{"id":11711,"date":"2026-06-04T17:31:22","date_gmt":"2026-06-04T09:31:22","guid":{"rendered":"https:\/\/www.cncmachiningshops.com\/?p=11711"},"modified":"2026-07-16T11:28:06","modified_gmt":"2026-07-16T03:28:06","slug":"cnc-undercuts","status":"publish","type":"post","link":"https:\/\/www.cncmachiningshops.com\/es\/cnc-undercuts\/","title":{"rendered":"C\u00f3mo dise\u00f1ar muescas CNC sin aumentar el coste de fabricaci\u00f3n"},"content":{"rendered":"
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Quick Answer:<\/strong> A CNC undercut is any feature that cannot be reached by a standard end mill moving in a straight vertical or horizontal direction \u2014 internal grooves, T-slots, thread reliefs, dovetail joints, and O-ring grooves are common examples. Undercuts increase machining cost not because of geometric complexity but because they force non-standard tooling (lollipop cutters, T-slot cutters, form tools), additional setups (cycle time increase of 20\u201350%), slower cutting conditions, and more complex CMM inspection. The most effective cost-reduction strategy is a three-step DFM approach: (1) eliminate undercuts with no functional purpose, (2) standardize surviving undercut dimensions to match off-the-shelf cutter sizes (3, 4, 6, 8, 10 mm and standard inch equivalents), and (3) limit undercut reach depth to \u22643\u00d7D to maintain tool rigidity. Functional undercuts \u2014 O-ring grooves, thread reliefs, keyways, T-slots \u2014 should be preserved; their cost is justified by assembly and sealing requirements that cannot be met otherwise.<\/p><\/blockquote>\n

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Why Undercuts Increase CNC Machining Cost<\/h2>\n

Undercuts are not inherently problematic from an engineering standpoint. The cost increase comes from a specific manufacturing constraint: standard end mills move in the X, Y, and Z axes and can only cut geometry they can reach in a straight approach path. When geometry is “hidden” from this direct approach, the machining workflow breaks down.<\/p>\n

The five cost drivers from a supplier perspective:<\/strong><\/p>\n\n\n\n\n\n\n\n\n\n
Cost Driver<\/th>\nMechanism<\/th>\nTypical Impact<\/th>\n<\/tr>\n<\/thead>\n
Specialized tooling<\/td>\nStandard end mills cannot reach undercuts; requires lollipop, T-slot, or form cutters<\/td>\n+10\u201330% tooling cost<\/td>\n<\/tr>\n
Additional setups<\/td>\nPart must be repositioned or re-fixtured for each new access direction<\/td>\n+15\u201340% cycle time<\/td>\n<\/tr>\n
Reduced cutting efficiency<\/td>\nLonger, less rigid tools require lower feed rates and shallower depths per pass<\/td>\nLower material removal rate throughout<\/td>\n<\/tr>\n
Inspection complexity<\/td>\nUndercut geometry cannot be measured with standard calipers; requires CMM or custom gauges<\/td>\nExtra QC time and cost<\/td>\n<\/tr>\n
CAM programming complexity<\/td>\nStandard toolpaths produce tool-workpiece collisions; requires custom collision-avoidance programming<\/td>\nLonger pre-production engineering time<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

The real cost mechanism:<\/strong> A standard part with four vertical walls, flat floor, and simple holes can be programmed and machined in a single setup with standard end mills at near-maximum cutting parameters. Add an internal retaining groove that requires a lollipop cutter and a second setup, and the cycle time increases 25\u201340% \u2014 not because the groove itself takes long to cut, but because the second setup requires re-fixturing, alignment verification, and tool changes.<\/p>\n

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Functional Undercuts: Which Ones Must Be Kept<\/h2>\n

Before any DFM review eliminates undercuts, engineering must distinguish features that are structurally or functionally necessary from features that are present for cosmetic, legacy, or unexamined reasons.<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n
Undercut Type<\/th>\nKeep or Redesign<\/th>\nEngineering Reason<\/th>\n<\/tr>\n<\/thead>\n
O-ring groove<\/td>\nKeep<\/td>\nSealing function requires specific groove depth, width, and tolerance to compress the O-ring to the correct compression ratio<\/td>\n<\/tr>\n
Thread relief<\/td>\nKeep<\/td>\nAllows the threading tool to complete the thread form at the bottom of the thread engagement; without it, the last thread pitch is incomplete<\/td>\n<\/tr>\n
Keyway<\/td>\nKeep<\/td>\nProvides positive torque transmission between shaft and hub; no alternative without a complete redesign<\/td>\n<\/tr>\n
T-slot<\/td>\nKeep (optimize dimensions)<\/td>\nEnables sliding retention with standard T-nuts; optimize to standard T-slot cutter widths<\/td>\n<\/tr>\n
Dovetail joint<\/td>\nKeep if required<\/td>\nProvides mechanical interlocking that resists pull-out forces; evaluate whether a simpler external feature can replace it<\/td>\n<\/tr>\n
Snap-fit retaining groove<\/td>\nKeep if required<\/td>\nEnables blind assembly retention; evaluate whether the assembly sequence can be changed to allow an external feature<\/td>\n<\/tr>\n
Decorative internal groove<\/td>\nRemove<\/td>\nNo functional contribution; purely cosmetic<\/td>\n<\/tr>\n
Legacy groove from casting design<\/td>\nRemove<\/td>\nCarried forward from a casting or injection-molded predecessor; has no function in the CNC machined version<\/td>\n<\/tr>\n
Hidden internal recess<\/td>\nRemove<\/td>\nIf not used for fluid flow, component retention, or assembly, there is no engineering justification for the cost<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

O-ring grooves in detail:<\/strong> An O-ring groove is a precision undercut requiring tolerances of \u00b10.025\u20130.050 mm on groove width and depth to achieve the specified O-ring compression ratio (typically 10\u201330% of O-ring cross-section diameter). The groove cannot be replaced by a flat seal or gasket in most pressure applications without significant redesign of the mating interface. This is the prototypical functional undercut \u2014 the machining cost is real, but the engineering function is indispensable.<\/p>\n

Thread reliefs in detail:<\/strong> Thread reliefs are short (1\u20133 mm) grooves at the thread run-out that allow the threading tool to withdraw without cutting an incomplete final pitch. Without a thread relief, the last one to two thread pitches have an irregular form that produces assembly difficulty and incorrect thread engagement depth. Thread reliefs are machined with the threading tool already in use, typically adding minimal cycle time, and should never be removed.<\/p>\n

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DFM Review: Eliminating Non-Functional Undercuts<\/h2>\n

The most cost-effective undercut reduction strategy does not require redesigning geometry \u2014 it requires systematically asking whether each undercut serves an engineering function.<\/p>\n

DFM checklist for each undercut feature:<\/strong><\/p>\n

    \n
  1. Does removing this feature affect sealing, fluid retention, or pressure performance?<\/li>\n
  2. Does removing this feature affect assembly \u2014 retention, alignment, or engagement?<\/li>\n
  3. Does removing this feature affect torque transmission or mechanical locking?<\/li>\n
  4. Is this feature visible or accessible after final assembly?<\/li>\n
  5. Can a standard end mill reach this feature without special tooling?<\/li>\n<\/ol>\n

    If the answers to questions 1\u20133 are all no, the feature is a candidate for removal. If the answer to question 4 is no (feature is hidden after assembly), and there is no engineering function, removal is straightforward \u2014 it will not affect the product in service.<\/p>\n

    The most common case for removal:<\/strong> Internal decorative grooves, chamfers, or recesses on surfaces that are completely enclosed after assembly. These features were sometimes added during initial design for aesthetic reasons (visible in CAD renderings) without recognizing they would be invisible in the assembled product. They add zero product value but require special tooling and additional setups every time the part is machined.<\/p>\n

    Legacy features from previous manufacturing processes:<\/strong> Products converted from casting, die casting, or injection molding to CNC machining frequently carry geometric features that were functional in the original process (draft angles, parting line features, casting aids) but have no function in CNC machining. These should be systematically identified and removed during the DFM review.<\/p>\n

    \n

    Standardizing Undercut Dimensions to Match Off-the-Shelf Tools<\/h2>\n

    For undercuts that must be retained, the single most impactful cost reduction is ensuring that undercut dimensions correspond to available standard tool sizes. Non-standard dimensions are the most common source of unnecessary cost in undercut machining.<\/p>\n

    Standard cutter sizes for common undercut tooling:<\/strong><\/p>\n

      \n
    • T-slot cutters (metric): 6, 8, 10, 12, 16, 18, 20 mm cutter diameter; standard neck diameters and depth ranges<\/li>\n
    • Lollipop\/ball-end undercut cutters: 3, 4, 6, 8, 10 mm ball diameter; corresponding neck diameters<\/li>\n
    • Keyseat cutters (inch): 1\/8″, 3\/16″, 1\/4″, 5\/16″, 3\/8″, 1\/2″ cutter diameter<\/li>\n
    • O-ring groove dimensions: standardized per AS568 (inch) or ISO 3601 (metric) O-ring sizes, with corresponding groove width and depth<\/li>\n<\/ul>\n

      The non-standard dimension trap:<\/strong> An undercut specified at 7.3 mm width has no matching standard T-slot or lollipop cutter. The machining shop has two options: order a custom cutter (adding $150\u2013$500+ and 1\u20133 weeks lead time) or use a closely-sized standard tool with modified programming (producing a slightly inaccurate feature that may require engineering approval). Changing the specification to 8 mm matches the closest standard cutter, eliminates the custom tooling requirement, and typically reduces per-part cost by 20\u201330%.<\/p>\n

      Even small deviations from standard sizes trigger custom tooling:<\/strong> A 0.5 mm deviation from a standard cutter size is not a manufacturing compromise \u2014 it is a custom tool specification. Engineering and procurement teams frequently underestimate how strictly standard tool sizes are defined and how readily machinists escalate even small non-standard dimensions to custom tooling.<\/p>\n

      Standard O-ring groove dimensions eliminate guesswork:<\/strong> O-ring grooves specified according to AS568 or ISO 3601 standards have well-documented groove width, depth, and surface finish requirements that correspond to specific O-ring cross-section diameters. These standard groove dimensions are machined routinely with standard groove tooling. Non-standard O-ring grooves that do not correspond to any standard O-ring size require engineering justification and often custom tooling.<\/p>\n

      \n

      Controlling Undercut Depth to Maintain Tool Rigidity<\/h2>\n

      Tool stiffness for the long-reach tools required for deep undercuts decreases with the cube of the tool’s reach length. This means that doubling the reach depth reduces tool stiffness by a factor of 8 \u2014 not 2. Deep undercuts therefore produce disproportionate problems with tool deflection, chatter, dimensional accuracy, and surface finish.<\/p>\n

      Depth guidelines by risk level:<\/strong><\/p>\n

        \n
      • \u22642\u20133\u00d7D (tool diameter): stable machining, standard feeds and speeds, acceptable surface finish<\/li>\n
      • 3\u20134\u00d7D: moderate risk; reduce feed rate 20\u201330%, take lighter depths per pass<\/li>\n
      • 4\u20135\u00d7D: high risk of chatter; requires full assessment of tool path, feed rate, and spindle speed<\/li>\n
      • Above 5\u00d7D: very high risk; consider redesigning the feature, using a larger-diameter tool, or accessing from a different direction<\/li>\n<\/ul>\n

        What happens with excessive depth:<\/strong> A 6 mm diameter lollipop cutter reaching 25 mm into a feature (\u22484\u00d7D) deflects under cutting forces, producing dimensional inaccuracy and chatter marks. The surface roughness (Ra) can jump from 0.8\u20131.6 \u00b5m (stable conditions) to 3.2\u20136.3 \u00b5m (chattering long-reach conditions). Dimensional accuracy in the undercut feature degrades from \u00b10.025 mm to \u00b10.050\u20130.100 mm. Reducing the undercut depth from 25 mm to 15 mm (2.5\u00d7D) restores stable machining conditions.<\/p>\n

        Cycle time impact:<\/strong> Deep undercuts require conservative parameters that increase machining time by 30\u201380% compared to the same feature at shallower depth. A machining operation that takes 3 minutes at 2\u00d7D may take 5\u20136 minutes at 4\u00d7D \u2014 an increase the drawing specification produces directly by exceeding the stable operating range of the tooling.<\/p>\n

        \n

        Designing Undercuts for Better Tool Access<\/h2>\n

        Tool access is the primary engineering variable that separates expensive undercuts from affordable ones. Two undercuts with identical dimensions can have dramatically different machining costs depending on how the surrounding geometry affects tool entry, exit, and engagement.<\/p>\n

        Clear tool entry path:<\/strong> A cutting tool needs to enter and exit the undercut feature in a controlled manner. Enclosed internal geometries with no direct approach path require the tool to be inserted, repositioned, and engaged at unusual angles \u2014 increasing setup complexity and programming time. Open-side designs that allow the tool to approach in a straight line from the part exterior are dramatically simpler.<\/p>\n

        Clearance space around the feature:<\/strong> Undercut tools are typically smaller in diameter than the spaces they are cutting to allow the neck to pass. The tool needs radial clearance to rotate without collision. A 6 mm undercut groove requires approximately 8\u201310 mm of surrounding clearance for the tool body. Designing the surrounding geometry with insufficient clearance forces the programmer to use special collision-avoidance toolpaths and slower feeds.<\/p>\n

        Open-side vs enclosed undercuts:<\/strong><\/p>\n\n\n\n\n\n\n\n\n
        Design Type<\/th>\nTool Access<\/th>\nSetup Requirement<\/th>\nCost Level<\/th>\n<\/tr>\n<\/thead>\n
        Open on one face (tool enters from side)<\/td>\nDirect, one-pass<\/td>\nSingle setup<\/td>\nLow<\/td>\n<\/tr>\n
        Open at top (tool enters vertically from tool change)<\/td>\nDirect with standard approach<\/td>\nSingle setup<\/td>\nLow-medium<\/td>\n<\/tr>\n
        Fully enclosed (inside a cavity)<\/td>\nRequires lollipop or specialty cutter<\/td>\nOften two setups<\/td>\nHigh<\/td>\n<\/tr>\n
        Internal groove in blind bore<\/td>\nMaximum restriction<\/td>\nTwo setups minimum<\/td>\nVery high<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

        Opening one side of a feature eliminates an entire setup:<\/strong> An internal retaining groove in a housing bore is a two-setup operation \u2014 the part must be fixtured to allow the tool to access the bore interior. If the same retaining function can be achieved with a groove on the exterior of a shaft or housing, one setup is eliminated, standard turning tools replace the lollipop cutter, and inspection becomes straightforward.<\/p>\n

        \n

        Internal vs External Undercuts: Cost Comparison<\/h2>\n

        Internal undercuts cost more than external undercuts for every cost factor simultaneously.<\/p>\n\n\n\n\n\n\n\n\n\n\n
        Factor<\/th>\nInternal Undercut<\/th>\nExternal Undercut<\/th>\n<\/tr>\n<\/thead>\n
        Tool access<\/td>\nRestricted; tool must enter cavity<\/td>\nOpen; tool approaches from exterior<\/td>\n<\/tr>\n
        Required tooling<\/td>\nLollipop cutters, T-slot cutters, custom tools<\/td>\nStandard end mills, turning tools<\/td>\n<\/tr>\n
        Setup count<\/td>\nOften 2\u20133 setups<\/td>\nTypically 1 setup<\/td>\n<\/tr>\n
        Cutting parameters<\/td>\nReduced feed and depth; longer tool<\/td>\nStandard parameters; shorter, rigid tool<\/td>\n<\/tr>\n
        Cycle time<\/td>\n+20\u201350% vs equivalent external feature<\/td>\nBaseline<\/td>\n<\/tr>\n
        Inspection<\/td>\nCMM or custom gauge required<\/td>\nCalipers, standard gauge<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

        The reason internal undercuts cost more is not geometric complexity \u2014 it is that the surrounding material blocks the tool, forcing the use of longer and therefore less rigid tools, which must be operated at conservative parameters. External undercuts remove this constraint: the tool approaches the feature from outside the part envelope, allowing short, rigid tool setups at standard cutting parameters.<\/p>\n

        When internal undercuts are unavoidable:<\/strong> In some cases \u2014 internal snap-fit grooves, O-ring grooves in blind bores, bearing retaining grooves inside housings \u2014 the internal undercut serves a function that no external feature can replace without fundamentally changing the assembly design. In these cases, accept the cost premium and focus on optimizing the depth and dimensions to minimize it.<\/p>\n

        \n

        5-Axis Machining and Undercuts<\/h2>\n

        5-axis machining addresses the tool access problem by allowing the spindle to tilt and the workpiece to rotate, presenting the cutting tool to the feature at an optimal angle. This changes some undercut features from “inaccessible with 3-axis” to “accessible with standard tools at an angle.”<\/p>\n

        Where 5-axis machining reduces undercut cost:<\/strong><\/p>\n

          \n
        • Features that require 2\u20133 setups in 3-axis can often be completed in a single setup by tilting the part to provide tool access<\/li>\n
        • Features that require a lollipop cutter in 3-axis can sometimes be reached with a standard end mill at a tilted angle<\/li>\n
        • Multi-surface parts with undercuts on several faces benefit most from 5-axis consolidation<\/li>\n<\/ul>\n

          Where 5-axis does not solve the problem:<\/strong><\/p>\n

            \n
          • Deep, narrow undercuts that exceed the tool’s reach-to-diameter ratio remain difficult regardless of machine capability<\/li>\n
          • The 5-axis machine hourly rate is typically 40\u201380% higher than a 3-axis machining center; for parts where 3-axis with two setups is faster than 5-axis programming and setup, 3-axis remains more economical<\/li>\n
          • Complex 5-axis programming requires CAM engineers familiar with collision avoidance and tool axis optimization \u2014 not universally available at lower-cost machining suppliers<\/li>\n<\/ul>\n\n\n\n\n\n\n\n\n
            Scenario<\/th>\n3-Axis Approach<\/th>\n5-Axis Approach<\/th>\n<\/tr>\n<\/thead>\n
            Simple single undercut<\/td>\nLow cost<\/td>\nHigher cost (machine rate premium not justified)<\/td>\n<\/tr>\n
            Multi-setup undercut from one direction<\/td>\nModerate cost<\/td>\nOften lower cost through setup elimination<\/td>\n<\/tr>\n
            Complex part with undercuts on multiple faces<\/td>\nExpensive (many setups)<\/td>\nOften significantly lower total cost<\/td>\n<\/tr>\n
            Deep narrow undercut<\/td>\nExpensive (special tooling)<\/td>\nStill expensive (tool stiffness limit)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

            The design implication:<\/strong> The most cost-effective approach for most products is not to rely on 5-axis machining to handle difficult undercuts, but to design the undercuts to be accessible on 3-axis machines. 5-axis capability is most valuable for genuinely complex multi-surface parts where the undercut geometry is unavoidable, not as a remedy for avoidable DFM problems.<\/p>\n

            \n

            Key Takeaways<\/h2>\n
              \n
            • Undercuts increase cost through access limitation, not geometric complexity<\/strong>: the cost driver is the need for special tooling (lollipop, T-slot, form cutters), additional setups, and conservative cutting parameters \u2014 not the size or shape of the feature itself.<\/li>\n
            • Functional undercuts must be kept<\/strong>: O-ring grooves, thread reliefs, keyways, and T-slots enable sealing, thread engagement, torque transmission, and mechanical retention respectively. These functions cannot be eliminated without fundamental design changes.<\/li>\n
            • Non-functional undercuts should be removed in DFM review<\/strong>: internal grooves not visible after assembly, decorative recesses, and legacy features from previous manufacturing processes add 20\u201350% machining cost with zero product-performance benefit.<\/li>\n
            • Matching undercut dimensions to standard cutter sizes is the fastest single cost reduction<\/strong>: changing a 7.3 mm undercut width to 8 mm eliminates custom tooling, reduces cost 20\u201330%, and shortens lead time by up to 3 weeks.<\/li>\n
            • Undercut depth must not exceed approximately 3\u00d7D of the tool diameter<\/strong>: beyond this limit, tool stiffness decreases cubically with depth, causing chatter, dimensional inaccuracy, and cycle time increases of 30\u201380%.<\/li>\n
            • Internal undercuts cost significantly more than external undercuts<\/strong>: for every cost factor \u2014 tooling, setup count, cutting efficiency, inspection \u2014 internal undercuts carry a premium. When function allows, moving a retaining groove from inside a bore to outside a shaft is one of the highest-leverage DFM changes possible.<\/li>\n
            • For OEM procurement teams<\/strong>: when requesting quotes for parts with undercuts, provide the machining drawing with all undercut features explicitly identified with depth, width, and tolerance. Suppliers quoting without this information typically add contingency pricing for unspecified special-tooling requirements, or discover the undercuts after quoting and issue change orders. Clear upfront specification of undercut geometry, combined with DFM collaboration before drawing release, consistently produces lower and more accurate initial quotes.<\/li>\n<\/ul>\n
              \n

              Frequently Asked Questions<\/h2>\n

              What is an undercut in CNC machining?<\/h3>\n

              An undercut in CNC machining is any feature that cannot be machined by a standard end mill or turning tool moving in a single, straight approach direction. The feature is “hidden” from the tool’s direct line of approach, requiring either special tooling (lollipop cutters, T-slot cutters, form tools) or repositioning the workpiece to access it from a different direction. Common examples include internal retaining grooves inside bores, O-ring grooves on sealing faces, T-slots on clamping fixtures, thread reliefs at thread terminations, keyways, and dovetail joints. The defining engineering characteristic is not the shape of the feature but the fact that the surrounding geometry blocks a standard tool from reaching it in a single setup.<\/p>\n

              Why do undercuts increase CNC machining cost?<\/h3>\n

              Undercuts break the standard machining workflow in three simultaneous ways. First, they require specialized tooling \u2014 lollipop cutters, T-slot cutters, or custom form tools \u2014 that cost $50\u2013$500+ per tool, have limited availability, and require slower cutting parameters because of their reduced stiffness compared to standard end mills. Second, they typically require additional setups \u2014 repositioning and re-fixturing the workpiece \u2014 which adds 20\u201350% to cycle time per additional setup. Third, deep or enclosed undercuts require longer tools with reduced stiffness (tool stiffness decreases with the cube of reach length), forcing further reductions in feed rate and depth of cut. The cumulative effect on a moderately complex part with several internal undercuts can be 35\u201350% higher total machining cost compared to an equivalent part designed to avoid unnecessary undercuts.<\/p>\n

              How deep can an undercut be in CNC machining?<\/h3>\n

              The practical depth guideline for undercuts is \u22642\u20133\u00d7 the tool diameter (D) for stable, cost-effective machining. At this depth, the tool has adequate rigidity to maintain consistent geometry and surface finish at near-standard cutting parameters. At 3\u20134\u00d7D, reduced feed rates and multiple passes are required. Above 4\u20135\u00d7D, chatter, dimensional inaccuracy (dimensional drift of \u00b10.050\u20130.100 mm rather than \u00b10.025 mm), and poor surface finish (Ra 3.2\u20136.3 \u00b5m rather than 0.8\u20131.6 \u00b5m) become likely even in soft materials. For undercuts requiring depth above 4\u00d7D, the design should be reviewed for function \u2014 the required function may be achievable with a shallower groove, a larger-diameter tool (allowing the same groove to be at a lower D-multiple), or a different access direction that allows a shorter tool reach.<\/p>\n

              When should external undercuts be used instead of internal ones?<\/h3>\n

              External undercuts should be used whenever the same function can be achieved on an external surface rather than inside a bore or cavity. Internal undercuts require the tool to reach inside the workpiece, forcing long, less-rigid tooling and typically requiring a second setup for access. External undercuts are reached from the part exterior with short, rigid tools in a single setup. The cost difference is significant: internal undercuts add 20\u201350% to cycle time and often require special tooling; external undercuts can typically be machined with standard end mills or turning tools at full cutting parameters. The design question is whether the undercut’s function \u2014 typically retention, sealing, or alignment \u2014 requires it to be inside a bore or whether the assembly can be redesigned to locate the feature on an external surface.<\/p>\n

              What tools are used to machine undercuts?<\/h3>\n

              The four primary undercut tool types are: lollipop cutters (a ball or spherical end on a narrow neck shank) for internal grooves and undercut recesses accessible from above; T-slot cutters (a disc-shaped cutter on a cylindrical neck) for horizontal slot features that require cutting in both directions perpendicular to the tool axis; keyseat cutters (similar geometry to T-slot cutters but narrower) for keyway and similar precision groove applications; and form tools (custom-profiled tools) for non-standard undercut cross-sections. All four tool types share the characteristic of having a neck diameter smaller than the cutting head diameter, which is what allows them to machine the hidden geometry of undercuts. This neck construction also reduces the tool’s stiffness compared to a solid end mill, which is why undercut depth must be limited to maintain acceptable accuracy.<\/p>\n

              \n

              Written by the CMS engineering team with 15+ years of precision CNC machining experience, including systematic DFM review for undercut features in aluminum, stainless steel, titanium, and engineering plastics for aerospace, medical device, industrial automation, and consumer electronics OEM manufacturing programs. Technical references: Machinery’s Handbook (Milling Cutters and Undercut Machining), SME Fundamentals of Tool Design (Form Cutters and Special Operations), Sandvik Coromant Milling Application Guide, AS568 (O-Ring Groove Dimensions, SAE), ISO 3601 (O-Ring Seals \u2014 Groove Dimensions and Tolerances).<\/em><\/p>\n

              \n

              Sourcing CNC Machined Parts with Undercut Features?<\/strong><\/p>\n

              At CMS, we provide DFM review at the quoting stage that identifies unnecessary undercuts, recommends standardized dimensions for required features, and confirms tool access feasibility before machining begins \u2014 reducing both quoted price and production risk.<\/p>\n

              [Request a DFM undercut review and CNC machining quote \u2192]<\/p>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

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