite.
• Core bits (like 40mm core bit)—for sampling or geotechnical work. These need a slower rotation speed and stable rod string.

I always verify the bit head diameter matches the rod's expected working load. For a 40mm core bit, you usually want a rod with a shank that's at least 22mm diameter. Using a 5mm DTH drill rod? Check the impact energy rating—DTH bits need heavy hammer energy.

Dodged a bullet last year when I double-checked the bit specs for a new DTH rod order. Was one click away from ordering cross bits for a DTH application that required button bits. The supplier's sales rep probably would have caught it, but maybe not.

Step 4: Confirm DTH Drill Rod Compatibility Before You Sign

DTH drill rod is a different breed. You're not just buying steel pipe—you're buying a transmission system for impact energy.

Check these three things:

• Hammer type—is it a valveless or valved hammer? Each needs a different tube wall thickness.
• Coupling design—some DTH rods use a male/female API connection; others use a threaded pin. If you mix them, you'll end up stuck.
• External diameter tolerance—for DTH rods, even a 0.5mm variance can cause binding in the hole.

I messed this up in 2022. Ordered steel drill pipe that was marked as 'DTH compatible' but had a 1mm OD variance. The rods rattled in the hole, causing accelerated wear on the coupling. The project ran 3 days over schedule.

Step 5: Build Your Spare Parts and Lead Time Buffer

You can't control geology, but you can control your inventory. For any job using 5mm drill rod or core bit 40mm, I always add 15% to the initial order quantity. For DTH drill rod, I keep at least 2 spare couplings and one spare bit per rod.

If I remember correctly, our typical lead time from drill pipe companies is 4–6 weeks for specialty rods. For standard steel drill pipe in 5mm, it's 2 weeks. But that's if the warehouse has stock. In 2024, we had a 9-week lead time on a specific DTH rod because the mill was down.

Rule of thumb: if the project is in hard rock or abrasive ground, double your spare bit order. A 40mm core bit can wear out in 15–20 meters of drilling in quartzite. I learned that the expensive way.

Common Mistakes I've Made So You Don't Have To

• Assuming 'one size fits all' suppliers. Not all drill pipe companies stock both steel drill pipe and DTH drill rod. Check their inventory before you build a schedule around them.
• Ignoring thread standards. I once ordered 50 units of 5mm drill rod with R32 thread when our rigs used R25. The bits, the shank adapters, everything was wrong. The return shipping cost $45 and cost me a weekend.
• Skipping the test run. I now order a sample set (1 rod + 1 bit) before committing to a full order of drill heads or rods. For $120, it's cheap insurance. That sample run saved us from buying 40 incompatible drill head types in Q2 last year.

Pricing is for general reference only. Actual prices vary by supplier, steel quality, and quantity. Always verify current pricing and lead times with your chosen drill pipe companies before placing an order.