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How to use a 3/8 inch socket set

Updated: 22 October 2026

The 13 mm nut on the mower deck is rusty, the ratchet is in your hand, and the socket is only half on the square. That is how a fastener gets rounded before it moves. How to use a 3/8 inch socket set comes down to three checks: the square is seated and holds, the direction is proved before you load the nut, and you stop when the socket starts to slip. Our [3/8 inch socket set comparison](/hub/hand-tools/3-8-inch-socket-set) is the buying table. This page assumes you already own a 3/8 inch ratchet and sockets. What to look for in the box is on the [3/8 inch socket set buying guide](/hub/hand-tools/3-8-inch-socket-set/sub/3-8-inch-socket-set-buying-guide). There was no workshop trial. A qualifying purchase can earn a commission at no extra cost to you.

The 13 mm nut on the mower deck is rusty, the ratchet is in your hand, and the socket is only half on the square. That is how a fastener gets rounded before it moves.

Our top picks

Draper Draper Expert 18-piece 3/8 inch socket set

Best overall

Draper Draper Expert 18-piece 3/8 inch socket set
8.9/10about £26.47
View offer
Silverline Silverline 13-piece 3/8 inch socket rail

Rank 2

Silverline Silverline 13-piece 3/8 inch socket rail
6.6/10about £10.95
View offer
WORKPRO WORKPRO 14-piece 3/8 inch socket set

Rank 3

WORKPRO WORKPRO 14-piece 3/8 inch socket set
6.3/10about £12.99
View offer
On this page
  1. 1.Seat the 3/8 inch square
  2. 2.Set the direction before the nut is loaded
  3. 3.Turn, reset, and watch the flats
  4. 4.When you stop

Seat the 3/8 inch square

The hole in the socket and the square on the ratchet both have to be 3/8 inch. A 13 mm stamp is the fastener. If the square will not start, stop. An adapter adds a joint and is not the first choice on a tight nut. Press the socket on until the detent ball snaps. The Draper set in this sample needs the release button pressed before the socket will seat. Tug it once. If it pulls off, do not load it. That click is the square seating, not a torque wrench.

Set the direction before the nut is loaded

The lever is not universal. One brand marks tighten on the left, another on the right, and a stiff lever, as some buyers found on the WORKPRO 14-piece ratchet, is easy to leave in the wrong place. Hold the socket so it cannot turn, and move the handle. Looking down on the head, clockwise should tighten and anti-clockwise should loosen. If the handle swings the wrong way, flip the lever and prove it again before the socket is on the car. A 72-tooth ratchet needs only a short swing, about five degrees, to catch the next tooth.
Draper Draper Expert 18-piece 3/8 inch socket set

Testsieger

Draper Draper Expert 18-piece 3/8 inch socket set
8.9/10about £26.47
View offer

Turn, reset, and watch the flats

Put the socket fully on the nut so it bears on the flats, not on the top edge. Turn the handle in the loaded direction, then bring it back without lifting the socket off. If you lift, the socket can sit crooked and catch a corner. On a rusty hex, start with a 6-point socket that fits with no slack. A 12-point socket seats faster and puts more load on the corners, which suits a 12-point fastener and rounds a soft hex more easily. If the socket slips, or you see a bright shaved corner, stop. The best 3/8 inch socket set page sorts the 6-point hand kits.

When you stop

If the nut is dirty, wire-brush the flats and use a penetrating fluid, then wait. Do not hang a long bar through a seized stud. PartsForMachines’ band of about 100 Nm for a typical 3/8 inch drive is a rule of thumb, not a test of any set here. The click on the return stroke is the freewheel, not a measured torque. Stop when the job is a wheel nut or a seized hub. Those jobs are the 3/8 vs 1/2 inch socket set decision. Stop if the socket is cracked or the ratchet skips. Orange high-voltage cabling is a garage job, and a chrome socket set is not a VDE set.

Common questions

Which end of the socket goes on the ratchet?
The square hole goes on the 3/8 inch drive. The shaped end goes on the nut. The number stamped on the wall is the nut size, not a second drive size. If you reverse the socket, it will not seat on the ratchet and it will not hold the fastener. Check the square before you are under the car.
How do you know the square is seated?
Press the socket on until the detent ball snaps, then tug it. A seated socket stays put. Some ratchets need the release button held in before the socket will slide on. If it falls off, or it sits at an angle, do not load it. A loose square rounds the nut and can damage the drive.
What do you do when the handle runs out of room?
Bring the handle back with the socket still seated on the nut, then take another bite. A 72-tooth ratchet needs only a short arc to catch the next tooth, which helps against a bulkhead. If you still cannot swing, an extension can move your hand out of the bay. It also adds a joint, so keep the socket in line with the bolt rather than levering sideways.
How do you choose the socket so it does not round the nut?
Use the stamped size that sits with no play, fully down on the flats. On a rusty hex, prefer 6-point. Use 12-point when the fastener is 12-point. A socket that is one size too big feels close and then spins on the corners. Clean the flats first so the socket is not sitting on rust.
What should you do if the socket starts to slip?
Stop. A slipping socket is shaving the corners, and another pull makes the nut worse. Check that the size is right, that the socket is fully seated, and that you are not using 12-point on a soft hex. Penetrating fluid and a wait can free a dirty thread. If it still slips, the next tool is not a longer lean on the same ratchet.
Is the click from the ratchet the same as a torque-wrench click?
No. The ratchet click is the free return as the teeth skip backwards. A torque wrench clicks when it reaches a set load, and only if you set that load. Hearing the ratchet tick does not mean a wheel, a sump plug or a bracket is at the figure in the manual. If you must meet a published torque and you cannot measure it, stop and use the right wrench or ask someone who can.

Related pages

3/8 inch impact socket

3/8 inch socket set

Best 3/8 inch socket set: compact kit, case, or rail

3/8 inch socket set buying guide: check the square

3/8 vs 1/2 inch socket set: choose the next square

Sources

Public UK sources from the research digest, last checked on 20 October 2026. Shelf prices and star lines are the amazon.co.uk figures in the product display for this comparison.

  1. HSE: PUWER overview (retrieved 20 October 2026)
  2. HSE: using the right type of PPE (retrieved 20 October 2026)
  3. Wonkee Donkee: what is an impact socket (retrieved 20 October 2026)
  4. Wonkee Donkee: what are sockets made of (retrieved 20 October 2026)
  5. Cromwell: sockets and socket sets (retrieved 20 October 2026)
  6. KS Tools 3/8 inch hexagon impact socket (retrieved 20 October 2026)
  7. PartsForMachines: mechanics and automotive socketry (retrieved 20 October 2026)
  8. Bradfords: socket sets (retrieved 20 October 2026)