PSN-L Email List Message

Subject: Re: knife edge materials & horological update
From: ChrisAtUpw@.......
Date: Wed, 14 Nov 2007 08:11:40 EST


In a message dated 14/11/2007, holmstro@.......... writes:

The HSN  website has some preliminary information on knife edges for horology 
located  at http://www.hsn161.com/knife.php  A rounded edge is the key to  
success as Chris points out.  If done properly, knife edge supported  pendulums 
for clocks can be a great success - Reifler clocks for  example.
Hi Bob,
 
    Making a triangular rod and then accurately  rounding, lapping and 
polishng the edge involves precision engineering. However,  milling a short flat 
section on the tip end of say a 60 deg rod and  then milling a small 90 deg V 
slot in this face to support a  small diameter circular rod is quite possible. 
You can clean the components and  glue the rod in place with two part acrylic 
glue. 
    One other consideration not mentioned is that the  materials need to be 
very resistant to oxidation / corrosion if used in damp  air. Martensitic 
Stainless Steel, Tungsten Carbide and Sapphire are  obvious 'candidates'. Materials 
suitable for use in high vaccum are more  limited. If you use metals, you are 
likely to get welding when  the protective oxide coats wear off. Some hard 
ceramics like sapphire  are likely to be successful. 
 
    Regards,
    
    Chris Chapman






   





In a message dated 14/11/2007, holmstro@.......... writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>The HSN=20 website has some preliminary information on knife edges for horology locat= ed=20 at http://www.hsn161.com/knife.php  A rounded edge is the key to= =20 success as Chris points out.  If done properly, knife edge supported=20 pendulums for clocks can be a great success - Reifler clocks for=20 example.
Hi Bob,
 
    Making a triangular rod and then accurately= =20 rounding, lapping and polishng the edge involves precision engineering. Howe= ver,=20 milling a short flat section on the tip end of say a 60 deg rod and=20 then milling a small 90 deg V slot in this face to support a=20 small diameter circular rod is quite possible. You can clean the components=20= and=20 glue the rod in place with two part acrylic glue.
    One other consideration not mentioned is that t= he=20 materials need to be very resistant to oxidation / corrosion if used in damp= =20 air. Martensitic Stainless Steel, Tungsten Carbide and Sapphire are=20 obvious 'candidates'. Materials suitable for use in high vaccum are mor= e=20 limited. If you use metals, you are likely to get welding when=20 the protective oxide coats wear off. Some hard ceramics like sapph= ire=20 are likely to be successful.
 
    Regards,
    
    Chris Chapman
 

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