Adjustable hand reamer
An adjustable hand reamer can cover a small range of sizes. They are generally referenced by a range which equates to a size range. The act of tightening and loosening the restraining nuts at each end varies the size that may be cut.
A straight reamer is used to make only a minor enlargement to a hole. The entry end of the reamer will have a slight taper, the length of which will depend on its type. This produces a self centering action as it enters the raw hole. The larger proportion of the length will be of a constant diameter.