Reamer Hole Tolerance Table

Reamer hole tolerances – reamer hole dimensions are one of the topics to watch out for in the reaming process. Before reaming, a reamer is chosen based on the diameter of the hole to be reamed. Based on the reamer’s nominal diameter, the tolerance the reamer offers is looked up from the reamer hole tolerance table. The reamer hole dimensions are given in the table below.

Calculating Reamer Hole Tolerances

In cases where drilling can’t achieve the diameter tolerance and surface quality we want — that is, when hole surface quality matters — using a reamer will be the smartest choice. For this reason, to hit the desired hole dimensions within tolerance using reamers, the reamer’s manufacturing tolerance needs to be chosen to suit the hole tolerance.

In addition, to be able to hit the desired hole tolerance dimensions, the most suitable conditions should be provided by considering factors like cutting conditions, the type of material being machined, how the workpiece is clamped, cooling conditions, and, if the workpiece is being rotated, any runout in the workpiece.

To find the largest and smallest dimensions of the reamer tolerance:
For the reamer tolerance’s upper limit; we take it as 15% below the hole tolerance’s upper limit
For the reamer tolerance’s lower limit; we take it as 35% below the hole tolerance’s upper limit.

For example:
Desired diameter values for the hole: Ø 18 H8
Hole Diameter
Our Hole Nominal Diameter=Ø 18 mm
Hole Maximum Diameter=Ø 18.027 mm
Hole Minimum Diameter ==Ø 18.000 mm

If we want to calculate the tolerance value of the reamer to be used:

Reamer: Ø 18 H8
To find the reamer’s upper tolerance limit, we take 15% (0.15IT8) of the H8 tolerance value.
That is, 0.027 mm=0.15 × 0.027 = 0.00405 mm≈0.004 mm=0.027 – 0.004=0.023 mm
To find the reamer’s lower tolerance limit, we take 35% (0.35IT8) of the H8 tolerance’s upper limit value.
That is, 0.027 mm=0.35 × 0.027 = 0.00945 ≈ 0.010 mm = 0.027 – 0.010 = 0.017mm
The maximum and minimum diameter dimensions that should be on the reamer used for a job requiring a Ø 18 H8 tolerance are,
D1 maximum =18.000 + 0.023=18.023 mm
D1 minimum =18.000 + 0.017=18.017 mm

Good luck with your work. We hope this was helpful.