beryllium copper grade for suspension spring.

[dandydude]

Hello,

What grade of BC is appropriate for suspension springs? From the research i did, c17200 looks appropriate. However does is need to be half hard or full?

Thanks
Dandy

 

[itspcb]

Dandy
In the latest Horological Science Newsletter (2017-2) Robert Matthys advises against the use of BC. The article sites two reasons: a short term humidity speed up problem affecting time keeping and 1 to 3 day lag problem was seen in a bellows pressure correction system. Matthys recommends Phospor Bronze 510, Alumininium Silicon Bronze 642 or Ni Span C type 902.
Peter

 

[dandydude]

Dandy
In the latest Horological Science Newsletter (2017-2) Robert Matthys advises against the use of BC. The article sites two reasons: a short term humidity speed up problem affecting time keeping and 1 to 3 day lag problem was seen in a bellows pressure correction system. Matthys recommends Phospor Bronze 510, Alumininium Silicon Bronze 642 or Ni Span C type 902.
Peter

Hello peter,

thanks for that. In fact in Robert matthys book accurate clock pendulums, he recommends BC as the ideal material... maybe this is recent finding... thanks for bringing this to my notice.

regards
dandy

 

[itspcb]

Dandy,
Yes it is a recent finding, the learning never stops!
Peter

 

[Phil Burman]

Hello peter,

thanks for that. In fact in Robert matthys book accurate clock pendulums, he recommends BC as the ideal material... maybe this is recent finding... thanks for bringing this to my notice.

regards
dandy

Matthys book revision 2004 page 150 concludes that 642 aluminium silicon bronze is the best suspension spring material. BC is identified on page 149 as "normally the best spring material for general applications."

Phil