1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
|
from __future__ import division
import yaml
from string import Template
from skdb import Unit
import skdb
try:
import geom
using_OCC = True
except ImportError:
using_OCC = False
#used to inherit from skdb.Package but that no longer works?
class Thread(yaml.YAMLObject): #inherit from Helix?
yaml_tag = '!thread'
'''examples: ballscrews, pipe threads, bolts - NOT any old helix'''
def __init__(self, diameter, pitch, gender='male', length=None, handedness='right', starts=1):
self.diameter, self.pitch = Unit(diameter), Unit(pitch)
self.gender, self.length, self.handedness = gender, length, handedness
self.starts = starts #number of threads per turn
#pitch is distance from the peak of one thread to the peak of the next
self.lead = self.pitch * self.starts #Lead is the axial advance of a helix for one complete turn
#TODO delete crap below
self.interfaces = [
(self.pitch_diameter, 'in'), # conversion function .. so this is wrong.
(self.minor_diameter, 'in'),
(self.clamping_force, 'lbf')]
def pitch_diameter(self):
assert self.form=="UN" and Unit(self.pitch).compatible('mm/rev'), "this only works for triangular threads atm"
s = Template('($diameter)-0.6495919rev*($pitch)') #machinery's handbook 27ed page 1502
string = s.safe_substitute(diameter=self.diameter, pitch=self.pitch)
return Unit(string).to('in')
def minor_diameter(self):
assert self.form=="UN" and Unit(self.pitch).compatible('mm/rev'), "this only works for triangular threads atm"
s = Template('($diameter)-1.299038rev*($pitch)') #machinery's handbook 27ed page 1502
string = s.safe_substitute(diameter=self.diameter, pitch=self.pitch)
return Unit(string).to('in')
def clamping_force(self, torque, efficiency=0.1):
s = Template('($torque)*($pitch)*$efficiency')
string = s.safe_substitute(torque=torque, pitch=self.pitch, efficiency=efficiency) #fill in template keywords
force = Unit(string).to('lbf') #I guess this looks better than kg*m/s^2, but there should be a default Units setting somewhere
return force
def tensile_area(self):
assert Unit(self.pitch).compatible('mm/rev')
s = Template('pi/4*(($Dm+$Dp)/2)^2') #machinery's handbook 27ed page 1502 formula 9 "tensile-stress area of screw thread"
string = s.safe_substitute(Dm=self.minor_diameter(), Dp=self.pitch_diameter())
return Unit(string).to('in^2')
#max torque requires finding the combined "von mises" stress, given on MH27 page 1498
#because the screw body will twist off as a combination of tensile and torque shear loads
class BoltThread(Thread):
'''thread found on common nuts and bolts'''
yaml_tag = '!UN'
included_angle = Unit('60 degrees')
icon = skdb.package_file('threads', 'ISO_and_UTS_Thread_Dimensions.svg')
def __init__(self, diameter, pitch):
if diameter.compatible('inch'): self.diameter = diameter
#TODO note to self for future: skdb.parameter('diameter', 'inch')
else: raise skdb.UnitError, 'diameter must be a distance. got:'+str(diameter)
if pitch.compatible('rev/inch'): self.pitch = Unit('1')/pitch
elif pitch.compatible('mm/rev'): self.pitch = pitch
#TODO skdb.parameter('pitch', 'mm/rev')
else: raise skdb.UnitError, "thread pitch must be a ratio of angle and distance. got:"+str(pitch)
#is it worth worring about the distinction between UN and UNR?
def root_radius(self):
pass #something like .108P to .140P, also min and max radii
class ISO_Thread(BoltThread):
'''thread found on metric nuts and bolts'''
yaml_tag = '!thread_ISO'
urls = ['http://en.wikipedia.org/wiki/ISO_metric_screw_thread',
'http://www.efunda.com/DesignStandards/screws/screwm_coarse.cfm']
_diam_regex = '(?P<diam>M\d+)'
_pitch_regex = '(?P<pitch>\s*\d+(\.\d+)?)'
preferred_sizes ={1:0.25, 1.2:0.25, 1.6:0.35, 2:0.4, 2.5:0.45, 3:0.5,
4:0.7, 5:0.8, 6:1, 8:1.25, 10:1.5, 12:1.75, 16:2,
20:2.5, 24:3, 30:3.5, 36:4, 42:4.5, 48:5, 56:5.5, 64:6,
72:6, 80:6, 90:6, 100:6}
second_choice = {1.4:0.3, 1.8:0.35, 3.5:0.6, 7:1, 14:2, 18:2.5, 22:2.5,
27:3, 33:3.5, 39:4, 45:4.5, 52:5, 60:5.5}
class ISO_Fine_Thread(ISO_Thread):
'''thread found on some metric nuts and bolts'''
#not sure about i.e. M10-1 vs M10-1.25 (10, 12, 18, 22)
preferred_sizes ={8:1, 10:1.25, 12:1.5, 16:1.5, 20:2, 24:2, 30:2, 36:3,
42:3, 48:3, 56:4, 64:4}
second_choice = {14:1.5, 18:2, 22:2, 27:3, 33:2, 39:3, 45:3, 52:4, 60:4}
class ISO_Extra_Fine_Thread(ISO_Thread):
#this can't be complete..
prefered_sizes = {10:1, 12:1.25, 20:1.5}
second_choice = {18:1.5, 22:1.5}
#i hate this. i wish it were a @staticmethod of UN_Thread, but then UN_Thread can't call it
def numbered_thread_diameter(size):
'''numbered thread diameter: a #2 thread has a major diameter of 0.086".'''
if size == '00': size = -1
if size == '000': size = -2
return 0.060+0.013*int(size)
_num = numbered_thread_diameter
class UN_Thread(BoltThread):
'''base class for constructing UN thread series. don't use.'''
yaml_tag = '!thread_UN'
sources = ["machinery's handbook 27th, p.1774"]
_diam_regex = '((#(?P<size>\d+))|((?P<whole>\d+)\s+)?(?P<frac>(?P<numer>\d+)/(?P<denom>\d+)))"?' #'1 5/16' or '1/4' or '#10'
_separator = '\s*-\s*'
_tpi_regex = '(?P<tpi>\d+\s*(TPI|tpi)?)'
def parse_thread_spec(self, spec):
'''returns diameter and pitch given something like '#8x32' or '3/8" - 16'. '''
match = re.match(_diam_regex+'('+_separator+_tpi_regex+')?')
if not match: raise ValueError, "couldn't parse "+self.__class__.series+" series bolt spec '"+str(spec)+"'"
print match.groups()
diameter = 0
whole = match.group('whole')
if whole: diameter += float(whole)
frac = match.group('frac')
if frac: diameter += float(match.groups('numer'))/float(match.groups('denom'))
if match.group('size'):
assert not whole and not frac
diameter = self.numbered_thread_diameter(match.groups('size'))
if match.group('size') in self.preferred_sizes.values():
print 'yay, a standard bolt!'
if match.group('tpi'): pitch = match.group('tpi')
else: #no pitch specified
if hasattr(self.__class__, 'preferred_sizes') and diameter in self.__class__.preferred_sizes:
pitch = self.__class__.preferred_sizes[diameter]
return self.__class__(diameter, pitch)
class UNC_Thread(UN_Thread):
'''unified national coarse thread. found on most american nuts and bolts'''
sources=['http://www.efunda.com/DesignStandards/screws/screwunc.cfm',
'http://en.wikipedia.org/wiki/Unified_Thread_Standard',
"machinery's handbook 27th, p.1735"]
yaml_tag = '!thread_UNC'
series = 'UNC'
preferred_sizes={_num(2):56, _num(4):48, _num(6):32, _num(8):32, _num(10):24,
1/4:20, 5/16:18, 3/8:16, 7/16:14, 1/2:13,
9/16:12, 5/8:11, 3/4:10, 7/8:9, 1:8,
1+1/8:7, 1+1/4:7, 1+3/8:6, 1+1/2:6, 1+3/4:5,
2:4.5, 2+1/4:4.5, 2+1/2:4, 2+3/4:4,
3:4, 3+1/4:4, 3+1/2:4, 3+3/4:4, 4:4}
secondary_sizes = { _num(1):64, _num(3):48, _num(5):40, _num(12):24}
class UNF_Thread(UN_Thread):
'''unified national fine thread. found on some american nuts and bots'''
yaml_tag = '!thread_UNF'
series = 'UNF'
sources=['http://www.efunda.com/DesignStandards/screws/screwunf.cfm',
'http://en.wikipedia.org/wiki/Unified_Thread_Standard',
"machinery's handbook 27th, p.1735"]
preferred_sizes ={_num(0):80, _num(2):64, _num(4):48, _num(6):40, _num(8):36, _num(10):32,
1/4:28, 5/16:24, 3/8:24, 7/16:20, 1/2:20,
9/16:18, 5/8:18, 3/4:16, 7/8:14, 1:12,
1+1/8:12, 1+1/4:12, 1+3/8:12, 1+1/2:12}
secondary_sizes = { _num(1):72, _num(3):56, _num(12):28}
class UNEF_Thread(UN_Thread):
'''often used on thin tubing'''
yaml_tag = '!thread_UNEF'
series = 'UNEF'
sources = ['http://www.efunda.com/DesignStandards/screws/screwunf.cfm',
"machinery's handbook 27th, p.1735"]
preferred_sizes={1/4:32, 5/16:32, 3/8:32, 7/16:28, 1/2:28, 9/16:28,
5/8:24, 3/4:20, 7/8:20, 1:20, 1+1/8:18, 1+1/4:18,
1+3/8:18, 1+1/2:18, 1+5/8:18}
secondary_sizes={_num(12):32, 11/16:24, 13/16:20, 15/16:20,
1+1/16:18, 1+3/16:18, 1+5/16:18, 1+7/16:18,
1+9/16:18, 1+11/16:18}
#TODO http://www.ring-plug-thread-gages.com/ti-UNJ-vs-UN.htm
#TODO http://www.ring-plug-thread-gages.com/ti-UNR-vs-UN.htm ?
|
