Re: grade 8 (was Re: Engine stand)

[bearbvd@domain.elided (Greg Hermann)]

Agree with Richard on Grade 5 vs. Grade 8 _EXCEPT_ that grade 5 is every
bit as hard as grade 8 ON THE SURFACE--but softer in the core. Grade 5
stuff is case hardened, Grade 8 is through hardened.

As for the washers-- you need a GOOD hardware or parts store to find them,
but it's WAY better to use HARD washers for this sort of thing, NOT fender
washers. The hard washers come in TWO OD sizes for each bolt size--the
larger being ANSI and the smaller being SAE. If you REALLY look, generally
in an aircraft hardware place, it is also possible to find hard washers
that are small enough OD for the bolt size to fit under the head of a
socket head (Allen) cap screw--and to fit down a counterbore sized to JUST
swallow such a socket headed cap screw.

Not much point in trying to torque grade 5 OR grade 8 bolts which have soft
washers under EITHER end--all you will do is extrude the washer out of the
way !!

BTW-- there isn't a metric thread standard out there--be it DIN, JIS,  some
french or italian bologna,  BS, or Whitworth, that comes even CLOSE to
being as GOOD a thread standard as the good old ANS and SAE stuff is---
This is just something that we Yanks happen to have done  RIGHT.

Greg

At 4:40 PM 9/2/02, Richard Welty wrote:
>On Mon, 26 Aug 2002 18:39:37 -0700 Tony Sims <simstony@domain.elided> wrote:
>>  IIRC, I ended up with 2 of
>> the
>> arms sharing one slot on the pivot plate.  Also, get some grade 8
>> hardware
>> with plenty of big fender washers to support the upper block holes so you
>> don't mangle 'em.
>
>ok, i'm going to ask a loaded question here?
>
>why grade 8? what do you mean by grade 8, the SAE designation (used only on
>traditional non-metric fasteners) or do you really intend to state 8.8? (a
>metric designation, corresponding roughly to SAE grade 5).
>
>i can see no compelling reason why this application requires an SAE grade 8
>equivalent bolt. many people insist on using SAE grade 8 "because it's
>better" when usually it's nothing of the kind.
>
>SAE grade 5 is softer, more ductile, which means it will bend some time
>before it breaks. SAE grade 8 is less ductile, less inclined to bend, but
>will tend to break more suddenly when it lets go.
>
>people are very insistent about things like grade 8 when they're bolting,
>say, roll cages to the floors of production cars. i've never quite figured
>out why. the floor will give way long before a grade 5 bolt will.
>
>likewise, a properly installed grade 5 bolt should support an engine on an
>engine stand just fine, if there are enough of them and they're torqued
>properly.
>
>richard
>--
>Richard Welty                                         rwelty@domain.elided
>Averill Park Networking                                         518-573-7592
>              Unix, Linux, IP Network Engineering, Security
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