Filtration

I spend more time managing coolant on my deep hole drilling machines than on any of my conventional CNC equipment. The reason is simple: deep hole drilling pushes coolant through the tool at high pressure, blasts chips out through the drill flute or annular gap, and in the process generates a massive volume of contaminated fluid that needs continuous treatment. After ten years of running BTA and gun drilling machines, I have learned that treating coolant as a disposable consumable is far more expensive than treating it as a managed resource. ...

We had a machine that had been losing coolant pressure for about three months. Not dramatically, but steadily. The pressure at the tool had gone from 1200 psi down to about 900 psi, and it kept dropping a little more every week. I had changed the filter elements. I had checked the pump motor current. I had inspected the pressure relief valve. Nothing helped. The machine was still making good parts, so the slow pressure loss got treated as a low priority. The operators adjusted their peck cycles to compensate for the reduced chip clearing. The production schedules got padded to account for the longer cycle times. Everybody just worked around it. ...

Coolant filtration is critical for deep hole drilling. Chips that recirculate through the coolant will damage the drill edge and score the bore surface, causing poor surface finish and short tool life. The two common filter types for deep hole drilling coolant systems are paper band filters and cartridge filters. I have used both extensively and each has strengths depending on the application. Filter Comparison: Paper Band vs Cartridge Paper band filters use a continuous roll of filter paper that advances as the filter media loads up with chips. The paper catches particles down to 20 to 50 microns. The dirty paper is discarded and clean paper feeds in automatically. Cartridge filters use replaceable filter elements with ratings down to 5 to 20 microns. ...

Deep hole drilling machines use a significant volume of coolant. For a machine running oil-based coolant, the coolant cost can be a significant operating expense. Recycling the coolant saves money and reduces waste. I have used various coolant recycling systems. Here is what works. Why Recycle Coolant recycling reduces: Coolant purchases. Recycled coolant costs less than new coolant. Disposal costs. Used coolant is hazardous waste in most jurisdictions. Downtime. Coolant changes take the machine out of production. For a machine using 500 gallons of coolant that is changed quarterly, recycling extends the coolant life to annual changes. That is 1500 gallons of coolant that does not need to be purchased or disposed of. ...

What I Mean by Coolant Contamination Coolant in deep hole drilling does more than cool. It flushes chips, lubricates the cut zone, and protects the machine from corrosion. When contamination sets in, every one of those jobs suffers. I have walked onto floors where operators blamed the tool, the feed rate, or the material — only to find the real culprit was degraded coolant. Here is what I look for. ...