[{"data":1,"prerenderedAt":143},["ShallowReactive",2],{"content:guides:design-for-cnc-turning:en":3},{"slug":4,"category":5,"locale":6,"title":7,"subtitle":8,"metaDescription":9,"intro":10,"sections":13,"designTips":69,"applications":77,"pricingLeadTime":107,"faq":109,"cta":125,"keywords":126,"image":134,"related":138},"design-for-cnc-turning","guides","en","Design for CNC Turning: Shafts, Grooves and Threads","Practical rules for shafts, bores, grooves and threads that keep lathe-turned parts fast and accurate","Design for CNC turning: shaft length-to-diameter ratio, groove width, thread relief and tolerance rules with a worked example. Upload STEP for a quote.",[11,12],"CNC turning produces round parts such as shafts, bushings and fittings by rotating stock against a cutting tool. Designing within the process's natural limits (length-to-diameter ratio, groove and thread relief geometry, achievable tolerance) avoids chatter, tool deflection and rejected parts. A shaft that ignores these limits can cost double to machine and still miss tolerance.","This guide covers the numeric rules for shaft proportions, undercuts, threads and surface finish, with a worked example, followed by what to send CutLinq for a turning quote.",[14,38,60,65],{"heading":15,"paragraphs":16,"table":19,"bullets":37},"Length-to-diameter ratio",[17,18],"A turned shaft held only in a chuck without tailstock support should keep its length-to-diameter (L\u002FD) ratio below 3:1 to avoid deflection and chatter. With tailstock or steady-rest support, L\u002FD up to 10:1 is workable, but feed rates must slow as the ratio increases.","Beyond L\u002FD of roughly 12:1, whip and taper become difficult to control even with support, and the part may need centre-drilling at both ends or a different process.",{"headers":20,"rows":24},[21,22,23],"L\u002FD ratio","Support needed","Practical result",[25,29,33],[26,27,28],"under 3:1","chuck only","good tolerance, fast",[30,31,32],"3:1 to 10:1","tailstock\u002Fsteady rest","workable, slower feed",[34,35,36],"over 12:1","special fixturing","taper and whip risk",null,{"heading":39,"paragraphs":40,"table":43,"bullets":37},"Grooves, undercuts and thread relief",[41,42],"External grooves should be at least 1.5 mm wide to allow standard grooving tools; narrower grooves require custom tooling and add cost. Where a thread meets a shoulder, add a thread relief groove at least 1x the thread pitch wide so the tool can retract cleanly without leaving a partial thread.","Internal bores under 6 mm diameter limit tool access and increase deflection risk; where possible, keep internal bore diameter above 8 mm for depths beyond 3x diameter.",{"headers":44,"rows":47},[45,46],"Feature","Minimum practical size",[48,51,54,57],[49,50],"External groove width","1.5 mm",[52,53],"Thread relief width","1x thread pitch",[55,56],"Internal bore (deep)","8 mm diameter for depth > 3x D",[58,59],"Chamfer on edges","0.3-0.5 mm x 45 degrees",{"heading":61,"paragraphs":62,"table":37,"bullets":37},"Threads and tolerance",[63,64],"Standard metric threads (M3 to M24) are cut directly on the lathe or added with a die\u002Ftap after turning; single-point threading on the lathe is more accurate for load-bearing threads. Standard turning tolerance on diameters is ±0.05 mm; tolerances down to ±0.01 mm are achievable on critical diameters such as bearing seats but add cost and inspection time.","Concentricity between turned diameters on the same part is typically held to 0.02-0.05 mm when machined in one setup without removing the part from the chuck.",{"heading":66,"paragraphs":67,"table":37,"bullets":37},"Worked example: a stepped shaft",[68],"A 6061-T6 aluminium shaft, 12 mm diameter and 90 mm long (L\u002FD = 7.5), needs tailstock support. It has an M8 thread at one end with a 2 mm thread relief groove, a 0.05 mm tolerance on the bearing seat diameter, and 0.5 mm x 45 degree chamfers on all ends. This geometry machines in one setup with standard tooling, avoiding the cost of custom grooving tools or a second chucking operation.",[70,71,72,73,74,75,76],"Keep L\u002FD ratio under 3:1 for chuck-only turning; use tailstock support up to 10:1.","Make external groove width at least 1.5 mm to use standard grooving inserts.","Add a thread relief groove at least 1x pitch wide before any shoulder.","Specify ±0.05 mm tolerance by default; reserve ±0.01 mm for bearing or sealing diameters only.","Chamfer all sharp edges 0.3-0.5 mm x 45 degrees to avoid burrs and ease assembly.","Keep internal bores above 8 mm diameter when depth exceeds 3x the bore diameter.","Design the part to be finished in one chucking where possible to hold concentricity within 0.02-0.05 mm.",{"headers":78,"rows":82},[79,80,81],"Industry","Example parts","Typical material",[83,87,91,95,99,103],[84,85,86],"Machinery OEM","Shafts, bushings","S235JR, 6061-T6",[88,89,90],"Automotive aftermarket","Spacers, pins","Mild steel, brass",[92,93,94],"Electrical","Standoffs, connectors","Brass CuZn37",[96,97,98],"Oil and gas","Fittings, adapters","316L stainless",[100,101,102],"Furniture","Threaded feet, pins","6061-T6 aluminium",[104,105,106],"Medical\u002Flab","Precision shafts","316L, titanium Grade 5",[108],"Turned part cost is driven by three factors: material and bar-stock diameter, machining time (length, number of diameter steps, thread cutting), and tolerance on critical diameters. Lead time for standard turned parts runs 4-7 working days; parts needing tight bearing-fit tolerances or secondary grinding typically take 7-10 working days.",[110,113,116,119,122],{"q":111,"a":112},"How long a shaft can you turn without it flexing during machining?","Without support, keep length under 3 times the diameter; with tailstock or steady-rest support, up to 10 times the diameter is workable at slower feed rates.",{"q":114,"a":115},"Can you cut a thread directly on the lathe or do I need a separate tap?","Standard metric threads can be single-point cut on the lathe in the same setup, which is more accurate for load-bearing threads than tapping afterward.",{"q":117,"a":118},"What tolerance can you hold on a shaft diameter?","Standard turning holds ±0.05 mm; critical diameters such as bearing seats can be held to ±0.01 mm with additional grinding and inspection time.",{"q":120,"a":121},"Do I need a relief groove next to every thread?","Yes where the thread meets a shoulder or larger diameter, a relief groove at least 1x the thread pitch wide lets the cutting tool retract cleanly and avoids a damaged partial thread.",{"q":123,"a":124},"What file do you need to quote a turned part?","A STEP file with the part geometry, plus a note on material, critical tolerances and thread callouts; a binding quote follows within 12 hours.","Upload a STEP file of your shaft or turned part to receive a binding quote within 12 hours.",[127,128,129,130,131,132,133],"design for CNC turning","shaft design rules","thread relief groove","length to diameter ratio turning","CNC lathe design guide","turned part tolerance","groove width turning",{"src":135,"alt":7,"width":136,"height":137},"guides\u002Fdesign-for-cnc-turning.jpg",1400,933,[139],{"category":140,"slug":141,"title":142},"processes","cnc-turning","CNC Turning",1790793880352]