{"id":3528,"date":"2026-10-22T01:23:01","date_gmt":"2026-10-21T17:23:01","guid":{"rendered":"http:\/\/www.intermediaecuador.com\/blog\/?p=3528"},"modified":"2026-10-22T01:23:01","modified_gmt":"2026-10-21T17:23:01","slug":"how-to-calculate-the-torque-required-for-a-screw-jack-4aec-5d2f6b","status":"publish","type":"post","link":"http:\/\/www.intermediaecuador.com\/blog\/2026\/10\/22\/how-to-calculate-the-torque-required-for-a-screw-jack-4aec-5d2f6b\/","title":{"rendered":"How to calculate the torque required for a screw jack?"},"content":{"rendered":"

Hey there, if you\u2019ve ever used a screw jack to lift something heavy\u2014like a truck for repairs, a stage for a concert, or even a construction formwork at a job site\u2014you might\u2019ve wondered: how do I actually figure out how much torque I need to turn that handle (or motor) to make it work? Spoiler: it\u2019s not just guessing how strong your arm is, and if you get it wrong, you could either not lift the load at all or burn out your jack before you even get started. As a screw jack supplier, I get questions about this all the time\u2014people think it\u2019s rocket science, but it\u2019s actually pretty straightforward once you break it down. Let\u2019s walk through it like we\u2019re chatting over a coffee (no fancy equations that\u2019ll make your eyes glaze over, promise). Screw Jack<\/a><\/p>\n

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First, let\u2019s get one thing straight: screw jacks aren\u2019t magic. They use that classic simple machine trick\u2014screws as inclined planes\u2014to turn rotational force (that\u2019s torque, by the way) into linear force (the actual lifting power). So torque is what you put in, and the lifting force is what you get out. But to calculate how much torque you need<\/em>, you\u2019ve got to know a few key numbers first, and no, you don\u2019t need a PhD in engineering. Let\u2019s list \u2018em out like we\u2019re checking items off a to-do list: the load you\u2019re lifting, the screw\u2019s lead, the screw\u2019s pitch diameter, and the coefficient of friction between the screw and the nut. That\u2019s it\u2014four main things.<\/p>\n

Wait, let\u2019s define those quick, \u2018cause \u201clead\u201d and \u201cpitch\u201d are terms everyone mixes up. Pitch is the distance between two adjacent threads on the screw, right? Lead is how far the nut moves in one full turn of the screw. For a single-start screw (the most common one you\u2019ll find on standard screw jacks), lead equals pitch. If it\u2019s a multi-start screw (like for faster lifts), lead is more than pitch\u2014we don\u2019t need to overcomplicate that for this basic calculation, just remember single-start = lead = pitch for most everyday jobs. Got it? Good.<\/p>\n

Now, let\u2019s start with the ideal case\u2014no friction, just pure mechanical advantage. That\u2019s the easiest way to wrap your head around it. The ideal torque (let\u2019s call it T_ideal) is what you\u2019d need if there was zero friction, which never actually happens, but it\u2019s a starting point. The formula for that is T_ideal = (Load \u00d7 Lead) \/ (2 \u00d7 \u03c0). Let\u2019s plug in a real example to make this concrete. Say you\u2019ve got a 5,000 lb load (that\u2019s about the weight of a small pickup, for reference) on a single-start screw jack with a lead of 0.2 inches. Let\u2019s do the math: (5000 \u00d7 0.2) \/ (2 \u00d7 3.14) = 1000 \/ 6.28 \u2248 159.2 lb-in. That\u2019s the torque if there was no friction. But here\u2019s the catch: friction is always there\u2014between the screw and nut, between the nut and the jack\u2019s housing, even a tiny bit from the load pushing down on the assembly. That ideal number is way too low for real life, so we have to add friction into the mix.<\/p>\n

Now, let\u2019s talk about friction. The coefficient of friction (let\u2019s call that \u03bc) is just a number that tells you how slippery two surfaces are. For steel screws running against a standard bronze nut (that\u2019s the most common pairing in screw jacks, trust me), \u03bc is usually between 0.1 and 0.15. If you\u2019re using a different nut material\u2014like plastic for light loads\u2014it\u2019s lower, but bronze is the go-to for durability and consistency. We also need the pitch diameter (let\u2019s call that D) of the screw, which is basically the average diameter of the threads\u2014for a standard 1-inch diameter screw, D is usually around 0.875 inches, but you can find this in your screw jack\u2019s specs (we always post that for every model we sell, by the way, so you don\u2019t have to guess).<\/p>\n

The formula for actual torque (T_actual, which is what you\u2019ll really need) adjusts that ideal number to account for friction. The full formula is T_actual = (Load \u00d7 (Lead\/(2\u00d7\u03c0) + \u03bc \u00d7 (D\/2))) \/ (1 – (\u03bc \u00d7 Lead)\/(\u03c0 \u00d7 D)). Wait, I know that looks scary, but let\u2019s plug in our same example to make it simple. Let\u2019s say our screw has a pitch diameter of 0.875 inches, \u03bc = 0.12 (right in the middle of that bronze range). Let\u2019s calculate step by step:<\/p>\n

First, the top part of the numerator: Lead\/(2\u00d7\u03c0) is still ~0.0318 inches. \u03bc \u00d7 (D\/2) is 0.12 \u00d7 (0.875\/2) = 0.12 \u00d7 0.4375 = 0.0525 inches. Add those together: 0.0318 + 0.0525 = 0.0843 inches. Multiply by load (5000 lb): 5000 \u00d7 0.0843 = 421.5 lb-in. That\u2019s the top.<\/p>\n

Now the denominator: 1 – (\u03bc \u00d7 Lead)\/(\u03c0 \u00d7 D). Plugging in numbers: (0.12 \u00d7 0.2) \/ (3.14 \u00d7 0.875) = 0.024 \/ 2.7475 \u2248 0.00873. So 1 – 0.00873 \u2248 0.99127.<\/p>\n

Now divide the top by the bottom: 421.5 \/ 0.99127 \u2248 425 lb-in. Oh, that\u2019s way higher than the 159 lb-in ideal! That\u2019s why friction is such a big deal\u2014you can\u2019t ignore it. And notice I used a middle-of-the-road \u03bc; if your surfaces are rusty or dirty, \u03bc could jump to 0.2 or more, so your torque would be even higher. That\u2019s why it\u2019s smart to use a lubricant too\u2014grease or anti-seize can cut that friction down, so you need less torque, which is easier on your jack and the drive system.<\/p>\n

Wait, but what about when you\u2019re lowering the load? That\u2019s a different scenario, right? When you lower, the friction works against you instead of with you, so you need less torque (or even none, if the screw is self-locking). Oh right, self-locking is a key point for screw jacks\u2014if the lead of the screw is small enough compared to the friction, the load won\u2019t unwind the screw on its own, which is what you want for safety. If your screw isn\u2019t self-locking, you\u2019ll need to apply torque to hold the load as you lower it, so you can\u2019t just use the lowering torque number and call it a day. As a supplier, I always check for self-locking when we recommend jacks\u2014you don\u2019t want a load crashing down \u2018cause you picked the wrong screw type.<\/p>\n

Let\u2019s also talk about real-world factors that the formula doesn\u2019t account for, \u2018cause formulas are great, but actual use matters. For example, if you\u2019re lifting a load that\u2019s not perfectly centered on the jack, that creates side load on the screw, which increases friction. If you\u2019re using a gearbox to drive the jack (instead of a manual handle), you have to add in the efficiency of the gearbox too\u2014gearboxes aren\u2019t 100% efficient, so some torque is lost there. We always include efficiency ratings for our gear-driven screw jacks on our product pages, so you can adjust your calculations for that. Another thing: wear and tear. A jack that\u2019s been used for years has worn threads, which increases friction, so you\u2019ll need more torque over time. That\u2019s why regular lubrication and inspection are important\u2014we send a quick care sheet with every jack we sell, just to keep things running smoothly.<\/p>\n

Maybe you\u2019re thinking, \u201cThis is cool, but I don\u2019t want to do all this math!\u201d Fair enough. That\u2019s why all the screw jack models we supply have a torque rating listed right in the specs. Let\u2019s say you have a 5,000 lb load\u2014if you check our 1-ton screw jack (wait, 1 ton is 2,000 lbs, so make that a 3-ton jack) specs, you\u2019ll see it needs about 400-450 lb-in of torque to lift that load, which lines up with the example we did earlier. That\u2019s the beauty of working with a supplier who\u2019s actually got real-world numbers, not just textbook formulas\u2014we\u2019ve tested these jacks with actual loads, so you don\u2019t have to crunch the numbers yourself.<\/p>\n

Wait, let\u2019s go over a common mistake people make: only using the ideal torque and forgetting friction. A customer once told me they picked a jack based on the ideal torque, and it wouldn\u2019t even move a 1,000 lb load. Turns out they forgot about friction, so the actual torque needed was like three times what they thought. That\u2019s why we always tell customers to add a 20-30% safety factor to their calculated torque. Stuff happens\u2014threads aren\u2019t perfectly smooth, lubricant wears off, the load shifts a little. Adding that safety margin means you don\u2019t get stuck mid-lift, or overload your motor or handle.<\/p>\n

Let\u2019s wrap this up with a quick recap, \u2018cause I know that formula felt like a lot. Here\u2019s the step-by-step cheat sheet we give to every customer: 1. Get your actual load weight (don\u2019t guess\u2014weigh it if you can, it\u2019s worth it). 2. Get the lead and pitch diameter of your screw (if you\u2019re buying a jack from us, we send that to you). 3. Use the standard bronze nut friction number (0.1-0.15) for most jobs. 4. Plug into the actual torque formula (or just use our pre-tested specs, which is way easier). 5. Add 25% safety factor minimum. 6. If lowering, remember self-locking and adjust accordingly.<\/p>\n

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If all this math still makes your head spin, that\u2019s exactly why we\u2019re here. We don\u2019t just sell screw jacks\u2014we help you pick the right one for your load, and walk you through any torque questions you have. Whether you need a manual jack for occasional use, or a motorized one for heavy industrial jobs, we\u2019ve got you covered. No confusing jargon, no hidden fees, just straight answers to make sure your lift goes off without a hitch. If you\u2019re working on a project and need help figuring out the right torque or jack size, just reach out and chat with our team\u2014we\u2019re happy to help. We\u2019ve been in this game long enough to know that getting the torque right isn\u2019t just about making the jack work, it\u2019s about keeping you safe and your project on track. Don\u2019t overcomplicate it, but don\u2019t cut corners either\u2014 that\u2019s the sweet spot.<\/p>\n

Stepper Motor<\/a> References: 1. Shigley, J. E., & Mischke, C. R. (2001). Mechanical Engineering Design (6th ed.). McGraw-Hill. 2. American Society of Mechanical Engineers. (2017). ASME B106.1M-2017: Design of Screw Jacks. ASME. 3. Halliday, D., Resnick, R., & Walker, J. (2021). Fundamentals of Physics (12th ed.). Wiley.<\/p>\n

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Hangzhou ANG Drive Co., Ltd.<\/a>
As one of the most professional screw jack manufacturers and suppliers in China, we’re featured by quality products and good service. Please rest assured to wholesale custom made screw jack from our factory. Good service and quality products are available.
Address: No.185, Jincheng Rd., Hangzhou 311202, China
E-mail: export2@angdrive.com
WebSite: https:\/\/www.anjodrive.com\/<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

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