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Choosing The Correct Socket

IMPERIAL-Newton impact sockets are generally designed to be as versatile as possible in order to provide the maximum benefit for the end user. However, there are some points to keep in mind when considering if the socket you order is suitable for your application. Our knowledgeable Sales and Engineering staff are always willing to assist with answering any questions you may have, or to help you find the information you need. Feel free to contact us with any questions and we’ll do our best to get you answers. Please read the important notice at the bottom of this page prior to considering the information presented here.


The information below speaks to common heat treated alloy steel drives (black steel) made to ANSI or DIN specifications. Exotic and non-sparking alloys will have different values which are typically lower than for heat treated black steel.

Generally speaking, the limiting factor on torque for most larger impact sockets is the size of the square drive, due to the fact that on such sockets the square drive size is smaller than the nut opening size. Just as a chain is only as strong as its weakest link, an impact socket/power tool connection is generally limited by the smaller mass of the two connections.

For example, a typical 3-1/2″ AF hex impact socket may well be capable of handling many thousands of Ft-Lbs of torque, but if the square drive on that socket is only 3/4″ drive, the torque it can be used for is extremely limited by drive size, but not the drive of the impact socket itself. It will be effectively reduced in the load it can be used for, not at all by wall thicknesses or the type of alloy or hardness – or any property of the socket at all for that matter – but instead reduced by the inherent limitations of the 3/4″ section of steel driving it, on the end of the impact wrench itself. In this example, the impact wrench square drive is thus limiting the load, not the impact socket.

Conversely, if the square drive is large, and nut end is small (such as a 1-1/2″ drive socket with a little 7/8″ 12-point nut size), you will be limited to what is appropriate for a 7/8″ nut, even though your 1-1/2″ drive tool might be capable of delivering 10,000 ft-lbs. The smallest connection (nut size versus square drive) is generally the limiting factor when evaluating socket sizes and square drives to determine reasonable torque limits.

Industry standard impact sockets (those meeting ANSI, ASME, specifications for example) are generally designed to handle the amount of torque typical to the NUT SIZE it fits with, regardless of square drive size. So generally speaking a size 7/8″ socket will be deemed appropriate for loads common to a 7/8″ nut, whether the drive size is 3/8″ or 1-1/2″ drive. All of IMPERIAL-Newton Corp steel designs exceed ANSI/ASME B107 load test requirements, and all of our products are designed for heavy duty industrial applications where loads are taken to the maximum limits. In applications where rust, fouled threads, or other problems are causing extremely high loads  – contact us about our special line of Extreme Duty designs which are capable of handling even the most extreme loading or high duty cycle applications. Including non-sparking, acidic and high magnetism applications.

Modern materials innovations in steel alloys have extended the amount of force common square drives can withstand well above the limitations of the past, however, specific limitations still exist between drive sizes, and the following guidelines should be kept in mind when deciding on which drive size to choose for your application.

The strength of the socket will generally be designed to deliver torque appropriate to the nut size it fits onto, regardless of how large the square drive is. If you require an Extreme Duty design please feel free to discuss your application with us, to determine if an Extreme Duty impact sockets is the best choice, or if our normal industrial grade designs will do the job.

Drive Size Reasonable Torque Rating Limit*
3/4″ Square Drive 1,500 ft-lbs [2,035 Nm]
#4 Spline Drive 1,700 ft-lbs [2,300 Nm]
1″ Square Drive 3,500 ft-lbs [4,750 Nm]
#5 Spline Drive 5,000 ft-lbs [6,780 Nm]
1-1/2″ Square Drive 11,500 ft-lbs [15,600 Nm]
2-1/2″ Square Drive 45,000 ft-lbs [61,015 Nm]
3-1/2″ Square Drive 100,000 ft-lbs [135,590 Nm]
4-1/2″ Square Drive 200,000 ft-lbs [271,165 Nm]

*Impacting torque methods will reduce these amounts due to the inherent spikes in force which result when applying torque via impact methods. Additionally, keep in mind that anytime you heat up or stress a part in more than one direction simultaneously, there is a substantially deleterious effect on overall strength, resulting in lower performance versus what you would achieve had any of those forces been applied individually. The most common affect of this when working with nuts and bolts is to cause both bending forces and twisting forces to be applied at the same time on the square drive. Avoiding this effect by keeping the tool inline with the axis of the socket will minimize this effect and provide the best performance.


When it comes to sockets, all 8 pointed shapes are not the same. There are two very different and incompatible shapes which need to be considered prior to ordering. One shape is the octagon, and the other is referred to as a double square. The 8 point double-square is the most commonly available socket due to the common use of square headed fasteners versus less common octagonal ones. The difference between these shapes which makes them incompatible is illustrated for you in the drawing below.

You can see that even though the size is the same across flats, there is material missing in the critical areas of surface contact when a common 8pt socket is used with an octagon nut. In fact, the socket does not even contact the octagon nut even though the size is the same across flats. Please note that there are NO sizes of 8-point double square sockets which can be effectively or safely used on octagon fasteners.


The amount of force a socket can withstand before failure varies largely on many factors such as dimensional variations in manufacturing, specific material batch chemical and physical properties variation, permissible heat treat variances, the type and direction(s) of simultaneous force applied to the socket and many other factors which make it impossible to give absolute torque ratings for any socket. Without exception to this, the following table illustrates what might be reasonably expected of a common heavy-duty hex (6 point) impact socket manufactured of high quality materials and workmanship, compliant with industry standards in all regards.

If you believe your application could exceed the limits of commonly manufactured impact sockets, contact our Sales Department for assistance with custom designed sockets substantiated with testing and design analysis to sufficiently support the demands of your special application. The information below should not be solely relied upon for any purpose, especially where safety concerns are present, and is provided for reference only. If in doubt, consult a qualified professional third party advisor such as those available here.

Hex Size Ft-Lbs Torque ASME Test Ft-Lbs (B107)
1- 1/8 2,500 808
2- 1/4 3,800 1500
3- 3/8 10,700 2333


For customers who face harsh environmental storage and use issues, IMPERIAL-Newton offers several factory coating options to keep your sockets protected from the elements even in subsea service conditions. The following finishes are available as standard offerings, with additional special platings and finishes available upon request. Platings in compliance with government and consensus standards certificated for additional charge.

  • VERIDIZETM – Double Layer Anti-Corrosion Baked-On Surface Treatment
  • Electroless Nickel – plating option offering corrosion resistance
  • Decorative Chrome – brite finish, though not recommended for impact applications due to chrome’s brittleness and extra processing required to alleviate issues of hydrogen embrittlement.
  • Black Oxide – the standard surface treatment for impact tools, offers very light corrosion resistance


IMPERIAL-Newton makes no warranty or representation of accuracy regarding the information contained herein specifically as it applies to your application. The following information is offered in the complete absence of particulars about your application and is therefore presented for reference and informational purposes only and must not be construed as advice or recommendation for any application or purpose. While the information presented here may be a part of your considerations it should not be relied upon for your final decision nor to form the basis for any approach without verifying the specifics of your application with a qualified professional or agency knowledgeable in your specific industry. Consult your company’s Safety Officer or your country’s governmental safety authority (e.g., OSHANOHSCNEBOSCHCCOHSIOSHILOCIWCE) for directives on the safe and proper use and selection of tools such as those offered by IMPERIAL-Newton.