[Healeys] Anti Sway Bar Straps

[Curtis Arndt]

Perry,

Here in lies one problem with some 5/16" bolts...  A 5/16" UNC bolt has 18
TPI.  A 5/16"BSW bolt also has 18 TPI.  HOWEVER they are not
interchangeable.

Case in point, the Aluminum front plate on the BN1/2 generators where the
adjusting link attaches is tapped for a 5/16" bolt... *A 5/16" BSW bolt*!
However, over the years they were replaced by owners with 5/16" UNC bolts
from their local hardware store, because... They also have 18 TPI.. Yes
they will thread in and tighten down, but Whitworth, by definition is a
thread form with a 55 degree thread pitch angle while UNF/UNC are a 60
degree thread pitch angle.

Because of this 5 degree difference, sooner or later the bolt will loosen,
and the threads in the front plate will be destroyed.  Buyeye Sprite
generator front plates are exactly the same!

Cheers,

Curt

On Sat, Jul 20, 2019 at 6:29 PM Perry Small via Healeys <
healeys at autox.team.net> wrote:

> Ok... enthralled by another guess the bolt game. Went to the garage and
> pulled out the BN 1 front frame section, cleaned the threads and iD’d the
> holes as 5/16 threads not 3/8.
> Pulled one of the bolts on our BN2 and is a 5/16 -24. Hole on BN1 is
> courser (if there is such a word) so pulled out what I thought was a 1/4
> Whitworth bolt (only indentified by the odd head size at 0.525 and it
> threaded in reasonably well. Other holes the same.
> Since a 5/16 BSW has the same size head as the 1/4 Whitworth bolt in hand
> may have been a BSW.
> Conclusion, either someone with too much time on his hands was running
> around with an old tap many years ago or that the subject threaded holes
> are definitely not 5/16 UNF.
> I retreated from the garage to the house to resume enjoying the air
> conditioning. The east coast is roasting today.
> Perry
>
>
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