What can cause reamers to cut oversize?

Excessive stock allowance is a primary factor that can cause reamers to cut oversize. When the material being reamed has more stock than necessary, the reamer may not be able to effectively remove the material to achieve the desired final dimensions. This is because the reamer typically operates on the principle of removing a small amount of material to achieve precision. If there is too much stock, the cutting edges can wander, leading to an oversized hole.

In contrast, while high spindle speed can affect the performance of cutting tools, it usually leads to problems like chatter or premature wear rather than oversizing directly. Similarly, using an incorrect reaming tool could result in improper hole dimensions, but it’s typically the design or wear of the tool rather than just being incorrect that would influence size directly. The use of coolant is generally aimed at reducing heat and improving tool life, and while improper application of coolant could theoretically lead to issues, it does not inherently cause oversizing as excessive stock does.