PS Magazine - TB 43-PS-429
PS, The Preventative Maintenance Monthly
ISSUE 429
AUGUST 1988
The mechanical advantage you get by twisting with a wrench is fntastic.
By tuRing and turning you can stretch me completeLy out oF shape, snap o±F
my head, strip my threads or the nut threads, crack the nut, destroy my washers
... not to mention damaging whatever I'm holding together.
²et's say you torque me beyond my built-in Limits. IF my head or nut doesn't
give First, I stretch out so Far I can't snap back. I've lost my elasticity. But
you don't Know I'm sprung so you keep on torqu³ng. Even iF you get the torque
reading you're Looking FOr, it's going to ´e wrong. Comes the µ¶rst bit oF stzess or
strain, I'm ·ither going to snap¸ or else my nut will sta¹t bacKing oº. It's a
sure bet that what you've joined together is sooner or later going to spLit asunder.
DIAMETER/
tORQUE LB·FT
TORQUE LB-fT
TORQUE lB·fT
tHREaDS
NO DASHES
3 DASHES
6 DASHES
PER INCH
(GRADE 2)
(GRADE 5)
(GRADE 8)
1/4±20
3·5
6²8
³0²12
1/4²28
4´6
8²³0
9²³4
5/16²18
7²11
13-17
19-24
5/³6²24
7µ11
14µ19
23-28
3/8´16
14²18
26-31
39.44
3/8´24
15-19
30-35
46²51
7/16´14
23²28
44¶49
65-70
7/16´20
23´28
44¸54
69-79
1¹2·13
32²37
65-75
95-³05
³¹2º20
34²41
73»¼3,
113´123
9
/
16½³2
46´56
100º110
145-155
9/16²³8
47.57
³07¾117
165-³75
5/8²³1
62-72
³40²150
200²210
5/8´³8
67²¿7
³53´163
235-245
3/4´10
³06´116
260²270
365-375
3/4²16
115²125
268²278
417-427
7/8²9
165²175
385²395
595·605
7/8²³4
³78´188
424²434
663´673
³·8
251-261
580-590
900´9³0
1-³4
255²265
585²634
943.993
³ 1/4-7
451À461
1070-1³20
1767-³817
1 1/4²12
488´498
12³³-126³
1963-2013
1 ³¹2·6
727-737
³899²1949
3³1³¾3161
1 1/2²12
816½826
2144-2³94
3506-3556
The Áirs scÃew oÁ eÄch dÅÄmeÂeà Ås UnÅÆÅed CoÄrse ÂhÃeÄdsÇ Änd Âhe second
Ås UnÈÁÅed FÅne ÂhreÄdsÉ
use ÂhÈs chÄÃÂ onÊy ÅË yoÌÃ TÍ gÈves Îo ÂoÃqÌe vÄÏÌesÐ
Also, iF you tried to torque a grade eight with grade »Ve torque, you'd never
¼
get the bolt to stretch ½iKe it shou½d. ¾esult¿½oose connections.
So, never substitute a bolt graded lower than one ca½led FOr. IF you substitUte
a higher grade bo½t, the extra torque needed may be too much FOr the job. You
Àcou½d ¹uin tHe connection.
34
AUG 88
WET TORQUe VS DRY TOrQUe
ÁboÂt
so
percent oF ÃÄe ÃorQÂe yo ÅppÆy goes to overcoMe ÇÈictioN; oNÉy
I 0
percenà ¶s Âsed ÇOr tighten¶Ng. ÁNÊtÄing Êo Âse to ÆÂËricÅte FasteNers reDÂces
̶cöon. ÍÄe saMe ÅmoÂnt oF torQÂe w¶LÆ creÅÃe more t¶gÄÃening ÇorceÎprobÅËly
too MÂch. IF yo ÂÏe ÆÐËriÑat¶oN¸ Make sÂre yo Âse Å Wet ÃorQÂe vÅLÂe¸ noà ŠdrÊ
oNe. Òn tÄe otÄer haNDÓ Âsing a Wet vaLÂe torQÂe on a drÊ FÔsÃeNer w¶lÕ Not get the
right amoÂnt oF cLamp¶Ng FÖrce.
/
IF
wasÄers
are
calLed ×r¸ tÄey MÂst
be able to W¶thstanD
tÄe
torQÂe
w¶thoÂÃ
tÄinning oÂt. Á soFt
washer
will
"beaÃ
outØ under Load¸ LeavÙ
¶ng the Fastener Loose
enoÂgÄ
Ão
ÚaÂse
a
FŶLÂre. IF yoÂr ÍÛ
caLLs FOr wasÄers¸ use
only those speciF¶ed.
Ány
washer
jÂst
won't do.
AUG 88
wHAT ABOUT WASHerS?
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