Using Reamers in the Manufacturing Space: A Practical Guide

In precision manufacturing, producing holes that are accurate in size, roundness, straightness, and finish is often a challenge. Drilling or boring alone often leave surface marks, burrs, or tolerances wider than acceptable. That’s where reaming comes in. When done properly, reaming yields consistent holes with tight tolerances and excellent surface finish. This post explores what reamers are, how they work, how to choose them, how to perform reaming correctly, and the benefits reaming brings. 

What is Reaming & How Reamers Function 

Definition: Reaming is a finishing operation performed on an existing hole (pre-drilled or pre-bored) to improve surface finish, roundness, diameter accuracy, and sometimes straightness. It removes only a small amount of material.  

Tool: A reamer is the tool used. It has multiple cutting edges/flutes, and may be straight or helical (spiral), with various shank and flute geometries. The cutting edges are ground to precise diameter, with some allowance for cutting margin. The shank must be rigid and held precisely to avoid misalignment.  

Process: 

1. A hole is first created via drilling (or in some cases boring) to slightly under the final desired diameter. 

2. The reamer is inserted, aligned, rotated, and fed gently through the hole. 

3. The reamer removes a thin layer of material to bring the hole to its final size and finish. 

4. Use lubrication/coolant, control feed and speed, ensure alignment.   

   
   

What to Look for in a Reamer (Selection Criteria) 

When selecting a reamer, there are several important variables. Choosing the right reamer for your workpiece, material, volume, and machine setup will influence how well the reaming operation goes — in terms of quality, speed, tool life, and cost. 

How to Perform Reaming Correctly (Process & Best Practices) 

Using a reamer properly involves more than just selecting the right tool. Here are best practices and steps to maximize quality, efficiency, and tool life. 

Prepare a good pre-hole 

• Drill the hole to an undersized diameter appropriate for the reamer. If it’s too small, the reamer will be overstressed; too large, it won’t cut properly or meet size. Ensure the hole is straight and clean, with minimal burrs, so the reamer doesn’t wander. 

Secure workpiece rigidly 

• The workpiece must be held firmly; vibration, movement will degrade finish and dimensional accuracy. 

• Use fixtures, chucks, or workholding that ensures alignment between reamer and hole axis. 

Use correct speed (RPM) and feed 

• Reamers run slower than drills typically, because the reamer has more cutting edges and you need to avoid overheating or chatter. Choosing the right cutting speed (surface feet/min or m/min) and feed per revolution will depend on the reamer material, workpiece metal, flute design. Feed needs to be steady; avoid stopping or reversing inside the hole. 

Lubrication / coolant 

• Use proper coolant (or cutting fluid) to lubricate and cool the cutting edges, reduce friction and heat, carry away chips. For some materials, flood coolant; for others, light oil or synthetic fluid; sometimes even air or minimal lubrication where appropriate.  

Chip control / evacuation 

• Chips must be removed efficiently. In blind holes, spiral flute reamers help; ensure that you have enough clearance. If chips accumulate, they can mar the hole or cause tool damage. 

Solid alignment of tool and machine setup 

• Ensure minimal run-out in the spindle, high stability in tool holding. Overhang should be minimized. 

• The reamer should enter straight; using a pilot or countersink/chamfer can help guide it. 

Gentle exit 

• As the reamer exits the hole, retract it only after the cutting is done; avoid withdrawing under load or backing it out while still turning, which can cause damage or pull-out. 

Inspect frequently 

• After reaming, measure hole diameter, roundness, surface finish, maybe using micrometers, bore gauges, or coordinate measuring machines. Check for burrs, irregularities. 

• Also monitor the tool: check if edges are wearing, if coating is degrading, if flutes are damaged/chipped. Replace or regrind when necessary. 

Benefits of Reaming 

Reaming, when done properly, offers multiple advantages. 

High dimensional accuracy 

• Tighter diameter tolerances, better roundness and cylindricity. This is critical in assemblies where holes must match pins, dowels, shafts, or mating components.

Excellent surface finish 

• Smooth hole walls reduce friction, improve sealing, reduce wear, enhance performance in bearing / sealing applications.  

Consistency and repeatability 

• Fewer parts out of tolerance; lower scrap; better predictability in manufacturing. Ideal in production settings.  

Reduced additional finishing 

• Less need for expensive finishing steps like hand polishing, honing, or grinding if reaming is used. Saves time and cost. 

Lower tooling/wear cost per hole 

• Since reamers remove relatively little material, the wear per hole can be small; with proper maintenance (cleaning, sharpening, using coatings), a reamer can be used for many operations. 

Better fit for assembly / performance 

• Holes that truly match their engineering drawings allow for better fits (press fits, dowel fits), better sealing, or smoother movement of shafts etc. Failures often happen where holes aren’t accurate. 

  

When to Use Reaming (vs Drilling, Boring, Honing etc.) 

• Use reaming when you have a hole already roughly sized and need to bring it to a tight tolerance and finish. Drilling alone often won’t meet fine tolerances.  

• If a hole is large, deep, or misaligned, sometimes boring may be needed before reaming to correct shape/axis. Honing might follow reaming if super-fine finish is needed. 

• For low volume or field repair, hand reamers may suffice; for high volume, machine reamers in CNC or specialized machines give speed, consistency. 

  
  

  Cost Considerations & Return on Investment 

• Up-front cost for high quality reamers (good material, coatings, precise tolerances) is higher than for cheap tools. But life-cycle cost usually works out well thanks to their longevity and reduced scrap. 

• Cost of scrap, rework, downtime when holes are out of tolerance or assembly's misfit is often far greater. 

• Savings also come from less finishing, faster cycle times when reaming is properly integrated. 

  
  

 Summary / Key Takeaways 

• Reaming is a finishing process: small material removal, but with large payoff in hole quality. 

• Select the right reamer for your material, geometry, tolerance, machine setup. Pay attention to flute design, shank, chamfer, coatings. 

• Follow best practices in setup: rigid workholding, correct pre-hole size, good alignment, proper feed & speed, lubrication, chip control. 

• Inspect often, monitor tool wear, replace or regrind when needed. 

• The benefits — especially for precision components, repeatability, reduced rework — easily justify the effort and cost. 

Precision matters. Trust Butler Bros for all your reaming needs. Shop our reaming solutions or contact us today to find the right reamer and ensure your holes are always spot-on.