A lot of discussion here about wrenches and designs. Generally speaking box ends are all largely the same in function and has been described as "the real business end of the wrench" and for the most part, that's true. But what if you're entirely limited to putting all your force on the open end? Who makes the best design? Is there any merit to these fancy designs or are they just ways to part you with more money as they try to tell you your old wrenches that have served you well for countless tasks are inferior?
Other than the plain old wrench jaws, there are essentially two main designs in use today. Just variations of the same goal if you will. One with teeth, and another design where notches are cut out to essentially create off corner engagement between the two open end walls as the fastener is turned. The latter is a sound idea and exactly the way a modern socket functions. I suppose I should mention Cornwell's design since its slightly unique in that they're still using the old fashioned V groove so the bolt, at least in theory, is supported on 4 sides however there is no off corner engagement or teeth. This design has been dropped by most everyone else as the design is inherently weaker than an arch making a failure at the 'V', which is where most of the pressure is, likely.
During lunch I decided to see what I could do with just a few examples on hand. I'd like to add more later but I think this is a good start. The 3 I tested were a MAC Knuckle Saver, a basic Snap-On, and a Snap-On flank drive plus. First a bit of background.
The drive size is 5/8" and the bolt is a grade 8. No pipe was applied, everything was done with just arm strength. I would of loved to of been able to record torque numbers, alas i'm not that sophisticated. Just some "garage tests" so to speak.
Here are the contenders
First the regular Snap-On. This has an open end with a standard smooth design with nothing to obstruct the bolt. This is how most wrenches sold over the counter today are designed.
Moderate force applied to one good pull caused the jaws to spread and rounded the bolt almost instantly. This actually surprised me a bit as I was expecting a little more resistance before the wrench went around.
Here the wrench can be seen going around the bolt.
This is what was left of the corner (other corner looked the same)
Next the MAC Knuckle Saver. This system functions off two barely noticeable cut-outs on both of the jaws toward the open side. In essence the bolt is allowed to slip a little and should, in theory, force off corner engagement on the lower section where most of the force is applied. This system is designed so it can be used with the wrench in either direction.
It took a good single yank but this system too spread and rounded off the bolt fairly quickly. There was absolutely an improvement in gripping before it rounded compared to the standard Snap-On but i'm unsure if this is due to the off corner engagement or more due to the fact that the MAC open end is substantially thicker and as a result should be less prone to spreading. If the latter is the case, and I have a feeling it is, then that would make the "Knuckle Saver" design essentially moot. ***** too because I was eyeballing the new MAC labeled ASD (Proto) copies, which share this open end design with MAC.
The MAC going round the corners
And the damage (again the other corner looked the same)
Lastly, the Snap-On Flank Drive Plus system (often abbreviated FD+). Discussed at length here its been called everything from "the Cadillac of wrenches" to "overrated". This system is essentially Snap-On throwing everything including the kitchen sink at the open end wrench design. In addition to two pronounced cut-outs toward the open end (again to create off corner engagement like a socket) they've formed teeth into the back ends of both jaws. Again this system can be used with the wrench in either direction.
This wrench bit and held like a ******* even after repeated attempts at yanking it with as much force as I could. Essentially the way its been designed is as soon as the bolt tries to round it moves against the teeth and essentially mushrooms into them so while its possible to round the bolt off after repeatedly yanking on the wrench with all your weight, you're essentially shearing off a side of the bolt. Another amazing thing was that the wrench could then be re-installed on the rounded section and would bite again and yes, while it went right around much quicker, it still bit and takes force to due so.
Here you can see the bolt trying to round, the metal in the top right section of the the upper jaw is the bolt mushrooming into the teeth.
And the resulting damage from yanking on it a few times with most of my weight (before I intentionally rounded the bolts). This is the carnage you can expect on a really stuck fastener that you eventually get to break free with the FD+ open end.
The teeth marks. Please ignore the damage to anywhere but the area with the teeth marks, those areas were not damaged by the FD+ wrench.
The area in the red circle is the opposite side of the bolt. where the lower jaw made contact
and this is what happened when I forced it to round off. Picture is of the area where the teeth were engaged.
Some people don't like FD+ due to the fact that it mars the fastener. For show cars/plated fasteners, I absolutely agree, don't get a wrench with teeth. Other systems are fine because there is nothing to dig into the bolt. However for every day use I don't agree about the damage being a big deal. For the most part in general use you'll see 1 light tooth mark and maybe the ghost of a second on a fastener and if you're pulling so hard you cause the fastener to mushroom well guess what, with any other wrench it would of rounded and it would look terrible anyway. The only true difference is the FD+ has a chance to get the job done instead of making you get out the cut-off tool/torch. That's just my 2 cents on that.
I plan to test two other systems at least, one being the Cornwell 4 sided engagement, and the other being the one found on Matco/Armstrong/GW products which allows for off corner engagement on both corners instead of just the leading corner but i'll be extremely surprised if anything comes close to the success of the Flank Drive Plus. Infact if you purchase some Matco 9 series ratcheting wrenches the Taiwanese factory manufacturing them has essentially used a knock-off of flank drive plus instead of the normal opti-torque pro found on American made Matco wrenches. As the saying goes imitation is the sincerest form of flattery.
Lastly I think its very much worth mentioning that I was initially going to test 13mm bolts however the MAC and flank drive plus actually sheared the bolts off rather than rounding so, at least for good conditioned fasteners in smaller sizes, it seems a bit of a wash. However for smaller fasteners that are heavily corroded or partially rounded i'd absolutely opt for FD+. To me Snap-On is certainly justified in claiming they have the best wrenches on the market.
Other than the plain old wrench jaws, there are essentially two main designs in use today. Just variations of the same goal if you will. One with teeth, and another design where notches are cut out to essentially create off corner engagement between the two open end walls as the fastener is turned. The latter is a sound idea and exactly the way a modern socket functions. I suppose I should mention Cornwell's design since its slightly unique in that they're still using the old fashioned V groove so the bolt, at least in theory, is supported on 4 sides however there is no off corner engagement or teeth. This design has been dropped by most everyone else as the design is inherently weaker than an arch making a failure at the 'V', which is where most of the pressure is, likely.
During lunch I decided to see what I could do with just a few examples on hand. I'd like to add more later but I think this is a good start. The 3 I tested were a MAC Knuckle Saver, a basic Snap-On, and a Snap-On flank drive plus. First a bit of background.
The drive size is 5/8" and the bolt is a grade 8. No pipe was applied, everything was done with just arm strength. I would of loved to of been able to record torque numbers, alas i'm not that sophisticated. Just some "garage tests" so to speak.
Here are the contenders
First the regular Snap-On. This has an open end with a standard smooth design with nothing to obstruct the bolt. This is how most wrenches sold over the counter today are designed.
Moderate force applied to one good pull caused the jaws to spread and rounded the bolt almost instantly. This actually surprised me a bit as I was expecting a little more resistance before the wrench went around.
Here the wrench can be seen going around the bolt.
This is what was left of the corner (other corner looked the same)
Next the MAC Knuckle Saver. This system functions off two barely noticeable cut-outs on both of the jaws toward the open side. In essence the bolt is allowed to slip a little and should, in theory, force off corner engagement on the lower section where most of the force is applied. This system is designed so it can be used with the wrench in either direction.
It took a good single yank but this system too spread and rounded off the bolt fairly quickly. There was absolutely an improvement in gripping before it rounded compared to the standard Snap-On but i'm unsure if this is due to the off corner engagement or more due to the fact that the MAC open end is substantially thicker and as a result should be less prone to spreading. If the latter is the case, and I have a feeling it is, then that would make the "Knuckle Saver" design essentially moot. ***** too because I was eyeballing the new MAC labeled ASD (Proto) copies, which share this open end design with MAC.
The MAC going round the corners
And the damage (again the other corner looked the same)
Lastly, the Snap-On Flank Drive Plus system (often abbreviated FD+). Discussed at length here its been called everything from "the Cadillac of wrenches" to "overrated". This system is essentially Snap-On throwing everything including the kitchen sink at the open end wrench design. In addition to two pronounced cut-outs toward the open end (again to create off corner engagement like a socket) they've formed teeth into the back ends of both jaws. Again this system can be used with the wrench in either direction.
This wrench bit and held like a ******* even after repeated attempts at yanking it with as much force as I could. Essentially the way its been designed is as soon as the bolt tries to round it moves against the teeth and essentially mushrooms into them so while its possible to round the bolt off after repeatedly yanking on the wrench with all your weight, you're essentially shearing off a side of the bolt. Another amazing thing was that the wrench could then be re-installed on the rounded section and would bite again and yes, while it went right around much quicker, it still bit and takes force to due so.
Here you can see the bolt trying to round, the metal in the top right section of the the upper jaw is the bolt mushrooming into the teeth.
And the resulting damage from yanking on it a few times with most of my weight (before I intentionally rounded the bolts). This is the carnage you can expect on a really stuck fastener that you eventually get to break free with the FD+ open end.
The teeth marks. Please ignore the damage to anywhere but the area with the teeth marks, those areas were not damaged by the FD+ wrench.
The area in the red circle is the opposite side of the bolt. where the lower jaw made contact
and this is what happened when I forced it to round off. Picture is of the area where the teeth were engaged.
Some people don't like FD+ due to the fact that it mars the fastener. For show cars/plated fasteners, I absolutely agree, don't get a wrench with teeth. Other systems are fine because there is nothing to dig into the bolt. However for every day use I don't agree about the damage being a big deal. For the most part in general use you'll see 1 light tooth mark and maybe the ghost of a second on a fastener and if you're pulling so hard you cause the fastener to mushroom well guess what, with any other wrench it would of rounded and it would look terrible anyway. The only true difference is the FD+ has a chance to get the job done instead of making you get out the cut-off tool/torch. That's just my 2 cents on that.
I plan to test two other systems at least, one being the Cornwell 4 sided engagement, and the other being the one found on Matco/Armstrong/GW products which allows for off corner engagement on both corners instead of just the leading corner but i'll be extremely surprised if anything comes close to the success of the Flank Drive Plus. Infact if you purchase some Matco 9 series ratcheting wrenches the Taiwanese factory manufacturing them has essentially used a knock-off of flank drive plus instead of the normal opti-torque pro found on American made Matco wrenches. As the saying goes imitation is the sincerest form of flattery.
Lastly I think its very much worth mentioning that I was initially going to test 13mm bolts however the MAC and flank drive plus actually sheared the bolts off rather than rounding so, at least for good conditioned fasteners in smaller sizes, it seems a bit of a wash. However for smaller fasteners that are heavily corroded or partially rounded i'd absolutely opt for FD+. To me Snap-On is certainly justified in claiming they have the best wrenches on the market.
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there was about 10 thousandths between each bolt and jaw when I measured it. I took the pictures with the wrenches under load spreading; as they try to round the jaws of each wrench are being forced open.
