Chip-Control

I used to think chip breaking was entirely about feed rate. If the chips were too long, I increased the feed until they broke. That works up to a point, but the drill’s chip breaker geometry sets the baseline for what feed rate will work. Understanding chip breaker geometry helps you choose the right drill for the material and know whether a regrind is maintaining the correct geometry. What a Chip Breaker Does A chip breaker is a groove or step ground into the rake face of the gun drill tip, just behind the cutting edge. As the chip slides across the rake face, it hits the chip breaker and curls. The curl creates bending stress in the chip, and when that stress exceeds the material’s fracture limit, the chip breaks. ...

Feed and speed optimization is the most effective way I have found to reduce cost per hole in deep hole drilling. The right parameters balance material removal rate against tool life, and the sweet spot can double or triple the number of good holes per drill. A systematic approach beats guesswork every time. Starting Point: Manufacturer Recommendations I start every new material or tool with the manufacturer recommended parameters. Tool manufacturers have tested their drills across a range of conditions and their starting point is reliable for getting the first part through safely. ...

The Unique Demands of Agricultural Hydraulic Cylinders Agricultural equipment uses large hydraulic cylinders for tractors, combines, and loaders. A typical cylinder might have a 150mm bore through 2 meters of barrel. BTA drilling is the standard method for these large diameters because single-lip gun drills cannot handle the material removal rate required for production efficiency. I have set up BTA drilling cells for three different agricultural equipment manufacturers, and each one had slightly different requirements based on their cylinder designs. ...

When Aircraft Structures Need Deep Holes Aircraft structural components like wing spars, bulkheads, and floor beams sometimes need through-holes for wiring harnesses, fluid lines, or fastener access. I have drilled these on CNC gun drilling machines with standard parameters. The holes are usually not structural themselves — they are pathways for systems that need to pass through the structure. But the parts they go through are highly stressed, so the drilling process cannot introduce stress risers or heat-affected zones. ...

I adjust feed rate to control chip breaking more than any other single parameter in deep hole drilling. Chip breaking is essential for deep hole drilling because the entire process depends on reliable chip evacuation through a narrow flute or inner tube. Long stringy chips pack up in the flute and cause tool breakage in seconds. Short broken chips evacuate easily, and consistent chip breaking is what separates a stable deep hole drilling process from a nightmare of broken tools and scrapped parts. ...

I read chip shape to tell whether my parameters are correct. I have caught three imminent drill failures this year alone by spotting a change in chip color before the tool broke. Chip shape is the best indicator of process health in deep hole drilling. Good chips mean good parameters. Bad chips mean trouble. There is no sensor on the machine that tells you what chip shape tells you. I check chips at every tool change on production runs — it takes about five seconds and tells me more about process health than any gauge on the machine. ...

Gun Drilling Brass, Bronze, and Copper Alloys: Soft Materials, Specific Challenges I have spent years behind gun drilling machines, and if there is one thing I have learned it is that “easy to machine” does not mean easy to gun drill. Brass, bronze, copper, and beryllium copper are the classic examples. They are soft, they are gummy, and they will fight you in ways that steel never does. This article covers what I have found actually works. ...