MAK-A-KEY - Just "Cut, File, & Fit"

Keystock is a general industry term for flat, rectangular, square, or otherwise-shaped bars of metal that are used in power transmission applications or to make other fasteners. Technically, keystock must be at least one foot in length and conform to tight tolerances. All other similarly shaped metal bars are technically bar stock (which is still lumped under keystock in general terms).  

MAK-A-KEY is a precision brand that represents true keystock with specific tolerances. Here, we discuss the tolerances and fits that describe keystock, what makes MAK-A-KEY keystock a high-quality brand, how to use it, and other benefits and elements of the brand. 

The main difference between the two components is the tight tolerances necessary for the component to be recognized as keystock. Sizing tolerances communicate how much the actual size of the bar is allowed to fluctuate from the nominal – or given – size of the bar indicated in its specifications. Keystock is categorized under one of three tolerances:  

In addition to the sizing tolerance, the fit communicates how the keystock will sit between the keyway and the shaft. There are three specific types of fit, two of which are classified under the ANSI B17.1 Keys and Keyway Fit Classes standard. They are, from left to right:  

Class 1: Sometimes called a clearance fit, the key width will be slightly smaller than the key way, allowing the shaft and component piece to slide over each other. 

Class 2: Also known as a transition fit, the key width and the keyway can have a slight clearance fit or a slight interference fit. Generally, this fit is sufficient to hold mating parts together while still allowing for disassembly.  

Class 3: This is an interference fit, meaning the key will be larger than the keyway and will encounter interference during installation. Some means of force or the use of temperature differential is required for installation. ANSI B17.1 does not have specific standards for this class of fit.  

Learn more about keystock fits and tolerances in our Getting the Right Fit guide.

MAK-A-KEY is a precision brand keystock that is manufactured to an oversized tolerance (although undersized is available). As keyways can be distorted, worn, or damaged from use, oversized tolerances allow the component to fit a wider array of mating keyways because it can be filed down to fit. MAK-A-KEY is generally an aftermarket product used in repairs and maintenance. The product is typically sold in one-foot and three-foot bars that the user can “cut, file, and fit™” at the worksite. 

MAK-A-KEY is available in carbon steel and stainless steel. Both imperial (inch) and metric (mm) sizes are offered and extend to an array of sizes, up to about 2” square. Shapes include hex, rectangular, square, and step options. It is also available in keystock assortments.

Keystock in general is used in power transmission applications for shaft alignment, in-field repairs, and a wide variety of other industrial uses (take a more in-depth look at this product in our Keystock and Keystock Materials guide). It is often cut down into machine keys, which are smaller components that serve similar purposes (learn more in our Machine Key Comprehensive Guide). One of keystock’s and machine keys’ main functions is to protect the power transmission component by failing first. The application wears down on a cost-efficient fastener instead of other essential transmission elements – when the fastener breaks, it is easier and cheaper to replace.  

MAK-A-KEY is used exactly like other keystock, but its oversized tolerance allows it to be sized down to the required fit.

The most conventional means to “cut, file, & fit” (a trademarked slogan) MAK-A-KEY keystock is to use a hacksaw and metal file. You can also use an abrasive cut-off saw. What is important is to cut the key perpendicular to its axis, and after cutting it, to remove burrs on the end. Once cut to the length of the keyway, it is recommended that you file both sides of the key to fit, as opposed to removing material from only one side. It is possible that the keyway could be slightly out of parallel due to wear on one side of the keyway. 

You will want to mark each side of the key so that you know which side is oriented to which side of the keyway. Some people will use a stain such as DyKem™ marking fluid. The key should fit into the keyway with a moderate tapping of a rubber mallet.  

Never use a metal hammer to pound in the key. If the key requires significant effort to install, slightly file until the key is installed with moderate force. A light lubrication might aid in the installation. 

Be sure that the material you are using matches the keyway. Do not use carbon steel to mate with a stainless-steel keyway. For sprockets or pulleys with more severely damaged keyway slots, it is best to reform the keyway slot using a broach. Then use MAK-A-KEY step keystock in the same way – cut to length, file, and fit. Step keystock allows you to salvage the pulley or sprocket and avoid replacement costs. 

There is sometimes confusion between the names Moltrup and MAK-A-KEY , so it is helpful to clarify the relationship:  

The name “Moltrup” is derived from the Moltrup Steel Company, which was founded in 1914. The company was well known for its ability to draw a wide range of steel profiles, including close-toleranced bright steel for machine keys and keystock. The company designated its specific keystock quality level as “Moltrup Quality,” and “Moltrup” stuck in the industry as a way to communicate that high-quality product. Today, the name is understood to reference oversized keystock that conforms to ANSI B17.1 Class 2 Fit product, also known as “transition fit.”  

Moltrup keystock is most often used in OEM applications – where the mating keyways are unworn and precision made – in order to optimize the interference fit and extend the product lifecycle. Moltrup is available in medium carbon steel (AISI C1045), alloy steel (AISI 8630), and low carbon steel (AISI C1018). Medium carbon and alloy steels allow for heat treatment, with alloy providing some additional strength characteristics. Moltrup is often referenced in blueprints, though often misspelled as “Moltrip.” 

Huyett offers a wide range of MAK-A-KEY keystock in multiple shapes, sizes, specifications, tolerances, and more. Shop today to find the right parts for your application.