1、UDC 621.914.2 : 003.62 : 001.4 DEUTSCHE NORMEN October 196 Design Dimensions and Errors of Hobs for Involute Spur Gear8 Fundamental Terms 3 ?: 3 -G s E t Z c P - a o c .- E 5 BestimmungegrSen und Fehler an Wi5frsern fr Stirnrder mit Evolventenverzahnung; Grundbegriffe Contents 1. General 1.1. Genera
2、l fuadamenta terms 1.2. Symbols and notation 1.3. Hand of rotation 1.4. Right-hand cutting edges, left-hand cutting edges (right-and flanks, left-hand flanks) 1.5. Rightward pitch, leftward pitch . 1.6. Method of counting tooth rom 1.7. Method of counting hob teeth and tooth spaces 1.8. Designations
3、 of hub faces and proof flange0 (cutting faces) . 2. Fundamental terms of hob tooth elements . 2.1 Enveloping helix . 2.1.1. Setting angle YQ . 2.1.2. Pitch cylinder 2.l.3. Reference cylinder . 2.1.4.1. Noormal pitch trio 2.1.4.2. Transverse pitch ta0 2.1.4.3. Base pitch tne . 2.1.4.4. Axial pitch t
4、a . 2.1.5. Lead H 2.1.6. Base cylinder . 2.1.7. Base lead =le yg 2.1.8. Pressure angle, angle of action a . 2.1.8.1. Normal angle of action ano . 2.1.8.2. Transverse angle of action aso 2.1.8.3. Axial pressure angle aay . . 2.1.9. Tooth thickness s , space width . 2.1.9.1. Tooth thickness ano 2.1.9.
5、2. Tooth thickness Snb 2.1.9.3. Tooth thickness sao 2.1.9.4. Tooth thicknesa 8ab 2.1.9.5. Tooth thickness say 2.2. Gash helix . 2.2.1. Gash clearance u . 2.2.2. Gash lead Hg . 2.2.3. Gash spacing . 2i1.4. Pitch . . Page 2 2 2 3 3 3 3 3 3 3 3 3 3 4 4 4 4 4 4 5 5 5 5 5 5 5 5 6 6 6 6 6 6 6 6 7 2.3. Hob
6、 tooth flanks 2.3.1. Lead Ha (m) of right-hand (left- hand) flanks. 2.3.2. Axial relief he of tooth flanks 2.3.3. Radial top relief hr 2.3.4. Axial pressure angie a the following terms in particular are used: I7oBclnal size This is the size to which the allowances assigned to a dimension are related
7、. Actual size Thia is the value of a dimension as found by measurement. Actual allowance This is the difference between the ascertained actual size and the nominal size of a dimension, namely actual size minus nominal size. Uwer allowance This is the difference between the permissible higher limit a
8、nd the nominal size of a dimension, namely higher limit minus nominal size. Lower allowance This is the difference between the permissible lower limit and the nominal size of a dimension, namely lower limit minus nominal size. Tole rance This is the difference between the permissible higher limit an
9、d the permissible lower limit of a dimension. 1.2. Symbols and notation d = Diameter For accurate identification the following - - ev = fe = ff = fr = fs = ft = f, = fH = fa = h= i= l= m= r= t= s= u= x= e= x-m = F= Ff = Ft = H= ao = = Y= sk = E= Involute function Base pitch error Flank form deviatio
10、n Radial run-out Tooth thickness error Individual pitch error Tooth to tooth pitch error Lead error Angle of action error Whole depth of tooth Number of gashes Space width Module Radius Tooth thickness Pitch Distance of a transverse section of a cutting face from the hob axis Profile error factor Ma
11、gnitude of profile error Number of threads (number of helix teeth) Error in measurement over a range Resultant flank form deviation Cumulative pitch error Lead Crest clearance Angle of action Helix angle Lead angle Re-grind angle TOth Tooth rom 1, subscripts are used, as necessary, with the above qu
12、antities: O = relating to the normal pitch circle or the normal pitch cylinder a = relati* to the axis or the direction of the axis b = relating to the reference circle or the reference cylinder e = relating to the line of action f = relating to the root circle or root cylinder or to the hob tooth h
13、elix or to the profile (e. 2.2.2. G a s h 1 e a d EN Gash lead (imaginary) points of intersection of a cutting face with a line HN is expressed as the distance apart of the parailel to the hob axis. (;ash lead Ha length. In most cases, therefore, only a fraction of Ha can be measured, e.g. by moving
14、 a measuring instrument parallel to the hob axis whereby the hob is revolved simultaneously about its own axis (rotation combined with lengthwise movement through HN ). Both movements can also be carried out step by step or performed by the hob. is usually very large in comparison with hob Figure 7.
15、 Hob with positive rake DIN 8000 Page 7 2.2.3.Gash spacing The gash spacing is the length of arc on a cylinder coaxial with the hob measured between two adjacent cutting faces. 2.3. Hob tooth flanks 2.3.1.Lead Hg (HI,) 0.f right-hand (left-hand) flanks The lead Hg (HL of the right-hand (left-hand) f
16、lanks is expressed as the distance apart of the (imaginary points of intersection of a right-hand (left-hand) flank with a line parallel to the hob axis. 2.3.2.Axial relief ha of tooth flanks The axial relief ha of the tooth flanks is the difference between the leads Hg and H or HL and H divided by
17、the number of gashes with allowance for the lead of the gashes in the case of a right-hand hob: -_-_-_- (26) (27) %-E Har “-=L % ha“-* or %=-*- If the hob threads and the gashes have the same lead direction the positive signs in the denominators change to minus signs. 2.3.3.Radial top relief hr adia
18、l top relief the hob is expressed as the length of that portion of the cutting face extending from the tip down to the point where the cutting face is intersected by the extended top face of the preceding tooth (Fig.8). 2.3.4.xia1 pressure angle (aaLy) of right-hand (ieft-ha?$) flanks The axial ress
19、ure angle aaY (or ad ) of the right-hand (left-hand7 flanks lies in an axial secTion and is the angle between the perpendicular to one of their lines of axial section at the intersection of said line with a cylinder coaxial with the hob of the diameter cylinder through the same point of intersection
20、 (Fig.5). Its value is given by hr as measured in a transverse section of dy and the surface of this Figure 8. Effect of radial top relief applied to a hob tan aaW = tan y sin a tan asLy = tan yg * sin a The value of the axial angle of action flanks is given approximately by the fol%fng expressions
21、in the case of right-hand hobs: i br cot aaRO IJ cot aaO - g or (or aaLo) of the right-hand (left-hand) (30) “ i Dr cot ado IJ cot aaO + - or “ and in the case of left-hand hobs: i - hr cot aaRO = cot aaO + EEN i hr cot aaLo = cot aaO - or “ (32) (33) 2.3.5.1ooth thickness sz The tooth thickness sz
22、of a hob tooth is the length of a cylinder generating line or of a helix between its two flanks. 2.3.5.1. Tooth thickness S,NO The tooth thickness face on the pitch cylinder (Fig.6). It is given by SEBO of a hob tooth is its tooth thickness along a helix of a cutting fvg S = a0 * H + H (34) If the h
23、ob threads and the gashes have the same lead direction the plus sign in the denominator changes to a minus sign. 2.3.5.2. Tooth thickness szm The tooth thickness face on the reference cylinder. It is given by sZaA of a hob tooth is its tooth thickness along a helix of a cutting If the hob threads an
24、d the gashes have the same lead direction the denominator changes to a minus sign. 2.3.5.3. Chordal tooth thickness Zm The chordal tooth thickness otherwise the minus sign is used. Fm is the lead error between any chosen Cutti Figure 15. Measurement of hob lead edges of a single thread within one tu
25、rn (Fig.18. in the direction of hand between chosen cutting edges of a single turn Page 10 Dia 8000 3.3.4.Base pitch error fe The base pitch error fe of that element z tne/i (Fig. 16). Plotting of the base pitch errors fe over a contact region in the form of a diagram yields the contact test diagram
26、 (Fig.17). The base pitch error Fe distance apart of the two lines AA and BB drawn parallel to the abscissa axis of the test diagran through its highest and lowest points respectively. is the difference between the actual value and the design value of the base pitch between two successive teeth of a
27、 hob thread within a contact region is the Figure 16. Base pitch check - + Contact region4 Figure 17. Contact test diagram DIN 8000 Page 11 4. Alphabetical index Actua3 allowance 1.1 Actual size 1.1 Addendum hk 2.4.1 Allowance 1.1 bngl e -, angle of action a 2.1.8 -, axial angle of action -, axial p
28、ressure angle 2.3.4 -, base lead angle yg -, helix angle o 2.1.2 -, normal angle of action ano -, pressure angle 2.1.8 -, re-grind angle E 2.4.4 -, setting angle Yo 2.1.1 -, transverse angle of action aso 2.1.6.2 Angle of action a 2.1.8 Axial angle of action 2.1.8.3, 2.3.4 Axial pitch ta 2.1.4.4 Axi
29、al pressure angle 2.3.4 Axial relief ha 2.3.2 Axial run-out fps 3.1.3 Base cylinder 2.1.6 Base lead angle Yg 2.1.7 Base pitch trie 2.1.4.3 Base pitch error fe 3.3.4 Chordal tooth thickness Contact test diagram 3.3.4 Cumulative pitch error FtN 3.2.2.3 Cutting depth of hob 2.4.1 Cutting face form erro
30、r ffN and PfN 3.2.1 Cutting faces 1.6 Dedendum hf 2.4.1 Diameter -, base cylinder diameter dg 2.1.6 -, pitch cylinder diameter do 2.1.2 -. reference cylinder diameter 2.1.8.3, 2.3.4 2.1.7 2.1.8.1 2.3.5-3 db 211.3 Direction of hand 1.3 Entering end 1.8 Enveloping helix 2.1 Error -, axial run-out fps
31、3.1.3 -, base pitch error fe 3.3.4 -, cumulative pitch error FtN -, cutting face form error ffH -, flank form deviation ffS -, gash lead error fm 3.2.3 -, gash pitch error 3.2.2 -, individual pitch error ftN -, lead error fm and PHp 3.3.3 -, pitch error ft 3.1.5 -, proof flange radial run-out -, rad
32、ial run-out 3.1.2, 3.1.4 -, radial run-out on tooth -, tooth thickness error f, -, tooth to tooth pitch error 3.2.2.3 and Ffg 3.2.1 and FfS 3.3.1 3.2.2.1 frp 3.1.2 tips frk .3.1.4 3.3.2 fd 3.2.2.2 Flank form error ffs and FIS 3.3.1 Gaah clearance u 2.2.1 Gash helix 2, 2.2 Gash lead HN 2.2.2 Gash lea
33、d error fm 3.2.3 Gash pitch error 3.2.2 Gash spacing 2.2.3 Helix angle o 2.1.2 Helix of the hob 2 Individual pitch error ftx 3.2.2.1 Lead H 2.1.5 Lead HL of left-hand flanks Lead HR of right-hand flanks Lead error f and Pm 3.3.3 Leaving end T.8 Left-hand cutting edges 1.4 Left-hand flanks 1.4 Leftwa
34、rd pitches 1.5 Nominal size 1.1 2.3.1 2.3.1 Normal angle of action ano Normal pitch t 0 2.1.4.1 Number of teet% E 2.1 Number of threads z 2.1 Pitch -, axial pitch ta 2.1.4.4 -, base pitch trie 2.1.4-3 -, gash spacing 2.2.3 -, leftward pitch 1.5 -, rightward pitch 1.5 -, transverse pitch tsO Pitch cy
35、linder 2.1.2 Pitch error it 3.1.5 Pressure angle 2.1.8 Proof flange radial run-out 2.1.8.1 -, normal pitch tnO 2.1.4.1 2.1.4.2 frp 3.1.2 Rack tooth system 2.1.2, &adia1 relief hr 2.3.3 Radial run-out 3.1.2, 3. Radial run-out on tooth t Reference cylinder 2.1.3 Re-grind angle E 2.4.4 Bight-hand cutti
36、ng edges Right-hand flanks 1.4 Rightward pitches 1.5 Rows of teeth 1.6 Setting angle Yo 2.1.1 Space width 1 2.1.9 Tolerance 1.1 Tooth depth h 2.4.1 Tooth form 2.4 Tooth thickness s 2.1.9, Tooth thickness error f, 2.1.3 frk 3.1.4 2.3.5 3.3.2 .4 PS 1 e4 Toth to tooth pitch error Transverse angle of ac
37、tion Transverse pitch tsO 2.1.4.2 fa 3.2.2.2 aso 2.1.8.2 Working depth hg 2.4.1 Other relevant standards: For hobs for spur gears, module 1 to 20 mm, see DIM 8002 !i For hobs for spur gears, module 0.1 to 1 mm, see DIN 58 411 (at present circulating as draft) For tolerances for single-start hobs for
38、 spur gears with involute teeth, see DIN.3968 For reference profiles of cutting tools for involute tooth systems to DIN 867, see DIN 3972 For form of tooth for spur gears and bevel gears, see DIN 867 For tolerances for spur gear tooth systems to DIN 867, see DIN 3961 to DIN 3964 and DIN 3967 For specification factors and errors relating to spur gears, fundamental terms, see DIB 3960 For general definitions, notation and symbols for gears, see DIN 868
