How much torque breaks a rusty bolt? Use a torque bar to prevent breaking?

[jamespharvey20]

Newbie, starting to work on my own cars, and I'd like to use air tools to save wear and tear on my wrists and arm muscles, and not aggravate back pain from a car accident years ago.

There are many discussions about making sure not to over-tighten bolts with air tools. I understand I need to restrict the pressure given to the air tools, and perhaps even use torque extension bars/sticks with an impact driver at least in the higher ranges they usually come in like 65-150 ft-lbs. (What is a torque bar? It's an extension that flexes at a specific torque amount, to prevent giving more torque to the bolt.)

There are also many discussions about the risks of air tools breaking a bolt that's rusted on.

I'm wondering if I could use torque extension bars/sticks with an impact driver when removing a rusty bolt, to prevent most of the breaks that might happen. Assuming they work in reverse, anyway, which I'm hoping they can either for this purpose or left handed bolts.

My hope is to let the impact driver hit the bolt with a high but limited amount of force, and if that doesn't work, then try a torch or penetrating oil. Basically, to avoid torching or oiling when it's not necessary.

A couple of YouTube videos (I can't post links yet, but YouTube search for Penetrating Oil on channel "Project Farm", including "Episode 2") comparing various things like a torch, penetrating oil, CRC, acetone/ATF homebrew, etc, showed at least in those tests that the maximum needed without anything applied was about 132ft-lbs. (Although, an article by Machinist Workshop Magazine about 30-year old bolts shows way more, 516ft-lbs.) I'm hoping limiting the impact driver to 150ft-lbs might let it give it a shot, and cut down most of the risk of breaking it. I'm not seeing torque bars/sticks anywhere over 150 ft-lbs. But, then again, maybe 150 ft-lbs is limiting it way too much, if in the real world that won't be enough but is still far from what would be needed to break it.

I guess it would be worth knowing the lowest torque that most rusted bolts break at, basically a "safe zone", but I haven't had luck finding someone looking at that.

 

[ZRX61]

If it breaks when you remove it, it needed replacing anyway.

 

[plinker]

The amount of torque needed to break loose a rusty fastener can vary a lot depending on how stuck it is. I dont think you can really put a number on it. Sometimes an impact will remove what a ratchet wont, other times a ratchet will remove what a impact wont. Not sure why, just an observation over time. Sometimes rattling a bolt/nut with an impact on a low setting can help, but not often IME. A hand impact driver typically works better, especially for screws like those holding brake rotors.

Many times working a bolt/nut back & forth with some sort of penetrating oil will work well, main reason to use the oil is to keep the threads from seizing. The nut/bolt may break loose easy then get stuck & gall on the rusty threads. Wire brushing (die grinder/other) the threads helps. Heat can usually make a difference as well.

Weld nuts and clip nuts that are rusted are best heated and oiled if possible, using an impact on a rusted one usually means the clip will break and you'll have a free spinning stuck fastener which is a complete joy to deal with.

Some stuff will break just because, whether using an impact or ratchet. There really isnt a good substitute for experience in this case. Using heat, penetrating oil & cleaning exposed threads as needed will reduce, but not eliminate the occurrence of **** breaking.

YMMV.

 

[giants]

Weld nuts and clip nuts that are rusted are best heated and oiled if possible, using an impact on a rusted one usually means the clip will break and you'll have a free spinning stuck fastener which is a complete joy to deal with.

Thanks for the great post and great reply.

plinker, do you mean that, all things equal, welding a nut that can be removed is the best strategy?

 

[sberry]

You want the air gun to hit.

 

[fatfillup]

Hand impact driver for me on questionable bolts.

Unfortunately, the only way to learn how to not break bolts is to experience breaking some

 

[giants]

Hand impact driver for me on questionable bolts.

Unfortunately, the only way to learn how to not break bolts is to experience breaking some

Thanks for the great idea!

What brands and models do you recommend?

 

[454ragtop]

Good judgement comes from experience, experience comes from bad judgement.

 

[DakotaMan]

I have used this tool that connects to an air hammer with good results. Instead of a chisel, it's almost like a 1/2" extension but in the middle there is a hex part.

==||==[[[

That's the best I could draw. The [[ -> is where a socket would go and the || is a section you turn using a combination wrench while the air hammer is going. I think it acts like a weak impact or something. If I can get it to move, then I add heat and penetrating oil over the course of a day or so.

 

[RedneckWelder]

I have used this tool that connects to an air hammer with good results. Instead of a chisel, it's almost like a 1/2" extension but in the middle there is a hex part.

==||==[[[

That's the best I could draw. The [[ -> is where a socket would go and the || is a section you turn using a combination wrench while the air hammer is going. I think it acts like a weak impact or something. If I can get it to move, then I add heat and penetrating oil over the course of a day or so.

Called a shake and break. Mayhew sells them

Best thing for rusty fasteners is an O/A torch or if unable to use one then a bolt induction heater. I hit them with lots of Kroil while still hot and smack them with a hammer to break the rust bond

 

[DakotaMan]

Called a shake and break. Mayhew sells them

Best thing for rusty fasteners is an O/A torch or if unable to use one then a bolt induction heater. I hit them with lots of Kroil while still hot and smack them with a hammer to break the rust bond

Yes, that is it...thanks.

I've wanted an induction heater but they are so expensive for a DIYer.

 

[PCustoms]

Everyone realizes this is likely a spam post, correct?

 

[jamespharvey20]

Everyone realizes this is likely a spam post, correct?

Not sure why you'd think that.

But, it isn't. I have a 2008 Town & Country, and until 2 weeks ago, hadn't even changed oil before. I'm a programmer and former computer repairman and have done a lot of DIY home repairs, but just never spent the time to learn anything about cars.

It was diagnosed with seized rear calipers from rust needing them to be replaced along with rotors and pads, front wheel bearings that are going bad, and has a lot of other small stuff bad with it like rear wiper doesn't work, and the driver's lock button doesn't work. The oil pan rusted through a pinprick size hole. (Yeah, they often don't do that, but it's a semi-known problem on Dodge/Chrysler minivans around this year, and you can see a pinprick of sunlight holding it up.) When all this hit around the same time, and repair cost was getting closer and closer to value of vehicle, I decided it was finally time to start doing the easier DIY car repairs myself. Oil pan, oil change, and rear brakes successfully changed. I've discovered a few other things that need fixing like the exhaust manifold heat shield has come apart (OEM shield is 2 pieces of something that feels like cardboard bolted together, and its bolt holes have disintegrated) and the integrated flex connector on the catalytic converter has one of its seals loose and way out of position.

So, back to my question at hand, I was just looking for a way to try to use an air tool on all bolts to remove them, and if that didn't work, to then try a torch or penetrating oil.

I figured it made sense to try something before penetrating oil, so I wasn't using it on absolutely every bolt I came across that didn't actually need it.

As I said, I don't really want to use hand tools fighting with rusty bolts anymore. The rear caliper bolts were a huge pain even with PB Blaster, and aggravated my back which was injured in a car accident years ago. Not yet having learned about problems doing this or realizing the wrench could even break, tried a long pipe on a 3/4" drive ratchet wrench and broke the internals of the ratchet mechanism. I really thought that noise was the rusty bolt finally turning, but nope! (I know now to use a breaker bar...) So, I want to continue doing these easier jobs myself (I know it wouldn't be worth me handling anything complicated like with heavy diagnosis needed) but minimize pain on future jobs.

When I first heard about a bolt being able to break from an impact driver, that sounded terrifying to me. So, I was looking for a way to use air tools but minimize the chance of it happening. But, it looks like the consensus is it's just going to happen at some point and be part of my learning experience, and maybe I don't have to fear it happening quite as badly as I was originally.

I REALLY appreciate everyone's responses about methods they use. I tend to over-analyze and over-think things before jumping into them and making mistakes that will be very costly.

 

[American Locomotive]

In my experience it's pretty rare to break a bolt removing it with an impact. Usually it either loosens up - or it doesn't. It's not uncommon to break them tightening with an impact though.

However there are two types of impact mechanisms these days: Twin-hammer, and impact-driver mechanisms. The impact-driver mechanisms have a big spring in them, which pre-loads everything and allows you to drive screws. In my experience, those types of mechanisms are far more likely to break screws and bolts when removing them. Most "big" impacts are twin-hammer, while anything with "driver" in the name usually has the spring mechanism.

 

[MattT]

I figured it made sense to try something before penetrating oil, so I wasn't using it on absolutely every bolt I came across that didn't actually need it.

On a 12 year old chrysler in michigan they all need it. Hose everything down with Liquid Wrench ahead of time so it has time to work. The stuff is like 3 bucks a can so you ain't gonna go broke "wasting" a can or two.

 

[plinker]

In my experience it's pretty rare to break a bolt removing it with an impact. Usually it either loosens up - or it doesn't. It's not uncommon to break them tightening with an impact though.
.

Many times it's beneficial to remove with an impact then tighten by hand or use an air/electric ratchet, then torque. Rattling something on tight with an impact isnt the best method normally. Knowing the limits of the tools you're using is important.

Sizing the tools needed to remove fasteners is something to keep in mind, the smaller the drive size means the less likely something will break with everything being equal.

Now, sometimes you may want to break off a bolt (depending on the situation) and using a 1/2 drive impact on an 8mm bolt is a good way to achieve this. Example, I changed out some shocks this morning, the lower mount had two studs and lock nuts holding the shock to the control arm. The new shocks came with nuts & bolts for installation, so it didnt matter if they got broke off or not. As it was, only one did.

 

[plinker]

plinker, do you mean that, all things equal, welding a nut that can be removed is the best strategy?

Weld nuts are basically a nut welded or crimped to say a sub frame or similar, the piece is then permanent and isnt supposed to break off, ete.. but leverage can do interesting things at times. These are just the nuts (one of many styles), couldnt find a good picture of what they attach to.
https://www.bing.com/images/search?view=detailV2&id=0DAA3BCFF3E503274060E1D0122AE8820DEE7D95&thid=OIP.3nqIc7ymgv0PGYO76J6p-AHaFH&mediaurl=http%3A%2F%2Fg02.a.alicdn.com%2Fkf%2FHTB1tpT7LFXXXXXXXpXXq6xXFXXXX%2FStainless-steel-weld-nut-four-claws-spot-welding-nuts-DIN928-410-full-range.jpg&exph=313&expw=453&q=Spot+Weld+Nuts&selectedindex=46&ajaxhist=0&vt=0&eim=1,2,6

This is a clip nut (also called U nut), very common, made in several styles.
https://www.bing.com/images/search?view=detailV2&id=78BCE27FF39BAA0D95AAC159876F46B478C828A0&thid=OIP.RthMp_3ucxl_u2NtvVjWuQHaFM&exph=310&expw=442&q=Weld+Nut+Installation&selectedindex=48&vt=0&eim=1,2,6

This is a cage nut/captured nut, also common. Basically a square nut in a sheetmetal cage to keep the nut from turning. Depending on how seized it is , the nut can be broke free of the cage and cause problems removing. Heat & oil will be you're friend dealing with these.
https://www.bing.com/images/search?view=detailV2&id=FB29980A8D17CD93908E58CF092FA54BCBBD1F4A&thid=OIP.oMPJKw0Qe4A-okvcrF_1ZQHaED&exph=263&expw=480&q=Weld+Nut+on+frame&selectedindex=60&vt=0&eim=1,2,6

Now welding a nut to broken off/rounded fastener is a very common and effective method of removing said damaged fastener though it can take practice to do so. If the fastener is rusted in place an easy out type of extractor isnt likely going to get it out IME.

 

[WVBrady]

In my experience it's pretty rare to break a bolt removing it with an impact. Usually it either loosens up - or it doesn't. It's not uncommon to break them tightening with an impact though...

My experience has been just the opposite. Most wrenches are adjustable for torque in the clockwise direction and you should have a good idea of what torque you should be using for a given fastener. If not, you could find online a table for a given size and grade of fastener. However, in the reverse direction, most wrenches give you their maximum, which is sometimes more than the max in the forward direction. To reduce that, you could use the torque sticks or lower the air pressure.

 

[American Locomotive]

My experience has been just the opposite. Most wrenches are adjustable for torque in the clockwise direction and you should have a good idea of what torque you should be using for a given fastener. If not, you could find online a table for a given size and grade of fastener. However, in the reverse direction, most wrenches give you their maximum, which is sometimes more than the max in the forward direction. To reduce that, you could use the torque sticks or lower the air pressure.

It has to do with how an impact delivers its energy. An 1100 lb-ft impact is not actually generating 1100 lb-ft of torque (otherwise it'd twist your hand right off your arm). If you put a torque-meter on the end of an impact, you would not see numbers anywhere near that high. That's why to measure impact torque, you need a special test rig that basically has a screw clamping down on a force gauge.

When you see the torque ratings on an impact, they're basically saying "For a given bolt, it will achieve the same clamping force as if you tightened the bolt to 1100 lb-ft with a torque wrench".

Sometimes with smaller bolts, or bolts that were damaged to begin with, the impact can shear the bolt just from the impact energy.

 

[lardy1]

If you are as inexperienced as you say, maybe just invest in a fifteen dollar hand impact wrench and try to gain insight and experience without breaking the bank or the bolt.

 

[Gladiator]

Since you just did a brake job you probably noticed that you don't have enough room to use an impact wrench except for wheel removal. Using a 1/2" breaker bar with the exact length extension plus a pipe cheater will loosen most. You can use a ratchet after it is broke loose. You need a torque wrench for finale tightening.
As far as impact wrench goes, the plug in are the cheapest for given torque. Pneumatic are often adjustable by a knob. The Cadillac is a Milwaukee Fuel battery powered.
Good luck wrenching! Alot of us became mechanics by necessity.

 

[sberry]

I use 1/2 impact for all of it.

 

[Shark Pilot]

The key to doing this type of work, especially on an older vehicle in the rust belt, is to do everything possible to get the odds of success in your favor. There are two types of fasteners - those that come off easily and those that don't. Always best to assume from the start that you are dealing with the latter. So definitely wire brush the threads and apply penetrating fluid beforehand, even a day before. The difference between good quality wrenches and sockets is usually only realized at the margin, ie when dealing with really difficult fasteners. Smaller sizes like 10 to 14mm tend to cause more problems than larger ones. I find a smaller and more compact cordless 1/4" hex impacts with 1500 inch-lbs work pretty well on the smaller sizes. But definitely penetrating fluid and even heat if you think you will have a problem is best to do before you round or snap a fastener.

 

[RKA]

I'll offer an unpopular opinion, but I feel like it needs to be said. I get the sense you're looking for a textbook solution that will work and you might have the idea that air tools are the cure all. Unfortunately, it just doesn't work like that, and you can get an idea reading the posts in this thread. Rust creeps into everything in a rust belt car, not just nuts and bolts. So even if an impact gun would solve one rusty problem, by definition it can't solve all over them, since it only deals with nuts and bolts. Heat, vibration, penetrating oil and force are all needed to tackle each issue. And each rusty encounter might be a little different. A torch can be effective in one, but in another it will cause more damage to perfectly good parts.

This isn't to say it can't be done, but dealing with these rusty cars day in and day out almost earns a mechanic an honorary certification. A pro could handle rusty **** far more efficiently than I could. And it can be taxing on your body, even if you have a good assortment of tools and options available to you. I'll applaud you for wanting to learn and try. But given your stated limitations, if it's at all possible, get something a little newer that's less taxing to maintain yourself. Save your body from all this extra trauma. As you work on that (newer) car, add anti seize and proper lubrication (fluid film) to common pain points to limit the effects of salt. This way it will be much easier to work on as it ages. The car you're starting with sounds like it's far enough gone that everything will be a struggle. The brand has been historically unreliable in my eyes as well. And the worst part is, most of the time you'll start a job thinking you can do it...and then get halfway into it only to realize it's a lot more work than you bargained for and it has to go to a shop (possibly on a flatbed). So you've taken a physical toll trying to do the job, lost time trying to do the job, and still paid a shop (and tow truck?) to do the job saving nothing.

 

[clubairth]

With 12 years in Michigan the heart of the rust belt heat is your best friend.
At this point the only thing these fancy impact tools do is break things.

Remember the pro's use impacts for time savings, we are not pros and the danger of breaking things is far worse than spending a little more time. I have stopped using any impact tools on rusty bolts. Unless you want to break them and that can be a faster repair method sometimes too.

If your interested in penetrates you might try Acetone and transmission fluid. Second best for me is Kroil. Plan on replacing all fasteners whenever you get them off.

I don't envy you guys in salt area's either!
.
.
.

 

[fatfillup]

Thanks for the great idea!

What brands and models do you recommend?

I like Snap on's 3/8 hand impact driver PIT120 but realize, I buy and sell used tools so I am not paying truck price. I will say after using one and having great success, if need be, I would pay retail for one. The driver itself is $76 but the kit with the bits is $305

https://shop.snapon.com/product/Impact-Drivers-(3-8")/8-pc-3-8"-Drive-Impact-Driver-Set/208EPIT

 

[matt_i]

Somewhat jokingly, I feel like if you get a new-er car you should take apart the chassis, 1 bolt at a time and put anti-seize on every fastener and then right back in. I feel like I'm doing that anyway, just one set of parts at a time. The cars of my youth (mid 80s models) were horrible compared to what I see now. I learned to plan to basically replace every bolt I was going to touch. The old fasteners had zero corrosion protection on them. The newer ones mostly seem like the first 10 years are pretty good then it goes downhill.

As mentioned there are many methods. If you have the time to soak down the affected bolts with Kroil (etc) every day for a week beforehand the job will go much easier. I've also had good luck melting paraffin wax into threads which were previously heated with the torch. However you have to let them cool just a bit. The red hot steel will seemingly vaporize the wax, reducing its effectiveness until it gets somewhat cooler and can melt and run down into the recess between the threads.

 

[DGersic]

Newbie, starting to work on my own cars, and I'd like to use air tools to save wear and tear on my wrists and arm muscles, and not aggravate back pain from a car accident years ago.



There are many discussions about making sure not to over-tighten bolts with air tools. I understand I need to restrict the pressure given to the air tools, and perhaps even use torque extension bars/sticks with an impact driver at least in the higher ranges they usually come in like 65-150 ft-lbs. (What is a torque bar? It's an extension that flexes at a specific torque amount, to prevent giving more torque to the bolt.)



There are also many discussions about the risks of air tools breaking a bolt that's rusted on.



I'm wondering if I could use torque extension bars/sticks with an impact driver when removing a rusty bolt, to prevent most of the breaks that might happen. Assuming they work in reverse, anyway, which I'm hoping they can either for this purpose or left handed bolts.



My hope is to let the impact driver hit the bolt with a high but limited amount of force, and if that doesn't work, then try a torch or penetrating oil. Basically, to avoid torching or oiling when it's not necessary.



A couple of YouTube videos (I can't post links yet, but YouTube search for Penetrating Oil on channel "Project Farm", including "Episode 2") comparing various things like a torch, penetrating oil, CRC, acetone/ATF homebrew, etc, showed at least in those tests that the maximum needed without anything applied was about 132ft-lbs. (Although, an article by Machinist Workshop Magazine about 30-year old bolts shows way more, 516ft-lbs.) I'm hoping limiting the impact driver to 150ft-lbs might let it give it a shot, and cut down most of the risk of breaking it. I'm not seeing torque bars/sticks anywhere over 150 ft-lbs. But, then again, maybe 150 ft-lbs is limiting it way too much, if in the real world that won't be enough but is still far from what would be needed to break it.



I guess it would be worth knowing the lowest torque that most rusted bolts break at, basically a "safe zone", but I haven't had luck finding someone looking at that.

I’ve been working on rusty cars for 30+ years. Hit it with your choice of penetrating oil, then hit it with an impact gun. If it breaks loose, great. If it breaks off, and it will, swear at it, then start working on removing the remains.

I would never intentionally limit torque applied on removing something.



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[DGersic]

Not sure why you'd think that.

But, it isn't. I have a 2008 Town & Country, and until 2 weeks ago, hadn't even changed oil before. I'm a programmer and former computer repairman and have done a lot of DIY home repairs, but just never spent the time to learn anything about cars.

It was diagnosed with seized rear calipers from rust needing them to be replaced along with rotors and pads, front wheel bearings that are going bad, and has a lot of other small stuff bad with it like rear wiper doesn't work, and the driver's lock button doesn't work. The oil pan rusted through a pinprick size hole. (Yeah, they often don't do that, but it's a semi-known problem on Dodge/Chrysler minivans around this year, and you can see a pinprick of sunlight holding it up.) When all this hit around the same time, and repair cost was getting closer and closer to value of vehicle, I decided it was finally time to start doing the easier DIY car repairs myself. Oil pan, oil change, and rear brakes successfully changed. I've discovered a few other things that need fixing like the exhaust manifold heat shield has come apart (OEM shield is 2 pieces of something that feels like cardboard bolted together, and its bolt holes have disintegrated) and the integrated flex connector on the catalytic converter has one of its seals loose and way out of position.

So, back to my question at hand, I was just looking for a way to try to use an air tool on all bolts to remove them, and if that didn't work, to then try a torch or penetrating oil.

I figured it made sense to try something before penetrating oil, so I wasn't using it on absolutely every bolt I came across that didn't actually need it.

As I said, I don't really want to use hand tools fighting with rusty bolts anymore. The rear caliper bolts were a huge pain even with PB Blaster, and aggravated my back which was injured in a car accident years ago. Not yet having learned about problems doing this or realizing the wrench could even break, tried a long pipe on a 3/4" drive ratchet wrench and broke the internals of the ratchet mechanism. I really thought that noise was the rusty bolt finally turning, but nope! (I know now to use a breaker bar...) So, I want to continue doing these easier jobs myself (I know it wouldn't be worth me handling anything complicated like with heavy diagnosis needed) but minimize pain on future jobs.

When I first heard about a bolt being able to break from an impact driver, that sounded terrifying to me. So, I was looking for a way to use air tools but minimize the chance of it happening. But, it looks like the consensus is it's just going to happen at some point and be part of my learning experience, and maybe I don't have to fear it happening quite as badly as I was originally.

I REALLY appreciate everyone's responses about methods they use. I tend to over-analyze and over-think things before jumping into them and making mistakes that will be very costly.

The OEM heat shield was probably aluminum. When mounted to steel, in the presence of salt water, electrolysis happens, and the aluminum turns to ****.

Penetrating oil is your friend. Use it first. Buy it in bulk when a local store has a sale or you have a coupon. I’d buy it by the dumpster sized vat and dip my whole truck in it if I didn’t think the EPA would have issues.

Spray and tap with a hammer. Some really stuck ones you may want to do this repeatedly for a few days. The hammer helps break the bond, the oil helps let it turn.

The impact gun helps with breaking the rust bond as well.

Your next best friend will be anti seize, for bolts that you don’t want to have to break loose a second time.

An air hammer can also be helpful getting rusty stuff loose or apart. So can a small sledge hammer.

Use eye protection. Googles, not just glasses. Rusty bits of steel in your eyes is something you want to avoid.




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