# Online tools

We offer our customers and other interested users some useful tools on this site, making the daily routine in handling production parts easier.

- The first
**online calculator to convert roughness values Ra to Rz**in all directions. - The first
**fit calculator**with a quantity processing function and reciprocal calculation (nominal dimension + limit dimensions → tolerance class)

__Terms of use:__

FACTUREE – The Online Manufacturer provides online tools that are permanently free of charge to all interested users. We always look forward to amiable reviews and recommendations, online as well as offline. All tools have been tested, but we assume no liability for the correctness of results.

# Rz-Ra calculator

**Roughness depth Rz**

To determine the **averaged roughness depth Rz**, a measuring segment is first established and, in turn, this is divided into (usually five) individual measuring lengths of equal size. The range of the two extreme values in the roughness profile for the respective, individual sections is subsequently divided by the number of measuring sections.

**Average roughness value Ra**

The **arithmetic average roughness value Ra** describes the arithmetic average of all deviations in the roughness profile from the median line within the measuring length. The surface roughness established by the calculation is thereby less vulnerable to extreme values than the roughness depth.

A conversion of Rz to Ra and the reverse is not possible as 1:1. However, a conversion interval that contains all possible values can be specified. The rule of thumb that repeatedly emerges for converting Rz = Ra*7 does not go far enough and, based on the extensive scattering of values, can lead to bad surprises in practice.

**Roughness class N**

Additionally, the surface quality is frequently subdivided into 12 roughness classes or roughness grades. Each roughness class from N1 to N12 has a maximum permissible Ra value according to DIN ISO 1302.

__Usage note:__ A direct allocation of an Rz value to a roughness grade is not possible, due to the conversion interval. In this Rz-Ra calculator the input Rz value is first converted to the average value of the Ra interval and the N class is determined based on this value.

# Fit calculator

For the **fit**, the dimensional relationship of two workpieces of identical nominal dimension and subject to tolerances is designated, the tolerance fields of which, however, can differ in position and size. The permissible nominal dimensions are defined through fits, for example for holes and shafts that are to be connected to one another. The corresponding fundamental tolerances and limit values are thereby established in ISO 286-1:2010 und ISO 286-2:2010.

Fits always consist of three pieces of information:

- Nominal dimension: Nominal dimension for the diameter of the hole or the outer diameter of a shaft.
- Degree of tolerance: marked with numbers from 01-18. The smaller the number, the smaller the tolerance field.
- Tolerance position: Designated with the letters A - ZC. Describes the position of the tolerance field. The farther a letter is from A, the tighter the fit.

The following types of fits thus arise:

- Clearance fit (maximum shaft dimension is always smaller than the minimum dimension of the hole)
- Interference fit / press fit (minimum dimension of the shaft is always greater than the maximum dimension of the hole)
- Transition fit (depending on the attained nominal dimensions, either clearance fit or interference fit)

Our **online fit calculator** not only calculates the maximum tolerated dimensions for a given nominal dimension and type of fit but, as the first fit calculator, also does the reverse. This can be helpful on drawings when, in addition to the nominal dimension, the tolerance variations alone are indicated. If the inner and outer fit are specified, the fitting type is additionally output and visualized.