Hand tools vs impact tools: which are better at protecting fasteners?

[AEAdam]

This ain’t the my mechanic stripped my lug nuts and my wheel fell off thread. This is the whether or not power tools should even be used on nuts and bolts thread. I can assure you thousands of mechanics and techs remove and install dump truck loads of hardware daily without any damage. I worked flat rate for 25 years and the overwhelming majority of techs did very good work. The very nature of the business weeds out underperforming or ham fisted types. If you frequent a shop that messes your ride up a lot, it’s time to find a new shop.

A flat rate mechanic once told me the torque spec for my MB 560 SEL brake caliper bolts was BRRPPT BRPPPT. I get it. You do what you must to make a living. But let’s not confuse that with best practices.

I’ve often said auto mechanics are a lot like MDs. They diagnose with a mixture of data and experience. They get their hands dirty doing things no one else wants to do. They are tool users, sensitive to symptoms being misleading, underlying conditions and lastly: provide care customized to the patients age and condition.

I personally treat every car like it’s a mclaren super car, worthy of the best possible care. I clean as I go and leave the camp site far better than I found it.

 

[M635_Guy]

A flat rate mechanic once told me the torque spec for my MB 560 SEL brake caliper bolts was BRRPPT BRPPPT. I get it. You do what you must to make a living. But let’s not confuse that with best practices.

Exactly. If a tech told me that I'd never darken the door that that shop again. Luckily I've got a shop where the guy does it right because he does it right.

 

[CoogarXR]

I might be in the minority, but I only use impact tools for loosening. I don't wrench for a living though.

 

[AEAdam]

I might be in the minority, but I only use impact tools for loosening. I don't wrench for a living though.

Same.

Exactly. If a tech told me that I'd never darken the door that that shop again. Luckily I've got a shop where the guy does it right because he does it right.

last german car I did (VW) had angles spec’ed for those bolts. That tells me, don’t guess.

That mechanic had better feel for his gun than I will ever have. But the “git er dun quick and dirty” attitude doesn’t sit well with me. I keep my cars too long So it’s likely I’ll be back to that job that mechanic did. For the record, that shop let me work there on a lift on saturdays, and I don’t want to bash them. But it was an interesting insight into their world.

SO: This isn’t a bash the flat rate guys thread as redwrench rightly pointed out. I see this as best practices. I think using impacts for installations is risky AF. That’s a risk I’m not willing to take to save a few minutes.

As I said earlier, I think impacts have their place and can be gentle on both fasteners and your hands. I do not own a 3/8” gun, but I suspect if I had one I’d use it more. Thoughts?

I’ve long praised my bottom rated Bosch gun, which can now be considered a mid torq gun. It’s lighter and easier to control thss ask the big guns out there. My SO gun is a heavy beast; good when you need it, but clumsy otherwise.

 

[M635_Guy]

Same.

last german car I did (VW) had angles spec’ed for those bolts. That tells me, don’t guess.

That mechanic had better feel for his gun than I will ever have. But the “git er dun quick and dirty” attitude doesn’t sit well with me. I keep my cars too long So it’s likely I’ll be back to that job that mechanic did. For the record, that shop let me work there on a lift on saturdays, and I don’t want to bash them. But it was an interesting insight into their world.

SO: This isn’t a bash the flat rate guys thread as redwrench rightly pointed out. I see this as best practices. I think using impacts for installations is risky AF. That’s a risk I’m not willing to take to save a few minutes.

As I said earlier, I think impacts have their place and can be gentle on both fasteners and your hands. I do not own a 3/8” gun, but I suspect if I had one I’d use it more. Thoughts?

I’ve long praised my bottom rated Bosch gun, which can now be considered a mid torq gun. It’s lighter and easier to control thss ask the big guns out there. My SO gun is a heavy beast; good when you need it, but clumsy otherwise.

I love my impacts - no way I'd do a lot of what I do without them. They're obviously great for "off", and for "on" there's a mode to run it down until it starts to tighten and stop. For lugs, I'll pop into Mode 1 and give it a couple of pops, which generally puts me a few cranks away with a torque wrench to tighten to proper torque. I skip the mode 1 thing for stuff like brakes and just go for the torque wrench after the soft-run-in.

I've got no issues with a tech using tools to make their job go faster. I do have a problem with abuse of my property. I don't give a flip how good they think they are or how they come to the decision that torque specs don't matter. If they wrench like that, they're not wrenching on my car. I'm not saying I demand a torque wrench on everything - I do trust my guy to know the right snug for an oil drain bolt or the filter housing (I don't trust myself for those things, but I'm not a pro). But for some stuff the ugga shouldn't be setting torque, at least for what I'm paying for, and I want stuff like spark plugs, oil drain bolts, lugs, brake calipers, etc. torqued properly. I keep my cars a long time too, and ultimately I'm picky about certain things. That's one of them.

 

[Leaflessshadetree]

A flat rate mechanic once told me the torque spec for my MB 560 SEL brake caliper bolts was BRRPPT BRPPPT CLICK. I get it. You do what you must to make a living. But let’s not confuse that with best practices.

I think he left off the most important part. FIFY

 

[2ndGearRubber]

I love my impacts - no way I'd do a lot of what I do without them. They're obviously great for "off", and for "on" there's a mode to run it down until it starts to tighten and stop. For lugs, I'll pop into Mode 1 and give it a couple of pops, which generally puts me a few cranks away with a torque wrench to tighten to proper torque. I skip the mode 1 thing for stuff like brakes and just go for the torque wrench after the soft-run-in.

I've got no issues with tech using tools to make their job go faster. I do have a problem with abuse of my property. I don't flip how good they think they are or how they come to the decision that torque specs don't matter. If they wrench like that, they're not wrenching on my car. I'm not saying I demand a torque wrench of everything - I do trust my guy to know the right snug for an oil pan bolt or the filter housing (I don't trust myself for those things, but I'm not a pro). But for some stuff the ugga shouldn't be setting torque, at least for what I'm paying for, and I want stuff like spark plugs, oil pan bolts, lugs, brake calipers, etc. torqued properly. I keep my cars a long time too, and ultimately I'm picky about certain things. That's one of them.

What's crazy is, the stuff most needing torqued is the stuff like oil pan bolts or filter housings. It's all about the consequences of over tightening. A drain plug may have a torque spec of 30 ftlbs and support maybe 50max without damage instantly sustained, a subframe bolt will likely support 200+. And most people aren't gonna impact the hell out of an m12-m16 bolt and snap it. But I see plenty of stripped small stuff.

I'm not one to normally torque a control arm bolt the the subframe, but the M10 bolt with a spec of 30 ft/lbs gets a wrench. Now if I'm dealing with threads I suspect are bad, I'll use a techangle if I can fit it. As torque starts to fall while tightening, you know the treads are failing. Sometimes you need to do this by hand due to space. Typically if space allows I simply helicoil every suspect thread rather than playing games.

 

[M635_Guy]

What's crazy is, the stuff most needing torqued is the stuff like oil pan bolts or filter housings. It's all about the consequences of over tightening. A drain plug may have a torque spec of 30 ftlbs and support maybe 50max without damage instantly sustained, a subframe bolt will likely support 200+. And most people aren't gonna impact the hell out of an m12-m16 bolt and snap it. But I see plenty of stripped small stuff.

I'm not one to normally torque a control arm bolt the the subframe, but the M10 bolt with a spec of 30 ft/lbs gets a wrench. Now if I'm dealing with threads I suspect are bad, I'll use a techangle if I can fit it. As torque starts to fall while tightening, you know the treads are failing. Sometimes you need to do this by hand due to space. Typically if space allows I simply helicoil every suspect thread rather than playing games.

To be clear, I always use a torque wrench with those kinds of things (spark plugs, oil plugs, oil pan bolts, etc) - I have absolutely zero trust in my feel for stuff like that. It's the reason I have an overkill torque wrench drawer (and wouldn't have it any other way...).

 

[M635_Guy]

I guess this thread confuses me. As a guy that is very protective of my old BMW, the idea of protecting fasteners falls into three categories:

Cosmetic - Since a lot of folks look inside the engine bay at car shows and everything I've laid tools on in there has been a low-torque situation, the impacts never come out in the engine bay and it's essentially all hand-tools. I also don't want beat-up lugs or the impact I use on them causing scratches on the wheels, so I use a sleeved socket to protect them. I'm less-picky about my other cars on this point, but mainly work is achieved with hand tools or the battery ratchet (I just realized I never use it on the old car, which is probably habit as much as anything).
Torqued - To protect from a situation where I'm damaging the fastener or what it's going into and/or the torque is important to correct function and/or longevity, I'm using a torque wrench every time. I don't have any trust in my wrist-o-meter. For most things I expect the same from anyone working on my car(s), but I can deal with the wrist-o-meter of my very-experienced mechanic for oil drain bolts and oil filter housing caps (I'm pretty sure he uses a torque wrench on drain bolts though).
Everything Else - I'm not worried about 'protecting' things like suspension bolts, etc. so an impact gets used just about anywhere else (I do dial down the power in some situations). If something is really rusty, I'm going to take a more careful approach, mainly to avoid snapping it. I'm not sure if that falls into the OP's definition of 'protection' or not. I guess this category is situational for the impact, but it's not about cosmetics.

What's crazy is, the stuff most needing torqued is the stuff like oil pan bolts or filter housings.

I must have been very distracted when I was typing all that (I went back and edited/fixed it) - oil pan bolts should always involve a torque wrench, especially in motors with an aluminum block.

 

[Walkers]

Not sure if trolling or not. I've worked on cars from the Southwest and the rust belt. You're talking about apples and watermelons in comparing the two.

Apparently you don't even know what trolling is. This was simply a mildly humorous response to what the guys in the rust belt work on daily. If any of that stuff came into my shop I wouldn't work on it, it is such nasty, dirty, awful work. I would simply recommend replacement.

 

[cannuck]

One thing often overlooked is the difference between applying a purely torsional load vs. torsion plus bending. I try to support the head of a swing bar or ratchet to minimize bending loads (ESPECIALLY when an extension or even just deep socket is involved). When you see someone jumping on the end of a breaker bar the chance with will tilt its way off a fastener and damage will occur is fairly high. Win to T bars and impact tools. Another thing for seized fasteners is that an impact can "hammer" rust off without a lot of displacement, often saving a bolt or stud that could otherwise have broken.

Once again: "it depends".