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Understanding Rotary Toolholders


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This is a basic outline of the concepts, designs, and application of Steep Taper and HSK tooling

Understanding Rotary Toolholders

  1. 1. Understanding Taper Connections
  2. 2. Toolholder Overview <ul><li>Steep Tapers </li></ul><ul><li>Flanges </li></ul><ul><li>Big Plus </li></ul><ul><li>HSK </li></ul><ul><li>Shrink Fit </li></ul><ul><li>Connections (Collets, etc) </li></ul>
  3. 3. Toolholder Identification: Steep Taper
  4. 4. Toolholder Characteristics: CAT <ul><li>American Standard </li></ul><ul><li>V-flange for auto changing </li></ul><ul><li>Dimple in the notch of flange </li></ul><ul><li>Top and bottom of flanges are equal in width </li></ul><ul><li>Drive dog knotches are unequal depth </li></ul><ul><li>CV is often referred to as “CAT” or Caterpillar V-flange tooling as described under ANSI B5.50, and typically has inch threads for the retention knob. Some CV holders have a counter bore for a piloted retention knob. This is typically used in higher spindle speed applications. </li></ul>
  5. 5. Toolholder Characteristics: BT <ul><li>Asian or Japanese standards </li></ul><ul><li>Have round top in drive dog notches-looks like top of the key in BB </li></ul><ul><li>Top of flange is thicker than bottom </li></ul><ul><li>Drive dog notches are equal distances from the center. Better balanced by design </li></ul><ul><li>V-flange for auto changing </li></ul><ul><li>The BT taper is a JIS B6339 specification (Japan Industrial Standard). BT tooling carries a wider flange than a CV or DV tool and contains metric retention knob threads. </li></ul>
  6. 6. Toolholder Characteristics: DIN <ul><li>European standards </li></ul><ul><li>V-flange for auto changing- very similar to CAT except for additional whistle knotch </li></ul><ul><li>Has 3 notches in flange-2 drive dogs and one triangular-whistle knotch </li></ul>
  7. 7. Toolholder Characteristics: ISO <ul><li>Made exclusively for the woodworking industry </li></ul><ul><li>Have no drive dog slots </li></ul><ul><li>Same specs has DIN </li></ul><ul><li>Works on the 2 main woodworking spindles-Colombo and HSD </li></ul><ul><li>Balanced by design due to no drive dogs </li></ul><ul><li>Has wrench flats to hold the chuck from turning when tightening the nut </li></ul><ul><li>Comes in manual changing and quick change </li></ul>
  8. 8. Toolholder Characteristics: HSK <ul><li>Hollow Shank Taper (Kegel) </li></ul><ul><li>Comes in manual changing and quick change </li></ul><ul><li>Taper is short and non tapered to eliminate the problems associated with tapered spindles in milling applications </li></ul><ul><li>Gives both Radial and axial contact.htm to the spindle </li></ul><ul><li>Used in high speed applications (HSK-63A is most common in metalworking) associated with soft material machining-wood, aluminum and plastics </li></ul><ul><li>Six styles of HSK (known as a &quot;FORM&quot; A-F; e.g. HSK63, Form A) depending on manual or quick change, ultra high speeds and coolant through </li></ul>
  9. 9. Understanding Tapers <ul><li>16 Degree Included Angle </li></ul>CV, DV and BT tapers are all identical and known as 7/24 tapers. These tapers are commonly referred to as a “self-releasing” or “fast tapers.” The primary differences between the toolholders are the flange design and retention knob threads . Socket Shank Perfect Taper <ul><li>Allowable </li></ul><ul><li>Socket </li></ul><ul><ul><li>Tolerance </li></ul></ul>Allowable Shank Tolerance
  10. 10. AT3
  11. 11. Fretting <ul><li>STD’s on a machine </li></ul><ul><li>Causes are unknown </li></ul><ul><li>Form or corrosion </li></ul><ul><li>Friction welding </li></ul>
  12. 12. Flanges <ul><li>BT 40 </li></ul><ul><li>CAT 40 </li></ul>Note the differences between the Flange: The Taper is the same but how the toolchanger fingers engage the holder is different
  13. 13. DIN-B Coolant <ul><li>Din B tool holders have coolant through the flange.. DIN B style coolant can be a requirement on either a CAT or a BT Holder. DIN B designates &quot;through the flange&quot; </li></ul>
  14. 14. Steep Taper Problems <ul><li>Only taper contact </li></ul><ul><li>Changes in Z </li></ul><ul><li>Outside grippers </li></ul><ul><li>Good to 10-18,000 RPM </li></ul>
  15. 15. Big Plus Advantage
  16. 16. Big Plus More contact
  17. 17. LyndexNikken 3Lock <ul><li>When a 3Lock Holder is inserted into a 3Lock Spindle (before clamping), the gap between the spindle flange and the tool flange is 0.2mm for a 40 taper, or 0.5mm for a 50 taper.When the tool is clamped, the taper cone preloaded by the disc springs deforms radially and slides axially to create contact between the spindle face and the tool flange. </li></ul>
  18. 18. 3Lock after clamping <ul><li>When the tool is clamped, the taper cone preloaded by the disc springs deforms radially and slides axially to create contact between the spindle face and the tool flange . </li></ul>
  19. 19. LyndexNikken 3Lock <ul><li>Flange contact is good </li></ul><ul><li>Taper contact is good </li></ul><ul><li>Renention Knobs? </li></ul>
  20. 20. Wait a second! <ul><li>None of these solutions address the centrifugal forces affecting the retention knob grippers </li></ul>
  21. 21. HSK <ul><li>Hollow Shank Kegel </li></ul><ul><li>Dual Contact </li></ul><ul><li>Grippers internal </li></ul><ul><li>Expanding taper </li></ul><ul><li>Left side: clamped </li></ul><ul><li>Right Side unclamped </li></ul>
  22. 22. Toolholder Identification: HSK
  23. 23. HSK Forms <ul><li>Hollow Shank Kegel </li></ul><ul><li>6 forms </li></ul>
  24. 24. HSK-A & HSK-C <ul><li>HSK-A for automatic tool changing </li></ul><ul><li>HSK-C for manual tool changing </li></ul>Moderate Torque; Moderate- high spindle speeds; drive slot
  25. 25. HSK-B & HSK-D <ul><li>HSK-B for automatic tool changing </li></ul><ul><li>HSK-D for Manual tool changing </li></ul>High Torque; Moderate to high spindle speeds; drive slot
  26. 26. HSK-E & HSK-F Low Torque; Very High spindle speeds; Automatic tool change
  27. 27. Torsional Rigidity <ul><li>CAT40 = 670 Nm/mm </li></ul><ul><li>HSK63 = 3,600 Nm/mm </li></ul><ul><li>CAT50 = 2,400 Nm/mm </li></ul><ul><li>HSK100 = 17,000 Nm/mm </li></ul>
  28. 28. Balance & “G” <ul><li>&quot;U&quot; is the allowable unbalance in </li></ul><ul><li>&quot;G&quot; is the standard for balance quality of rotating rigid bodies. (For machine tool drives it is G 2.5). </li></ul><ul><li>&quot;W&quot; is tool holder assembly weight in (kg). Our example chuck has a weight of 2.75 kg. </li></ul><ul><li>&quot;9549&quot; is a constant. </li></ul><ul><li>&quot;RPM&quot; is our rotational speed </li></ul>
  29. 29. Sources of Imbalance <ul><li>Controllable (Fixed) Sources </li></ul><ul><ul><li>Unground Diameters </li></ul></ul><ul><ul><li>Drive Slot Depth </li></ul></ul><ul><ul><li>Centerline deviations </li></ul></ul><ul><ul><li>AT tolerance </li></ul></ul><ul><li>Uncontrollable (Variable) forces </li></ul><ul><ul><li>Cutting Tool Shank Tolerance </li></ul></ul><ul><ul><li>Non-Symetric tools (boring bars) </li></ul></ul><ul><ul><li>End Mill Flats </li></ul></ul><ul><ul><li>Different length/depth of flutes </li></ul></ul>
  30. 30. Single Plane Balance <ul><li>Single plane </li></ul><ul><li>balancing applies to toolholders which: </li></ul><ul><ul><li>Have operating speeds less than 18,000 RPM </li></ul></ul><ul><ul><li>Have been pre-balanced by the manufacturer </li></ul></ul><ul><ul><li>Have a length less than two times the diameter at the gage line </li></ul></ul>
  31. 31. Parameters for Duel Plane Balance <ul><li>Dual Plane </li></ul><ul><li>balancing should be considered for Toolholders which: </li></ul><ul><ul><li>Have operating speeds in excess of 18,000 RPM </li></ul></ul><ul><ul><li>Have a length more than two times the diameter at the gage line </li></ul></ul>
  32. 32. Toolholder Balance
  33. 33. Which is best <ul><li>Cat 40 up to 15,000 RPM </li></ul><ul><li>BT40 up to 18,000 RPM </li></ul><ul><li>CAT50 up to 15,000 RPM </li></ul><ul><li>BT50 up to 18,000 RPM </li></ul>
  34. 34. End Mill Holders & TIR
  35. 35. Bore & Shank Tolerance <ul><li>For every 0.0001&quot; improvement T.I.R. </li></ul><ul><li>You Gain 10% Tool Life </li></ul>Min Dim Max Dim H5 H6 H7 H8 - .118&quot; -.00015&quot; -.00039&quot; -.00055&quot; .118&quot; .236&quot; -.00019&quot; -.00047&quot; -.00070&quot; .236&quot; .394&quot; -.00023&quot; -.00035&quot; -.00059&quot; -.00086&quot; .394&quot; .709&quot; -.00031&quot; -.00043&quot; -.00070&quot; -.001&quot; .709&quot; 1.181&quot; -.00035&quot; -.00051&quot; -.00082&quot; -.0012&quot; 1.181&quot; 1.968&quot; -.00063&quot;
  36. 36. Toolholder Manufacturing <ul><li>All Steep taper toolholders are made from some derivative of 8620 </li></ul><ul><li>They are case hardened </li></ul><ul><li>Remember AT3 on the holder; AT2 on the spindle </li></ul>
  37. 37. Retention Knob Torque <ul><li>30 Taper = 40 ft/lbs </li></ul><ul><li>35 Taper = 40 ft/lbs </li></ul><ul><li>40 Taper = 85 ft/lbs </li></ul><ul><li>45 Taper = 100ft/lbs </li></ul><ul><li>50 Taper = 110 ft/lbs. </li></ul>MAS Style ANSI Style
  38. 38. Controlling TIR <ul><li>Leads to </li></ul><ul><li>Better Tool Life </li></ul><ul><li>Better Finish </li></ul><ul><li>More parts </li></ul><ul><li>More $$$$ </li></ul>
  39. 39. Best methods <ul><li>The best toolholding method for most standard shop operation is a collet. </li></ul><ul><li>But which one? </li></ul>
  40. 40. DA (RDA) Collets <ul><li>8 Slots </li></ul><ul><li>4 Point engagement </li></ul><ul><li>“ bunch up” at smaller diameter </li></ul><ul><li>Ok for Drilling </li></ul><ul><li>Bad for Milling </li></ul>
  41. 41. TG(RTG) Collets <ul><li>16 Slots </li></ul><ul><li>.0004” TIR </li></ul><ul><li>1/64” increments </li></ul><ul><li>Better holding power </li></ul><ul><li>Good for ranges 1.0” - 1.5” dia. </li></ul><ul><li>Large head diameter </li></ul>
  42. 42. ER Collets <ul><li>16 slots </li></ul><ul><li>.0004” TIR standard </li></ul><ul><li>.0002” TIR UltraPrecsion </li></ul><ul><li>Smaller nose dia </li></ul><ul><li>.039” range </li></ul><ul><li>16 degree angle </li></ul><ul><li>Most Versatile </li></ul><ul><li>Most common </li></ul><ul><li>Most readily available </li></ul><ul><li>DIN Standard 6499 -1993 </li></ul><ul><li>Fritz Weber </li></ul>
  43. 43. DNA Collets <ul><li>Best Solution under 6mm in diameter </li></ul><ul><li>.0002” TIR </li></ul><ul><li>Fits in an ER Pocket </li></ul><ul><li>40% less projection out of collet pocket </li></ul>
  44. 44. Collet Accuracy <ul><li>L = DX4 </li></ul><ul><li>Runout at the end of the tool should be within .0002&quot; or less </li></ul><ul><li>Tool Shank engagement: Minimum engagement should be 2/3 of the collet bore length. 3/4 of the collet bore length is preferred. </li></ul>
  45. 45. Collet Recommendations <ul><li>Use ER style collets </li></ul><ul><li>Use the largest bore diameter in the smallest envelope </li></ul><ul><li>Use shank sizes that are equal to the nominal collet bore. In other words, use a 3/8 collet (.375&quot; max opening) for a 3/8&quot; shank tool, no the equivalent 9-10mm metric collet (.394&quot; max opening) </li></ul>
  46. 46. Collet Nuts-Solutions
  47. 47. Torque Specs ER Collets <ul><li>ER11 = 20 ft/lbs </li></ul><ul><li>ER16 = 50 ft/lbs </li></ul><ul><li>ER20 = 75 ft/lbs </li></ul><ul><li>ER25 = 95 ft/lbs </li></ul><ul><li>ER32 = 125 ft/lbs </li></ul><ul><li>ER40 = 140 ft/lbs </li></ul><ul><li>ER50 = 200 ft/lbs </li></ul>*Recommended torque range is 80-90% of maximum torque
  48. 48. Shrink Fit <ul><li>Made from H13 in US </li></ul><ul><li>Made from H11 in EU </li></ul><ul><li>Tempered to 1050 ºF in US </li></ul><ul><li>.0001” TIR </li></ul><ul><li>Most Rigid </li></ul><ul><li>Better Balance </li></ul><ul><li>10,000 lbs Holding Power </li></ul><ul><li>1 Piece holder </li></ul><ul><li>Slim Design </li></ul><ul><li>G2.5 @ 24,000 RPM </li></ul><ul><li>Extends tool life up to 700% </li></ul>
  49. 49. Shrink Fit - Expansion <ul><li>Safe, controlled induction heat from the shrink fit machine expands the inside diameter of the tool holder bore so the tool shank can be inserted. </li></ul>
  50. 50. Shrink Fit - Contraction <ul><li>Automatic air cooling contracts the bore to hold the tool with up to 10,000 lbs of holding power creating an extremely rigid connection between the spindle and the cutting tool. </li></ul>
  51. 51. Shrink Fit - Pull Out Force
  52. 52. Shrink Fit - Radial Torque
  53. 53. Shrink Fit vs. ER <ul><li>CAT40 </li></ul><ul><li>4140 prehard; 30-32R/c </li></ul><ul><li>3 flute uncoated end mill </li></ul><ul><li>4 passes </li></ul><ul><li>.125” DOC </li></ul>
  54. 54. Shrink Fit vs. ER <ul><li>ER Collet </li></ul>Shrink Fit
  55. 55. Tool Removal Temperatures Removal Temperature is based on carbide shanks at mean dimensions. Increase heat 100-250ºF for High Speed & Steel .
  56. 56. Tool Removal Temperatures Smaller Diameters are where the problems can happen
  57. 57. Shrink Fit - Limitations <ul><li>Thermal Expansion properties of End Mills </li></ul><ul><li>HSS and Cobalt cannot be used </li></ul><ul><li>Can get the tool IN but not OUT </li></ul>
  58. 58. Shrink Fit - Limitations <ul><li>.010”, .015”, .020” end mills all made on 1/8 Shank </li></ul><ul><li>Diameters typically held to -0.0001”/-0.0002” shank </li></ul><ul><li>10% -14% cobalt </li></ul><ul><li>Cobalt measured by WEIGHT NOT VOLUME </li></ul><ul><li>BY VOLUME Cobalt content up to 28% </li></ul>
  59. 59. Best type: Price? Rigidity? <ul><li>1. Accuracy value of 10 defined as 3 microns, 1 is .015&quot; TIR </li></ul><ul><li>2. 10 is the lowest price, 1 is the highest price. </li></ul><ul><li>3. 10 defined as widely available </li></ul>End mill holder = greatest holding power Collet chuck = greatest versatility
  60. 60. Best Practices <ul><li>Best ways to maintain accuracy of your toolholder </li></ul><ul><li>1. Minimize Runout </li></ul><ul><li>2. Grip the cutting tool well </li></ul><ul><li>3. Make sure the cutting tool shank is accurate </li></ul>