I'm sorry if I am stating the obvious but a countersunk hole is one that
has been made using a countersink bit>

These can have just countersink teeth to countersink the top of a hole
or can be obtained with a standard drill bit
at the bottom & a countersink bit at the top to drill & countersink in
one drilling action.

If the hole is (for example) for fitting screws through the PCB and
leaving a flush side with no raised obstructions, drilling countersunk
holes would allow countersunk head screws to be used.

This can be done by using special countersunk drill bits or depending
upon the size/angles of the countersink required the tip of an ordinary
larger drill bit.

The edges of the hole are at an angle (see below)

___________     ___________
___________\   /___________ PCB laminate
                   hole

Alternatives to countersunk holes can be routed holes with differing
steps/diameters (a bit like stairs but in a circle).

You just have to be careful not to take too much material out or the
screw can pull through the hole easily.

Hope that this helps...

T.T.F.N

Matthew Lamkin
Printed Circuit Board Draughtsman
Protec Fire Detection PLC
Churchill Way,
Nelson, Lancs
BB9 6RT.
Tel 01282 717393
Fax 01282 717273
Email = [log in to unmask]

Company Web Site = http://www.protec-fire-detection.plc.uk


>-----Original Message-----
>From:  Howard Lin [SMTP:[log in to unmask]]
>Sent:  Thursday, March 25, 1999 4:09 AM
>To:    [log in to unmask]
>Subject:       [TN] countersink hole
>
>Hi all,
>
>Has anybody seen countersink hole on PCB? What is it? How to make it?
>Any input I will be very appreciated.
>Howard
>Maxedge Electronic Corp.
>[log in to unmask]
>
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