ASME B94.48-1976 — Precision Indexable Insert Cartridges

🔩 ASME B94.48-1976 is the American National Standard that specifies the dimensional specifications, styles, and designations of indexable insert cartridges. A cartridge is a self-contained insert carrier: it mechanically holds an indexable insert within a larger tool body. Its shank may be square, rectangular, or cylindrical with various attachment methods, providing a standardized means of locating the cutting edge of an insert inside boring bars, milling cutters, and other large tools. The Standard was developed by Technical Committee 1 (Carbide and Oxide Tools) of the B94 committee jointly with ISO/TC29/WG9 and was approved as ANSI B94.48-1976 on July 23, 1976. It opens with published errata summarized in Section 8 below.

1. Scope, Definitions, and General 📌

Clause 1 (Scope) states that the Standard covers dimensional specifications, styles, and designations of cartridges for indexable inserts. Clause 2 key definitions:

• Indexable Insert: a solid made from a suitable cutting material having a number of cutting surfaces, all of which are used until dull and replaced with a fresh insert;
• Cartridge: a carrier in which an indexable insert is mechanically held in place. Shanks may be square, rectangular, or cylindrical with various attachment methods, providing a means of locating the cutting edge of an insert within a larger tool body; cartridges may be supplied with or without adjusting features;
• Preset Point: the location on a gage insert that fixes length, height, and width dimensions to determine the mounting location for a cartridge in its block or bar, and determining the workpiece shape or size.

2. Cartridge Styles and Construction 🔧

Cartridges are classified by shank cross-section (square/rectangular/cylindrical), attachment method (clamp, threaded, flanged), and adjusting capability (axial/radial). The Standard also sets the gage-insert requirement: cartridges are to be manufactured over gage inserts per industry practice. A gage insert is a combination of shim and insert thickness, used to verify the locating dimensions of the cartridge.

The “F” and “L” dimensions in Tables 2 and 3 are nominal dimensions over a specified nose radius for each given insert size; the exact preset point for each cartridge style is given in Table 4. As part of standardization, the cartridge design uses metric threads for axial and radial adjusting screws, clamp screws, and all other threads peculiar to the cartridge.

3. Identification System (12 + 2 Positions) 🏷️

The identification system consists of 12 mandatory positions with two supplementary positions that may be used at the manufacturer’s option (14 positions in total). It follows the nomenclature outlined in ANSI B94.45-1973 with slight modifications. Example:

MTFNR-10CA-11

The 12 positions specify the design and dimensions of the tool — holder style, cartridge style, insert shape and relief, insert size, nose radius, hand, and so on; the suffix digits are the manufacturer’s own types. All twelve mandatory positions must be used for designation of a tool covered by this Standard; except for the two manufacturer positions, no extension of the code shall be made.

4. Preset Points and the Gage System 📏

The preset point is one of the most valuable concepts in this Standard:

• Defines the mounting datum: a fixed location on the gage insert fixes the three-dimensional position of the cartridge in the length, height, and width directions;
• Determines work size: the position of the cartridge in its block or bar directly determines the shape and size of the machined bore or surface;
• Enables offline presetting: the cartridge is preset to size on a presetting machine against the preset point, then installed ready to machine — minimizing in-machine trial cuts.

The gage insert — a combination of shim and insert thickness — simulates the position of a real insert in the cartridge so that dimensional verification does not depend on a specific insert style.

5. Dimensional Series and Tolerances 🧮

The Standard tabulates key dimensions for each cartridge size covering insert inscribed-circle series, cartridge numbers (e.g., 10, 25), and axial/radial dimensions. Representative sizes (exact values in the Standard; U.S. customary units are controlling):

6. Engineering Practice Essentials 🛠️

• 🔍 Selection workflow: define bore/surface size and tolerance → choose cartridge style (with or without adjustment) from the tooling concept → select cartridge number by insert size and pocket → preset against the preset point;
• 🔧 Mounting and locking: install the cartridge in the boring bar and lock to the standard torque without shifting the preset point; use the side micrometer screw for compensation where needed;
• 📐 Preset verification: before mounting a combined tool, re-measure the preset-point height difference of every edge on the presetter; allowable deviation is set by the machining tolerance (typically ±0.01 mm class);
• 🧼 Maintenance: periodically clean pockets and threads and apply rust-preventive lubricant; replace worn adjusting screws before thread clearance drifts the edge;
• 📋 Documentation: keep a cartridge configuration ledger per combined tool (cartridge numbers, preset points, torques) for rapid rebuild and traceability.

7. Relationship with Related Standards 🔗

• B94.45-1973: nomenclature base; the B94.48 identification system follows its conventions;
• B94.46-1973 / B94.47M-1980: seats and chip breakers, completing the insert support system together with cartridges;
• B94.4-1976: identification system for indexable inserts, the common language for insert sizes in cartridges.

8. Errata Notes 📝

The errata published for ANSI B94.48-1976 are as follows; use the corrected values whenever citing data from the Standard:

9. Frequently Asked Questions ❓