Cutting speed formula for lathe

Cutting speed formula for lathe. But to prevent seizing of the rolls on the pin, we recommend a maximum surface speed of about 150 SFPM (Feet/Min) or 50 m/min. Drilling operations are those in which a cutting tool with sharp teeth, such as a twist drill, rotates and feeds into the workpiece axially, forming a hole with a diameter equal to Feb 20, 2024 · Start by selecting the appropriate cutting tool for the thread you wish to create. On a lathe it is the speed that the cutting tool is passing over/through the spinning work piece. Calculate Revolution (rev. Note: Observation and common sense will also help determine the correct speed. Lathe Operations Calculator. 262 x RPM x D RPM: revolutions per minute/rotational speed: (3. Cutting speed for solid carbide drills and exchangeable tip drills. 5 – 1. 4 x 50 / 2 = 200 / 2 = 100 RPM. 6 m/min. A cut is to be made with a high-speed steel (HSS) tool on a 2-inch diameter piece of 1018 steel with a brinnel hardness of 200. MRR = D x F x S cc/min. Back . By understanding how to calculate and adjust the various parameters of the cutting tool, such as rake angle, clearance angle, and side Feb 20, 2024 · The speed at which the lathe rotates is determined by the motor or the gearing mechanism of the lathe. Figure 8. It is expressed in meter/min. Apr 9, 2022 · Calculation. 5 mm (0. BTW, that’s from our article on RPM from Surface Speed if you want the details. 12. Speeds & Feeds for Knurling. Nov 20, 2018 · It is the speed that the cutter is moving through the material. Any motion CNC code that will be entered afterward will behave accordingly. For example, during turning, the calculation shall be based on the value of the surface Hence the cutting time is the length divided by the linear speed: T = l V f = l F n × n. For example, if your workpiece is 3 inches in diameter v = Cutting Speed (SFPM) f = Feed (Dist. That is all it is. Slide the diameter back and forth and the table will update for the various materials. It is measured by the unit—revolution per minute (rpm) and designated by N. These variables collectively determine the precision and success of the operations on a CNC lathe. If you are looking for threading cutting conditions, please use the Thread Calculator. Material removal rate formula for turning. Diameter at which the tool is doing the cutting. May 13, 2024 · The simple machining formula you’ll use is the following equation: Spindle RPM = SFM / Circumference. N = Spindle speed This is the value the formula outputs to, once we have fed all the information into the equation, we are given the spindle speed as a result. You may find you get longer knurl life and improved In metal cutting, calculating the correct values for the different machining parameters such as cutting speed and spindle speed is a crucial factor for achieving the best result from the cutting tools. Other factors that differentiate between feed rate and cutting speed include: Units of measurement. What is the feed per revolution when main axis spindle speed is 500min-1 and cutting length per minute is 120mm/min ? Answer Substitute n=500, I=120 into the formula. Exceeding this maximum speed for your Cutting Speed Definition. 262 x D) IPM: inches per minute/machine feed rate: RPM x IPR (or) T x IPT Speeds and feeds are calculated based on the maximum work diameter for the tool. 82/tool diameter. The CNC Taper Turning Formula Jan 27, 2024 · Surface Speed = RPM * Pi * Diameter [ From Cutting Speed Formulas] So, our surface speed is 2000 * 3. In this section, you will find parting and grooving formulas and definitions for how to calculate cutting speed, feed rate, or other parameters that affect the machining in your turning center, lathe tool, or multi-task machine. Feb 20, 2024 · Calculating lathe cutting tool geometry is an essential skill for anyone working with a lathe machine. You will also see some practical examples and tips on how to use the Cutting Speed Calculation : Cutting Speed is the speed at which the metal is removed by the cutting tool from the workpiece. Step 1: Determine The Material Type. the RPM would be 3978. The difference between speeds and feeds is that the cutting speed provides the generatrix while the feed motion provides the directrix. Also, determine the feed rate for a single tooth having feed per tooth of 10 mm. For a given tool and workpiece material, there is a range of recommended cutting or surface speeds between the two materials. Cutting speed is the rotational speed of either workpiece or cutting tool (based on which is rotating). Example: Cutter diameter (DC) = 100 mm Spindle speed (n) = 400 min-1 In this case, the cutting speed (vc) is approximately 125. To find the cutting speed, one must know the diameter and the RPM. SFM: surface feet per minute/cutting speed: . Knurling comes in 4 main patterns: Straight. The cutting speed can be obtained from the formula: How to Calculate Wood Lathe Speed. diameter the RPM would be 2652. get instant cutting data recommendations. mode) RPM = 3. 5 = 6112 RPM. The harder the material, the slower the cutting speed should be. Lathe Cutting Speeds in Feet and Meters per Minute Using High-Speed Steel Toolbit. Example: By taking 0. 8 IPM. 3 IPM. Adjust the lathe machine's speed and feed settings based on the workpiece material and taper turning requirements. Knowing how to calculate correct cutting speed, feed per tooth or metal removal rate is crucial for good results in any milling operation. For general purposes, ratio of the depth of cut to the feed varies from_____. Example: Material = Aluminum 3” Cutter, 5 Teeth Chip Load = 0. In the case of lathe machine cutting speed is the peripheral speed of the work past the cutting tool. Take 9,000 and divide by the bowl diameter (D) 9000 / D = Maximum RPMs. source: CADEM NCyclopedia multimedia CNC training software. That combination took the Material Removal Rate from about 18 cu in/min to 23. g. The faster the spindle turns, and/or the larger the diameter, the higher the SFM. Switching on the TSC option for a basic cut in a workpiece material of 6061 aluminum took spindle speed from 9980 rpm to 11277 rpm and feed rates from 71. The pitch typically ranges between 8 to 80 TPI (3 – 0. After plugging these values into the equations below, the adjusted internal feed becomes 2. However, in most cases, we know the cutting speed, not the spindle speed. Cutting speed (V) = π DN/60 × 1000 mm/min. Nov 11, 2021 · Hence, these two parameters are required in machining processes. Use the recommended cutting speed charts in Table 4. Mar 24, 2023 · Determine the spindle speed required to mill a steel workpiece with a diameter of 30 mm. Using the spindle speed formula: Mar 14, 2024 · Different Factors Affecting Lathe Speed. Let's put this formula to work in calculating the RPM for the machining example below. Inch mode. The RPM calculated in the Turning (Lathe) Speed and Feed Calculator refers to the spindle speed in turning process, and the IPM refers to feed rate. The way we utilize the above definition depends on When machining in lathes, turning centers, or multi-task machines, calculating the correct values for different machining parameters like cutting speed and spindle speed is a crucial factor for good results. The rotational speed in turning is related to the desired cutting speed at the surface of the cylindrical work-piece by the equation where N = rotational speed, rev/min; v = cutting speed, m/min (ft/min); and Do= original diameter of the part, m (ft). Additionally, you consult a chart that suggests a feed rate of 0. It is expressed in meters per minute. The formula for calculating the lathe RPM is as follows: RPM = (Cutting Speed x 12) / (π x Diameter) Let's break down the formula further and explain each component: Cutting Speed: The cutting speed refers to the speed at which the material is removed by the cutting tool. Fill in the cutting speed, V = 5 m/min. 06 Here you find a collection of good to have milling formulas and definitions that are used when it comes to the milling process, milling cutters, milling techniques and more. 562”, which is used for the inner and outer diameter in both adjustments. D = Tool or part diameter When working in metric or imperial on a milling machine, we pop the diameter of the tool in place of 'D'. Jan 5, 2024 · MRR = (D x W x F / 1000) cc/min. The formula for calculating cutting speed is: Cutting Speed (m/min) = π x Diameter (mm) x RPM / 1000 Jul 2, 2022 · Read Also: List of Important Terms Used in Lathe Machine Formula. Here’s your formula for wood lathe speed: RPM = π x Cutting Speed x 12 / Workpiece Diameter. Its like Oct 4, 2019 · Machining time of Lathe Machine: The machining of the lathe machine can be calculated for a particular operation if the speed of the job, feed and length of the job is known. For Milling operations speeds may be increased by 50%. Surface speed is traditionally expressed in either feet per minute or meters per minute, so we can divide by 12 inches to the foot and arrive at 523 SFM. d) 1:100. The harder the work material, the slower the cutting speed. 2. Cutting Speed. When machining in lathes, turning centres or multi-task machines, calculating the correct values for different machining parameters like cutting speed and spindle speed is a crucial factor for Feed Rate = ChipTooth × #T × RPM. Speeds should be halved when using Carbon Steel bits and can be doubled for Carbide bits. On a mill it is the rotational speed of the outer diameter of the cutter. The hardness of the work material has a great deal to do with the recommended cutting speed. Inch. Chip Area perpendicular Speed Unit Constant M R R = W × F n ⏞ × V c ⏞ × K ⏞. In this section you find boring formulas and definitions needed for your boring operations, such as how to calculate correct boring cutting speed, feed per revolution and metal removal rate. Determine the spindle speed (RPM) and feed rate (IPM) for a drilling operation, as well as the cut time for a given cut length. Sanfoundry Global Education & Learning Series – Machine Tools and Machining. F n - Feedrate in mm or inches. Table feed, v (mm/min) Mar 20, 2024 · On lathes, where the part is rotating, the cutting speed depends on: 1. Rotation speed of the part. 262 x DIA x RPM Revolutions per Minute (In. Use the same speed formulas as for mills. , for turning on a lathe). In machining, the words “Speed”, “Cutting Speed”, “SFM” and “Surface Speed” all refer to the relative linear velocity between the tip of the cutting edge and the workpiece. What to Get: If you need only the cutting speed, select “Speeds Only”, and you will be asked to enter fewer parameters. The exact RPM is not always needed, the following calculator (formula) may be used to estimate the value closely. W – Width of Groove in mm or inches. Step 3: Find The Recommended Cutting Speed. Calculate the RPM setting to perform this cut. The calculation is “RPM x Diameter = speed” this means that if you have an rpm of 800 and a piece 2 inches in diameter, the outermost edge will spin at 1600 rpm. 01 inches per revolution is suitable for the thread pitch you are cutting. s=Feed of the job. Formula for Lathe Operation Cutting Time TCm = Time Cutting in Minutes TCs = Time Cutting in Seconds TPI = Threads Per Inch W = Width of Cut Abbreviations & Measurement Units Mill and Lathe Formulas Decimal Equivalent Chart . f. 5 mm) They come in different patterns (See below). The diameter is usually between 0. 5 Inches (6 – 32 mm). May 13, 2024 · The "speeds" part of the speeds and feeds calculator is the rotation speed of either the tool (e. Once you have the right tool, mount it onto the lathe's tool holder and ensure it is secure. , for drilling) or the workpiece (e. Step 4: Determine the taper angle Mar 18, 2024 · A lathe is a machine that rotates the workpiece about an axis to perform different operations such as turning, facing, taper turning, knurling, grooving, parting off, thread cutting, reaming, etc. Fill in the cutting speed, V = 7 m How to use this calculator: Choose a type of operation (drilling, reaming, boring, counterboring, face milling, slab milling/side milling, end milling, or turning), select your stock material, choose a material for the tool (high-speed steel or carbide), input the quantity of teeth for the tool and the diameter of the workpiece/cutter. Example: 1/2" diameter aluminum. Go to CoroPlus® ToolGuide. Feed rate and cutting speed determine the rate of material removal, power requirements, and surface finish. On a shaper (OLD school equipment) its a straight line, so its really easy. S in m/min, D in mm, N in RPM. ) SFM = 0. 4. 14 * 1, nearly 6300 inches per minute. Text and pics. Example: Diameter (Dm) = 60 mmSpindle speed (n) = 500 min-1In this case, the cutting speed (vc) is approximately 94 m/min. / Rev. Metal Removal Rate in Parting and Grooving. Therefore it is common that we need to compute the RPM from a given SFM either for programming or to ensure that the SFM we want to run at is within By dividing the full cutting depth of the thread into smaller cuts, the sensitive nose radius of the insert is not overloaded. Cutting speed is defined as the speed (usually in feet per minute) of a tool when it is cutting the work. Find the cutting tool for your specific task and. Assume that the cutting speed V is 7 m/min. Find the cutting tool for your specific task and get instant cutting data recommendations. Feed per Tooth (f) Feb 21, 2024 · The animation below shows how the spindle speed changes as the tool moves towards the axis in facing. Speed – Surface Feet per Minute (SFM) Feed – Inches per Minute (IPM) Feed per Tooth (FPT) Adjusted Feed per Tooth – Chip Thinning (AFPT) Feed per Revolution (FPR) Depth of Cut (DOC) Width of Cut (WOC) Tool Diameter (D) # of Teeth in Cutter (Z) Metal Removal Rate – Cubic Inches per Minute (MRR) Feb 26, 2024 · Step 3: Set the lathe machine. Where Vc – cutting speed (m / min); dw – diameter of workpiece surface to be machined (mm); n – workpiece speed (r / min). The 1000 (or 12) on the top half of the equation takes Mar 1, 2011 · Tangential velocity on the surface of the tool or workpiece at the cutting interface. When boring holes, correct values for different machining parameters are a crucial factor for good result. It is typically measured in surface feet per minute (SFPM) or meters per Cutting speed is the rotational speed of either workpiece or cutting tool (based on which is rotating). The thread diameter of a 9/16 thread is . Sep 5, 2022 · Cutting speed in turning operations - Formula for calculating the cutting speed in turning operations and the presentation of its practical applications in p May 22, 2024 · Cutting Speed Formulas and Their Pitfalls Feeds and Speeds Calculator Wood Turning and Lathe Feeds and Speeds Free Lathe Speeds and Feeds Calculator The 4 Fastest Ways to Break an Endmill: Chip Clearing, Built Up Edge, Runout and Deflection Little-Known Factors That Make G-Wizard Great for Both Big and Small CNC Machines What is the feed per revolution when main axis spindle speed is 500min-1 and cutting length per minute is 120mm/min ? Answer Substitute n=500, I=120 into the formula. Boring formulas and definitions. circumference of tap = PI * tap diameter. 82 x SFM ÷ DIA Revolutions per Minute (mm mode) This formula is used to calculate the cutting speed from the spindle speed and the outer diameter of the cutter. Mode – Advanced / Simple: In simple mode, you need to enter fewer parameters, and the calculator will rely on the system defaults. up to 100% of v c max. Step 5: Adjust For The Number Of Teeth On The Cutting Tool. Given SFM from the table, plus the tap’s diameter, we can calculate rpm with this formula: Spindle RPM = SFM / circumference of tap. In this section you find a compilation of the most relevant machining formulas and definitions for the machining areas: General turning To convert the SFM to RPM, use the following formula: RPM = 4 X SFM / MATERIAL DIAMETER. 018 per tooth RPM = 3000 IPS = 0. On the other hand, the CNC machine is programmed with the RPM (Spindle speed). 8 IMP, while the external feed becomes 13. An illustration of CNC drilling. To calculate spindle speed: Enter the diameter of the part, D = 20 mm. And circumference is diameter times pi. The cutting time for a lathe operation depends on factors such as cutting speed, feed rate, depth of cut, tool geometry, and the complexity of the workpiece. (See the Gcode examples below) Formulas to calculate the required RPM that will yield the needed cutting speed. Following are many of the commonly used formulas for calculating operating parameters for cutting tools: NOTE: for all formulas, D = diameter. Machining time = l/s×n min. 1 SFM equals 0. The table at the bottom shows the values of surface speed (in Calculate the optimal cutting speed for your machining operations with this online tool from Sandvik Coromant. 82, where diameter is the cutting tool diameter or the part diameter on a lathe in inches, and 3. Cutting speed, also known as surface speed, refers to the speed at the outside edge of the tool as it is cutting. 4 x 300 / 0. 00508 surface meter per second (meter per second, or m/s, is the SI unit of speed). Note: The Surface Speed and Chip Load tables below assume the tool material is carbide. It is measured in surface feet per minute (SFM). You can also enter a custom surface speed in metres per minute and see the cutting speed in RPM for the specified diameter. The spindle speed N in RPM is calculated using this equation, where V is the cutting speed and D is the diameter at which the tool is cutting. The cutting speed of a milling cutter is its circumferential linear motion that results from rotation. Cutting speed (often abbreviated Vc) on a lathe is the velocity of the surface of the material as it moves across the cutting tool. View Answer. Spindle Speed RPM Formula = (12 * SurfaceSpeed) / (PI * Cut Diameter) (Formula for finding turning speeds) Feed Rate Formula = Chip Load * RPM. . Sep 30, 2013 · Learn how to calculate the optimal cutting speed and RPM for your lathe and mill projects with this informative video tutorial. a) 10:1. 037 inch)) are turned on a 1. 94 mm (0. May 26, 2023 · 3. In this section, you will find the formulas and definitions needed for general turning. Mar 20, 2021 · 1. In this section you find parting and grooving formulas and definitions for how to calculate cutting speed, feed rate or other parameters that affect the machining in your turning centre, lathe tool or multi-task machine. Use coolant judiciously. Feb 27, 2021 · Calculating Cutting Speed, Feed, and Machining Time for Turning a Part on a Lathe Jul 8, 2020 · Cutting parameters of lathe machineCutting speed, feed, depth of cut and machining time G96 is the modal Gcode command that instructs the CNC controller to enter a “constant surface cutting speed”. or mm/min. Where the circumference is that of the workpiece on a lathe or the cutter on a mill. 5 = 2,400 RPM. The depth of cutting, on the other hand, can be controlled by adjusting the position of the cutting tool in relation to the workpiece. RECOMMENDED CUTTING SPEED AND FEED Nodular cast iron Feed per tooth (inch/tooth) ISO HRC With Coolant Hole VDI 3323 Material Description HB Non-alloy steel. 950. Transform production and profits dramatically, in just a few months. 004 inch) in cutting depth per pass (radial infeed), the full cutting depth ( a p ) and the profile depth of the thread (0. Calculate Cutting Speed from Dia of job to be turned and Revolution of job. Cutter orientation, feed rate, depth of cut, and cutting speed are the primary elements that come into play. Cutting speed vc (m/min) Cutting speed vc (ft/min) Apr 19, 2024 · Spindle speeds can get pretty crazy if you are cutting at a small workpiece diameter. 82) / 0. Nov 18, 2023 · Calculations For Drilling Operations. Turning Operations D O D f d d D O = Original Diameter D f = Final Diameter d = Depth of Cut 3 d = This calculator gives guideline cutting speeds for a specified diameter. Two edges from the centre to the periphery. 26 5 spindle speed (rpm). The cutting speed declines from 100% at the periphery to zero at centre. The geometry of the cutting tool directly affects the quality and precision of the workpiece produced. Time for a little math, but let’s keep it straightforward. In other words, you want the circumference of whatever is spinning. The calculation shall be subject to the maximum cutting speed. 82 is a constant that comes from an algebraic simplifica-tion of the more complex formula: rpm = (sfm × 12) ÷ (diameter × π). For Example: 10 Inch Bowl = 9,000 / 10 = 900 RPMs Maximum. Calculate Time for Drilling. Speed, Feed, and Depth of Cut. 1200. Step 4: Calculate The Spindle Speed. S = (V s x 1000)/ (π x D) Where V s denotes cutting speed in meters per second (m/sec) and D denotes the diameter of the tool in millimeters (mm). T = l × π × d 12 × F n × V c. Cutting speed (SFM): the rate at the workpiece surface, measured in surface feet The cutting tools catalogs or our experience tells us the SFM (Cutting Speed) we need to use for a given application. Aug 27, 2021 · The calculation formula is as follows: Vc= ( π d w n )/1000. 640. Turning formulas and definitions. 5. The calculation to get a maximum ballpark speed for your bowl blank on a wood lathe is as follows. 9531 Cutting Speed (surface feet/min. May 11, 2024 · Find the spindle speed for milling a steel workpiece having a diameter of 20 mm. Velocity is measured in units of length per unit time, for example surface feet per minute (SFM) or or meters per minute. Step 2: Determine the thread specifications. b) 1:10. The formula for cutting speed (sfm) is tool diameter 5 0. Determine the feed rate for a single tooth with a feed per tooth of 12 mm as well. For convenience, Knurling is often performed at the same speeds used for turning operations when using high speed steel tool bits. Cutting speed is mainly depending on the type of materials and cutting tools, related to their hardness. The speed is typically measured in revolutions per minute (RPM). Mark and rough the material: Use a center punch to mark the position of the threads, and rough the material to the desired diameter using a facing tool. To get the low RPM, you have to divide the diameter of the workpiece by 6000 rpm to get the lowest rpm possible. 3 cu in/min. 3. D: Depth of cut, mm. S: Cutting speed, m/min. c) 100:1. The formulas below calculate the spindle Jan 8, 2024 · Calculating the cutting speed in a lathe operation involves determining the rotational speed of the workpiece and converting it to surface speed. ) from Cutting Speed and Dia of job to be turned. Hit the SFM is a combination of diameter and the velocity ( RPM) of the material measured in feet-per-minute as the spindle of a milling machine or lathe. Step 2: Identify The Cutting Tool. The formula for feed per tooth (fpt) is table feed (ipm)/number of flutes/spindle speed (rpm). At 20 dia. The 1000 in the denominator is to convert the D in mm to meters. Calculate Time for Boring. n=RPM of the workpiece. Example: 2" diameter stainless steel. Knurling Wheels: Knurling wheels are usually made from PVD -coated HSS. The turning It involves grasping essential variables in the process. , a cylindrical workpiece is used. Take cutting speed V to be 5 m/min. 018 × 5 × 3000 = 270 Inches Per Minute. For example, cutting speed in turning is 295rpm. The softer the work Feb 18, 2024 · You refer to the lathe's manual and determine that the recommended speed for cutting stainless steel threads is 300 RPM. Feb 1, 2013 · Tangential velocity on the surface of the tool or workpiece at the cutting interface. Similarly for drilling operations, the speeds and feeds can be calculated as follows. The central insert operates from cutting speed zero to approximately 50% of v c max, The peripheral insert works from 50% of v c max. 854 to 93. 5 = 3056 / 0. Cutting speeds depend primarily on the kind of material you are cutting and the kind of cutting tool you are using. 760. Mar 20, 2021 · All cutting tools work on the surface footage principle. 10 mm (0. 009–0. Result will be displayed. F: Feed rate,mm/rev. Title: Oct 2, 2017 · The calculated speed is 2,064 RPM and the linear feed is 8. Oct 1, 2023 · It’s easy to calculate the lathe speed if you’re turning wood. Drilling Speed and Feed Calculator. You can play around with this Apr 26, 2024 · Milling Cutting Speed Formulas. l (mm/min): Machined length per minute n (min-1): Spindle speed memo This formula is used to calculate the feed rate per revolution from the spindle speed and the length cut per minute. The tool should have the correct shape and pitch for your desired thread. 1. Apr 29, 2024 · Zinc – Diecasting 80. Cutting Speed is given in feet per minute (often provided in the chart for various woods). The definition is the same for all machining operations turning, milling, etc. For easier Human Grip. ) d = Depth of Cut 2 . Feed rate is defined as tool’s distance travelled during one spindle revolution. Let’s discuss all lathe machine operations one by one as follows. 23: Speed Formula (Simplified) Speedis the machine spindle RPM (how fast the part turns). 375. MRR – Metal Removal Rate in CM 3 /min or Inch 3 /min. It is calculated by the below formula. Where: RPM is the Revolutions Per Minute. 23–0. You set the lathe's speed to 300 RPM and adjust the feed rate accordingly. Set the threading tool: Mount the threading tool into the tool post of the lathe, ensuring that it is square to the workpiece and set to the correct height. Speeds in Surface Feet per Minute are specified for High-Speed Steel drill bits, and are approximate for normal drilling operations. Jul 1, 2014 · The following equation is used to calculate spindle speed: rpm = sfm ÷ diameter × 3. How To Calculate Lathe Speed Chart: A Step-By-Step Guide. 0469 – . To determine spindle speed, use the following steps: Enter the diameter of the part, D = 30 mm. 5 = 1,200 / 0. #1 Cutting Speed. Where, l=Length of the job. At a cutting speed of 250, at 30 mm. Metric. For Decoration. You generally want the part you are working on to have an RPM of 1000 to 2000, preferably never any higher than that. 82 x SFM)/D or SFM/ (. Slow speeds are typically used for larger diameters, while faster speeds are suitable for smaller diameters. Tapping Feed Rate & Tapping Feed Rate Formula. For clarity, this is the maximum speed under any conditions. V c – Cutting Speed in m/min or feet/min ( SFM ). In case lathe operations, such as turning, grooving, centre drilling, parting, etc. Calculate Time for Turning. If we substitute n with the spindle speed formula, we can calculate the machining time directly: n = 12 × V c π × d. Enter value and click on calculate. To perform different lathe machine operations on a lathe, the workpiece may be Lathe operations can be performed on a wide range of materials, including metals, plastics, and composites. SFMis the Surface Feet per Minute based on the insert manufacturers' recommendation for the material and cutting conditions. The formula for spindle speed (rpm) is cutting speed (sfm) 5 3. To practice all areas of Machine Tools and Machining, here is complete set of 1000+ Multiple Choice Questions and Answers. Metric mode. Cutting Speed Formula for Spindle Speed based on Surface Speed and Diameter of Tool: For example, if you’re running a surface speed of 800 surface feet per minute, and a tool diameter of 1/2″, your spindle speed (RPM) should be: (800 x 3. To get the high rpm, divide the diameter of the workpiece by 9000 rpm, and you’ll get the right lathe speed. ob wl ck uh kh cn gm vi vw sq