Annular cutters for rails: diameter, depth and shank
An annular cutter cuts out a ring and leaves a core, instead of grinding the whole hole into swarf like a twist drill. Rotabroach highlights that this gives clean, burr-free holes — but the cutter must suit both the machine and the material.
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Three things must be right: the diameter, the cutting depth and the shank.
Diameter
The catalogue has Rotabroach annular cutters from 18 to 36 mm, in whole millimetres. The bolt holes in a rail have fixed dimensions, so here it is the drawing that decides, not judgement.
Cutting depth: 25 or 50 mm
Rotabroach's Raptor Rail TR series comes in two lengths for each diameter — 25 mm and 50 mm cutting depth. The long version is supplied on request. The part numbers differ by an L: for 20 mm it is RAPTR200 for 25 mm depth and RAPTRL200 for 50 mm.
Use the short one where the material is thin.
Shank
The standard shank is 3/4 inch (19.05 mm) with drive flats. That is what most magnetic drilling machines accept, but check it against your machine before you order — Rotabroach has adapters that let the cutters be used in magnetic drilling machines without a Weldon fitting.
Material and hardness
The cutters are made of carbide — tungsten carbide, TCT — and are rated for material with a tensile strength below 1400 N/mm². Rail steel falls within this. If you are unsure what you are drilling into, state the material grade when you order.
Practical points on service life
Annular cutters are wear parts. According to Rotabroach, breakage is usually caused by the machine not being clamped securely enough, and excessive feed pressure can damage the cutter and shorten its life considerably.
It is a good idea to order pilot pins at the same time.
How to order the right cutter
State the diameter, cutting depth and which machine they will be used in, and we will find the right part number. Order from Rail parts sales on +47 23 26 78 00, or use the parts order form on Spare parts.
The machines this guide covers
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