Key Stock and Machine Key Quick Reference Guide (2023)

Written by G.L. Huyett Marketing Department on 03/22/2021 with 0 comments

Understanding the standards and tolerances (permitted variance) of key stock can be complicated. Key stock is called out by nominal or named size. Among squares and flats, tolerances are referred to as "oversize" (over nominal) or "undersize" (under nominal).

UNDERSIZE

Actual size is nominal to less than nominal.

Common Names: Bar Stock; Redi‑Key; Key Bar Stock; Machine Key Bar Stock; Broad Key Stock; Negative Key Stock

Applicable Standards: ANSI B17.1, Class 1 fit; Metric DIN 6880 for key stock; DIN 6885 for machine keys

Fabrication: Typically cold drawn. DIN may be polished to make bright.

Common Grades (AISI and DIN References): 1018; 1045; 1060; 4140; SS303; SS314; SS316; DIN 6880; A2; A4; DIN 178; DIN 179

Common Uses: Used in field applications for repair, with no filing normally needed.

Comments: Some commercial tolerances deviate from the ANSI spec. Plated parts are marked with the size. Plating normally adds .0005" to the height and width. Relatively free fitting bar stock keys. Only applies to parallel keys.

MOLTRUP

Actual size is very slightly over nominal.

Common Names: Moltrup Steel; True Key Stock; Bright Steel; Close Key Stock

Applicable Standards: ANSI B17.1, Class 2 fit

Fabrication: Typically cold drawn. May be polished to make bright.

Common Grades (AISI and DIN References): 1045; 8630; 4140

Common Uses: Most popular in original equipment manufacturing due to precision finish and tight fit in key way.

Comments: This is true +.0010" Class 2 ANSI spec key stock with tight tolerances. Material is difficult to draw and is not always easy to find in the U.S.

OVERSIZE

Actual size is nominal to greater than nominal.

Common Names: Bar Stock; Redi‑Key; Key Bar Stock; Machine Key Bar Stock; Mak‑A‑Key™; Close Key Stock; Plus Key Stock

Applicable Standards: None known, though popularized as Mak‑A‑Key™

Fabrication: Cold drawn steel.

Common Grades (AISI and DIN References): 1018; 1045; SS303; SS304

Common Uses: Based on Mak‑A‑Key™ specifications, which require filing in the field for repair applications.

Comments: Used when a custom fit is required or desired for an oversize key way, for field repairs, or in worn key ways.

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SPECIALTY GRADES

Actual size can be above or below nominal.

Common Names: Bar Stock; Mak‑A‑Key™

Applicable Standards: Depends on material grade. ASTM 829; ASTM 484; ASTM 582; ASTM B16; ASTM A276

Fabrication: Cold drawn material. Some nonferrous may be extruded.

Common Grades (AISI and DIN References): 1095; 6061; CDA 360; some grades of stainless steel.

Common Uses: Typically used in field applications for repair.

Comments: Does not match ANSI spec, and is a frequent source of confusion. Most desirable grade in maintenance repair operations, and has wide acceptance, but limited commercial availability.

STEP KEY STOCK

T‑form, offered in both oversize and undersize tolerances.

Common Names: Offset Key Stock; Repair Key Stock

Applicable Standards: Sizing aligns to ANSI B17.1 Class 1 fit, bar stock.

Fabrication: Cold drawn steel. Milled for step and to size; usually plated and marked with size.

Common Grades (AISI and DIN References): 1018; 1045; SS304; SS316

Common Uses: Used in repair of damaged key ways in shafts, sprockets, and pulleys.

Comments: Step key stock is often erroneously called "offset key stock," which generally refers to "Z" shaped rectangle key stock machined with inverse steps on opposing faces.

ROUND

Round form, with undersize tolerances.

Common Names: Round LInear Shaft; Round Bar; Round Stock; Rod; Round Axle; Mak‑A‑Pin

Applicable Standards: Depends on material grade. ASTM A108; ASTM A681; ASTM A686

Fabrication: Cold drawn steel. Sometimes turned and polished.

Common Grades (AISI and DIN References): 1018; 1045; O‑1; W‑1; 1095; SS303; SS304; 6061; CDA 360

Common Uses: Versatile material used as shafting, straight pins, rails, or for locating in a wide range of applications and industries.

Comments: Round key stock is not drill rod. Drill rod is precision ground to size and surface finished.

HEX

Hex form, with undersize tolerances.

Common Names: Hex Bar Stock; Hexagon Shaft; Hex Shaft Stock; Hex Stock; Hex Rod; Hex Axle

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Applicable Standards: ASTM A108

Fabrication: Cold drawn steel.

Common Grades (AISI and DIN References): 1018; 1045; 8630; 4140

Common Uses: Machinery, gears, machine parts, structural components, automobile parts, axles, and drive shafts.

Comments: The primary benefit of hex key stock is that there is no key needed and no key way to cut which saves machining time.

Depending on your application, a secondary process may be necessary.

Heat Treating
Heat treating is used to increase strength by raising the temperature of the steel and then cooling it in a controlled manner to change the grain structure of the steel.

Key Stock and Machine Key Quick Reference Guide (8)

Tumbling
Parts are umbled to remove burrs prior to shipment or plating. Using friction, the tumbling media is engineered to polish the parts in a controlled manner.

Key Stock and Machine Key Quick Reference Guide (9)

View a copy of the G.L.Huyett Key Stock Catalog or download your own today.

Machine keys are used to transmit torque from a rotating shaft to a gear or sprocket. They can be finished in a variety of shapes, sizes, and materials for just about any application. Standard sizes are ready to use with little or no cutting or filing.

MACHINE KEY - FORM B

Common Names: Machine Keys; Sunk Keys; Key Stock

Applicable Standards: ANSI B17.1; DIN 6885

Fabrication: Cold drawn steel; cut to length; tumbled to remove burrs.

How to Identify: Imperial is measured height x width x length. Metric is measured width x height x length.

Common Uses: Original equipment, including motors, gear boxes, gear reducers, and transmissions.

Comments: Square ends are more common in U.S.

MACHINE KEY - FORM A

Common Names: Feather Key; Pratt & Whitney Key

Applicable Standards: ANSI B17.1; DIN 6885

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Fabrication: Cold drawn steel; cut to length; both ends radiused.

How to Identify: Imperial is measured height x width x length. Metric is measured width x height x length.

Common Uses: Original equipment, including motors, gear boxes, gear reducers, and transmissions.

Comments: Radiused ends are more common in Europe.

GIB HEAD

Common Names: Gib Head Key; Cotton Picker Key

Applicable Standards: DIN 6884/6887; Industry norm

Fabrication: Cold drawn steel; cut to length; machined tapered surface; tumble to deburr.

How to Identify: Imperial is measured width x length. Metric is measured width x effective height x length. Commercial keys do not usually meet the ANSI specification

Common Uses: Original equipment, including motors, gear boxes, gear reducers, and transmissions. Farm equipment, especially cotton pickers, harvesters, and combines.

Comments: Used to progressively install the key and take up slack from one access end. The head serves as a concussion point for hammering without damage to the shaft of the key. Common taper is 1/8" taper per foot.

WOODRUFF

Common Names: Half‑moon Key; Round Key

Applicable Standards: ANSI B17.7; DIN 6888

Fabrication: Cold drawn profile; cut to width; grind; tumble.

How to Identify: Imperial is measured diameter x width. Metric is measured width x height. Woodruff keys may have round or flat bottoms depending on specifications.

Common Uses: Original equipment, where an arbor cutter is used to cut a key way that is half‑moon shaped.

Comments: Alloy hardened keys usually have has marks (small lines) embedded into the surface of the key along the top.

HI‑PRO

Common Names: High Profile Keys

Applicable Standards: ANSI B17.7; Industry norm

Fabrication: Cold drawn profile; cut to width; grind; tumble.

How to Identify: Width x length x lip height. Hi‑pro keys have small "feet" to keep them from rocking in the key way.

Common Uses: Original equipment, where an arbor cutter is used to cut a key way that is half‑moon shaped.

Comments: Alloy hardened keys usually have has marks (small lines) embedded into the surface of the key along the top.

Special Order Metric DIN 6885

Machine keys can be designed with special dimensional features like set screws, tapers, and other attributes. Mechanical features like tensile strength, shear strength, and wear resistance can be enhanced by material and secondary processes (like heat treating) that give parts added benefits.

Key Stock and Machine Key Quick Reference Guide (16)

Form C

Key Stock and Machine Key Quick Reference Guide (17)

Form D

Key Stock and Machine Key Quick Reference Guide (18)

Form E

Key Stock and Machine Key Quick Reference Guide (19)

Form F

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Key Stock and Machine Key Quick Reference Guide (20)

Form G

Key Stock and Machine Key Quick Reference Guide (21)

Form H

Key Stock and Machine Key Quick Reference Guide (22)

Form J

Key Stock and Machine Key Quick Reference Guide (23)

Form K

Key Stock and Machine Key Quick Reference Guide (24)

FAQs

What is the purpose of a key stock? ›

Key stock is a small metal block or wedge inserted between a shaft and the hub of a pulley, gear, sprocket, or other rotating power device. It provides driving torque and prevents movement. One part of the key fits into a precut slot in the shaft known as a key seat.

What material is key stock made from? ›

Typically, key stock is made from carbon steel or stainless steel, but can also be made from aluminum, brass, copper, monel, and even nylon, all with varying material grades.

What is undersized key stock? ›

Undersize key stock is key stock 12 inches or greater in length with an actual size slightly smaller than a specified size while remaining within an acceptable tolerance range.

How are woodruff keys measured? ›

How are woodruff keys measured? Woodruff keys, identifiable by their half-moon shape, are measured two ways depending on if it is an imperial or metric key. Imperial woodruff keys are measured by their width and diameter, whereas metric woodruff keys are measured by their width and height.

How do you determine keyway? ›

Look at the large end of the key (also called the bow). If the bow has straight sides and a triangle-shaped top (like a house), you probably have a KW1 keyway. If the key is diamond-shaped (narrower at the top and bottom and wide in the middle), you probably have a SC1 keyway.

How do you cut a key stock? ›

Lap 2 Cut Key Stock - YouTube

What grade steel is key stock? ›

The material is 1018 carbon steel and is available with either zinc plated or plain finish. Also available in 303 stainless steel.

How do machine keys work? ›

Explanation of Different Type of Keys | Machine Design - YouTube

How thick is a key? ›

Thickness and Gauge Tables
Thickness Comparison Table
ThicknessImperialMetric
Nickel.074 in1.95 mm
House key.08 in2 mm
Standard car windshield.25 in6.35 mm
14 more rows

Is key stock hardened? ›

Standard key stock does not have enough carbon to harden well, it will still be pretty soft afterwards. It could be case hardened but that process is too much trouble for a tool bit.

What is key steel used for? ›

Key Steel is widely used for many general engineering applications. Typical key steel applications include taper, gibhead, plain and parallel keys.

What grade steel is key stock? ›

The material is 1018 carbon steel and is available with either zinc plated or plain finish. Also available in 303 stainless steel.

What is stainless steel key stock? ›

Key stocks are designed to transmit torque (rotational force) in keyways without causing wear on a machine. They can be made from a number of different metals, including stainless steel.

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