[sdiy] Reply-to: music.maker at gte.net

[Scott Gravenhorst]

Thanks to all, I scored it with a box cutter 
and it broke perfectly.  Thanks again, great list.

Magnus Danielson <cfmd at swipnet.se> wrote:
>From: Scott Gravenhorst <music.maker at gte.net>
>Subject: [sdiy] Cutting PCB Material
>Date: Fri, 02 Nov 2001 15:57:42
>
>> I need to cut a piece of pre-etched PCB in half so I
>> can use the other half for something else later.  The
>> package says "polyester glass".  I think I read
>> (here) that this stuff is really abrasive and can wear
>> out tools for cutting??  My intention was to use a coping
>> saw, which is really the only tool I have for this other
>> than simply holding it against a table edge and breaking
>> it along a line of pre-drilled holes.  The material is
>> cream colored if that makes a difference.  Will this
>> ruin my saw blade?  The cut will be a little longer
>> than 4 inches.  (René, I'm finally putting the 4069 VCO 
>> on a permanent board!).
>
>There are a few things you can do:
>
>1) Cooling. You are cutting through a hard material, this converts
>   your applied force into heat. That heat softens the blade and the
>   applied force does the rest. It is comparable to that of cutting
>   through metal. I am not an expert on practical mechanics, but I am
>   sure that someone with more of those skills will get the right
>   triggers by this.
>
>2) Weakening the material and then break it.
>   This is an old trick. In PCBs like this the fibers are woven into a
>   mesh. If you weaken the material along one of the fiberlines
>   (actually between two of them) by cut into it alongside a ruler you
>   can then quite easilly break it, since this introduced faultline
>   will see more stress when you bend it then other parts of board. If
>   you flex it in both directions multiple times, you let the
>   faultline grow bigger and bigger and suddenly it is almost done.
>   
>   You can also drill, but the fault-line concept has the benefit of a
>   rather narrow breakdown area. If you want to narrow the disaster
>   area (which may be crackled) you need to narrow down the distance
>   between the holes and also the size of the holes. If you create the
>   faultline and then drill, you migth quicken the process.
>
>   Remember, if you drill you *also* have to do cooling.
>
>I use the faultline method on those predrilled pertinax boards, for
>smaller things I only need to start the fault line by a cut in the
>edge, since that creates sufficient amount of faults into the matrix
>and the predrilled holes do the rest, bending it of is quickly done.
>
>This later technique is used in sewing to cut open a rift. You simply
>cut in a few centimeters, then you just pull them appart. It goes much
>quicker than cutting, and it is straigth!
>
>BTW. Bob Moog did his PhD dissertation on the study of fault locations
>in NaCl crystals under pressure. He used ultrasounds from 5 to 150 MHz.
>
>Cheers,
>Magnus
>

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