AISI 1045 is the most widely specified medium-carbon steel in general engineering. Its combination of strength, machinability, and availability makes it the default choice for shafts, hydraulic cylinders, axles, gears, and machinery components that require deep hole drilling. For most deep hole drilling shops, 1045 represents a larger share of production volume than any other material.
Despite its reputation as a straightforward material, 1045 presents distinct challenges in deep hole drilling. It has a higher carbon content (0.43–0.50%) than low-carbon steels, giving it greater strength but also a tendency to form built-up edge (BUE) at the cutting interface. Its chip formation characteristics fall between the free-chip-breaking behavior of low-carbon steels and the controlled chip formation of alloy steels — requiring particular attention to feed rate and coolant delivery.
This guide provides comprehensive, manufacturer-sourced cutting data for deep hole drilling AISI 1045 carbon steel in all common conditions, covering gun drilling and BTA methods, with a documented case study.
Material Properties
AISI 1045 is a medium-carbon steel with the following composition and mechanical properties.
Chemical Composition (Weight %)
| Element | Range |
|---|---|
| Carbon (C) | 0.43–0.50% |
| Manganese (Mn) | 0.60–0.90% |
| Phosphorus (P) | 0.04% max |
| Sulfur (S) | 0.05% max |
| Iron (Fe) | Balance |
Mechanical Properties by Condition
The condition of 1045 steel — hot rolled, normalized, cold drawn, or quenched and tempered — significantly affects its deep hole drilling behavior.
| Condition | Tensile Strength | Yield Strength | Elongation | Hardness | Relative Machinability |
|---|---|---|---|---|---|
| Hot rolled | 570 MPa (83 ksi) | 310 MPa (45 ksi) | 18% | 163–179 HB | Good (baseline) |
| Normalized (830–880°C, air cool) | 600–750 MPa (87–109 ksi) | 355–450 MPa (51–65 ksi) | 16–22% | 180–220 HB | Good — refined grain structure |
| Cold drawn | 585–760 MPa (85–110 ksi) | 450–585 MPa (65–85 ksi) | 12–19% | 170–223 HB | Best — cold working improves machinability |
| Quenched & tempered | 800–1,000 MPa (116–145 ksi) | 600–750 MPa (87–109 ksi) | 10–14% | 229–269 HB | Reduced — requires parameter adjustment |
Machinability rating: Approximately 64% relative to AISI 1212 free-machining steel (100%).
Key implications for deep hole drilling:
- Cold drawn 1045 offers the best dimensional consistency and straightness for deep hole drilling. The cold working improves surface finish and tool life.
- Normalized 1045 provides good baseline machinability with a consistent structure throughout the bar. Standard parameters apply.
- Hot rolled 1045 has mill scale on the surface that is abrasive to cutting edges. The surface must be turned or spot-faced before deep hole drilling. Hot rolled bars also have poor straightness (approximately 6 mm per 1.5 m) that may cause drill wander.
- Quenched and tempered 1045 at hardness above 250 HB requires speed reductions of 20–30% from normalized values.
Cutting Parameters for Gun Drilling
The following tables compile data from multiple tool manufacturers including Allied Machine, Mitsubishi Carbide, Arch Cutting Tools, and published research, specific to AISI 1045 carbon steel.
Carbide-Tipped Gun Drills — Recommended Starting Parameters
Normalized / Cold Drawn Condition (160–220 BHN)
| Diameter (mm) | Diameter (inch) | Speed (SFM) | Speed (m/min) | Feed (IPR) | Feed (mm/rev) |
|---|---|---|---|---|---|
| 2.0 | 0.079 | 180–260 | 55–80 | 0.0016–0.0031 | 0.04–0.08 |
| 3.2 | 0.126 | 195–230 | 60–70 | 0.0024–0.0051 | 0.06–0.13 |
| 5.0 | 0.197 | 165–245 | 50–75 | 0.0039–0.0079 | 0.10–0.20 |
| 6.3 | 0.248 | 195–280 | 60–85 | 0.0051–0.0102 | 0.13–0.26 |
| 8.0 | 0.315 | 195–295 | 60–90 | 0.0071–0.0110 | 0.18–0.28 |
| 10.0 | 0.394 | 215–330 | 65–100 | 0.0087–0.0126 | 0.22–0.32 |
| 12.0 | 0.472 | 230–345 | 70–105 | 0.0110–0.0134 | 0.28–0.34 |
| 16.0 | 0.630 | 230–345 | 70–105 | 0.0110–0.0150 | 0.28–0.38 |
| 20.0 | 0.787 | 230–345 | 70–105 | 0.0118–0.0157 | 0.30–0.40 |
Values at the lower end of each range are for small-diameter gun drills (under 3 mm), where heat concentration limits surface speed. Above 8 mm diameter, speeds in the 280–345 SFM range are practical with sharp tooling and adequate coolant.
By Material Condition and Hardness
The hardness of 1045 has a direct effect on both speed and feed. The following data from Allied Machine’s published technical guides shows recommended parameters by hardness range for carbide gun drilling.
| Hardness (BHN) | Speed (SFM) | Feed (IPR) by Series (Diameter Range) |
|---|---|---|
| 100–150 (annealed) | 460 | Y/Z: 0.006; 0: 0.009; 1: 0.012; 2: 0.015; 3: 0.020 |
| 150–200 (normalized/cold drawn) | 400 | Y/Z: 0.005; 0: 0.008; 1: 0.010; 2: 0.014; 3: 0.018 |
| 200–220 (cold drawn/hard) | 360 | Y/Z: 0.005; 0: 0.007; 1: 0.008; 2: 0.012; 3: 0.015 |
| 220–260 (Q&T) | 310 | Y/Z: 0.004; 0: 0.006; 1: 0.007; 2: 0.010; 3: 0.013 |
| 260–320 (Q&T high strength) | 270 | Y/Z: 0.004; 0: 0.005; 1: 0.006; 2: 0.008; 3: 0.011 |
Series Y/Z: 0.374–0.500“ (9.5–12.7 mm); Series 0: 0.500–0.695“ (12.7–17.7 mm); Series 1: 0.695–0.960“ (17.7–24.4 mm); Series 2: 0.960–1.380“ (24.4–35.1 mm); Series 3: 1.380–1.882“ (35.1–47.8 mm)
Safety note: Always start at the lower end of the speed range for the first hole. Increase speed after confirming stable chip formation and acceptable tool pressure.
Cutting Parameters for BTA Drilling
BTA drilling allows significantly higher feed rates than gun drilling at equivalent diameters. The following data is from Allied Machine, ISCAR, and published research.
BTA — 1045 Carbon Steel (Carbide Inserts)
| Diameter (mm) | Diameter (inch) | Speed (SFM) | Feed (IPR) | Feed (mm/rev) | Expected Penetration (IPM) |
|---|---|---|---|---|---|
| 12.7–17.5 | 1/2“–11/16“ | 180–400 | 0.007–0.009 | 0.18–0.23 | 5–8 |
| 17.5–24.4 | 11/16“–15/16“ | 175–380 | 0.009–0.012 | 0.23–0.30 | 5–8 |
| 24.4–35.1 | 15/16“–1-3/8“ | 160–350 | 0.011–0.015 | 0.28–0.38 | 4–7 |
| 35.1–47.8 | 1-3/8“–1-7/8“ | 150–325 | 0.013–0.018 | 0.33–0.46 | 3–6 |
| 47.8–63.5 | 1-7/8“–2-1/2“ | 140–300 | 0.015–0.020 | 0.38–0.51 | 2–5 |
Penetration rates are estimated based on the spindle speed equivalent at the given surface speed and diameter.
BTA Case Study: 1045 Hydraulic Cylinder
A published case study from Allied Machine documents BTA drilling of a hydraulic cylinder in 1045 steel:
| Parameter | Competitor (Brazed BTA Head) | Allied BT-A System |
|---|---|---|
| Material | 1045 steel | 1045 steel |
| Hole diameter | 34.925 mm (1.375“) | 34.925 mm (1.375“) |
| Hole depth | 449.6 mm (17.7“) blind hole | 449.6 mm (17.7“) blind hole |
| Spindle speed | 800 RPM | 750 RPM |
| Feed rate | 0.0074 IPR (0.19 mm/rev) | 0.0118 IPR (0.30 mm/rev) |
| Penetration rate | 5.9 IPM (150 mm/min) | 8.85 IPM (225 mm/min) |
| Cycle time | 2 min 43 sec | 1 min 59 sec |
| Tool life | 750 linear inches | 900 linear inches |
| Coolant | Semi-synthetic, 900 PSI (62 bar) | Semi-synthetic, 900 PSI (62 bar) |
| Result | Drift issues — some tools exited cylinder side | Straight hole, < 0.010“ (0.25 mm) wall variation |
| Cost per hole | $1.60 | $1.36 |
This case study illustrates that parameter optimization in BTA drilling — specifically increasing feed rate while maintaining coolant pressure — improved cycle time by 27%, tool life by 20%, and hole quality compared to the baseline. The higher feed rate (0.30 mm/rev vs 0.19 mm/rev) also improved chip breaking, contributing to the straightness improvement.
Coolant Pressure and Flow Requirements
Effective chip evacuation in 1045 steel requires adequate coolant pressure and flow. The chips produced by medium-carbon steel are more cohesive than those from cast iron or free-machining steel, placing greater demands on the coolant system.
Gun Drilling — Coolant Requirements
| Drill Diameter | Recommended Pressure | Recommended Flow |
|---|---|---|
| 3–6 mm | 1,000–1,500 PSI (70–100 bar) | 2–5 GPM (8–19 L/min) |
| 6–12 mm | 700–1,200 PSI (48–83 bar) | 3–8 GPM (11–30 L/min) |
| 12–20 mm | 500–900 PSI (35–62 bar) | 6–15 GPM (23–57 L/min) |
| 20–35 mm | 300–800 PSI (21–55 bar) | 10–30 GPM (38–114 L/min) |
Minimum pressure: 50 bar (725 PSI) is the generally accepted minimum for reliable chip evacuation in gun drilling of 1045. Below this pressure, chip packing risk increases sharply.
BTA Drilling — Coolant Requirements
The case study on 1045 hydraulic cylinders used 900 PSI (62 bar) with semi-synthetic coolant. For BTA drilling of 1045, the following ranges are recommended:
| Drill Diameter | Recommended Pressure | Recommended Flow |
|---|---|---|
| 12–25 mm | 600–1,000 PSI (41–69 bar) | 20–60 GPM (76–227 L/min) |
| 25–50 mm | 400–900 PSI (28–62 bar) | 40–150 GPM (151–568 L/min) |
| 50–75 mm | 300–700 PSI (21–48 bar) | 100–250 GPM (379–946 L/min) |
BTA coolant tip: A sudden 10% drop in coolant pressure at the gauge is a reliable indicator of partial chip blockage or the early stage of drill tube damage. Monitor pressure continuously during production.
Tool Selection
Carbide Grade
For deep hole drilling 1045 carbon steel, the following characteristics are recommended:
| Parameter | Recommended |
|---|---|
| ISO grade | K15–K25 (uncoated) or P15–P25 (coated) |
| Coating | TiAlN or AlTiN (PVD) — provides lubricity to prevent BUE |
| Edge preparation | Honed edge, 0.02–0.05 mm radius |
| Coolant hole | Single or dual internal coolant holes, sized for the diameter |
TiAlN-coated carbide is the standard recommendation for 1045 steel. The coating provides a thermal barrier that reduces heat transfer to the carbide substrate and adds lubricity that resists built-up edge formation.
Gun Drill Head Profile
For 1045 carbon steel:
- Profile G (Universal) — First choice for general 1045 drilling. Provides balanced chip formation and stable burnishing across the full hardness range of normalized and cold-drawn 1045.
- Profile E — Recommended if built-up edge is observed with Profile G, or for deep holes exceeding 50×D. The E profile’s geometry reduces the tendency for material to stick to the outer corner.
BTA Drill Head
For BTA drilling of 1045:
- Brazed carbide heads for diameters under 20 mm
- Indexable insert heads for diameters 20 mm and above
- For normalized and cold-drawn 1045 (180–220 BHN), use a general-purpose carbide grade with TiAlN coating
- For Q&T 1045 above 250 BHN, use a tougher-grade substrate with increased edge hone
Speeds and Feeds for Short-Hole Drilling (Conventional Twist Drills)
For pilot hole drilling or short deep holes (under 5×D) in 1045 steel with carbide twist drills:
| Diameter | Speed (SFM) | Feed (IPR) |
|---|---|---|
| 1/8“ (3.2 mm) | 170–390 | 0.003–0.006 |
| 1/4“ (6.4 mm) | 170–390 | 0.004–0.008 |
| 3/8“ (9.5 mm) | 170–390 | 0.006–0.012 |
| 1/2“ (12.7 mm) | 170–390 | 0.007–0.015 |
| 3/4“ (19.1 mm) | 170–390 | 0.008–0.018 |
| 1“ (25.4 mm) | 170–390 | 0.009–0.020 |
Use the lower end of the speed range for 1045 in the low 100 BHN range, the middle for normalized (180–200 BHN), and the lower end for Q&T 1045.
Surface Finish and Dimensional Accuracy
| Method | Surface Finish (Ra) | Diameter Tolerance | Straightness |
|---|---|---|---|
| Gun drilling | 0.4–1.6 µm | ±0.01–0.05 mm (IT7–IT9) | 0.05–0.3 mm per 1,000 mm |
| BTA drilling | 0.8–3.0 µm (as-drilled) | ±0.03–0.10 mm (IT8–IT10) | 0.1–0.5 mm per 1,000 mm |
For 1045, surface finish is most sensitive to feed rate. Reducing feed by 50% can improve Ra by approximately 30–40%, but with a proportional increase in cycle time. When surface finish requirements are critical (Ra 0.8 µm or better for gun drilling), use the lower half of the feed range and verify tool condition before production runs.
Research on forged 1045 steel found that surface roughness improved by 40–98% compared to non-forged samples, depending on forging temperature and drilling parameters. For precision components, consider whether the rough stock condition affects achievable hole quality.
Condition-Specific Parameter Adjustments
The material condition of 1045 has a larger effect on deep hole drilling parameters than most machinists expect. A cold drawn bar and a quenched and tempered bar with the same chemistry will require fundamentally different cutting conditions.
Cold Drawn 1045
Cold drawn bars have improved machinability due to cold working strain. The tighter grain structure produces a better surface finish with less horsepower. Cold drawn bars are also straighter than hot rolled bars — typically 9.5 mm per 3 m (3/8“ per 10 ft) — reducing drill wander risk.
- Parameter adjustment: Use the upper end of the speed range for the given hardness. Cold drawn 1045 at 170–200 BHN can be drilled at 350–400 SFM with carbide gun drills.
- Note: Cold drawn bars have a thin, work-hardened surface layer. The entry feed may need to be reduced for the first 0.5 mm to prevent edge chipping.
Normalized 1045
Normalized 1045 (180–220 BHN) is the most common condition for deep hole drilling. The normalized structure provides consistent machinability throughout the bar.
- Parameter adjustment: Use the middle of the speed range for the given hardness. Apply standard depth adjustment factors for holes exceeding 7×D.
Hot Rolled 1045
Hot rolled bars are not recommended for deep hole drilling without surface preparation. The mill scale is abrasive and will accelerate tool wear at entry. The poor straightness (6 mm per 1.5 m typical) causes drill wander.
- Required preparation: Turn the bar to remove mill scale, or spot face the entry surface. If deep hole drilling into hot rolled bar is unavoidable, reduce entry speed by 30% and feed by 20%.
Quenched and Tempered 1045 (Above 250 BHN)
Q&T 1045 requires reduced cutting speeds but often produces better chip breaking than normalized material because the higher hardness makes the chips more brittle.
- Speed adjustment: Reduce by 20–30% from normalized values at equivalent diameter.
- Chip control: The chips will break more readily. Reduced coolant pressure may be acceptable for chip evacuation, but maintain pressure for cooling.
- Tool life: Expect 60–75% of the tool life achieved in normalized 1045 at the same feed rate.
Depth Adjustment Factors
The following factors from industry guidelines apply when drilling 1045 at depths exceeding 7× diameter:
| Drilling Condition | Speed Factor | Feed Factor |
|---|---|---|
| Standard depth (< 7×D) | 1.0 | 1.0 |
| 7×D to 12×D | 0.9 | 1.0 |
| 12×D to 20×D | 0.8 | 0.9 |
| 20×D to 30×D | 0.7 | 0.8 |
| Over 30×D | 0.6 | 0.7 |
Additional factors for extended-length tool holders:
| Holder Length | Speed Factor | Feed Factor |
|---|---|---|
| Standard | 1.0 | 1.0 |
| Extended | 0.9 | 1.0 |
| Long | 0.85 | 0.95 |
| Extra Long (XL) | 0.8 | 0.9 |
| 3XL | 0.7 | 0.8 |
Common Problems in Deep Hole Drilling 1045
Built-Up Edge (BUE)
Symptom: Rough bore surface, fluctuating cutting forces, poor chip formation, visible material adhered to the cutting edge after retraction.
Cause: 1045’s medium carbon content makes it prone to BUE at the cutting interface, particularly at moderate cutting speeds (100–250 SFM) where the temperature is high enough to soften the chip material but not high enough to fully soften the workpiece.
Solution:
- Increase cutting speed above 300 SFM — the higher temperature at the cutting interface reduces work hardening and BUE formation
- Use TiAlN-coated tooling — the coating provides lubricity that resists material adhesion
- Ensure coolant concentration is adequate (6–8% for emulsion; higher if BUE persists)
- Verify that feed rate is high enough — feeds below 0.05 mm/rev (0.002 IPR) increase BUE risk
Chip Packing
Symptom: Coolant pressure spikes or drops, torque increasing during drilling, tool overheating.
Cause: 1045 produces chips that are more cohesive than low-carbon steel but less well-broken than alloy steel. If the feed rate is too low, chips form long ribbons that pack in the flute or evacuation tube.
Solution:
- Increase feed rate incrementally until chips break into 6–12 mm segments
- Verify that coolant pressure meets the minimum values in the coolant table above
- Check the chip breaker geometry — for BTA, the chip former shape may need modification for 1045
- For gun drilling, ensure the V-flute is clean and free of nicks that could catch chips
Tool Wander at Entry
Symptom: Hole exits off-center; straightness measurement exceeds specification.
Cause: 1045’s mill scale (hot rolled bars) or surface work hardening (cold drawn bars) can deflect the drill at entry if the pilot hole is inadequate.
Solution:
- Use a pilot hole at least 1×D deep, with diameter 0.013–0.025 mm larger than the drill diameter
- Remove surface scale or hard layer by spot facing the entry surface
- Verify that the guide bush clearance is correct (+0.003 to +0.008 mm)
- Reduce entry feed to 50% for the first 2 mm of penetration
Deep Hole Drilling Procedure for 1045
Pilot Hole
For 1045 steel, a properly prepared pilot hole is essential:
- Depth: Minimum 1×D, recommended 2×D for L/D above 30:1
- Diameter: 0.013–0.025 mm (0.0005–0.001“) larger than the deep hole drill
- Point angle: Greater than the deep drill’s point angle to prevent center contact
Entry Sequence
- Drill pilot hole at 100% recommended speed and feed
- Feed the deep hole drill to within 1.5 mm of the pilot hole bottom at maximum 50 RPM and 300 mm/min feed with coolant OFF
- Drill 1×D past the pilot hole bottom at 50% speed and 75% feed
- Resume 100% speed and feed for the remainder of the hole
Running the Hole
- Continuous feed required — never dwell while the tool is cutting in 1045. Dwell creates a work-hardened ring that the cutting edge must break through on re-entry, causing chipping.
- Monitor chip form — check chips at regular intervals. Long stringy chips indicate feed is too low. Powdery chips indicate feed is too high for the edge geometry.
- Coolant pressure — watch the pressure gauge. A sudden drop of 10% or more indicates partial chip blockage.
Breakout and Retract
- Through holes: Reduce speed by 50% and feed by 25% before breakout. Do not break out more than 3 mm past full diameter.
- Retract: Reduce speed to maximum 50 RPM before retracting, with coolant OFF. This prevents the chip from wrapping around the tool during withdrawal.
Summary
AISI 1045 medium carbon steel is the most common material in deep hole drilling, but consistent results depend on recognizing how its condition affects cutting behavior:
- Cold drawn 1045 offers the best machinability and dimensional consistency for deep hole drilling. Use upper-range speeds.
- Normalized 1045 is the baseline condition. Standard medium-carbon parameters apply.
- Q&T 1045 above 250 BHN requires 20–30% speed reduction.
- Built-up edge is the most common problem — manage it with adequate cutting speed (above 300 SFM), TiAlN coatings, and proper coolant delivery.
- Coolant pressure of at least 700 PSI (50 bar) is required for reliable chip evacuation in gun drilling. BTA drilling with 900 PSI has demonstrated improved tool life and hole straightness in documented case studies.
- Feed rate is the primary control for chip breaking. 1045 requires higher feed rates than low-carbon steel to produce well-broken chips.
For related reading, see the Deep Hole Drilling 4140 and 4340 Alloy Steel Guide, the Speeds and Feeds for Deep Hole Drilling Reference Tables, and the Material Machinability Ratings for Deep Hole Drilling.