The drill does not produce the correct hole size sometimes with a good surface finish. A hole with precision size can be produced with a good finish of a pre-drilled hole using a reamer tool. The process of the enlarging hole is called reaming.
The reamer is commonly used to remove the minimum amount of metal (100 to 150 microns for rough reaming and 5 to 20 microns for fine reaming) from the hole. During reaming operations, the job should be properly supported and rigidly held. A stock wrench of the appropriate size for holding the reamer is used. The reamer must be kept in its correct position about the job. It must be rotated slowly, and excessive feed must not be given. It should always be-be turned in the cutting direction. A sufficient amount of cutting fluid should also be used. When removing the reamer, it must be turned in the cutting direction. Reamers with blunt or chipped edges must not be used.
Various kinds of reamers are classified and described as under:
- Hand Reamer
- Machine reamers
- Taper Reamer
- Spirally fluted reamer
- Straight fluted reamer
- Parallel reamer
- Adjustable reamer
- Expanding reamer
Some common types of reamer used in fitting workshops are discussed as under.
1. Hand Reamer:
It is operated by hand to finish the holes and remove their ovality. Its cutting edges are backed off in the same manner as those of twist drills to give suitable clearance. It is made up of carbon or high-speed steel material. It is used for excellent internal turning in the hole by placing a tap wrench on the square end of the reamer.
2. Machine Reamer:
It is designed for slow speeds for use on drill presses, lathes, vertical milling machines, etc. It is chamfered on the front side of the cutting edge. It possesses straight or tapered shanks and comprises either straight or spiral flutes.
3. Taper reamer:
It is widely used for finishing taper holes smoothly with precision. It is also used to provide a taper to a drilled hole when a taper pin is to be used. It is performed with either straight or spiral flutes. It has spaces ground into the cutting edges or teeth to prevent overloading the entire length of each tooth of the reamer. These spaces are staggered on the many teeth to help in stock removal.
4. Spirally fluted reamer:
It performs greater shearing action than one with a straight flute.