Reamers & Reaming Tools

A reamer is a rotary cutting tool used in the process of widening an existing hole / bore. They can be used on a lathe, milling machine, a drill or by hand using a wrench. They are used to widen an existing hole / bore by a small amount to leave a smoother interior wall or to meet a certain tolerance.

You cannot use a reamer to make the hole, the hole would need to be pre-drilled and finished with a reamer. When creating a hole / bore reamers are used to finish to an exact size.

There are a few factors to consider when selecting the right reamer for your job such as:

• Diameter

• Acceptable tolerance

• Length of the hole / bore

• Material being machined

• How you are holding the reamer

Reamers come in a wide variety of geometries lengths and diameters and can be supplied to suit almost any application.

Hand reamers: used with a tap wrench and used by hand rather than on a machine

Chucking / Machine reamers: used on milling machine, lathe or a drill.

Taper shank reamers: a reamer with a morse taper shank held in a morse taper adapter.

Straight shank reamers: a reamer with a round shank usually held in a drill chuck, collet chuck or sidelock toolholder.

Spiral flute reamer: used to pull the swarf (material chips) out of the hole making them ideal for blind holes.

Left hand spiral flute reamer: used to push the swarf (material chips) through the hole making them ideal for through holes.

Straight flute reamers: used on softer materials such as cast iron, bronze and brass due to the soft cutting geometry they can be used in through and blind holes.

The term tolerance is used a lot in the engineering sector. Tolerance is the range of variation allowed when trying to achieve a specific size. No cutting tool can produce a perfectly sized hole and will usually have a deviation +/- of a few microns.

Tolerance will give you the min or max size the tool will achieve e.g. if the finished diameter is 12mm and the acceptable tolerance is - 0.003 and + 0.003 the acceptable diameter would be between 11.997mm and 12.003mm.

Each manufacturer will be able to advise on the tolerances for their reamers and it is always a good idea to check with them if you have any queries.

This depends on your machine set up. In most cases you can bore a hole and finish to a desired size and tolerance, although this is a slower process. Boring is usually done on a lathe using a toolholder and carbide insert. This means the workpiece would need to be finished on the lathe.

Reaming is a quicker process as a larger area of the tool is in contact with the workpiece. Reamers are available in a wide range of materials, lengths, diameters and coatings and can usually be offered to finish any hole / bore size. Boring tools can be limited on length and diameter whereas reamers are available in much wider range.