Klein 7-Piece Nut Driver Set 631: The Professional's Choice for Long-Bolt Applications

Klein’s model 631 nut driver set delivers exactly what electricians and HVAC techs need: 3-inch hollow shafts that handle long bolts without removing the fastener. The color-coded Tip-Ident system means you’ll grab the right size without squinting at stamped markings — a genuine time-saver when you’re working in dim electrical panels or cramped mechanical rooms.

At 4.8 stars across retailers, this set has earned its reputation through daily jobsite use. Users consistently praise the hollow shaft design for deep-set nuts — the exact scenario where standard nut drivers force you to switch tools or remove hardware completely.

Core Specifications and Design Features

The 631 set covers the seven most common SAE sizes from 3/16” to 1/2”, each featuring Klein’s signature Cushion-Grip handles for enhanced torque without hand fatigue. Chrome-plated steel shafts resist corrosion — essential when these tools live in a service truck through Montana’s temperature swings and road salt exposure.

Specification	Value
Shaft Length	3 inches (76 mm)
Overall Length Range	6-3/4” to 7-5/16”
Weight	1.5 lbs (24 oz)
Shaft Material	Chrome-plated steel
Handle Type	Cushion-Grip

The color-coding follows Klein’s standard system: black (3/16”), red (1/4”), yellow (5/16”), green (11/32”), blue (3/8”), brown (7/16”), and red again (1/2”). That duplicate red might confuse at first, but the size difference between 1/4” and 1/2” makes them impossible to mix up in practice.

Internal flanges provide a solid, twist-resistant connection between shaft and handle — critical when applying serious torque. These aren’t hobby-grade tools that strip out after a season of real use.

631 vs 631M: To Magnetize or Not

The 631M adds magnetic tips for holding fasteners, while maintaining the same hollow shafts and cushion grips as the standard 631. The 631M uses rare-earth magnets — strong enough to hold nuts vertically while positioning.

Here’s the trade-off nobody talks about: magnetic tips collect metal shavings. Work around a drill press or metal lathe, and those magnets become liability magnets. The standard 631 stays clean in metalworking environments where the 631M would accumulate swarf.

One quirk with the 631M: the 3/16” driver lacks a hollow shaft. Klein apparently couldn’t engineer the magnet and hollow shaft together at that small diameter. If you regularly work with long 3/16” bolts, stick with the standard 631.

Professional Applications That Matter

These excel at electrical and mechanical maintenance, HVAC work, and automotive repair. The hollow shaft design shines when removing panel fasteners with protruding studs — common in electrical enclosures and HVAC equipment covers.

For Montana’s HVAC techs dealing with equipment exposed to temperature extremes from -30°F to 100°F, the chrome plating prevents corrosion better than plain steel alternatives. That matters when you’re servicing rooftop units in spring after a winter of freeze-thaw cycles.

Klein recommends keeping the tools clean and dry to maintain the chrome finish, storing them in a tool pouch or roll to protect the cushion grips. Good advice, though these tools handle jobsite abuse better than most.

FAQs

Are Klein nut drivers still made in the USA?

Yes, the 631 set is made in the USA. While Klein has moved some production overseas for certain product lines, many of their core electrical hand tools remain American-made.

What’s covered under Klein’s warranty for these nut drivers?

Klein Tools Limited Lifetime Warranty covers defects in material and workmanship for the normal life of the product. Normal life means until the tool wears out from regular use — not abuse.

Which certifications do these nut drivers meet?

ASME/ANSI B107.110 and MIL-spec compliance. The military specification matters for government contractors and anyone who values tools built to measurable standards.

Should you choose the magnetic version (631M) or standard (631)?

Depends on your work environment. The magnetics help with overhead work and prevent dropped fasteners. Skip them if you work around metal shavings or need the hollow 3/16” size. Both versions earn strong user ratings, so neither is a wrong choice.