Here’s How to Select the Holding Assemblies You Need
Begin by asking yourself the following questions. Your answers will point you in the right direction to find the assemblies that meet your specifications. If you want further advice after reading the following prompts, we’ll be glad to help you. Just call us and describe your application.

What are your shape and size requirements and mounting restrictions?
The Magnetic Holding Assemblies in this catalog are arranged by shape and size. Once you’ve determined what limitations your design imposes and answer some other questions, you can start your search by going to the Table of Contents and looking up the shape(s) that fit. Turn to the appropriate section, and you’ll find the standard stock sizes listed for each shape.

Is the mounting surface magnetic or nonmagnetic?
Certain holding assemblies need to be insulated for maximum holding effectiveness when mounted in ferrous materials. Call for more information.

How will your assemblies be mounted?
Press-fit mountings may require special insulation in ferrous materials. Place the uninsulated holding assembly inside a tightfitting stainless steel, aluminum, or other nonmagnetic sleeve and install. For bolted mountings, you’ll be looking for tapped or thru-hole assembly designs. Nonferrous fasteners are recommended for bolt-on applications.

What is the estimated holding force required for your application? What forces, in addition to gravity, will be acting on the parts while they are being held?
If you know how much your parts weigh and what other factors are likely to be involved, you can begin to make a rough estimate of how much holding power each individual magnet will need to have. In the parts listings, you’ll find magnetic holding values for every standard assembly. These holding values have been established in controlled laboratory tests and indicate vertical pull from flat ground steel.

For example, an assembly with a holding value of 5 pounds can hold a 5-pound steel part with a flat ground surface on a vertical pull under laboratory conditions. But outside the laboratory, you need to consider more than the weight of the parts you will be handling.

The size and shape of parts, as well as their surface condition, motion, vibration, friction, holding angle, and machining forces need to be factored in. Anything that gets in the way of direct magnet-to-metal contact or creates an air gap will also create the need for more magnetic holding force.

What are the size, shape, and weight of the parts you’re handling?
Use the size and shape of the parts to estimate the number of magnetic holding assemblies you’ll need to hold each part in your application. From the number of magnets, weight of the parts, and factors such as the ones noted in this section, you can figure approximately how much each magnet will need to hold.

What is the condition of the part surfaces? Are they flat or curved, smooth or rough cast? Are they clean, oily, rusted, or painted? Tabulated holding values are based on direct contact with flat metal. Curved surfaces or anything that reduces surface contact or creates an air gap will result in the need for more powerful holding assemblies. As a general rule of thumb, factor in 25% more holding force for parts with slightly curved, rough, or painted surfaces, as well as heavily oiled parts. Parts with sharply curved surfaces and significantly reduced magnet-tometal contact may require 100% or more additional holding power. We recommend experimenting to determine the holding values you require.

Will the parts be above or below the holding assemblies? Will the parts be held horizontally or will you need to factor in shear forces for vertical or inclined applications? Holding values are based on vertical “pulling power.” To allow for shear forces, additional holding force may be required. Call Bunting Magnetics for specific information.

What will the temperature of the operating environment be? For temperatures above 180°F, select assemblies that use Alnico magnets. See the following sections on magnet materials for more temperature information.