Reamer Hole

How To Choose The Best Back Reamer For HDD Drilling

A back reamer can make or break HDD drilling. Here is how to evaluate back reamers and make sure you pick the best one to suit your drilling needs.

A backreamer is arguably the most important piece of equipment used when drilling a borehole. A reamer that is even slightly the wrong size can make it impossible to insert the correct sized pipe into the borehole and can even render the hole useless. Choosing an affordable, high-quality piece of equipment is critical to being able to complete a job correctly.

If you are in the process of choosing a backreamer, replacing one or upgrading your existing inventory, here are some general tips from Underground Supply Solutions (UGS.)

Choosing the Wrong Backreamer

First, consider what could happen if you choose the wrong backreamer.

Backreamers are tough, to be sure, but each one is designed to address specific horizontal directional drilling (HDD) needs. Some, for example, are designed to drill through porous soil, like sand, while other reamers are built to get through rocky soil or clay.

There is some cross-purposing, but only in specific circumstances. The consequences of choosing a reamer that does not meet your project needs can be serious:

  • Your HDD reamer gets thrown off its path and the hole you need to be drilled is misaligned.
  • The borehole is enlarged too much, which can affect the surface, weaken the bore walls and even cause the bore to collapse.
  • Your reamer goes too fast and causes pitting, leaving you with expensive repairs to make to your client’s site.
  • Your HDD backreamer is not up to the job and becomes damaged or snaps off in a hole, requiring hours of extrication work or even losing the original borehole entirely.
  • You spend more time troubleshooting than drilling, delaying your project and costing you time and money.
  • You end up having to replace your initial HDD reamer, which costs money, with another reamer, which also costs money, just to get your project completed.
  • You choose a model that is too small for the job you need to complete and your hole ends up too small, causing you to use another reamer or run the reamer through the bore repeatedly until you carve out a sufficiently sized hole.
  • Your entire project is delayed because you have to get the right-sized bore, which on some projects, like road construction, can delay other contractors from doing their jobs.

If you choose the wrong horizontal drilling reamer, it is not a guarantee that a disaster will take place. Sometimes you will get lucky and nothing will happen. Other times the costs of fixing a poorly reamed hole will be outweighed by the cost of delaying a project and the subpar quality hole is tolerated.

Regardless, when you do not have the proper backreamer to do the job you need done, there is always a risk that the boring phase of a project will be problematic.

What to Consider

The purpose of a reamer is to back drill and enlarge a boring hole. Often, it takes multiple passes to make a drilled hole the exact size that is needed. Generally, a backreamer will make a hole 50% larger than the outer diameter of the central pipe in order to allow for product grips, make it easier to remove soil and prevent excessive stress on the reamer bit.

With that in mind, you must know 3 things before you select your backreamer in order to make sure you make the right choice, the first time:

Soil Type: The type of soil you will encounter and be drilling in makes a huge difference in terms of the type of backreamer you choose. For example, sandy soil requires a specialized reamer to address more porous conditions that can lead to soil cuttings falling to the bottom of the core. Rockier soil needs to have a level of toughness in order to withstand the jarring and smashing that takes place when a larger rock is encountered during the back drill.

Cutting Action: The type of cutting action you need depends on the type of soil and the type of cut you are doing. If you are running your backreamer in very sandy soil, for example, you want a reamer bit that can displace fine particles and thrive in sifting and possibly changing platforms. For rocky soil, you need a really strong reamer. For clay, you need a reamer that can handle lubricating liquid correctly so that the soil does not become muddy but the reamer does not overheat.

Reamer Size: The size backreamer you need depends on the size of the bore you are enlarging. You do not want one that does not cut enough and makes it difficult or impossible to get your base piping through. You also want to avoid overcutting and possibly create a cave-in scenario.

As mentioned, a good rule of thumb is that your reamer size must be at least 50 percent larger than the outer diameter of the pipe you are installing. It must also have a maximum clearance of 12 inches or if you are bundling piping, 24 inches in diameter.

As with any choices as important as a backreamer, you should consult with the professionals at your dealer in order to get their perspective. They have experience fitting reamers to address each of the three concerns above.

General Do’s and Don’ts

  • Do not assume your OEM reamer can do every job,
  • Do not assume that all ground conditions are equal,
  • Do not assume that even in one bore, all soil conditions will stay consistent,
  • Do not lock yourself into pre-conceived notions about backreamer size and purpose.
  • Do test your ground and try and get a sample from the bore to make sure your sized reamer will work throughout the drilling project,
  • Get the opinion of your Reamer Dealer regarding your backreamer options and final pick. They have the experience to tell you what make and model works for what types of projects,
  • Do constantly test and monitor your backreamer as it works to make sure it is doing the job you need it to do, especially in complicated jobs with long boreholes.

Choosing the right HDD backreamer is easy if you follow these general rules. Also, your choice will be much easier if you work with your dealer to make sure that the reamer you opt for matches your overall project needs.