Stripped or rounded out recessed Allen bolts can be incredibly frustrating to deal with. You go to loosen or remove the bolt only to find the hex socket has become damaged, making it seemingly impossible to grip with standard Allen wrenches. While stripped recessed bolts may seem impossible to remove without completely drilling them out, there are actually several methods you can try to remove them intact.
With the right tools and techniques, removing a stripped recessed Allen bolt is very doable. This comprehensive guide will outline step-by-step instructions for multiple effective methods, plus provide tips and recommendations for how to avoid stripping a recessed Allen bolt in the first place.
Understanding Recessed Allen Bolts
Before going further, let’s briefly go over what exactly a recessed Allen or Allen screw is and why stripping occurs.
What Are Recessed Allen Bolts?
Recessed Allen bolts, also sometimes called socket head cap screws, are a type of bolt that has a hexagonal socket recessed into the head. Usually the bolts are made of steel, but can also be found in stainless steel, brass, or other metals.
The hex socket allows for tightening or loosening the bolt with an Allen wrench (also known as a hex key or Allen key). Allen bolts are extremely common and utilized in many applications from machinery to furniture to appliances and electronics.
Recessed Allen bolts have their hex socket set down into the bolt head. This allows for a lower profile while still maintaining the grip and torque abilities of the hex shape. The bolt head around the outside of the socket is typically 6, 8, or 12 point flanges.
How Do Recessed Allen Bolts Get Stripped?
There are a few ways a recessed Allen bolt can become damaged or rounded out:
- Over-tightening – Applying too much torque when tightening can deform the hex socket. Especially easy to do with soft metals like aluminum.
- Wrong sized tool – Attempting to loosen a bolt with a metric tool on a SAE bolt or vice versa. Or using an Allen key that seems close but is slightly too small. This can easily round off the edges.
- Poor tool fit – A loose fitting or worn Allen wrench is more likely to “cam out” under torque and damage the bolt head’s socket.
- Corrosion – Rust or corrosion within the socket can cause material to flake out when attempts are made to loosen the bolt.
Options Once Stripped
Once an Allen bolt becomes stripped, conventional Allen wrenches will simply spin freely in the damaged socket when trying to loosen it. At this point, you have three options:
- Drill out the bolt and re-tap the hole for a larger replacement bolt.
- Use some method to gain purchase on the damaged socket to back the bolt out.
- Cut the head off the bolt and pry out or tap the shank.
Drilling out bolts is destructive and time consuming, so most DIYers will want to try extracting the bolt intact using one of the methods covered in this guide. But if all else fails, drilling and re-tapping the hole is an option.
Now let’s look at the best techniques and tools for removing those pesky stripped out recessed Allen bolts.
Tools Needed for Removing Stripped Allen Bolts
Having the proper tools on hand will make bolt removal much easier. Here are the essential items you’ll want to have before starting:
- Set of Allen wrenches in SAE and metric sizes
- Bolt extractor kit with reverse-threaded extractors and left-handed drill bits
- Vice grips or locking pliers
- 6-point socket set
- Bench vise to secure the workpiece
- Recipro saw with metal cutting blade (for bolt head removal)
- Drill with standard and left-handed bits
- Hammer
- Center punch
- Penetrating oil
- Rags and acetone or brake cleaner
- Patience!
Don’t try to shortcut too much on tools. Having the right equipment will save you time and frustration in the long run. Now let’s look at the best techniques for removing damaged Allen bolt heads.
Method #1 – Use Bolt Extractor
Bolt extractor sets are made specifically for removing stripped or damaged fasteners. It’s one of the most reliable options for removing a rounded Allen bolt without driling it out.
Here is the basic process:
Step 1 – Clean Bolt Head
Start by cleaning any dirt, grease, or debris off the bolt head so the extractor can get optimal grip. A stiff brush followed by a solvent like acetone or brake cleaner works well.
Step 2 – Center the Extractor
Most extractors look like beefy Allen wrenches with left-hand or reverse threading. You’ll want to center the extractor as straight as possible in the bolt socket.
Using a hammer, lightly tap the extractor into the bolt while applying firm pressure. This helps seat it properly to bite into the damaged socket sides.
Step 3 – Allow Penetrating Oil to Soak
Now apply penetrating oil generously into the extractor and bolt socket. Allow 10-15 minutes for the oil to soak in and loosen things up. Reapply oil if needed while waiting.
Step 4 – Tighten Extractor
Place the nut end of the extractor into a wrench, ratchet, or vice grip. Start turning counter-clockwise to allow the reverse threads to bite and loosen out the damaged bolt.
Apply firm steady pressure and avoid stripping out the extractor itself. Patience here pays off.
Step 5 – Remove Bolt Remains
Once the damaged bolt is extracted, you can use a punch or other tool to knock out any remaining shank from the hole and clean up the threads.
Bolt extractors are extremely effective for removing a rounded out Allen bolt as long as you follow the steps properly. Just take your time and allow the penetrating oil to work before forcefully trying to extract.
Method #2 – Use Left-Handed Drill Bit
Left-handed or reverse drill bits work similarly to extractors but are a little more accessible. Again you want to utilize the reverse threading to back the bolt out counterclockwise.
Follow these steps when using a left-handed bit:
Step 1 – Center and Spot Drill Bolt
Start by centering your drill tip in the bolt socket. Use a center punch to make an indentation that guides the bit.
Lightly spot drill just to score the surface of the bolt head to help prevent walking or slipping.
Step 2 – Soak with Penetrating Oil
Apply generous amounts of penetrating oil down into the bolt socket and let it sit for 10-15 minutes. Reapply if needed.
Step 3 – Drill Bolt with Left-Handed Bit
Now swap your standard drill bit for a left-handed bit of the appropriate size. Slowly drill into the center of the bolt while applying firm pressure straight down.
The reverse threading and counterclockwise spinning action will work to back the damaged bolt out as you drill.
Step 4 – Remove Bolt Remains
Similar to using an extractor, use a punch and hammer to knock out any shank remnants still stuck in the hole so you can clean the threads.
Left-handed bits sometimes lack the gripping power of a true extractor, but work great in a pinch. Just take it slow and let the oil penetrate fully before drilling.
Method #3 – Use Vice Grips or Pliers
Locking pliers or vice grips are a simple go-to option for getting traction on a rounded bolt head. The ridged jaws can gain purchase on smooth surfaces better than wrenches.
Step 1 – Clean and Lubricate Bolt
As always, start by cleaning any debris off the bolt head and apply penetrating lubricant into the socket. Allow time for it to soak in.
Step 2 – Firmly Grip Bolt Head
Fit the vice grips over and around the bolt head so the ridged jaws gain as much grip as possible on the damaged head.
Tighten the vice grips as much as you can without crushing or further damaging the bolt head.
Step 3 – Loosen Bolt Slowly
Now gently turn the vice grips counter-clockwise while maintaining downward pressure. Take your time and work the bolt loose slowly.
You may need to periodically re-grip the rounded surfaces as you continue turning. But eventually the bolt should break free.
Vice grips or locking pliers don’t work as well on smaller bolts, but can be very effective for removing larger diameter damaged Allen heads. Just get a firm bite and be patient working it out.
Method #4 – Use 6-Point Socket
A 6-point socket (also called hex socket) with matching bolt head size can also be used to remove a stripped Allen bolt.
Here are the steps when using a 6-point socket:
Step 1 – Match Socket Size to Bolt
Examine the bolt head diameter and determine the correct metric or SAE socket size that matches it. The socket must extend over and around the protruding edges.
Step 2 – Tap Socket Onto Bolt Head
Place the socket over the bolt and align it so the 6 points match up with the bolt flanges. Then use a hammer to firmly tap the socket completely onto the bolt head.
Step 3 – Loosen the Bolt
Attach a ratchet or breaker bar to the socket. Apply medium force and turn the ratchet counter-clockwise to loosen and remove the Allen bolt.
The protruding edges around the outside of the socket head are what provides the gripping surface when using this method. When well-seated, a 6-point socket can successfully back even heavily stripped Allen bolts out.
Method #5 – Cut Off Bolt Head
If you just cannot get any of the previous methods to work, last resort is cutting off the stripped Allen bolt head and removing what’s left of the shank. Here is how to do it:
Step 1 – Stabilize the Bolt
Clamp the workpiece tightly in a vise so the damaged bolt is held motionless and ready for cutting.
Step 2 – Cut Through Bolt Head
Use a reciprocro saw with sharp metal cutting blade to slice through the bolt head and detach it from the shank.
Step 3 – Remove Shank Remains
With the head removed, you can use vise grips or locking pliers to grip and rotate the remaining shank out of the hole.
Or use a punch and hammer to drive the shank through and out the other side. Then clean up the hole’s threads.
Obviously this method destroys the bolt. But if all else fails and you absolutely must get the bolt out, cutting off the stripped head will work.
Preventing Stripped Allen Bolts
They say an ounce of prevention is worth a pound of cure. That definitely goes for avoiding stripped Allen bolts in the first place. Here are some tips:
- Use the proper Allen wrench size – Never substitute with an imperial/metric mismatched wrench. And don’t use a worn wrench.
- Avoid over tightening – Only apply reasonable torque and stop when snug. Overtorquing is a common cause of stripped sockets.
- Use impact rated sockets – For power tools, ensure the socket is rated to handle the force without rounding off.
- Lubricate threads – Penetrating lube helps prevent seizing and stripping during tightening/loosening.
- Use quality hardware – Inferior grade bolts are more prone to stripping out. Spend a little more for good stuff.
- Take care with soft metals like aluminum – It’s easier to strip soft bolt heads than steel.
- Have patience! – Don’t force things. Stripping often happens when impatience leads you to overexert.
Paying attention to these tips will go a long ways towards preventing headaches from dealt with rounded out Allen bolts. But if one does become damaged, use this guide to get it removed without hassle.
Frequently Asked Questions About Removing Stripped Allen Bolts
Below are answers to some commonly asked questions about dealing with damaged recessed Allen bolts:
What is the easiest way to remove a stripped Allen bolt?
Using a good bolt extractor set is generally the quickest and easiest method for removing a rounded Allen bolt, followed by using left-handed drill bits. Both utilize reverse threads to back the bolt out.
What can I use if I don’t have bolt extractors?
Vice grips or locking pliers are handy alternatives. Get a very firm bite on the bolt head and slowly work it out by turning counterclockwise while maintaining pressure.
How do I remove a stripped Allen bolt without tools?
The only real option is to first cut off the head with a hacksaw or reciprocro saw. Then you can try gripping and turning the shank with pliers, or punch it all the way through.
How can I prevent my Allen bolts from stripping in the future?
Use proper fitting Allen wrenches, avoid over tightening, lubricate threads, get quality hardware, and take extra care with soft metals like aluminum. Also have patience and don’t force things.
Why does using a 6-point socket work to remove them?
The ridges inside a 6-point socket allow it to gain purchase on the exterior edges of the bolt head. When firmly seated, those grip points allow it to turn even a heavily stripped Allen bolt.
Conclusion and Summary
Dealing with a stripped or rounded out Allen bolt head can be incredibly frustrating. But armed with the right tools and knowledge of techniques like those covered here, you can remove even badly damaged recessed Allen bolts without having to completely drill them out.
To summarize, the best methods for removing stripped Allen socket head bolts are:
- Use a bolt extractor set with reverse threaded extractors
- Drill with left-handed or reverse threaded bits
- Firmly grip bolt head with vice grips or locking pliers
- Tap a 6-point socket over the bolt head for grip
Penetrating oil is critical for every method, so be sure to generously lubricate and allow time for it to soak in first. Remain patient, apply steady pressure, and work the bolt slowly loose.
Following the detailed steps and tips in this guide, you can successfully remove most stripped Allen bolts without further damage or needing to redrill the hole. Just utilize the proper technique for each situation. And you can prevent future headaches by taking measures to stop bolts from stripping in the first place.