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Re: [turbobike] head studs

Jeffrey K. Churchill (jcperformance@juno.com)
Mon, 13 Dec 1999 09:30:42 -0500

   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


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