How do i determine bolt torque for flanged connections. Tightening torque values are calculated from the formula t kdp, where t tightening torque, lbin k torquefriction coefficient. Bolt torque can be checked with a tool such as a torque wrench, but without a value as a guideline, a torque wrench offers no. Tightening the lug nuts on the wheels of your car is a good example of torque. Bolt, one of the most widely used fasteners in the industry, is usually tightened by applying torque to the head andor nut. Learn vocabulary, terms, and more with flashcards, games, and other study tools. The values for unbrako metric fasteners are calculated.
It takes more force to tighten a 3410 bolt than to tighten a 3816 bolt it is larger in diameter. F tensile force, in lbs c tightening torque, in nm c. Torque is the turning force measured in footpounds ftlb or inchpounds inlb applied to tighten turn the nut on a bolt. Bolt torque can be checked with a tool such as a torque wrench, but without a value as a guideline, a torque wrench offers no advantage. Accepted formulae relating torque and tension,based on many tests are. Metric bolts head and wrench sizes ansiso, din and.
How to calculate the tightening torque of bolt quora. Iso 724 metric threads dimensions of metric threads according iso 724. Fc29 2 proper bolt axial tightening force and proper. Effective sectional area of the boltmm2 axial force ff, by using equation1 ff0. This formula, although more complete, is seldom used, for the large errors sometimes as much as 25% involved in torque wrench readout usually renders using a more accurate. The required bolt clamping force for a joint is 20000 lbs.
Suggested tightening torque1 values to produce corresponding. In a bolted flange, the applied torque generates the axial load in the bolt. You generate torque any time you apply a force using a wrench. Recommended bolt torque table size recommended torque grade 2 grade 5 grade 8 188 ss bronze brass coarse fine coarse fine coarse fine coarse fine coarse fine coarse fine.
Sec8 div1 app2 will cover gasket seating, but does not directly address target bolt torque. Torquetension relationship iso 8981 property class 4. As the clamping force is a linear function of both the turning angle of the screw and the pitch of the thread, there is a direct relation between the. Torque is part of the basic specification of an engine.
All torque values shown are for turning the nut while holding the head of the bolt with a wrench, with the exception of socket head cap screws. Truthfully, product information rarely supplies torque values. Torque control is done as a substitute characteristic. Preload tension is necessary to keep the bolt tight, increase join strength, create friction between parts, and improve fatigue resistance. Analytic methods for determining the loads on a given bolt of a joint can be found in shigley 16 or other mechanical engineering texts. The following equation is the basic equation for the elastic resilience. Given an applied torque, t, the preload force f in the bolt is given by t f x factor where. The fatigue strength of bolt under repeated load should not exceed the specified tolerance. Torque can be measured during flange assembly with a properly calibrated torque wrench. Lubricated bolts and reduced torque lubrication effect on bolt tension and torque. Starting with this equation, which defines a linear relationship between torque and tension, you can develop models for the tightening process. They are of two types, metric flange bolts and metric hex bolts.
When you use a wrench, you apply a turning force to the handle. See torque force design equations webpage and torque chart page for recommended fastener torque and equation data this fastener bolt torque calculator will estimate the unknown torque, diameter, axial force applied and coefficient of turning friction for the given conditions. Torque estimating chart astm a193, grade b7 studs lubricant. By combining the torqueangle curves with a few simple calculations and a basic understanding of the. Understanding the nut factor in threadedfastener torque. Relation formula between screw and torque formula of screw. Torque pronounced tork is a force that you use to rotate or turn things. The torque values can only be achieved if nut or tapped hole has a proof load greater than or equal to the bolts minimum ultimate tensile strength. Example required torque for tightening a imperial bolt.
As a reality check if we approximate to a cross sectional area of 7 mm 2 and a load of n that gives a tensile stress of 140 mpa which is below yield even for low tensile steels in this particular context, where torque is known, the thread pitch doesnt come into it as you are calculating based on. Bolt tightening table table 14 table 15 figure 21 1. A popular formula for quick bolt torque calculations is t kfd, where t denotes torque, f denotes axial load, d denotes bolt diameter, and k torque coefficient is a calculated value from the formula. Bolt torque, axial clamp force, bolt diameter calculator. Values calculated using industry accepted formula t kdp where t torque, k torque coefficient dimensionless, d nominal diameter inches, p bolt clamp load, lb. The bolt efficiency will be low due to wide tolerance of the tension. All suppliers give a rosey picture of their equipmentss capability i suppose, but they also deal with the consequences in some way or another, whether it is claims or just loss of future sales. The reason all applications should be evaluated to determine the optimum tightening torque is that the k factor in this formula is always an estimate. When a bolt is tightened, by applying a torque to the bolt head or nut, the bolt. The recommended seating torques for unbrako headed socket screws are based on inducing preloads reasonably expected in practice for each type. Internalcombustion engines produce useful torque only over a limited range of rotational speeds typically from around 1,0006,000 rpm for a small car. D nominal bolt diameter, in and p bolt clamping load developed by tightening. Even experienced tradesmen over or undertorque bolts.
Metric bolts tightening torques engineering toolbox. Say you have a 8 inch wrench and figure you are applying 4 pounds of force on the wrench centered at 6 inches from the center of the nut. Torque control method bolt tightening is controlled by specific torque value. Bolt torque calculator determining proper torque to bolt.
In the application of torque to a fastener, it is important that the bolt is not stretched beyond what phase. Determining rock bolt or anchor tension using a torque. Engineering fundamentals of threaded fastener design and analysis. Factor d m 2 l d m sec d m l sec d c 2 see reference 3. Technical data proper bolt axial tightening force and. Tightening torque is not influenced by the bolt length so easy to standardize. The value for the friction coefficient provided by the. The application of bolt tightening method shall be carried in accordance with the following parameters. Torque formulas the first formula gives the recommended assembly torques for various grades of threaded fasteners and nuts with the following qualifications related formulas are also listed.
There can be as many as 200 or more factors that affect the tension created in a bolt when tightening torque is applied refer to paragraph 2. It is reasonable way for tightening control and operation. The torque method is widely used due to its simplicity and convenience. Engineering fundamentals of threaded fastener design and. Fortunately, torqueangle signature curves can be obtained for most bolted joints. Accepted formulae relating torque and tension, based on many tests are. Improvised torque wrench improvised torque wrench with luggage scale. Threads per inch 307a astm a307 grade a sae j429 grade 5 sae j429 grade 8 f n l g 9 fnl grade 9 clamp load lbs. Variation in friction coefficients affect the amount of preload achieved at a specified torque. It is a recommend practice too contact the lubricant manufacturer for kvalue information if a lubricant will be used. The values shown in the chart are to be used as a midrange guideline. Round shape bearing surface second, third type nut.
It takes more force to stretch an sae grade 8 bolt than it does to stretch an sae grade 5 bolt because of the greater material strength. Tightening and loosening torque of the adjusting nut. The tensile load a fastener can withstand is determined by the formula p st x as. The industry practice has been to measure the amount of torque required to tighten the bolt, and then attempt to relate that torque to tension. Bolt sizepitch lubricated with antiseize inlbs nm inlbs nm 61. When continuing to tighten a bolt that has already been tightened with a torque wrench until the bolt begins to turn again, this torque value can be calculated by using the. This online metric bolt torque calculator is used to find the torque of the ecoguard, lubricated and. Record the torque wrench reading, the date of test, and the rock bolt identifications. For torque, try sec8 div1 apps and asme pcc1 appendix o. What is the nut factor and how does it affect torque. M p x d 5000 these formulae may be used for bolts outside the range of the tables, m torque lbf. If the bolt diameter is 5 mm, thread series is coarse, iso 8981 property class is 8. By combining the torque angle curves with a few simple calculations and a basic understanding of the.
A short form equation for converting between torque and tension has been developed. Determining rock bolt or anchor tension using a torque wrench. Higher friction results in less conversion of torque to preload. Axial tightening force for bolt and fatigue limit the proper axial tightening force for a bolt should be calculated within an elasticity range up to load 70% of the rated yield strength when the torque method is used. Common bolt torque values can be looked up, but finding an accurate reference isnt always easy.
Torque can also be found by using the vector product of force f and position vector r. This standard bolt torque calculator is used to find the maximum torque for the given fractional bolt with the diameter, thread series and standard of the bolt. This expression is often called the shortform equation. Bolts that are fully or partially threaded, with washers and nuts are called as metric bolts. Clamp load calculated as 75% of the proof load when specified by the standard. Lubrication reduces the friction during tightening, decreases bolt failure during installation and increases bolt service life. The amount of force on a fastener is called as torque. Fasteners bolts, nuts and threaded rods torque, tension and loads. The load can be obtained from either analytic models or finite element analyses. Torque values chart for common bolt sizes intpi1 n m2 ftlb3 n m ftlb n m ftlb mm x pitch4 n m ftlb n m ftlb n m ftlb 14 20 7.
To arrive at the correct torque value, several other values must be found first. Bolt torque calculator calculate required bolt torque. As the bolt is tightened, it is stretched preloaded. Torque for flange bolting b7l7 studs stud diameter tension size ibf torque torque torque torque inch nm ft. Lubricated refers to fasteners in the as received condition, which is normally a light preservative oil coating on unplated fasteners and no oil coating on plated fasteners. Suggested tightening torque1 values to produce corresponding bolt clamping loads notes. The torque required for a 34 dry steel bolt to achieve this tension can be calculated as.