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Re: [turbobike] head studs

Craig S. Walker (csw_cmt@prodigy.net)
Mon, 13 Dec 1999 12:28:44 -0000

Also,

Those studs are "necked down" to keep them from cracking.  The cut or roll
of the thread causes damage to the crystalline structure, allowing cracks to
propagate.  Removing the  material at the outer edge of the stud is much
like drilling a hole at the end of a crack in plastic or fiberglass.

I believe you hit the nail on the head concerning why we buy aftermarket
parts (thinking they are better).  Why do we always assume the factories
have the least knowledge?

Craig

----- Original Message -----
From: Jeffrey K. Churchill <jcperformance@juno.com>
To: <shammar@nsk-corp.com>
Cc: <turbobike@natvideo.com>
Sent: Monday, December 13, 1999 2:30 PM
Subject: Re: [turbobike] head studs


>    Amen,   amen,    amen,  brothers and sisters !!!
>
> also,..heat treating has some effect,...and ultimate yield strength will
> depend on the care and characteristic of the thread ROLL ( as opposed to
> cut)
>
> JC
>
> On Mon, 13 Dec 1999 08:05:48 -0500 shammar@nsk-corp.com writes:
> >
> > That's interesting.  Was that a tensile test for ultimate strength?
> > How about
> > stiffness or torsional strength?  It raises an interesting question
> > since the
> > main function of the stud will be to apply the greatest clamp load
> > possible and
> > maintain it.  The only way to increase the clamp load is by
> > increasing the
> > torque on the fastener to further preload it, but a material strong
> > enough to
> > handle that torque without yielding throughout the operating
> > temperature range
> > is necessary.  The only way to appreciably increase the stiffness of
> > the stud is
> > to increase it's x-sectional area (diameter), since Young's modulus
> > is virtually
> > the same for all steel alloys.  The stock studs on the Kaws are
> > necked down near
> > the threads to match the thread root diameter.  This may not be the
> > way to go
> > since multiple threads share the load, but the reduced necked area
> > must support
> > it.  The aftermarket studs don't have that feature.
> >
> > Still, it's not totally clear cut and your friend's data is worth
> > considering.
> > It's funny that often we get sucked into replacing parts, assuming
> > that the
> > aftermarket parts are going to be better.  It's tough to beat the
> > design,
> > manufacturing expertise, and quality of material source of a major
> > manufacturer,
> > and unless the new part is significantly different AND is done
> > properly, it is
> > often a step backwards.  Pistons, rods, etc. often fall under this
> > category.
> > Ever have poorly machined pin bores or ring grooves on aftermarket
> > parts?  I
> > have.  Ever see it on stock stuff?  No.  I've taken a look at a few
> > aftermarket
> > wrist pins under the microscope and just about shit - they would be
> > cause for
> > shutting a plant down if we ground something like that.
> >
> > Buyers beware.
> >
> > Regards,
> > Bob
> >
> >
> >
> >
> >
> >
> > "Lorcan Parnell" <lorcan@mail.globalnet.co.uk> on 12/13/99 07:36:29
> > AM
> >
> > To:   Bob Shammas/EQA/Nsk-Corp@Nsk-Corp
> > cc:
> > Fax to:
> > Subject:  Re: [turbobike] head studs
> >
> >
> >
> > Just as an aside to this a friend of mine who runs a 7-second CBX
> > funnybike
> > had some aftermarket studs tested and found that they weren't any
> > stronger
> > than the standard Honda ones (which he had never had any trouble
> > with
> > anyway).
> >
> > Regards
> >
> > Lorcan
> >
> >
> >
> >
> >