ASTM E618 Machining Performance of Metals
ASTM E618 – 07 provides a production-type test for assessing ferrous metal machining performance in single-spindle or multiple-spindle automatic screw machines. The values in inch-pound units should be considered standard.
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ASTM E618 Machining Performance of Metals
- Overview
- Scope, Applications, and Benefits
- Test Process
- Specifications
- Instrumentation
- Results and Deliverables
ASTM E618 Machining Performance of Metals Overview
ASTM E618 is the standard test method for evaluating the machining performance of ferrous metals using an automatic screw machine or bar machine under standardized cutting conditions. Machinability -the ease with which a metal can be cut to produce a good surface finish at acceptable tool life and cutting speed -is a critical property for any metal that will be turned, drilled, threaded, or otherwise machined in production. It determines how fast parts can be produced, how long cutting tools last, and what surface quality is achievable without excessive secondary finishing.
The test uses a single-spindle or multi-spindle automatic screw machine to perform a standardized turning operation on bar stock specimens under fixed cutting speed, feed rate, and tool geometry conditions. The key output is a relative machinability rating expressed as a percentage of the machinability of AISI 1212 free-machining steel, which is the reference material assigned a rating of 100 percent. A material with a rating of 80 percent machines to 80 percent of the cutting speed achievable with 1212 steel for the same tool life. This relative rating allows direct comparison across material grades and heat treatments.
The standard is primarily used for free-machining steels, leaded steels, and other ferrous alloys where machinability is a key specification parameter. It provides a practical, production-representative measure of machinability rather than a laboratory simulation, since the test is actually run on the type of machine the material will see in service.
ASTM E618 Machining Performance of Metals Scope, Applications, and Benefits
Scope
ASTM E618 covers the determination of relative machinability ratings for ferrous metals using an automatic screw machine or single-spindle bar machine under standardized cutting conditions. The reference material is AISI 1212 free-machining steel with a machinability rating of 100 percent. Test specimens are bar stock at the diameter appropriate for the machine being used. The test evaluates tool wear (flank wear) at a defined cutting speed over a specified cutting length or number of parts, and the relative machinability is expressed as the ratio of cutting speed for the test material versus 1212 steel that produces equivalent tool wear over the same cutting length. Heat treatment condition, bar diameter, and surface condition are documented as variables affecting the result. The standard falls under ASTM Committee E28 on Mechanical Testing.
Applications
- Free-machining steel grade qualification -1215, 12L14, 1144, and other leaded and resulfurized grades
- Incoming bar stock machinability verification for screw machine shops and precision parts manufacturers
- Heat treatment effect on machinability for alloy steels and tool steels
- Material substitution evaluation when switching between free-machining grades
- Supplier qualification for ferrous bar stock used in high-volume automatic machining operations
- Effect of inclusion content, sulfur level, and lead addition on machining performance
- Research and development for new free-machining steel compositions
- Production process control where machinability consistency is a quality specification
Benefits
- Production-representative test run on actual screw machine equipment under realistic cutting conditions
- Relative rating referenced to AISI 1212 allows direct cross-material comparison
- Quantifies machinability as a single comparable number for specification and purchasing purposes
- Identifies material lots that will cause excessive tool wear or reduced production speeds before they reach the shop floor
- Applicable to all ferrous bar stock grades used in automatic screw machine production
- Results support material specification development and acceptance criteria for incoming inspection
- Practical test that reflects real production output rather than a laboratory analogue
ASTM E618 Machining Performance of Metals Process
Specimen Preparation and Reference Material Setup
Test bar stock is prepared at the required diameter and surface condition.
1Machine Setup and Cutting Condition Standardization
The automatic screw machine is set up with the specified tool geometry,
2Machining Test Run
The test material is machined at the specified cutting speed for the defined cutting length or number of parts.
3Machinability Rating Calculation and Reporting
The cutting speed that produces the specified flank wear criterion for a defined tool life is determined for both the test material and the 1212 reference.
4ASTM E618 Machining Performance of Metals Technical Specifications
| Parameter | Details |
|---|---|
| Standard | ASTM E618-22 |
| ASTM Committee | E28 – Mechanical Testing |
| Reference Material | AISI 1212 free-machining steel (machinability rating 100%) |
| Test Equipment | Single-spindle or multi-spindle automatic screw machine or bar machine |
| Key Variables | Cutting speed, feed rate, depth of cut, tool geometry, bar diameter, heat treatment |
| Tool Wear Criterion | Defined flank wear at specified tool life (cutting length or number of parts) |
Instrumentation Used for ASTM E618 Machining Performance of Metals
- Single-spindle or multi-spindle automatic screw machine with calibrated speed and feed settings
- Carbide or HSS turning tools with defined geometry
- Toolmaker’s microscope for flank wear measurement
- Tachometer or speed verification equipment for cutting speed confirmation
- Micrometer for diameter measurement of machined parts
- Reference material -AISI 1212 bar stock -for baseline comparison
ASTM E618 Machining Performance of Metals Results and Deliverables
- Relative machinability rating expressed as a percentage of AISI 1212 free-machining steel
- Cutting speed versus tool life data for the test material and reference material
- Tool flank wear measurements at each measurement interval
- Machining conditions -cutting speed, feed, depth of cut, tool geometry, bar diameter
- Material heat treatment condition and bar surface finish
- Reference material results confirming test validity
- Full test report with all data formatted for material qualification, incoming inspection, or material specification documentation
Frequently Asked Questions
ASTM E618 evaluates the machinability of ferrous metals by measuring their performance during machining on an automatic screw or bar machine. The results help compare materials under standardized cutting conditions.
The standard is primarily intended for ferrous materials, including carbon steels, alloy steels, stainless steels, and cast irons used in machining applications.
The test can evaluate factors such as tool wear, surface finish, chip formation, cutting forces, and machining efficiency, depending on the testing objectives.
Machinability data helps optimize material selection, reduce tool wear, improve production efficiency, and achieve consistent part quality in high-volume machining operations.
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