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the (424), and (164), taper (110), with (72), tool (66), shank (62), are (61), for (59), spindle (49), #tapers (43), machine (40), from (36), that (36), drill (32), tools (31), end (30), into (30), morse (29), hsk (27), drawbar (26), edit (23), which (23), sizes (22), 6000 (22), use (21), this (19), large (19), 4321 (19), 0500 (19), milling (18), can (18), plane (17), flange (17), also (17), used (17), iso (16), self (16), diameter (16), dimensions (15), not (15), but (15), may (14), was (14), holding (14), larger (14), than (14), small (14), socket (14), nmtb (14), contact (13), wood (13), lathe (13), shanks (13), when (13), other (13), toolholder (13), machining (12), collet (12), tooling (12), such (12), more (12), psc (12), there (12), force (12), 5000 (12), angle (11), tapered (11), axial (11), have (11), high (11), short (10), surface (10), interface (10), per (10), size (10), between (10), female (10), forms (10), will (10), archived (9), some (9), these (9), has (9), machines 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ford massachusetts in the mid 1860s 1 since then it has evolved to encompass smaller and larger sizes and has been adopted as a standard by numerous organizations including the international organization for standardization iso as iso 296 and the german institute for standardization din as din 228 1 it is one of the most widely used types and is particularly common on the shank of taper shank twist drills and machine reamers in the spindles of industrial drill presses and in the tailstocks of lathes the taper angle of the morse taper varies somewhat with size but is typically 1 49 degrees around 3 degrees included some modular orthopedic total hip implants use a morse taper to mate components together 2 similarly some dental implants use a morse taper to connect components 3 sizes edit morse tapers come in eight sizes identified by whole numbers between 0 and 7 and one half size 4 5 which is less common but used on some medium sized lathes where a slightly larger taper than mt4 is needed without jumping to the much larger mt5 often the designation is abbreviated as mt followed by a digit for example a morse taper number 4 would be mt4 another common abbreviation that comes from german is mk for morsekegel the mt2 taper is the size most often found in drill presses up to 13 mm 1 2 capacity stub short versions the same taper angle but a little over half the usual length are occasionally encountered for the whole number sizes from 1 through 5 there are standards for these which among other things are sometimes used in lathe head stocks to preserve a larger spindle through hole end types edit morse tapers are of the self holding variety and can have three types of ends tang illustrated to facilitate positive drive preventing slippage 4 threaded to be held in place with a drawbar flat no tang or threaded section self holding tapers rely on a heavy preponderance of axial load over radial load to transmit high torques problems may arise using large drills in relation to the shank if the pilot hole is too large the threaded style is essential for any sideloading particularly milling the only exception is that such unfavourable situations can be simulated to remove a jammed shank permitting chatter will help release the grip the acute narrow taper angle can result in such jamming with heavy axial loads or over long periods end milling cutters with a morse taper shank with a tang are occasionally seen for security these must be used with a c collar or similar fitting into the neck between cutter and shank and pulling back against the large end of the taper the taper itself is roughly 52 mm per meter 5 8 per foot or just under 1 5 degrees but exact ratios and dimensions for the various sizes of tang type tapers are given below dimensions edit taper morse taper dimensions mm in morse taper number taper a b max c max d max e max f g h j k 0 1 19 212 9 045 mm 0 3561 in 56 5 mm 2 22 in 59 5 10 5 6 4 1 3 3 9 1 29 27 1 1 20 047 12 065 mm 0 4750 in 62 mm 2 4 in 65 5 13 8 7 5 1 2 3 5 5 2 1 25 43 2 1 20 020 17 780 mm 0 7000 in 75 mm 3 0 in 80 16 13 5 6 1 6 5 6 3 1 25 50 3 1 19 922 23 825 mm 0 9380 in 94 mm 3 7 in 99 20 18 5 7 2 5 7 9 1 26 16 4 1 19 254 31 267 mm 1 2310 in 117 5 mm 4 63 in 124 24 24 5 8 2 5 6 5 11 9 1 29 15 4 5 1 19 128 37 833 mm 1 4895 in 133 5 mm 5 26 in 140 26 5 30 1 9 2 75 6 5 13 9 1 29 51 5 1 19 002 44 399 mm 1 7480 in 149 5 mm 5 89 in 156 29 35 7 10 3 6 5 15 9 1 30 26 6 1 19 180 63 348 mm 2 4940 in 210 mm 8 3 in 218 40 51 13 4 8 19 1 29 36 7 1 19 231 83 058 mm 3 2700 in 285 75 mm 11 250 in 294 1 34 9 19 05 19 1 29 22 b tapers edit b series tapers are a din standard din 238 typically used for fitting chucks on their arbors like the older jacobs taper series each taper in the b series is effectively the small or large end of a morse taper b10 small end of mt1 d 10 095 mm b12 large end of mt1 d 12 065 mm b16 small end of mt2 d 15 733 mm b18 large end of mt2 d 17 780 mm b22 small end of mt3 d 21 793 mm b24 large end of mt3 d 23 825 mm the number after the b is the diameter d of the large end of the taper to the nearest mm and about 1mm larger than the small end of the socket 2mm in the case of b22 and b24 5 6 7 nmtb taper family edit the us national machine tool builders association now called the association for manufacturing technology defined a steep taper that is commonly used on milling machines in 1931 the taper is variously referred to as nmtb nmt or nt the taper is 3 500 inches per foot and is also referred to as 7 in 24 or 7 24 the computed angle is 16 5943 degrees 8 all nmtb tooling has this taper but the tooling comes in otherwise sizes nmtb 10 15 20 25 30 35 40 45 50 and 60 these tapers were apparently also specified in asa now ansi b5 10 1943 nmtb was made to be a self releasing or fast taper unlike the more acute self holding tapers listed previous steep tapers are not designed to transmit high torque high torques are thus carried by driving keys engaging slots on the flange 9 10 the purpose is to allow a quick and easy change between different tools while ensuring the tool or toolholder will be rigidly connected to the spindle and repeatably coaxial with it the larger diameter end adjacent to the tool makes for better rigidity than is possible with morse or r8 tapers fitted to comparable machines us patent 1794361 filed 25 march 1927 describes milling machine spindle and tool shapes using a steep taper 11 the patent was assigned to kearney trecker corporation brown sharpe and cincinnati milling machine company the patent wanted a taper that would freely release the tool and found that a taper of 3 5 in 12 had that property 12 the patent also used the keys and slots and a tail on the tool shank to prevent the tool shank from falling out of a horizontal mill s spindle while the operator connected the drawbar 12 ansi b5 18 1972 specifies some essential dimensions for milling machine spindles and tool shanks using taper sizes 30 40 45 50 60 13 the specifications describe the position of the driving key and flange and the thread of the drawbar bolt that holds the shank in the spindle the tooling can be referred to as quick change national machine tool builders association 1927 nmtb american standard machine taper ansi b5 18 din 2080 is 2340 iso r 290 2583 14 there are slight variations in threads and flanges jis b 6339 mas 403 and the european standards e g iso taper din 2080 use metric drawbar threads aside from the drawbar threads the above standards are physically compatible with each other in most cases the nmtb tool shanks have the 7 24 taper but they also feature a constant diameter tail pilot at the end of the shank that was described in the 1927 patent nmtb derivatives edit toolholder for milling machine with cat 40 taper subsequent design variations dropped the cylindrical tail making the shank shorter and put a v groove in the flange that aided automated tool changing modern designs started using power drawbars that gripped pull studs also known as retention knobs that were screwed into the tool shank rather than screw in drawbars the power drawbar would grip the pull stud rather than screwing into the tool shank allowing for faster automatic tool changes the more modern toolholder designs became known as the caterpillar v flange cat v flange ansi b5 50 this was later codified under iso 7388 1 other derivatives include sk din iso 7388 1 very similar but require modifications to be interchangeable with cat v ansi b5 50 both designs are included under iso 7388 1 iso international int bt mas 403 jis b6339 iso 7388 2 japanese originated standard derivative of ansi b5 50 this is most common toolholder design used in east asia also not readily compatible with cat v they can be hand loaded into cat v spindle if a pull stud adapter with metric threads is used but do not work with tool changers used for the same once again there are modest variations in the tooling 14 although the basic taper dimensions are the same there are differences in the flanges v groove sizes drive keyways and pull stud dimensions the international versions use metric sizes and metric stud threads particularly hsk taper edit hsk a63 shank drawing of hsk a63 shank animation of hsk toolholder hsk toolholders were developed in the early 1990s hsk stands for hohlschaftkegel german for hollow shank tapers steep tapers e g nmtb and derivatives tend to lose rigidity and accuracy at high speed as their solid shanks are stiffer than the spindles they fit into under high centrifugal force the spindle expands more than the toolholder which changes the overall length that is as the spindle spreads outward the toolholder tends to move deeper into the spindle along the z axis which can cause the production of parts that are out of tolerance moreover the thinnest part of the spindle interface is the front shoulder which tends to expand the most this zone engages the stiffest part of the holder where radial forces are also the highest this significantly reduces the stiffness of the spindle interface allowing more deflection of the holder under cutting load particularly with long tools the holder can rock or walk slightly from side to side by way of elastic deformation usually this causes poor runout accuracy more chatter and unduly short tool life in the most extreme case it can cause fretting wear on the spindle surface due to slight relative motion of the holder against the female interface hsk s hollow shank is deliberately thin and flexible so it expands more than the spindle and tightens when rotating at high speed furthermore the hsk holder is dual contact it engages with the spindle on both the taper and the top of the flange which resists axial movement when thermal growth and or centrifugal force of the spindle occurs the flexibility is also used to provide accurate axial location an hsk toolholder has both a tapered shank and a flange with a mating surface the shank is short about half as long as other machine tapers with a shallow taper the shank is 1 9 98 and the receiver is 1 10 15 and slightly too large to allow the flange to seat fully in the socket the thin walls short shank and shallow taper provide a large opening in the back of the tool an expanding collet fits in there and mates with 30 chamfer inside the shank as the drawbar retracts it expands the collet and pulls the shank back into the socket compressing the shank until the flange seats against the front of the spindle this provides a stiff repeatable connection because it utilizes the centrifugal force inside the spindle for security and rigidity as centrifugal forces increase the expanding collet within the hsk forces the walls of the toolholder shank to stay in contact with the spindle wall the hsk design was developed as a nonproprietary standard the working group that produced the hsk standard consisted of representatives from academia the association of german tool manufacturing and a group of international companies and end users the results were the german din standards 69063 for the spindle and 69893 for the shank the hsk working group did not adopt a specific product design but rather a set of standards that defined hsk toolholders for different applications the group defined a total of six hsk shank forms in 9 sizes sizes are identified by the diameter of the shank s flange in millimeters these diameters are taken from the r10 series of preferred numbers from 25 to 160 mm today the shank forms are designated by the letters a through f and t the main differences between the forms are the positions of the drive slots gripper locating slots coolant holes and the area of the flange hsk forms a c e nominal dimensions 16 d1 mm forms d2 mm l1 mm l2 mm f1 mm f5 mm d8 b1 20 e 15 203 10 2 0 8 25 a c e 19 006 13 2 5 10 32 a c e 24 007 16 3 2 20 10 0 4 0 7 05 40 a c e 30 007 20 4 0 20 10 0 4 6 8 05 50 a c e 38 009 25 5 0 26 12 5 6 0 10 54 63 a c e 48 010 32 6 3 26 12 5 7 5 12 54 80 a c 60 012 40 8 0 26 16 0 8 5 16 04 100 a c 75 013 50 10 0 29 16 0 12 0 20 02 125 a c 95 016 63 12 5 29 25 02 160 a c 120 016 90 16 0 31 30 02 hsk forms b d f nominal dimensions 16 d1 mm forms d2 mm l1 mm l2 mm f1 mm d8 b1 25 32 40 b d 24 007 16 3 2 20 4 0 10 50 b d f 30 007 20 4 0 26 4 6 12 63 b d f 38 009 25 5 0 26 6 0 16 80 b d f 48 010 32 6 3 26 7 5 18 100 b d 60 012 40 8 0 29 8 5 20 125 b d 75 013 50 10 0 29 12 0 25 160 b d 95 016 63 12 5 31 12 0 32 a is the basic form the b form shank is a variant for high torque applications and has a flange one size larger relative to its shaft diameter thus an a 40 shank will fit into a b 50 socket forms c and d are simplified variants of a and b for manual use eliminating features to accommodate automatic tool changers like a v groove and associated orientation slots and a recess for an rfid chip forms e and f flanges and tapers are similar to forms a and b but designed for very high speed machining 20 000 rpm and up of light materials by eliminating all asymmetric features to minimize imbalance and vibration asme b5 62 hollow taper tooling with flange face contact 17 and iso 12164 3 2014 dimensions of shanks for stationary tools 18 include an additional form t which is bidirectionally compatible with form a but has a much tighter tolerance on the widths of the keys and keyways used for angular alignment this permits non rotating lathe tooling to be held accurately 19 an hsk connection depends on a combination of axial clamping forces and taper shank interference all these forces are generated and controlled by the mating components design parameters the shank and spindle both must have precisely mating tapers and faces that are square to the taper s axis there are several hsk clamping methods all use some mechanism to amplify the clamping action of equally spaced collet segments when the toolholder is clamped into the spindle the drawbar force produces a firm metal to metal contact between the shank and the id of the clamping unit an additional application of drawbar force positively locks the two elements together into a joint with a high level of radial and axial rigidity as the collet segments rotate the clamping mechanism gains centrifugal force the hsk design actually harnesses centrifugal force to increase joint strength centrifugal force also causes the thin walls of the shank to deflect radially at a faster rate than the walls of the spindle this contributes to a secure connection by guaranteeing strong contact between the shank and the spindle the automotive and aerospace industries are the largest users of hsk toolholders another industry that is seeing increasing use is the mold and die industry psc edit psc stands for polygonal shank conical originally developed in 1989 by ken andersson working for the swedish machine tool company sandvik coromant ab psc was introduced by sandvik at the 1990 imts in chicago under the brand name capto 20 in the early 2000s as various patent protections were set to expire sandvik was faced with the prospec...