3/8" Impact Lug Nut Socket: Deep or Shallow for Maximal Impact Torque Transfer?

[BikeRider]

Very specific question. This isn't about clearance or reach, but rather getting the maximal impact torque transferred from the impact wrench to the lug nut, and, all other things being equal, which is more likely to do that, a deep or shallow socket.

From my research there are arguments pro and con either way. A shallow socket means less torsional spring torque loss, but a deep socket means more rotational mass to maintain momentum.

We're talking cordless impact wrenches, which I understand have a somewhat different hammer mechanism than pneumatic wrenches.

This came up yesterday when I tried to remove 21mm lug nuts torqued down to 94 ft-lb with my new Milwaukee M12 Fuel stubby 3/8" impact wrench, using a Sunex shallow 6 point impact socket. It was able to take all of them off, but slightly slower than with my 1/2" Craftsman C3 18V impact wrench using a Tekton shallow 6 point impact socket.

We're talking 1-2 seconds vs. under 1 second. Not a huge difference but enough to be noticeable and even annoying if you're rotating tires. I'm wondering whether going with a deep version of the impact socket, also 6 point and by Sunex, would make a difference, for the above reason. Or is the speed difference I'm seeing much more if not entirely due to using a somewhat more powerful impact wrench with a 1/2" vs. 3/8" anvil?

Note that the shallow socket I used wasn't deep enough to cover the lug nuts' entire depth, only around 2/3 to 3/4 of them, so perhaps that also had something to do with this, and maybe a deep socket will transfer more impact torque simply because it will grab onto the nuts' entire depth (assuming it's a sufficiently deep broach socket of course).

I'll probably get the Sunex deep socket as it's just $4 at Amazon, but I'm just curious as to what others think or have experienced on this matter.

Btw, does anyone make a weighted impact adapter, with the same size input and output anvil, to simulate those expensive weighted sockets that are meant to remove lug nuts and crank bolts?

 

[signcrafter]

The 1/2" drive socket is probably heavier then your 3/8" socket so more rotational mass. Not sure what the torque specs are on the craftsman impact either.

So 1 to 2 seconds longer, so we are talking about 10 seconds longer per tire, so 40 seconds longer to rotate a set of tires? And that is annoying? I would say if that annoys you then buy the right impact for doing tires, the m18 high torque impact. An m12 stubby is not meant for tire work. Yes it will do some tires but that's not it's designed purpose.

 

[VolvoRyan]

Torque Test Channel did this. IIRC, shallow vs deep makes no practical difference. You need to get a socket *designed* to be heavier.... which may be too fat for lug nuts.

I love the little M12, but it's not my tool of choice for lug nuts, especially if there's rust involved.

-Ryan

 

[BikeRider]

Yeah, as annoyances go it's pretty minor, but still noticeable. It's not the additional time so much as being used to faster removal with the 1/2" impact. Zip, zip, zip vs. ziiip, ziiip, ziiip.

The 1/2" is rated at up to 300 ft-lb. The 3/8" up to 250 ft-lb.

I'll probably continue to use the 1/2" for lug nuts, crank bolts, axle nuts, etc., and use the 3/8" for nearly everything else, i.e. anything much under 100 ft-lb. That's what it's mostly designed for anyway.

 

[BikeRider]

Torque Test Channel did this. IIRC, shallow vs deep makes no practical difference. You need to get a socket *designed* to be heavier.... which may be too fat for lug nuts.

I love the little M12, but it's not my tool of choice for lug nuts, especially if there's rust involved.

-Ryan

I was just trying to see what it's capable of since I just got it. Cute little guy but beefier than I expected. I'll get the deep socket since it's cheap and I'm curious if it'll make a difference, more because it'll presumably grab the entire depth of the nut than because it's slightly heavier. But 1/2" is really more suitable for lug nuts and anything much over 100 ft-lb.

Btw I just saw that test. They used a special weighted lug nut socket with a sort of weighted flywheel projection near the top of the socket, where it connects to the wrench, with the rest of the socket thin enough to fit around the nut.

 

[VolvoRyan]

I was just trying to see what it's capable of since I just got it. Cute little guy but beefier than I expected. I'll get the deep socket since it's cheap and I'm curious if it'll make a difference, more because it'll presumably grab the entire depth of the nut than because it's slightly heavier. But 1/2" is really more suitable for lug nuts and anything much over 100 ft-lb.

Btw I just saw that test. They used a special weighted lug nut socket with a sort of weighted flywheel projection near the top of the socket, where it connects to the wrench, with the rest of the socket thin enough to fit around the nut.

Torque Test Channel did 3/8" vs. 1/2" as well..... the 3/8" versions of a number of cordless guns actually puts down a little more power.

Don't get me wrong, the M12 stubby is awesome. I have the 1/2" as a number of my special tools are 1/2". It's a very useful tool given its size and *power*. I'll pull wheels off with a bigger gun, and the M12 comes out to do suspension work.

-Ryan

 

[BikeRider]

Torque Test Channel did 3/8" vs. 1/2" as well..... the 3/8" versions of a number of cordless guns actually puts down a little more power.

Don't get me wrong, the M12 stubby is awesome. I have the 1/2" as a number of my special tools are 1/2". It's a very useful tool given its size and *power*. I'll pull wheels off with a bigger gun, and the M12 comes out to do suspension work.

-Ryan

It does seem like a great little tool and I look forward to using in on various projects I have lined up for spring as it's just too cold here to do anything too intense now (I don't have a garage, let alone a heated one). I was just trying to test out its limits. Like I said I'll probably continue to use the 1/2" for lug nuts, cranks, axles, etc.

And I got the 3/8" because I already have a somewhat more powerful 1/2" with both deep and shallow socket sets to match, and the 3/8" with shallow sockets gives me a little bit more clearance for tight spots.

I wish they made a model of this wrench with interchangeable 3/8" and 1/2" anvils, since the internals are exactly the same from what I've heard, and they make other power tools with this feature. Perhaps in the next version of this tool. It's been over 3 years since this came out so maybe it's in the works and why HD is heavily discounting deals with it.

 

[dnschmidt]

Shallow vs. Deep is a non-issue. Both the same. Where power is lost is at joints between drive ends and extensions. Swivel sockets, stuff like that. I live in Phoenix and my cars have 75 ft-lb torque ratings on their lug nuts. Stubby works fine for me. I was reading another thread about O2 sensor wrenches. A Knipex pliers wrench works just fine to remove them out here. As Mr. T once said: "I pity the fool that lives in the rust belt." or something like that.

 

[BikeRider]

But what about sockets that fit onto the entire depth of a nut vs. ones that fit onto only part of it? Would that make a noticeable difference if we're talking more than a mm or two? I'm thinking that's the real "problem" here.

I'll try this out when I get the deep socket. Meanwhile, I'll test out my deep and shallow 1/2" sockets, using a 3/8" to 1/2" impact adapter. And yes, I realize there will be torque loss there too.

 

[Bubba Fett]

Bumping this old thread to include this video from TTC. Frankly, I thought weighted sockets were a pure gimmick, but what do I know?
I'm still trying to understand the physics here. I'm guessing it has something to do with the conservation of angular momentum, but then again, what do I know?
Enjoy:

Edit: Weight seems to work better when it's further from the axis, crating a flywheel effect, I suppose. I guess it's like a screwdriver with a larger handle, which better transfers the torque to the fastener than a skinny handled driver would. But the force is constant, and coming from my hand. But I'm not entirely sure how this works with an impact gun.

 

[dnschmidt]

Bumping this old thread to include this video from TTC. Frankly, I thought weighted sockets were a pure gimmick, but what do I know?
I'm still trying to understand the physics here. I'm guessing it has something to do with the conservation of angular momentum, but then again, what do I know?
Enjoy:

Edit: Weight seems to work better when it's further from the axis, crating a flywheel effect, I suppose. I guess it's like a screwdriver with a larger handle, which better transfers the torque to the fastener than a skinny handled driver would. But the force is constant, and coming from my hand. But I'm not entirely sure how this works with an impact gun.

This isn't the complete reason but its close enough. F=ma (I believe this to be Newton's second law of motion) F = force (this is what you're trying to maximize) M = mass (the weight of the socket which is a variable and can be altered by making the socket heavier) and a = acceleration which is pretty much a constant due to the design of any particular impact wrench. This is hard to change and probably is unique to each style of impact wrench. SO, TO GET MORE TORQUE YOU NEED MORE MASS. And thus was born the Lisle Honda Crank Bolt socket. I think I can explain why Torque's super heavy socket didn't give the best results and my explanation for that was that the massive weight of it affected the acceleration of the impact slowing it down.

 

[Belanice]

torque = I*a = (mr^2)a

I = moment of inertia
a = angular acceleration
m = mass
r = radius

When the mass is constant, the farther the mass is from the axis of rotation, the greater the moment of inertia.

 

[vavet]

I watched the TTC's video. I came up with my own analogy that might not be 100% correct.
I think of it like a baseball player - the right player can do more with a heavier bat, but it's not the bat, it's matching the bat to the player. If I put Barry Bonds' bat in my 9 year old's hands, he's going to be lucky to hit a dribbler down the baseline with it because it's way too heavy for him.
A more capable impact gun can do more with a heavier socket. But that heavier socket would weaken a lesser impact gun.

Bottom line: There is a goldilocks socket for every impact gun. For most of us weekend warriors, it doesn't really matter. We can spend an extra 40 seconds rotating the tires compared to a NASCAR team where having that optimized could make the difference in 1st and 8th place.

 

[Bubba Fett]

Thanks for the replies. Fascinating stuff.

 

[theoldwizard1]

torque = I*a = (mr^2)a

I = moment of inertia
a = angular acceleration
m = mass
r = radius

When the mass is constant, the farther the mass is from the axis of rotation, the greater the moment of inertia.

Acceleration is delta velocity over time. If it is not moving over that period of time then the acceleration would be zero.

 

[dnschmidt]

Acceleration is delta velocity over time. If it is not moving over that period of time then the acceleration would be zero.

True, but in an impact wrench the acceleration goes from zero to max each time the anvil is hit by the hammer. So for all intents and purposes there is always acceleration. How much acceleration depends upon the design of the anvil and hammer which is likely different between impact wrenches.