Reaming is done with a reamer a type of rotary cutting tool used in metalworking. Precision reamers are designed to enlarge the size of a previously formed hole by a small amount but with a high degree of accuracy to leave smooth sides.  The process of enlarging the hole is called reaming.

• Get a tap wrench or T-handle wrench and a hand reamer
• Attach the wrench to the squared end of the reamer
• Ensure reamer is perpendicular with work and reamer with a square. As an alternate method you can use a reaming guide or a spring loaded centre guide.
• Evenly turn the reamer in the hole to ensure alignment with the hole. (The bevel on the end of the reamer will help.) A rule of thumb for feeding rate is one quarter of the reamers diameter per revolution. Never rotate the reamer backwards as you would in a tapping operation as this would dull the reamer quickly.
• Ideally pass the hand reamer through the hole, if not possible, remove the reamer from the top by continuing the rotating motion.

Adjustable reamer

• Select the appropriate-size reamer in the range needed for the work to be completed.
• Loosen the size adjustment nut on either end of the reamer, using the adjustable wrench.
• Turn the adjustment nut on one end of the reamer clockwise and the other nut counter-clockwise to set the blades to the desired size. The reamer shaft is tapered and, depending on which direction the nuts are turned, the diameter of the blades increases or decreases.
• Measure the cross section of the reamer blades with the micrometer to ensure you have set the proper size.
  Tighten the adjustment nuts so they are firmly against the collars that secure the blades. Do not overtighten. Recheck the reamer blades with the micrometer for the correct sizing after tightening.
• Attach the T-handle tool grip to the square end of the adjustable reamer. Twist the movable end to the correct size and tighten.
• Apply thread-cutting oil to the blades of the reamer and around the mouth of the drilled hole.
• Align the reamer over the hole and turn it clockwise. Turn only in one direction. Oil the reamer every few turns. Thin cuts are best, with an incremental graduating of the reamer blade's diameter, until the required hole size is satisfactory.