Hand reamers are a tool that helps to maximise the precision of a drilled hole for applications that require absolute accuracy. They are employed typically after a twist drill has made the hole to within 0.05 and 0.1mm of the required size, the reamer then removes the excess material to meet the sizing requirements.
Hand reamers are typically used with a t-handle wrench which is used to generate torque and feature parallel flutes. There are also reamers that feature a gradual taper towards the cutting tip, these tapered reamers allow for easier initial cutting and can be used to produce tapered holes.
The square part of the shank slots into the wrench and then the cutting edge is inserted into the hole and turned clockwise using the wrench. The spiral design of the flutes help guide the reamer into the hole as it cuts.
The user must ensure that the reamer remains straight whilst rotating the tool to ensure the hole remains straight.
• Straight - These reamers feature a cutting tip that runs straight from shank to tip. They incorporate spiral cutting flutes spaced parallel to each other and are used to ream straight holes.
• Tapered - These reamers feature a gradual taper from the beginning to the end of the cutting section of the tool. Like straight reamers they feature cutting flutes spaced parallel and an equal distance apart, arranged in a spiral. They are mostly used for tapered holes.
How does a hand reamer work?
Like most cutting tools hand reamers are used to remove stock from a workpiece. Their parallel shaped flutes are designed to be turned in a clockwise direction to even out the inside of a drilled hole.
The torque generated to turn them is created by a t-handle wrench and to maintain accuracy they should be checked after the starting turn to see if the reamer is sitting straight in the hole. Once this check has been carried out rotate the reamer clockwise, in a smooth movement, with a small amount of pressure downwards. The cut should not be reversed.
Add oil to ease the cutting, once cutting is complete remove the reamer by continuing to turn clockwise until the tip has cleared the hole.