Real problems, real solutions, no fluff. I have spent years working across multiple shops running gun drilling, BTA drilling, and ejector drilling machines — setting up jobs, troubleshooting coolant pressure and chip evacuation issues, drilling deep holes in everything from hydraulic cylinders to aerospace titanium. This site is where I share what I have learned.
Assessing the Breakage Before Extraction Every deep hole driller breaks tools eventually. When a gun drill breaks in the bore, the first step is not to panic. I assess the situation before deciding how to extract the broken tool. I ask myself three questions: where in the bore did it break, how deep is the broken piece, and is the tool jammed or loose. The location of the break matters more than most people realize. If the tool broke near the entry, I have more options. A break at the far end of a deep bore changes my strategy entirely. I use a borescope to examine the break point before committing to any extraction method. In my experience, thirty minutes of inspection saves hours of trial-and-error extraction work. ...
Internal Support Methods for Thin Wall Tubes Thin wall tubes are challenging for deep hole drilling because the wall can collapse under cutting forces and the tube vibrates easily. I use internal support and reduced parameters to manage these issues. Over the years, I have developed several support strategies that work reliably across different tube sizes and materials. I use a mandrel inside the tube for internal support. The mandrel fits the tube ID closely and prevents the wall from deflecting. The mandrel has a center hole that allows the drill to pass through while supporting the tube wall immediately around the cutting zone. I make my mandrels from hardened tool steel with a polished OD to reduce friction. A well-fitted mandrel reduces bore runout by 50% compared to unsupported drilling. ...
Ejector drilling uses a double-tube system where coolant flows between the outer and inner tubes and returns through the inner tube by Venturi effect. When problems happen, they are almost always related to coolant flow or nozzle condition. I have worked through enough ejector drilling issues to recognize the patterns fast. The double-tube design gives ejector drilling advantages in portability and setup simplicity, but the troubleshooting demands a different mindset than standard gun drilling or BTA drilling. ...
What Forging Scale Does to a Gun Drill Forging scale is the hard, abrasive oxide layer that forms on forged steel parts during heat treatment. It is one of the fastest ways to dull a gun drill. The scale is harder than the base material and contains sharp particles that act like sandpaper on the cutting edge. When a gun drill hits scale, the cutting edge micro-chips within the first few millimeters of engagement. I have seen a brand-new drill ruined in less than 15 seconds of cutting time because the operator did not realize the forging still had its as-heat-treated surface. ...
Based on what I have seen at trade shows like IMTS and EMO, in new machine introductions, and in conversations with machine builders, several trends are shaping the future of deep hole drilling technology. The industry is moving toward more automation, better data integration, and higher performance machines. I have been tracking these developments because they affect the decisions shop owners make about equipment investments. Automation and Lights-Out Manufacturing Automation is the biggest change in deep hole drilling over the last five years. Robotic part loading and unloading is becoming standard on new machines above a certain price point. I have seen cells that run unattended for hours, loading parts, drilling, checking them with in-process gauges, and sorting them by size. ...
I use gun drilling attachments for occasional deep hole jobs on machining centers. A dedicated gun drilling machine is better for production work, but an attachment makes economic sense when you only drill deep holes a few times per month. The attachment turns a standard VMC or HMC into a capable deep hole drilling setup for a fraction of the cost. Attachment Types: Spindle-Mounted vs Self-Powered Two attachment types are available and each covers a different application range. ...
The Geometry and Function of Textile Spindle Shafts Textile spindle shafts are long, thin shafts that rotate at high speeds. Many have a through-hole for lubrication or weight reduction. A typical spindle shaft might be 500-1000mm long with a 10-20mm through-hole. I have worked with shafts up to 1,500mm in length that required an 8mm through-hole. Those are the most difficult jobs because the length-to-diameter ratio exceeds 180 to 1. ...
When a CNC Lathe Makes Sense for Gun Drilling A dedicated gun drilling machine is the right tool for production deep hole work. But I have run plenty of successful gun drilling jobs on standard CNC lathes when the volume did not justify a dedicated machine. The key is knowing the limits. In my experience, a lathe with live tooling and through-coolant capability can handle L/D ratios up to about 10:1 reliably. Beyond that ratio, the alignment challenges and coolant pressure limitations make a dedicated machine necessary. ...
Deep hole drilling machines are built in horizontal and vertical configurations, and each has distinct advantages depending on the work. I have operated both types extensively and have helped shops choose between them based on their part mix, floor space, and production requirements. I have helped over a dozen shops make the selection and the decision always comes down to the parts they drill most often, not which configuration is theoretically superior. The choice is rarely about which is technically better and more about which fits the specific application. ...
I’ve worked on deep hole drilling machines from the 1970s through modern CNC equipment. The changes over 50 years are significant. What was once a craft dependent on operator feel has become a data-driven process managed by software. The Manual Era (1970s-1980s) Machines from this period were manual or NC controlled. The operator set feed rates by turning hand wheels and felt the cutting forces through the hand wheel. Experienced operators could tell when the drill was cutting properly by the resistance they felt. ...