How to Remove a Stripped Allen (Hex) or Torx Bolt

October 10, 2026

To remove a stripped Allen (hex) or Torx bolt, first clean out the recess and make sure you have the exact right bit, because a wrong-size or wrong-type bit is the usual cause. Then tap a fresh, full-length bit in and turn it on a ratchet, hammer in a slightly oversized Torx bit, or grip the outside of the head. If the recess is gone completely, a screw extractor cuts its own grip.

What you need

Hex and Torx bits in the right sizes, ideally on a ratchet. A 46-piece 1/4-inch socket and bit set includes hex and Torx (T10 to T40) bits, a bit adapter and a 1/4-inch ratchet for light and medium torque.
A pick or small screwdriver, and penetrating oil
A hammer and locking pliers
A 6-piece screw extractor set and a drill with reverse, for recesses that are rounded out
Optional: a hand impact driver
Safety glasses

Why hex and Torx heads strip

A hex recess has six flat walls and a Torx recess has six rounded lobes. Both grip well when the bit fills them completely, and both strip fast when it doesn't. Check these before you try anything else:

Metric vs inch keys. Some pairs look identical but aren't. A 3/16 in key is 4.76 mm, loose in a 5 mm hex. A 6 mm key is 0.35 mm loose in a 1/4 in (6.35 mm) hex. A 3/32 in key is 2.38 mm, loose in 2.5 mm. Only a few pairs are near-identical, such as 4 mm and 5/32 in (3.97 mm).
Torx vs triple square. Some German cars, VW and Audi especially, use 12-point triple-square (XZN) heads that look a lot like Torx. A Torx bit fits loosely in them and chews them up. Check the service manual if you're not sure.
Security Torx. A small pin in the middle of a Torx recess means you need a tamper-resistant bit with a hole in its tip.
Dirt and rust. Recesses under the car fill with packed dirt, so the bit only engages the top few millimeters.
Worn bits and ball ends. A rounded key tip slips, and the ball end of a hex key is for spinning bolts in and out, not for breaking them loose.

Step 1: Clean the recess and check the fit

Pick out dirt, rust and paint until you reach the bottom of the recess. Blow it out.
Spray penetrating oil around the head and into the thread if you can reach it, and give it at least 15 minutes.
Try your bit. It should slide in to full depth with almost no rotational play. If it wobbles, try the other measuring system or check whether it's a different head type.

Method 1: A fresh bit, tapped in and turned straight

If the recess is only partly rounded, full contact is often enough.

Use a new, sharp bit of the exact size, on a ratchet or breaker bar if you can. A bit on a ratchet lets you push straight in with one hand and turn with the other.
Tap the bit fully into the recess with a hammer. Only do this on solid metal parts.
If you're using an L-shaped key, put the short end in the bolt and pull on the long end.
Push hard into the bolt and turn slowly counterclockwise. Stop the moment you feel it slip.

A hand impact driver is even better here. Set it to loosen, fit the hex or Torx bit, seat it and strike the back with a hammer. The blow drives the bit in and turns it at the same moment, so it can't cam out.

Method 2: Hammer in a Torx bit

This is the classic fix for a rounded hex.

Pick a Torx bit that is just too big to slide into the hex.
Tap it in with a hammer. Its lobes cut into the soft, rounded walls of the hex and make new grip.
Turn it slowly with steady pressure, ideally on a ratchet.

For a stripped Torx, use the same idea: tap in the next Torx size up, for example a T30 into a damaged T27. Use a spare bit, because it may be ruined.

Method 3: Grip the outside of the head

This depends on the head shape.

Socket cap screws have tall, round heads. Clamp locking pliers on hard, or tap a bolt extractor socket onto the head in the size that needs a light tap. Its reverse spiral bites into the round head as you turn counterclockwise.
Button heads are low and domed, so pliers barely grip. Cut a slot across the head with a rotary tool and use a large flat screwdriver.
Countersunk (flat) heads sit flush, so there's nothing outside to grip. Go to Method 4.

Method 4: Use a screw extractor

When the recess is rounded smooth, an extractor makes its own grip. The JUSMIR set has six double-ended bits, sizes #0 to #4, and works with an ordinary drill.

Choose the bit whose cutting end sits inside the damaged recess without reaching the outer edge of the head.
Set the drill to reverse and low speed, hold it in line with the bolt and cut a shallow seat with clean, bright metal all around.
Flip the bit to the extracting end, keep the drill in reverse, press hard and run it slowly until the bolt turns.

Never use an impact driver with an extractor. For sizing tips and how to avoid snapping one, read how to use a screw extractor without breaking it.

Method 5: Weld, or drill off the head

A shop with a welder can weld an old hex key or bit into the recess, or a nut onto a cap head. The heat also helps break rust and threadlocker. Without a welder, the last resort is to drill off the head: center punch it, drill with a bit slightly larger than the bolt's shank, lift the part off, then deal with the stub. Our guide on how to remove a broken bolt covers that part.

Stripped hex or Torx bolts in tight spaces

An L-key in a tight spot is often what strips the bolt, because you can't push straight in. Use a short bit in a bit adapter on a small ratchet, with a universal joint if the angle is awkward, and keep the bit in line with the bolt. A hand impact driver needs room to swing a hammer, so it isn't always an option here.

Brake caliper bolts with hex or Torx heads

Some caliper guide bolts use a hex or Torx head and are often threadlocked. Use a full-length bit on a breaker bar, not an L-key. Keep heat away from the caliper, because it damages the piston seals and the brake hose. Replace a stripped caliper bolt with a new one of the correct specification and tighten it to the torque in your vehicle's manual. Some makers call for new bolts every time, so check.

How to stop it happening again

Use the exact size and system, and a bit that isn't worn.
Clean the recess and push the bit to full depth before you turn.
Break bolts loose with the straight end of the key or a bit on a ratchet, never the ball end.
Replace any bolt with a damaged recess, and torque the new one to spec.

When to call a pro

If the bolt holds a brake, steering or suspension part, sits in an engine, or is threadlocked and won't move after a careful extractor attempt, a shop with welding gear is the safer bet. For cross-head and slotted screws rather than hex and Torx, the methods in how to remove a stripped screw fit better.

FAQ

How do you remove a stripped Allen bolt without an extractor?

Clean the recess, then try a fresh bit tapped in, a hand impact driver, or a Torx bit hammered into the hex. On a socket cap screw, locking pliers on the outside of the head often work.

Can you use a Torx bit on a stripped Allen bolt?

Yes. Choose one that's just too big to slide into the hex and tap it in with a hammer. The lobes cut fresh grip into the rounded walls.

How do you remove a stripped Torx bolt?

Check it isn't a triple-square or security Torx head, then tap in a fresh bit of the right size, or the next Torx size up. If the recess is gone, use a screw extractor.