"Hi Lois,
You need to be aware that drills have two vastly different types of cutting edges—point edges and flute edges.
during resharpening only the point edges are sharpened; sharpening the flute edges would reduce the drill diameter.
It is the dull flute edges that cause most of the resin smear in drilling because the duller the flute edges the higher the frictional heat generated.
Therefore, 'resharpened' drills will never produce the same quality holes than will new ones.
That is why the number of hits as well as 'resharpening' of drills shall be limited by a NOTE in the specification drawing.
For more information, you may want to obtain my White Paper : "Recommendatioins for PCB FAB Notes and Specifications in Printed Circuit board Drawings for SnPb and Lead-Free Soldering Assemblies, the Qualification of PCB Shops and Activities to Assure Continued Quality."  
Werner

 


 

 

-----Original Message-----
From: Louis Hart <[log in to unmask]>
To: [log in to unmask]
Sent: Wed, Oct 6, 2010 12:07 pm
Subject: [TN] drill bits and resharpening - printed circuit fabrication


Technetters, regarding printed circuit fabrication and drilling of holes that 
will be plated, does anyone have experience comparing new drill bits to 
resharpened drill bits? If so, please let me know what your thoughts are 
regarding the two types. I'm especially concerned with comparative performance 
of new vs. resharpened on high-layer-count boards. As usual, many thanks for any 
comments.

Louis Hart
Compunetics
Monroeville, PA
USA
[log in to unmask]<mailto:[log in to unmask]>
412-858-1272

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