CNC Machining Brass and Copper: Tools, Feeds, and Best Practices

Brass and copper are two of the most commonly machined non-ferrous metals after aluminum as covered in our Feeds and Speeds Guide. They are used in plumbing fittings, electrical components, decorative hardware, musical instruments, and mechanical parts. Both materials machine differently than steel or aluminum and require specific techniques for best results.

Brass is one of the easiest materials to machine. It cuts cleanly, produces good surface finish, and is relatively easy on tools. Copper is more difficult because it is ductile and gummy. Copper tends to form built-up edge on the cutting tool and produces stringy chips that are difficult to control.

This guide covers tool selection, feeds and speeds, coolant strategies, and techniques for machining brass and copper alloys.

Material Properties

Brass vs Copper Machinability

Brass is an alloy of copper and zinc. The most common machining brass is C360 which is also called free-machining brass. C360 contains a small amount of lead which acts as a chip breaker and lubricant. This makes C360 one of the most machinable materials available. Other brass alloys like C464 naval brass and C385 architectural bronze are less machinable but still cut reasonably well.

Copper is a pure metal. The most common machining grade is C110 — electrolytic tough pitch copper with 99.9 percent purity. C110 is highly ductile. Copper work hardens quickly during machining and generates significant cutting heat.

Machinability Ratings

The machinability rating of C360 brass is 100 percent — the baseline reference for all machinable materials. C110 copper has a machinability rating of approximately 20 percent. This means copper requires slower cutting speeds, lighter cuts, and more frequent tool changes than brass.

Tool Selection for Brass

Carbide vs HSS

Brass can be machined with carbide or HSS tools. Carbide tools are recommended for production work because they hold an edge longer. HSS tools work well for small runs and are easier to sharpen. Use tools with sharp cutting edges and positive rake angles.

Polished flute end mills are strongly recommended for machining brass to prevent material from building up on the cutting edge. The polished surface reduces friction and helps chips evacuate. Use 2-flute or 3-flute end mills for most brass work.

Drilling Brass

For drilling brass components use standard HSS or solid carbide twist drills with a standard 118-degree point angle geometry. The split point modification is not required for brass because the material does not work harden like stainless steel does. Drill speeds for brass can be significantly higher than for steel because the material cuts freely without work hardening.

Tool Selection for Copper

Tool Requirements

Copper requires carbide tools with sharp cutting edges. The sharp edge shears the material cleanly and prevents built-up edge. HSS tools work for small runs but dull quickly in copper. Use tools with polished flutes to reduce friction.

Single-flute and 2-flute end mills are recommended for copper. The open flute geometry provides maximum chip clearance. Copper produces long stringy chips that fill the flutes of multi-flute tools quickly. Two-flute tools balance chip clearance with surface finish.

Drilling Copper

For drilling copper use carbide drills with a 135-degree split point. The split point reduces thrust force and prevents the drill from walking. Use a peck drilling cycle for holes deeper than three times the drill diameter.

Feeds and Speeds for Brass

Starting Parameters

The recommended cutting speed for carbide tooling in C360 brass is 400 to 800 SFM. For HSS tooling use 200 to 400 SFM. Brass cuts freely at high speeds without generating excessive heat. The feed rate should be 0.003 to 0.008 IPT for roughing and 0.002 to 0.004 IPT for finishing.

Example Parameters

Example starting parameters for a 1/4“ 2-flute carbide end mill in C360 brass: 8,000 RPM and 60 to 80 IPM. For a 1/2“ 2-flute end mill: 4,000 RPM and 50 to 70 IPM.

Brass produces a good surface finish at moderate feeds and speeds. For the best finish use a light finishing pass at 0.005 to 0.010 inches radial engagement with a sharp tool. Climb milling produces better finish than conventional milling.

Feeds and Speeds for Copper

Starting Parameters

The recommended cutting speed for carbide tooling in C110 copper is 200 to 400 SFM. For HSS tooling use 100 to 200 SFM. The feed rate should be 0.002 to 0.005 IPT for roughing and 0.001 to 0.003 IPT for finishing.

Example starting parameters for a quarter-inch 2-flute carbide end mill in C110 copper are 4,000 RPM and 25 to 40 inches per minute feed rate. For a half-inch 2-flute end mill use 2,000 RPM and 20 to 30 inches per minute.

The feed rate must be high enough to produce a clean chip. A chipload below 0.001 IPT causes the tool to rub instead of cut. Rubbing generates heat and work hardens the copper surface.

Example Parameters

Example starting parameters for a 1/4“ 2-flute carbide end mill in C110 copper: 4,000 RPM and 25 to 40 IPM feed rate. For a 1/2“ 2-flute end mill: 2,000 RPM and 20 to 30 IPM.

Coolant for Brass and Copper

Brass Coolant Strategy

Brass can be machined dry or with air blast for chip clearance. Coolant is not required for brass but it extends tool life and improves surface finish. If coolant is used, use a water-soluble coolant at 5 to 8 percent concentration.

Copper Coolant Requirements

Copper requires coolant or lubrication for best results. The heat generated must be carried away from the cutting zone. Without coolant, the heat builds up and causes the copper to gall and weld to the cutting edge. Use flood coolant when possible or mist coolant as a minimum.

For copper a high-quality cutting oil or water-soluble coolant at 8 to 10 percent concentration provides the best results. The lubricant reduces friction at the cutting edge and prevents built-up edge formation.

Speeds and Feeds Reference

Quick Reference Table

Workpiece Material	Tool Type	SFM	RPM 1/4“	Feed IPM 1/4“	Chipload
Brass HSS	2-flute	300	4,600	30-45	0.003-0.005
Brass carbide	2-flute	600	9,200	55-75	0.003-0.004
Copper HSS	2-flute	150	2,300	12-20	0.003-0.004
Copper carbide	2-flute	300	4,600	25-40	0.003-0.004

How to Use This Table

Find your material and tool type in the left column. Use the SFM value to calculate RPM for your specific tool diameter. Start at the lower end of the feed range and increase based on chip formation and surface finish.

Here is a sample program for facing brass:

; Facing C360 brass
G90 G94 G17 G54
G21
M03 S8000
M08                ; Coolant on
G00 X0 Y0 Z5
G01 Z-0.5 F200
G01 X50 F500       ; Face cut
G00 Z5
M09
M05
M30

Threading Brass and Copper

Tapping Guidelines

Both brass and copper thread well with standard taps. For brass use spiral point taps for through holes and spiral flute taps for blind holes. The tap speed can be 20 to 30 SFM for HSS taps. Use tapping fluid or cutting oil for best results.

Copper requires sharp taps and adequate lubrication. Dull taps cause the copper to gall and seize on the tap. Use spiral point taps with polished flutes. The tap speed should be 10 to 20 SFM for HSS taps. Use a high-quality tapping fluid.

Form Tapping

Form tapping works well for both brass and copper. Form taps displace the material rather than cutting it, which eliminates chip problems. Form taps require a larger tap drill size than cutting taps. For copper, use sharp taps with adequate lubrication — dull taps cause the copper to gall and seize on the tap.

Common Problems

Built-up edge is the most common problem when machining copper. Copper welds to the cutting edge which changes the tool geometry and degrades surface finish. The fix is to use sharper tools with polished flutes and ensure adequate coolant reaches the cutting edge.

Stringy chips produced when machining copper are difficult to control during operation. The long chips can wrap around the tool and workpiece causing damage. Use chip breaker toolpaths that interrupt chip formation. Air blast helps clear chips from the cutting zone.

Poor surface finish in brass is usually caused by a dull tool. Brass produces excellent surface finish with sharp tools. Replace or resharpen the tool if the finish degrades. Increase the feed rate slightly to ensure the tool is cutting rather than rubbing.

Tool wear in copper is significantly faster than in brass because copper is more abrasive to cutting tools. Check tool condition regularly and replace tools when the finish degrades. Carbide cutting tools last significantly longer than HSS tools when machining copper materials.

Turning Brass and Copper

Turning brass produces excellent surface finish. Use positive rake inserts designed for non-ferrous materials with sharp carbide tooling. The recommended cutting speed for turning C360 brass with carbide inserts is 500 to 800 SFM. Feed rate: 0.005 to 0.012 IPR for roughing, 0.002 to 0.005 IPR for finishing.

Copper turning requires sharper inserts and slower speeds. Use polished carbide inserts with positive rake geometry. Cutting speed: 300 to 500 SFM. Feed rate: 0.005 to 0.010 IPR.

Both materials produce stringy chips in turning operations. Use chip breaker inserts to break the chips into manageable segments. For copper use chip breakers designed for ductile materials.

Drilling Brass and Copper

Drilling brass is straightforward with standard HSS or carbide drills. Use a 118-degree point angle with conventional flute geometry. Cutting speed for C360 brass with HSS drills: 200 to 300 SFM. For carbide drills: 400 to 600 SFM. Feed rate: 0.003 to 0.008 IPR depending on drill diameter.

Drilling copper requires sharper drills and lower speeds than brass. Use carbide drills with a 135-degree split point for best results. The cutting speed for drilling C110 copper with carbide drills is 150 to 250 SFM. For HSS drills use 80 to 120 SFM. Peck drilling is recommended for holes deeper than three times the drill diameter.

Use coolant or cutting oil for drilling both materials. Brass can be drilled dry for shallow holes but coolant extends tool life. Copper must have coolant for any drilling operation.

Milling Operations

For face milling brass use carbide inserts with positive rake geometry. Cutting speed: 600 to 1,000 SFM. Feed rate: 0.004 to 0.008 IPT. Brass produces excellent surface finish with sharp tooling.

For face milling copper parts use polished carbide inserts at 300 to 500 SFM. The feed rate should be 0.003 to 0.006 inches per tooth. Ensure adequate coolant flow to prevent built-up edge on the insert.

Slotting in brass can be done at full tool diameter engagement. Use a chipload of 0.003 to 0.005 inches per tooth. Slotting in copper requires reduced parameters. Use a chipload of 0.002 to 0.004 inches per tooth and reduce the axial depth of cut.

Example Parameters

Example starting parameters for a 1/4“ 2-flute carbide end mill in C360 brass: 8,000 RPM and 60 to 80 IPM feed rate. For a 1/2“ 2-flute end mill: 4,000 RPM and 50 to 70 IPM. Brass produces a good surface finish at moderate feeds and speeds. For the best finish use a light finishing pass at 0.005 to 0.010 inches radial engagement with a sharp tool.

Surface Finish

Brass produces a naturally bright finish when machined with sharp tools. Typical surface finish: 16 to 32 microinches Ra. For decorative work, use a wiper insert or light finishing pass with a low chipload.

Copper produces a matte surface finish that is typically 32 to 63 microinches Ra. The surface finish can be improved by using a sharp tool with a small nose radius and a light finishing pass. Apply coolant to prevent the copper from smearing on the surface.

Both brass and copper machined parts can be polished after machining for a mirror finish. Use progressively finer grit abrasive paper starting at 400 grit followed by a polishing buffing compound wheel. Brass polishes more easily than copper.

Common Applications

Brass is used for plumbing fittings, valves, decorative hardware, musical instrument components, electrical connectors, and low-pressure fittings. The machinability of C360 brass makes it ideal for high-volume screw machine work.

Copper is used for electrical components, heat sinks, plumbing fittings, decorative work, and chemical processing equipment. The electrical and thermal conductivity of copper makes it essential for many electronic and thermal management applications.

Safety Considerations

Leaded brass requires special safety precautions. Lead is a toxic material that can be inhaled as dust during machining. When machining leaded brass alloys like C360, use coolant to control dust and avoid dry machining. Wear respiratory protection if machining creates airborne particles.

Copper dust and chips are not toxic but can cause skin irritation in some individuals. The sharp edges of copper chips can cause cuts. Handle copper chips with care and wear gloves when cleaning the machine.

Both materials produce chips that can be recycled. Brass has significant scrap value. Separate brass and copper chips from other materials to maximize recycling value. Keep chips clean and dry for best recycling prices.

Economic Considerations

Brass costs more than steel but less than copper. Material cost for C360 brass: approximately $4 to $6 per pound. The high machinability offsets the material cost through faster machining times and longer tool life.

Copper is more expensive than brass at $5 to $8 per pound. The slower machining speeds and shorter tool life significantly increase the manufacturing cost of copper parts. Design parts to minimize material waste and machining time when working with copper.

Both brass and copper materials hold their value as scrap metal. Brass scrap is typically worth $2 to $3 per pound. Copper scrap is worth $3 to $5 per pound. Recycling chips and scrap reduces the effective material cost.

Comparison to Other Materials

Brass machines 2-3x faster than steel. Cutting speeds for brass are two to three times higher than for mild steel. Surface finish is also superior to steel. Brass does not work harden like stainless steel. Copper is more difficult than aluminum but easier than titanium. Cutting speeds for copper are similar to mild steel but tool life is shorter.

Copper is more difficult to machine than aluminum materials but easier than titanium alloys. The cutting speeds for copper are similar to mild steel but the tool life is shorter due to the abrasive nature of copper materials. Copper requires more attention to coolant delivery and chip control during machining than aluminum does.

Both brass and copper materials produce better machined surface finish quality than most steels when machined with sharp cutting tools. The natural lubricity of brass and the high ductility of copper both contribute to the good surface finish quality achievable with these two materials.

Machining brass and copper requires understanding their different properties. Brass cuts freely and produces excellent surface finish with sharp tooling. Copper requires more attention to coolant, chip control, and tool condition. Both of these materials are rewarding to machine and produce high-quality machined parts when the correct techniques are applied. With the right cutting tools and techniques both brass and copper can be machined successfully and profitably. For more machining guides and resources see our Feeds and Speeds Guide and our CNC End Mill Selection Guide.