Fits and tolerances
How to use the development tolerance calculator
Enter the nominal diameter of the reamer in millimeters and select the hole tolerance field - the calculator will automatically calculate the maximum deviations ES and EI, the maximum and minimum diameter of the reamer, as well as the manufacturing tolerance according to GOST and ISO 286.
What do tolerance fields mean:
- H7—accurate deployment. Used for mounting holes in rolling bearings, guide bushings, spindle units and other critical connections where strict adherence to the hole geometry is required.
- H8—normal accuracy. Standard choice for most through holes in production machinery. Optimal balance of performance and accuracy.
- H9—average accuracy. Used in connections with guaranteed clearance, where H7 and H8 are redundant: brackets, flanges, non-critical guides.
- H10, H11—rough accuracy. Roughing passes, preparing holes for coating or welding.
- Why know the maximum sweep deviations?
Reamer is a finishing tool. Unlike drilling, there is no way to “adjust” the size after surgery. If you choose a development without taking into account the tolerance field, the hole will turn out to be either larger than the drawing one (spreading) or smaller (underreaming). Both defects are a return of the part or a defect.
Maximum deviations of the reamer diameter according to GOST take into account elastic pressing, thermal expansion and wear of cutting edges. Therefore, the lower deviation of EI is always positive - the sweep is intentionally made slightly larger than the nominal value.
Frequently Asked Questions
Why are both deviations positive? Because the tolerance system for reamers is built “plus” relative to the nominal value. The Ø12 H7 reamer has a diameter from 12.008 to 12.015 mm - this is the norm, not an error.
How to choose H7 or H8? Refer to the part drawing. If the landing designation contains H7, take the H7 scan. If the tolerance is not explicitly specified, use H7 for critical bearing holes, and H8 for the rest.
The diameter is not included in the table? The table covers the range from 1 to 120 mm according to GOST. For diameters over 120 mm or non-standard tolerance fields, contact our technologist - we will select or produce a reamer to suit your drawing.
Do you need a reamer with a non-standard diameter or with a special tolerance range? We manufacture to specifications - Ukraine and deliver throughout the country.