Hello Swati,

I have a few suggestions from my days as a CNC operator, when I was
responsible for drilling with and sharpening bits.  These were some of the
things that I found to cause the issues you are speaking of. Of course I
was working with stainless steel.  But the purpose of a drill bit is the
same no matter what the material, so I am certain they are subject to the
same issues.

I would check the rpm's of the machines that these bits are in?
Chipping/breaking can occur as a result of either not having enough rpm or
to much rpm. It depends on what the bit is rated for in terms of rpm, the
material it is made from and what it is cutting. I would also check the
feed rate (downward force) of the bit to make sure it has not changed as
well.

In terms of the used drill bits, that simply sounds to me like a poor
sharpening job where the best cutting angle of that bit was not achieved.
Bits are designed to have a specific cutting angle depending on what
material they are going to be drilling.  If you deviate that angle when
resharpening you will get the clogging, as you describe, because the
flutes can not clear out the cut material.  Also the holes that result
will be poor and have more burring, splintering, etc. Make sure whoever is
sharpening these for you has the appropriate angles for those bits. The
manufacturer can provide that information. Also there are devices that
make sharpening used bits almost error proof.  Using your eye is not
sufficient for precision drilling.

My 2 Pennies

Joe Russeau

Process Analyst

Precision Analytical Laboratory






Dear friends,
> We are facing a problem in PCB drilling.
> During inspection of the drill bits after the drilling process, we are
> observing a chip off in the drill bits.
> In some drill bits it is at the cutting lip of the drill bit. In some
> drill
> bits it is in the primary face of the drill bit web.
> We have observed the problem in the drills from both the drill suppliers
> that we have.
> Another problem is the used drill bits have a severe negative flair, in
> some cases it is as high as to
> give a triangular appearance to the drill bit primary instead of the
> normal
> rectangular appearance.
> We have even observed the clogging of dust and entry material coils in the
> flute of the drill bits.
> We are looking into the causes of these problems but with little success.
> Any feedback from the technet members will be highly appreciated.
>
> Warm regards,
> Swati Parial
> Scan by AT&S virus protection
>
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