Caring for annular cutters: blunt edges, pilot pin and swarf

The advice is taken from the troubleshooting tables and safety rules in Rotabroach's operating instructions. Speed, feed and cutting fluid during drilling are covered in the guide Annular cutting in steel: speed, feed and cutting fluid, and the choice of cutter in Annular cutters for rails.

When the cutter should be resharpened or replaced

Rotabroach lists a blunt, worn, damaged or incorrectly sharpened cutter among the causes when

• the cutter skips out of the centre punch mark as you start
• abnormally high feed pressure is needed
• the hole quality is poor, the cutter does not cut or the motor stalls
• the cutter breaks
• the cutter wears abnormally quickly

Resharpen or replace

The solution is to resharpen the cutter or replace it. A cutter that has been sharpened incorrectly should not be used. Keep a new cutter to hand together with the instruction sheet, so you have the correct tooth geometry to compare with.

Rotabroach also states that cutting tools should be kept sharp and clean, as this makes for better and safer work.

The pilot pin

A worn or bent pilot pin, or a worn pilot hole, is one of the causes of the cutter skipping at the start. If so, the parts should be replaced.

A weak pilot spring, a poor centre punch mark or a pilot that is not centred in the mark can have the same effect. Rotabroach recommends punching more accurately and replacing worn parts.

A bent pilot is also listed as a cause when annular cutters break quickly or the holes come out larger than the cutter.

When the pilot is pressed in, it should release oil to the cutter. If no oil comes out, check that the groove in the pilot and the inside of the spindle are free of dirt.

When ordering cutters and pilot pins, state the series type and part number. For example, the Rotabroach annular cutter 25 mm uses pilot pin SRA25.

Swarf inside and under the cutter

• Keep the inside of the cutter free of swarf. Swarf in there limits how deep the cutter can go, and packed swarf means more feed pressure is needed
• Swarf or dirt under the cutter can cause breakage. Remove the cutter, clean it thoroughly and refit it
• Do not start a hole on top of swarf lying on the surface
• Before the next hole, switch off the machine and, wearing gloves, remove swarf from around the cutter and spindle
• Do not lift the machine by the cutter. It is sharp

When the core gets stuck

When the hole is finished, the core should be ejected. The machine must not be used until the core has come out. If it is stuck in the cutter, move the machine to a flat surface, switch on the magnet and carefully lower the cutter onto the surface. As a rule, this straightens a core that is sitting at an angle, so it comes out as normal.

The fit in the spindle

The locking screws that hold the cutter can vibrate loose during use. Check that they are tight, and tighten the cutter if it is not secure in the spindle.

A worn spindle bushing or ejector collar is one of the causes of the cutter skipping at the start. Rotabroach states that only a few thousandths of wear are permissible, and that a new bushing is then needed.

If the cutter jams in the workpiece, switch off the motor immediately, disconnect the supply and turn the spindle back and forth. Do not try to free the cutter by starting and stopping the motor.

Cutting fluid and paste

Rotabroach states that its cutting fluid and lubricants are designed to help you get the most out of the cutters. The cutting fluid is undiluted and comes in 1 litre (RD208) and 5 litres (RD229), and as a 500 gram cutting paste (RD2094). Where fluid is unsuitable, for example when working at height, Rotabroach offers the Slick-Stik lubricant stick.

When you order

State the series type and part number for both the cutter and the pilot pin, as Rotabroach requests. Call rail parts sales on +47 23 26 78 00, or use the parts order form on Spare parts.