Flange Hole Tolerance and Surface Condition

To ensure that maximum benefits are gained from the Pilgrim Radial Fit Bolt, and to guarantee trouble–free installation and removal, it is vitally important that the correct quality of holes are achieved.

The following is a guide to the basic recommendations for the hole tolerance and surface condition.

Hole Tolerance

The hole must be circular, straight and parallel within the geometrical form tolerance stated in the table below:-

The tolerance may be interpreted as ‘cylindricity’, where the hole surface must be contained between two coaxial cylinders the form tolerance apart

The form of the hole must be continuous through both sides of the coupling. It is recommended thet both sides of the coupling are simultaneously line bored. The form of the hole must not change from one coupling half to the other by more than half of the form tolerance stated in the above table.

The end faces of the flanges under the Nuts should have a surface finish not exceeding 3.2 micrometres (125 microinches) and be square to bore within 0.2mm (.008"). Total Indicator Reading.

Hole Surface Condition

The surface finish of the holes should not exceed 1.6 micrometres (63 microinches). The maximum allowable amount of surface damage over any quadrant of the hole is approximately 15% of the quadrant area. Therefore the overall clean contact area required is 85% of the total area covered by the Radial Fit Bolt sleeve.

The maximum size of any individual areas of damage can be taken from the table below:-

Acceptable hole damage is avery difficult subject to quantify and can often only be fully assessed by an engineer on site.

Pilgrim International Ltd. will be pleased to offer advice and service beyond the general recommendations given herein.

Pilgrim International Ltd. recommend the use of the BFW Coupling Hole Boring Machine to achieve the best results and ensure re–achieving concentricity on subsequent re–installation of Pilgrim Radial Fit Bolts.