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Sarah Forst posted on May 10, 2010 14:47 
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| Don't get 12 point sockets, those suck for rounding off bolts, unless of course you have 12 point bolts, not likely unless you have an aircraft or use a lot of super high rated AN bolts and stuff. Get 6 point sockets with a flank drive profile. This is the least likely to round off a nut and can even take off mildly rounded off nuts. |
Maybe the best way to prevent rounding off a bolt is to use the correct tools. I prefer to use 6 point sockets with a flank drive cam profile to remove stubborn bolts. I don't understand why 12 point sockets are more common but a good six point with the cam profile goes a long way in not rounding off heads. Snap-On pioneered this sort of socket but now Craftsman and others make similar products.
Once you’ve rounded a nut or bolt, you’re screwed, right? Not really, but first you need to remove it. If a bolt extractor kit like the ones by Craftsman or Irwin doesn’t work, there are a few techniques I’ve had luck with in the past. You can soak a rounded nut/bolt in penetrating oil like Liquid Wrench or PB Blaster (my personal favorite is Aerokroil but its kind of hard to find) for about 5 minutes before attempting to loosen it with the closest sized open-ended wrench. Tapping the head of the bolt after applying Penetrating oil can help as well. Penetrating oil will reduce how much force is needed to remove the bolts. Heating a stuck bolt until red hot with a Mapp gas or propane torch, then reapplying penetrating oil often can help break loose a badly stuck bolt. Of course make sure that there are no other parts nearby that heat or flame might damage before trying this.
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| Stick a big flat bladed screwdriver between the flat side of the nut and the wrench for more leverage. |
If the head of the bolt is impossibly rounded off you can use channel lock pliers or vice grips to grab the nut/bolt so tightly that it will twist off. There are special channel lock pliers that have rounded jaws perfect for this kind of problem. Or use a sharp chisel or cut off wheel to slot the top of the nut/bolt and then use a flat head screw driver to twist it out. If it’s rounded on one side, use the blade of a flat head screwdriver as a wedge between the wrench and the flat side of the bolt for more leverage. You can also try filing down the side of the rounded nut/bolt with a metal file until it is flat, providing two flat sides on opposite sides of the bolt head. And as a last resort, you can always cut off the head of the nut/bolt carefully, provided you have some way to remove the remaining piece of the nut/bolt. Obviously, never reinstall a rounded nut/bolt or one that seems it will become rounded if you look at it funny.
Monday, May 10, 2010 5:37 PM
Kroil is the best stuff in the world. My dad has a bottle from 20 years ago and it really breaks bolts loose. the problem with Kroil is that it's only really good if you pre-treat and let the bolt sit overnight. PB Blaster is much quicker. Also, heating the bolt and melting a candle on the end can help loosen it. Another trick for really sticky bolts is to retighten the bolt a tiny bit before trying to loosen it. Tightening the bolt just a little bit will break the rust off and make it easier to remove. Obviously you don't want to overdo it because you can just snap the bolt, but a little tightening first can fix the bolt.
Monday, May 10, 2010 5:51 PM
This only goes to further confirm that I have the wrong set of tools. Nearly all my sockets are 12pt (except for the smaller sized ones) and all my combination wrenches have 12pt box ends. Booo. Yes, I've rounded my share of nuts... and used my torque wrench for loosening ("hey, the long handle will make it easier!"). =( Any tips for stripped screws? I actually snapped a bolt using a torque wrench... I foolishly trusted the wrench over my common sense and didn't realize my torque wrench doesn't work well in its lower range (I think it is marked 20-120 lb-ft and I was tightening to 27 or something). That was a lesson learned and put me out of a car for a couple days while I waited for a new bolt to arrive from the Honda dealership (I also discovered that Honda parts departments are closed on Sundays... lame when you need a part NOW). How do you determine if a socket set has the "flank drive cam profile" that's mentioned? I was quickly checking Amazon and there usually isn't much detail on the socket profile, aside from 6 or 12pt and standard or deep sized. Also, what do you recommend for treating lightly rusted nuts and bolts after they've been removed? Any recommended way to remove some of the built up corrosion and make future removal easier?
Monday, May 10, 2010 7:27 PM
If a bolt/nut is rusty, another tip is to wire wheel it clean. I've found this very effective, if you have access to it.
Tuesday, May 11, 2010 7:00 AM
Unfortuantely, sometimes you just have to beat it with a hammer and chissel.
Tuesday, May 11, 2010 10:19 AM
Shops use air tools because theyre fast. Fast = money when youre working flat rate.
Tuesday, May 11, 2010 1:53 PM
Don't spray penetrating oil then attempt to use a torch to heat it, you'll have a fire on your hands. Heat, then oil, much like liquor before beer.
Tuesday, May 11, 2010 9:07 PM
+1 for Davio! Tightening the bolt a little bit at first will DEFINITELY help on really stuck bolts like crankshaft pulley bolts. I hit the crankshaft pulley bolt on my 1.6 Civic all day full blast with my IR 1/2" impact wrench and it didn't do a DAMN thing.... until I gave it a quick trigger pull on the "rightey-tightey" setting first. Came right off after that! As for not rounding off bolts in the first place, the number one suggestion I have is to NEVER USE OPEN ENDED WRENCHES if you don't have to! They are terrible and will round a bolt off super fast. I have been working on cars for almost 10 years and the only time I have ever used them is when there's just no space, and even then it was mostly just to loosen something that was already broken free. You can get the box end in almost anywhere that the open end can fit, so just use that! I even found a set of wrenches where the box end isn't angled like on the craftsman set, that helps too.
Wednesday, May 12, 2010 10:40 AM
To speedball3: About choosing the right profile, the corners are radiused so the torque is applied on the side (“flank”) of the fastener and away from the corner of the nut/bolt, helping to keep from rounding bolts or breaking the chrome plating or polish on things like lug nuts. Besides Snap On who uses the “flank drive” name, look for Suregrip, Headlock (craftsman), Surface drive, Optitorque (matco), etc. These 6 point sockets usually have some sort of dual diameter profile where it is radiused, so it appears to have a tighter diameter where the torque wrench is connected and increases out towards where the fastener sits, which helps direct the torque to the sides of the fastener. And I know *why* shops use air tools (fast) but it's like finishing fast or finishing first- it doesn't take long to get the proper torque applied and not doing so could have some serious consequences. +1 for Wrecked. I love my BFH. When it doubt, pound it out?
Wednesday, May 12, 2010 8:51 PM
The other problem with open-end wrenches is that every once in a while the bolt is on there so tight, you just break the wrench. It's happened to me a few times, even with Craftsman tools. Sockets are the way to go unless you just can't fit one in. Craftsman also makes wrench adapters for sockets, so sometimes you can use one of them in awkward spots. Thanks for the compliment 13BD16.
Monday, May 17, 2010 9:42 PM
I have to say that 12 point sockets were very useful way back Way Back when. Before Snap On invented their super fine ratcheting ratchets. They would help in the super tight spots where you could no get a ratchet to click over with a 6 point socket due to the limit of handle movement. I agree that open ended wrenches stripe bolts. Speedball3 Craftsman has this tip kit for stripped screws. It basically grinds into the screw until it locks up. The screw you remove is basically destroyed. But it works great the times I've used it. http://www.craftsman.com/shc/s/search_10155_12602?vName=Tools+%26+Equipment&keyword=screw+remover&sLevel=0
Monday, May 17, 2010 9:55 PM
I could be wrong because I haven't wrenched in a while but I thought you were supposed to leave the clicker torque wrenches set to zero when not in use.
Sunday, May 30, 2010 10:33 PM
In the rust belt, bolts often need to be "walked" out. Tighten slightly, then loosen until you feel bolt-breaking resistance, then tighten again. It takes a calibrated forearm, but it can be done. I've saved soooo many bolts up here in MN its ridiculous. Penetrating oil helps, but it doesn't get around the obvious. Some bolts are better of being replaced from the get-go. On Subaru's, I know the few bolts I'd rather spend $20 replacing than take four hours saving.
Thursday, February 24, 2011 7:13 PM
@Rockwood Most of the current aerosol penetrating oils are non-flammable. I know PB blaster won't catch fire even if you spray it on while you're still holding the torch on the bolt. It sometimes will put the torch out though, I think CO2 is used as the propellant. When I suspect a bolt might be seized in an aluminum part I proactively tap the bolt head with a hammer, one sharp blow usually, and the bolt comes out easily on the first try. I also like to spray pentrating oil on exhaust manifold bolts (or rusted engine bolts) a few days before I plan to remove them, then drive the car, or at least run the engine to heat the bolts up a few times. I've never snapped a bolt on a car that I was able to do this on.
 
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