CNC Deep Hole Drilling Machine: 7 Proven Setup Decisions

Deep holes are among the most scrap-prone features on a machined part. A drawing calls out a 12 mm hole at 15 times diameter, the quote looks routine, and then the parts come off the machine with runout, taper, or a finish that fails inspection. The difference between a hole that holds tolerance and one that walks off center usually comes down to setup decisions made before the first chip. That is true whether the work runs on a dedicated CNC Deep Hole Drilling Machine or a machining center tooled for the job.

This article is for engineers, sourcing managers, and product teams who specify deep hole work and need it to be repeatable on a shop floor, not just feasible in a CAM simulation. We focus on seven setup decisions that drive hole straightness, surface finish, and cost per hole: tooling selection, coolant strategy, pilot and pre-drill practice, spindle and guide support, feed and speed control, workholding rigidity, and inspection planning.

Get any of these wrong and the failure mode is predictable. Poor coolant pressure at the cutting edge leads to chip recutting and drill wander. Weak workholding lets long tools deflect under load. Skipping a pilot hole on a CNC Deep Hole Drilling Machine that prefers one tool path over another can add cycle time without improving quality. Each decision also carries a cost, and the cheapest setup on paper is rarely the cheapest per good hole.

The goal is practical specification. You should finish this article able to describe a deep hole job in terms a shop can quote and hold: hole size and depth ratio, tolerance and finish requirements, material, and the process constraints that come with them. Every CNC Deep Hole Drilling Machine has a working envelope, and every setup has a limit. Matching the two is the whole job.

We cover each decision in order, with the tradeoffs that matter on the floor. Where a choice affects both quality and cycle time, we say so plainly. Readers who specify deep hole work regularly will recognize most of these decisions. The value is in making them deliberately rather than by default.

If you are evaluating a process for production, treat the seven decisions as a checklist. A CNC Deep Hole Drilling Machine set up with the right tooling, coolant, support, and inspection plan will hold straightness and finish across a run. A CNC Deep Hole Drilling Machine set up by habit will not. The gap shows up in your scrap rate and your per-hole cost.

GreatLight machines deep holes as part of its precision machining services, from prototype quantities through production runs, with 5-axis milling, turning, and quality inspection under one roof.

What Counts as Deep Hole Drilling

Ask five machinists where deep hole drilling begins and you will get five answers. The useful definition is not a number in inches or millimeters. It is the point where chip evacuation and coolant delivery stop being routine, and that point is governed by the length-to-diameter ratio.

In conventional drilling, coolant reaches the tip through the flutes and chips spiral out the same path. That works while the hole is short relative to its diameter. As the L/D ratio climbs, the flute channel becomes a long, narrow tunnel. Coolant pressure drops before it reaches the cutting edge, and chips have to travel a distance many times their own size to escape. Once that balance tips, peck drilling, parabolic flutes, and through-tool coolant stop being enough.

In practice, most shops treat holes beyond roughly 5:1 L/D as the transition zone. Between 5:1 and 10:1, you are still in high-ratio conventional drilling territory, but the process demands rigid tooling, through-spindle coolant, and disciplined peck cycles. Past about 10:1, single-flute gun drilling or ejector (BTA) systems become the norm, and that is where a dedicated CNC Deep Hole Drilling Machine earns its place on the floor.

The ratio, not the absolute depth, is what drives every downstream decision. A 0.5 in hole 6 in deep sits at 12:1 and needs gun drilling discipline. A 2 in hole 6 in deep is only 3:1 and runs comfortably on a standard vertical mill with a good coolant setup. Buying tooling by depth alone is how shops end up with the wrong machine and the wrong cycle time.

Material shifts the threshold in both directions. Aluminum evacuates chips easily and tolerates lower coolant pressure, so many shops push conventional drilling past 10:1 in aluminum with polished flutes and generous peck depths. Steels are less forgiving. Low-carbon and alloy steels generate stringy chips that pack the flutes, and heat builds quickly at the tip when coolant cannot reach it. Stainless is the hardest of the common three: it work-hardens, conducts heat poorly, and galls against the tool, so chip control and coolant volume matter even at moderate ratios.

That is why the specification conversation should start with the ratio and the material together. A CNC Deep Hole Drilling Machine sized for 20:1 in 4140 may be overkill for an aluminum manifold at 8:1, and a machine that handles 8:1 in aluminum will struggle with the same ratio in 316 stainless. The coolant pressure, spindle speed range, and chip removal method all follow from that pairing.

Tooling geometry follows the same logic. Deep holes favor single-flute or double-flute gun drills with internal coolant holes, because a single flute leaves more room for the chip to exit and the coolant to do its job. High-pressure coolant, often in the hundreds to low thousands of PSI range depending on diameter, keeps the chip moving and cools the tip. Without that pressure, a CNC Deep Hole Drilling Machine is just a long-stroke drill press with extra steps.

One more practical point: the L/D ratio should be measured on the finished hole, not the drilled portion. A cross-hole, an interrupted cut, or a stepped diameter changes how the chip behaves and how much support the tool has. Shops that plan around the worst-case ratio avoid surprises at the machine.

Get the ratio right at quoting, and the rest of the setup decisions fall into place. Get it wrong, and no amount of fixturing or feed tweaking will save the cycle. A CNC Deep Hole Drilling Machine is the right tool when the ratio and material demand it, and the wrong tool when they do not.

Background reading: the Milling (machining) overview is a useful reference on the fundamentals.

Gundrilling vs BTA on a CNC Deep Hole Drilling Machine

Two tooling systems dominate deep hole work: single-flute gundrilling and BTA (boring and trepanning association) with its ejector variant. The choice is not brand preference. It follows from hole diameter, depth ratio, and how tight you need straightness and finish to be. Get it wrong and you either pay for capability you cannot use or fight the process on every part.

Gundrilling covers roughly 1 mm to 40 mm in most shops, with the sweet spot around 3 mm to 20 mm. The tool is a tube with a carbide or indexable tip and a single cutting edge; coolant flows through an internal passage, cools the edge, and flushes chips back along the V-shaped flute. Because the tool is self-piloting and the cutting forces stay balanced, hole straightness is typically good, often within a few thousandths of an inch per foot of depth when the setup is right.

Tolerances commonly land in the IT8 to IT9 band, and surface finish in many materials runs around Ra 0.4 to 1.6 µm without a reaming pass, depending on material and setup.

BTA handles the larger end: roughly 16 mm up to 200 mm and beyond, depending on the machine. Here the tool is a hollow boring head on a tube. Coolant is pumped through the annulus between the tube and the hole wall, and the chip-laden fluid returns through the center of the tube. That reversed flow means much higher volumes, and the cutting head is supported by the hole itself, so straightness depends heavily on pre-drilled pilot quality and rigid guidance. Hole tolerance is typically wider than gundrilling, often IT9 to IT11, and finish tends to be coarser unless you add a skiving or reaming step.

Coolant pressure and flow separate the two systems more than any spec sheet. Gundrilling on a CNC Deep Hole Drilling Machine usually needs 40 to 100 bar at modest flow, because the small internal passage does the work. BTA needs far more volume, often several hundred liters per minute at 20 to 40 bar, and the machine’s pump, filtration, and tank size must match. Undersized coolant supply is a common reason a BTA setup produces poor holes and short tool life.

Ejector drilling sits between the two. It uses a double-tube design that pulls coolant back through the inner tube, so it works at lower pressure than full BTA and suits mid-size holes where a BTA pump is overkill. For small, deep, high-precision holes, gundrilling wins. For large bores in blocks and shafts, BTA is the practical route on a CNC Deep Hole Drilling Machine.

Match the method to the part before you quote. A 6 mm hole at 20:1 depth is gundrill territory on any CNC Deep Hole Drilling Machine. A 60 mm bore through a meter of bar stock is BTA work, and no amount of parameter tuning will change that. If your program spans both, confirm the machine can run both systems, or plan the routing through Custom CNC Machining Services with the right spindle and pump for each.

One more decision follows from this: pilot hole strategy. Gundrilling often starts from a spot or short pilot, while BTA needs a straight, on-size pre-drill to guide the head. Budget that step into cycle time. It is where inexperienced buyers lose margin, and where a well-specified CNC Deep Hole Drilling Machine pays for itself.

How the CNC Deep Hole Drilling Machine Handles Coolant

In deep hole work, coolant is not a convenience. It is the process. On a gundrilling or BTA-style setup, the fluid does three jobs at once: it cools the cutting edge, flushes chips out of the hole, and supports the drill against deflection. Get pressure, flow, and cleanliness right and a CNC Deep Hole Drilling Machine can hold straightness and finish shift after shift. Get them wrong and you get wander, chatter, and tool breakage buried 300 mm inside a part.

Pressure is the first decision. Gundrilling typically runs high pressure at moderate flow through the tool’s internal passage, while BTA and ejector systems move much larger volumes at lower pressure through the annular gap. The numbers depend on hole diameter and depth-to-diameter ratio, but in many shops gundrilling systems sit in the range of roughly 70 to 200 bar, and larger BTA systems often run lower. Undersized pressure means chips linger and the drill rubs.

Flow matters as much as pressure. Chip evacuation is a volume problem, not a force problem. If the pump delivers pressure but starves on flow, chips pack the flutes and the tool stalls. That is why the coolant specification on a CNC Deep Hole Drilling Machine should be quoted as a pressure-and-flow pair at the tool, not just a pump rating.

Filtration usually decides whether the process is stable or not. Deep hole drilling generates fine swarf, and recirculated particles score the hole wall, wear the tool’s guide pads, and clog internal passages. Many shops run multi-stage filtration, often down to the 10 to 25 micron range for gundrilling, with magnetic separation upstream for ferrous work. A CNC Deep Hole Drilling Machine with weak filtration may drill well for a while and then start drifting.

Temperature control is the quiet variable. Coolant that heats up through a long run changes viscosity and pressure at the tool, and thermal growth moves the workpiece. Tank sizing, a chiller, and a decent settling volume all help hold the process steady. On a CNC Deep Hole Drilling Machine, a coolant temperature swing of a few degrees is often enough to shift hole size at the tenths level.

Seals and chip-box design tie the whole system together. High-pressure rotary unions and tool-holder seals must be rated for the pressure the pump actually delivers, or you get leaks, pressure loss, and coolant mist in the work zone. The chip box, chip conveyor, and return path need to handle the swarf volume without backing up. A CNC Deep Hole Drilling Machine depends heavily on the loop that returns clean, cool fluid to the cutting edge.

Practical checks before you commit: confirm pressure and flow at the tool, not at the pump. Ask for the filtration micron rating and the swarf handling plan. Verify coolant temperature control and seal ratings against your deepest, smallest hole. Under Numerical control, the machine can hold position precisely, but the coolant loop is what keeps the drill on center. Specify it as carefully as the spindle, and the CNC Deep Hole Drilling Machine will reward you with straight holes and predictable tool life.

Tooling, Guides, and Hole Straightness Control

Deep hole drilling lives or dies on the tool and the guide. A gundrill is a single-lip tool with an asymmetric cutting edge, so the carbide head must be backed by a carbide guide pad that rides the bore and keeps the tip centered. Solid-carbide heads hold form longer than brazed tips, especially in cast iron and stainless, but they chip if feed is pushed too hard on entry. Match head grade to material first, then worry about coating.

Guide bush alignment is the decision most shops get wrong. The bush must sit concentric to the spindle within a few thousandths of a millimeter, and its clearance to the drill shank should be tight—often a few microns on the diameter. A worn or cocked bush lets the shank orbit, and the hole walks immediately. On a CNC Deep Hole Drilling Machine, the bush is part of the accuracy stack, not a consumable you swap when it rattles.

Runout shows up before the hole does. Indicate the drill shank near the bush and at the driver; total indicated runout over about 0.02 mm at the tip can produce measurable drift over a long pass. Check the driver coupling too. A worn collet or a loose coolant union can introduce runout that looks like tool wear but never goes away with a fresh drill.

Regrinding intervals depend on material and hole depth, but many shops touch up the carbide head after a defined number of holes or when diameter drift exceeds roughly 0.01–0.02 mm. Track hole count and diameter together; regrind on whichever limit comes first. A dull head increases thrust, and increased thrust is a common cause of drill shank bending.

Whip and drift are different failures with different signatures. Whip is dynamic—the shank bows and vibrates, leaving a lobed or oversized bore and audible chatter. Drift is geometric—the hole axis wanders steadily, and the exit position is off even though diameter looks fine. Both get worse with depth because unsupported shank length grows. That is why a CNC Deep Hole Drilling Machine with proper guide support and coolant pressure control usually outperforms a converted VMC on deep work.

Watch bore position at the exit, not just the entrance. If position drift grows with depth, suspect guide bush alignment or insufficient coolant pressure before blaming the drill. Diameter growth over a long pass usually points to head wear or guide pad wear. Log both numbers per part; the trend tells you which decision to change. Shops that track this data get predictable tool life, and the CNC Deep Hole Drilling Machine stops being a source of scrap.

For shorter holes or mixed work, a Bridgeport Milling Machine CNC Conversion can handle the shallow end of the range, but deep passes belong on dedicated gundrilling equipment with real guide support. Keep the tooling stack and the machine stack matched, and the CNC Deep Hole Drilling Machine will hold straightness across the full pass. That is the payoff of getting these setup decisions right. A well-guided CNC Deep Hole Drilling Machine, fed and cooled correctly, holds position and diameter within tolerance from entry to exit.

Workholding and Setup for Long Parts

Long parts move. That is the core problem this section addresses. A shaft with a length-to-diameter ratio above roughly 10:1 will deflect under cutting force and its own weight, and any error at the entry face compounds as the tool travels. On a CNC Deep Hole Drilling Machine, the workholding plan decides whether the hole runs true or walks off center.

Start with support, then alignment, then repeatability. Get those three in order and the rest of the setup follows.

Steady rests carry the load. For shaft-type parts, fixed or roller steady rests support the workpiece between the spindle and the tool entry. Spacing matters: place rests so no unsupported span exceeds a length-to-diameter ratio the part can tolerate without whip, often around 3:1 to 5:1 for slender shafts, tighter for thin-wall tubing. Adjust each rest to light contact, then check runout with a dial indicator at the rest and at mid-span. Overtightened rests distort the part and push the hole off axis just as surely as loose ones let it vibrate.

Part rotation versus tool rotation. Two architectures dominate. On gundrilling and similar setups, the part often rotates while the tool feeds without rotation; this averages out any residual straightness error in the workpiece and tends to produce a rounder, straighter hole. On BTA and ejector systems, the tool typically rotates and the part stays fixed or counter-rotates. Which one you use changes the fixturing: a rotating part needs a chuck or collet with low runout and a driver that does not induce bending, while a stationary part needs rigid clamping that still allows the tool to self-align at entry.

Match the fixture to the machine architecture, not the other way round.

Fixturing for shafts and manifolds. Shafts want a chuck at one end, a steady rest or two in the middle, and a guide bushing or pilot bore at the entry. Manifolds and blocks are a different job: they are short and stiff but often have intersecting passages and irregular outer geometry. Clamp on a machined datum face, support the underside to prevent sag, and use a drill bushing plate when the entry must be held to a tight position. A guide bushing does more than locate; it stabilizes the tool in the first few diameters, which is where most entry errors begin.

Setup checks keep a production run honest. Record and verify the following before the first part and at each shift change:

• Entry position relative to the datum, measured with an indicator or probe, not eyeballed
• Axis alignment between spindle, guide bushing, and part centerline, checked over the full stroke
• Steady rest contact and part runout at each support point
• Coolant pressure and flow at the tool entry, since starvation shows up as entry taper and poor finish

On a CNC Deep Hole Drilling Machine running a batch, the first-part check is not enough. Thermal growth in the part and fixture shifts entry position over hours. Re-probe the datum at intervals the shop defines from its own history, and log the readings so drift is visible before scrap appears. Keep a setup sheet with rest positions, bushing sizes, and clamp torque so the next run starts from a known state rather than an operator’s memory.

Repeatability comes from making the setup independent of the operator. Hard stops, keyed fixtures, and preset bushings remove judgment from the process. A CNC Deep Hole Drilling Machine that holds entry position across a long production run is usually one with a documented, repeatable setup, not a clever one.

One more check earns its place: verify the guide bushing clearance against the tool shank. Too much clearance lets the tool wander at entry; too little causes galling and heat. This single fit often explains entry-position scatter that no amount of re-probing fixes. Treat the bushing as a consumable and inspect it on a schedule.

Get the workholding right and the CNC Deep Hole Drilling Machine does what it was built to do. Support the part, align the axis, lock the setup down, and check it the same way every time. That discipline is what separates a stable production run from a pile of rework.

Speeds, Feeds, and Peeking at the Hole Bottom

A CNC Deep Hole Drilling Machine depends heavily on its numbers. Get surface speed and feed per revolution right, and the tool cuts cool and straight. Get them wrong, and you burn margins on a single hole. Start conservative, then tune upward while watching chips and spindle load.

For gundrilling in mild and alloy steel, surface speeds typically run 60 to 100 m/min with feed rates around 0.005 to 0.020 mm/rev depending on hole diameter. Smaller diameters take the lower end. Stainless and nickel alloys push speeds down to roughly 30 to 60 m/min, and feeds drop to 0.003 to 0.012 mm/rev because work hardening punishes any hesitation.

Aluminum allows much higher speeds on a CNC Deep Hole Drilling Machine, often 100 to 200 m/min, with feeds near 0.02 to 0.05 mm/rev. Titanium sits at the other extreme: 15 to 40 m/min and light feeds, with generous coolant flow to carry heat away from the cutting edge. Cast iron is forgiving at moderate speeds, but its chip breaks into dust, so coolant volume matters more than pressure.

Peck and retract strategy depends on depth-to-diameter ratio. Past roughly 10:1 on a CNC Deep Hole Drilling Machine, full retracts clear chips and let coolant re-flood the flutes. Past 20:1, peck increments of one to three diameters keep the chip load manageable. Blind holes need a shorter first peck to seat the tool, then uniform steps to depth.

Chip breakers shaped for the material do the rest. A narrow breaker on steel curls chips into tight cones that flush out easily. Aluminum wants a wider breaker so chips do not pack. If you see long strings or birds nests, the feed is too light for the speed, or the breaker geometry is wrong for the alloy.

Read the chips like a gauge. Short, silver, sixes and nines mean the process is running well. Blue or straw-colored chips signal heat building at the edge, so back off surface speed or raise coolant pressure. Fine powder in steel suggests rubbing, not cutting, and the feed needs a bump.

Coolant pressure is the quiet signal on any CNC Deep Hole Drilling Machine. Internal coolant-fed gundrills often want 40 to 100 bar, and pressure droop mid-hole usually means a clogged chip or a worn seal. Watch the gauge, not just the part.

If you are comparing hole-making options, The CNC Water Jet handles through-cuts differently, but for deep, round, high-tolerance holes, drilling remains the tool of choice. Log every parameter change on a CNC Deep Hole Drilling Machine so the next setup starts from data, not guesswork.

Inspection and Quality Checks After Drilling

Inspecting a deep hole is not the same as checking a shallow bore with a plug gauge. The depth-to-diameter ratio works against you: a bore that feels tight at the mouth can drift out of tolerance two hundred millimeters in. Plan the measurement method before the first chip flies, because some checks are impossible once the part leaves the machine. The good news is that a disciplined inspection routine on your CNC Deep Hole Drilling Machine catches drift early, while you can still correct it with tool wear offsets rather than scrapping the part.

Start with diameter. For holes under roughly 50 mm, a dial-bore gauge or a three-point internal micrometer gives fast, repeatable readings at multiple depths. Three-point gauges self-center, which matters on gundrilled bores that can be slightly lobed. Above that size, a bore gauge with interchangeable anvils or an inside micrometer set is common. Air gauging earns its place in high-volume cells: a two-jet air plug reads diameter and ovality in seconds, and the non-contact measuring principle means less wear on the gauge and no operator feel required. Whatever the instrument, verify it against a setting ring before the run and record the ring reading on the setup sheet.

Straightness is where deep holes get humbled. A hole can meet diameter tolerance at both ends and still bow in the middle. In many shops, a simple check uses a long mandrel or a laser alignment setup passed through the bore, with deviation read at intervals. For critical work, a dedicated hole-straightness gauge or a coordinate measuring machine with a long probe gives a documented profile. Record straightness as a runout value over the full depth, not as a single number, so the trend is visible across parts.

If a CNC Deep Hole Drilling Machine shows growing bow, suspect coolant pressure, guide bush alignment, or worn bushings before you touch speeds and feeds.

Surface finish deserves its own check. A deep hole that meets size but carries chatter marks will fail fatigue or sealing requirements later. Portable profilometers with long styli reach into bores, and replica tape works where the instrument cannot. Roughness in the range of Ra 0.4 to 1.6 µm is typical for fine gundrilling and honing operations, but confirm against the drawing rather than assuming. Also inspect the entry and exit zones; entry burnishing and exit breakout are the two places where finish problems usually start.

Cross-hole deburr verification closes the loop. Where a cross-drilled passage intersects the main bore, burrs sit exactly where they cause the most trouble: they break loose downstream, jam valves, or block flow paths. Check with a borescope after deburring, and confirm the method used, whether abrasive flow, thermal, or mechanical. A borescope image stored with the inspection record is worth more than a checkbox on a traveler.

Sampling plans should follow the risk. Aerospace work often calls for first-article inspection plus in-process checks on every part for critical bores, with full dimensional records retained. Medical parts typically demand tighter traceability, so pair a CNC Deep Hole Drilling Machine with documented gauge calibration and per-lot records. Energy components, especially long shafts and valve bodies, often justify 100 percent straightness and cross-hole inspection because a single failure is costly. Set the plan during setup, run it on the CNC Deep Hole Drilling Machine from the first part, and adjust only when the data says the process has earned it.

Cost Per Hole and Choosing a Shop

Quotes for deep hole work vary widely between shops, and the gap is rarely about greed. It usually comes down to how much time the hole takes, how fast tools wear, how carefully coolant is maintained, and how much scrap the process generates. Understanding those drivers lets a sourcing team read a quote instead of just comparing totals.

Cycle time dominates. On a CNC Deep Hole Drilling Machine, feed rates are conservative by necessity, and peck cycles, retraction, and chip clearing all add minutes that a standard drilling quote never includes. A shop running a purpose-built deep hole machine with high-pressure coolant can often undercut one pushing a converted VMC, simply because the hole clears faster and the tool survives longer.

Tool wear is the second cost line. Gun drills and ejector drills are not cheap, and their life depends heavily on coolant cleanliness, guide bushing condition, and how well the setup controls runout. In many shops, regrinding and tool replacement can account for a meaningful share of the per-hole price, especially in tough alloys like stainless, Inconel, or titanium.

Coolant upkeep is easy to overlook when comparing quotes. High-pressure systems need filtration, concentration checks, and regular maintenance, and a shop that skimps here will pay for it in tool breakage and scrapped parts. That cost eventually lands in the price you are quoted, one way or another.

Scrap risk is the quiet driver. A deep hole that goes off-axis or breaks a drill late in the cycle can scrap a part that already carries hours of upstream machining. Shops that quote realistically on a CNC Deep Hole Drilling Machine build that risk into the price rather than absorbing it silently.

When evaluating a supplier, ask specific questions rather than generic capability claims:

• What depth-to-diameter ratio can you hold reliably, and on which materials?
• What hole straightness and diameter tolerance can you guarantee, and how do you verify it?
• Do you use a dedicated CNC Deep Hole Drilling Machine or a converted milling center?
• What coolant pressure and filtration do you run, and how is it monitored?
• What inspection data comes with the parts, and is it per-lot or per-piece?
• How do you handle first-article approval and the handoff from prototype to production?

The prototype-to-production transition deserves real scrutiny. A shop that proves a hole on one part on a CNC Deep Hole Drilling Machine may struggle to repeat it across a production lot if the setup depends on a single operator or a fixture that was never documented. Ask how the process is captured and whether the same machine, tooling, and parameters carry through to volume.

Inspection data matters as much as the hole itself. Request diameter, straightness, surface finish, and concentricity records where relevant, and confirm whether they come from in-process checks or final inspection. A supplier who can show trend data on a CNC Deep Hole Drilling Machine is usually a supplier who understands the process, not just the machine.

Finally, compare quotes on a per-hole basis with the same tolerances and inspection scope. A low price on a CNC Deep Hole Drilling Machine can hide a narrower capability or thinner documentation. The right shop will explain its cost structure openly and stand behind the numbers when the parts arrive.

Getting the Most from Your CNC Deep Hole Drilling Machine

Most deep hole problems trace back to setup, not the machine itself. Coolant pressure and filtration, guide bushing fit, tool geometry, and the way a long part is supported all decide whether you hold straightness and surface finish or fight drift and chatter. A CNC Deep Hole Drilling Machine can reward disciplined setup with predictable holes, longer tool life, and fewer scrap events.

Pay particular attention to the peck and retract strategy at the hole bottom. Clearing chips there protects the tool and keeps the exit clean. Verify results with a bore gauge or air gauge, check straightness on a CMM, and log pressure, feed, and speed per job so the next run starts from data rather than guesswork.

• Match gundrilling or BTA to your diameter and depth ratio.
• Confirm coolant pressure and filtration before the first hole.
• Dial in guide bushings and steady support for long parts.
• Document speeds, feeds, and peck settings for repeatability.
• Inspect bore size, straightness, and finish on every first-off.

A well-run CNC Deep Hole Drilling Machine also drives cost per hole down through fewer tool changes and less rework. When you evaluate suppliers, ask how they control coolant, what inspection data they keep, and how they quote deep holes against shallower ones. Those answers separate shops that drill deep holes from shops that do it consistently.

If you have a deep hole job with tight straightness or finish requirements, send your drawings to GreatLight. Their precision machining team can review hole depth ratios, tolerances, and quantities, then quote a CNC Deep Hole Drilling Machine process built for repeatable production. A quick drawing review is the fastest way to confirm feasibility and get a clear next step.