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How much (maximum) torque can a normal 150 lbs. man deliver manually with a hand-ratchet wrench (say 8" ratchet arm and a 1/2" socket) assuming no rust-resistance, direct/easy access etc?

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    I'm not sure this is really on-topic for home improvement. Perhaps the Biology forum might be more appropriate? – jwh20 Feb 6 at 21:19
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    Yeah, the root issue is that this is an XY problem. You're asking about a method or a part of the problem, instead of asking about the core problem. Please edit your question to ask the core of your question, and it actually helps to state the research you have done before, or the background. – Harper - Reinstate Monica Feb 7 at 1:29
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    There's only one answer that matters - Too Much. If you tighten anything as hard as you can with the tool you have, you're going to damage something, either the work or your tool. – J... Feb 7 at 12:58
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    I think you'd get a better answer over at mechanics.stackexchange.com since a socket wrench is typically used by mechanics. – MonkeyZeus Feb 7 at 14:17
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    The craftsman torque wrench is 13 inches long, figure 12 inches for level arm, and is scaled from 20 to 150 ft-lbs. So the range of real torque wrenches should give a good indication of the expected range. – MaxW Feb 7 at 16:16
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Okay my curiosity was piqued. I am an average 60 something year old guy who turns a wrench for a living. I clamped my old school Beam Type Torque Wrench in a vise. Using a 1/2" square x 3/8 drive drive socket on the torque wrench and an 8" ratchet I hit 70 ft-lbs. This was just a straight steady pull. I did not test to see how long I could hold that number.

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    Mike, thank you SO very much. You confirmed the number that I had in mind. Based on my calculations the realistic range seems to be 50 ft-lbs to a maximum of 100 ft-lbs (depending on how much a 150 pounds DIY, handy-man pushes himself). This seems to be in the same range as a 12-volt impact driver. This is what I wanted to confirm. A heavyset man with strong arms could perhaps go as high as 300 ft-lbs. That is, he gets into the range of a strong professional grade impact wrench. – user97485 Feb 6 at 23:39
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    We were exceeding 100 ft-lbs, well 2 of us were but we were both over 6ft and 16 stone. When I can brace against something I have sheared a 3/4” shaft... Sometimes a valid solution can be to shear the nuts off instead of trying to get them undone. – Solar Mike Feb 7 at 6:36
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    This is a good baseline answer for one specific person, but there are a lot of factors that go into a number like this. The number found by experimentation like this is augmented by the muscles that are used as well as the strength of the user, and so should be tested in various configurations by a large sample of people to have any sort of real meaning. I'm not discounting mikes at all, I'm just saying that the number provided can vary greatly for too many reasons to list here, which means this really isn't an answer. – computercarguy Feb 7 at 17:13
  • ComputeCarGuy: I totally agree with the point you are making … that there a lot of parameters to consider. I tried to simplify my question as much as possible to make sure that 1) I/we get a reasonable understanding of human-torque range 2) the torque-limit at which one may need an electric impact torque-wrench 3) need for a DIY guy like many of us investing in a costly torque-wrench especially when you will use it rarely 4) a alternative to a handy/manual ratchet (that I found it to be an 20V, 3-4 amps/hour impact driver). – user97485 Feb 8 at 4:01
  • What does that mean in standard units ? (you see, newtons, kilograms, meters) – JB. With Monica. Feb 10 at 7:57
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Torque is simply the amount of force you apply (lbs) multiplied by the distance from the thing you're rotating (ft), hence the unit "ft-lbs" (foot pounds). If you apply 50 lbs of force 6 inches (.5ft) away from the bolt head, then you're applying 25ft-lb of torque. The same 50lbs applied at the end of a 2ft wrench would give 100ft-lb of torque.

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  • Thanks!! I did my theoretical calculations based on the same formula that you mention to come up with my prediction of 50-100 foot-pounds of torque with an 8" hand-tool ratchet wrench (from my tool-box). That is consistent with what Mikes mentioned above. – user97485 Feb 7 at 3:50
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    Concur - this is simple mathematics. Until you're strong enough to break your tool, when it becomes material science :) – Criggie Feb 7 at 7:14
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If you can apply upwards force using your leg muscles to supply the force and just hanging on with your arms you can probably put three times your weight on it so 450 pounds on an 8" handle is 300 foot-pounds.

if your're a weightlifter or other athlete probably much more. (you'll probably break the handle and skin your knuckles)

If torque is important use a torque wrench. if doing up wheel nuts stand on the end of the wrench, that will be "enough". (to undo face it the other way and jump on end, that will be more than "enough")

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  • Thanks Jasen for your practical tips! I am ~150 lbs so could simply not produce the extreme torque needed to "break" my snow-blower's auger-pulley's nut that rusted over the past 10 years. So I used "Liquid Wrench" to loosen it and then was able to impact-wrench it out. This is what got me wondering about my hand-tool ratchet wrench and my ability to manually unscrew the pulley. Looks like I was physically a little on the lower side and hence had to use my impact-driver with a socket adapter, – user97485 Feb 7 at 4:04
  • I don't think your 3x bodyweight is right for most people; most people are really quite unfit and even at the gym I don't see many people leg-pressing that much . 2x bodyweight would be similar to climbing stairs slowly without holding anything so is probably a good estimate. – Chris H Feb 7 at 8:52
  • Back when I weighed 75 kilos, I jumped on a jury-rigged five-foot handle on a torque wrench and the nut still didn’t move. Nut holding a clutch onto a crankshaft. I had to put it on the other side of the car, and put a floor jack under the end of it. Manufacturer’s spec said 750 ft-lb. Did not damage the torque wrench. – WGroleau Feb 7 at 16:08
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    DO NOT jump on the end of the lug wrench to tighten up lug nuts!!! That's a great way to OVER torque them and that can lead to lug failure. Trust me - it's no fun when it happens a 3am going 80MPH on the highway. (Yes, the shop that installed the new tires severely over-torqued the lug nuts and 3 of the studs sheared off 1 week later.) You only jump on the end of the lug wrench to loosen the nuts when the gorilla at the shop has severely over torqued them for you. – FreeMan Feb 7 at 19:22
  • yeah, that's to undo. – Jasen Feb 8 at 4:13
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It depends how long the "cheater" is. With a 3 foot cheater pipe over the handle ,it will be a LOT of torque. For my 3/8 drive , 1/2" thinwall conduit is a perfect fit over the handle so I have about a 10" length in my tool box. Large box wrenches ( like 2") in industry only have about a 12" stub handle , the user supplies what ever length pipe he wants for torque.

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    For very serious nut removal , like those on 3" diameter studs that have been at high temperature , I have seen linear shaped charges used to split the nuts ( only one time). Folks were in a hurry and the cost of about 60 new nuts was incidental. They did a surprisingly good job of not destroying the studs. – blacksmith37 Feb 7 at 1:14
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    Interesting!!! Learn every day. Thanks. – user97485 Feb 7 at 3:44
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    Yeah - the cheater bar can make a huge difference. I had to torque wheel bearing nuts to 150 ft/lb, then add 1/2 a turn. With a 6' piece of pipe over the 25" breaker bar, my 12yo son easily added two 1/4 turns to get the job done. Unfortunately, the OP asked about an 8" ratchet w/o a cheater... :) – FreeMan Feb 7 at 19:25
  • Great suggestion/idea FreeMan!! I did not think about it. Guess I could have used a 24" metal pipe to extend my ratchet wrench to torque it. Will keep it in mind!! Thanks again!! – user97485 Feb 8 at 19:26
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Thinking more of the underlying question, max torque isn't the only tradeoff between hand and power tools:

The power tool will provide the rated torque for as long as you can supply power (e.g. charged batteries). Can the person? On the other hand if you're working away from power most people would last longer. The power tool's maximum torque is likely to be with a fully charged battery, and will drop off before the rated runtime, and is a hard limit, while you can often find a cheater for a hand tool.

Many light high-torque power tools don't really have a suitable grip to resist that torque, at least not more than briefly, and can be quite harsh on your wrist if used to give maximum torque for long periods, especially single-handed. Heavier impact drivers are better for this for the same grip (conservation of angular momentum) but then you're holding a heavier tool for long periods, which is hard work in some positions.

An advantage of a (typical) impact driver over a ratchet&socket is that the power tool provides closer to pure torque, while a handheld spanner can require a lot more bracing of the workpiece to avoid moving it. That's fine if it's a car or a building, but for something lighter it can be troublesome (e.g. undoing the crank bolts on my bike - I have to do it on the ground rather than the workstand because the down/up force of the hand tool is too much for the stand - I wouldn't use an impact driver there anyway)

When comparing different power tools, runtime and ease of use (ergonomics, battery options) are at least as important. I often do the slow heavy part of the job with hand tools but use my non-impact power driver for the boring spinning of an overly-long bolt.

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    Most of the time, if you need to know how much torque you're applying, you don't need to apply it for more than a moment. – Mark Feb 7 at 21:10
  • True! Once a lug-nut is loosened with a short burst of high torque, the rest is easy!!! The point that you make combined with FreeMan's suggestion to use a cheater bar will get most normal DIY torque-jobs done!! – user97485 Feb 8 at 19:31

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