Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

Hi

I promised a description of the PCB shear i made.
First, imagine the standard pivoting-sword paper cutter, this is the basic
idea.

Then get some angle iron, we are going to make one.

depending on the size you need (i suggest A3) you will need:
A) one length of angle iron ~~50 cm long for the stationary blade
B) one length approx. 15 to 20 cm longer than A) (the extra is the handle)
for the pivoting blade
c) a short piece of angle iron, 5cm or so, for the hinge/pivot.

You also need one big screw for the hinge, and 2 other screws to mount C)
to A).
You will want a wood board or something to mount this unit too (it also
can be screwed to the
edge of the workbench).

Now, we need to make cutting edges on the pieces of angle iron. The
stationary blade A) will be mounted like
A upside down L when looking from the front of the cutter. (cutting
mechanism on the right hand side).
In other words, lit looks like a F without the short middle line.
(you can see a quick sketch at <st.such.info/pub/cutter.gif>. Yes, I drew
that, not a kindergarden child.)

For now stop laughing and look a the top sketch. this is the cutting
mechanism, sharpen the indicated edges with a angle grinder of file. make
sure the stationary blade is 100% straight.
You needn't make such a sharp angle, just over 90 degree.
The stationary blade is ground the whole length, but with the pivoting
blade don't grind the handle.

To get the whole thing together you make a short bracket. use 2 screws to
mount it to A) and a big screw to make the pivot. I expect you are aware
you need to drill holes ;-).
You can see a illustration in the bottom sketch (view from back).
The pivot bracket must have one side cut shorter to fit under A).

Really simple, wasn't it?

A few notes: having a low pivot point helps to keep a not too flat cutting
angle all the way of the blade.
Good paper cutters have a curved blade. That is not to make them look more
menacing, this keeps the cutting angle constant. (otherwise it will be
harder to cut at the front, much harder than the shorter lever alone).
You will not be able to cut PCBs the whole length, so make it double the
size as your PCBs.

It cuts both paper and PCB very well, but it might need another bar to
press the PCBs down. Simpe to add.

Only a few hours work, and no money involved, so a really good thing to
buy i think.
IMO the blades will be worn not too fast, and the way i arranged the
pieces makes sure you have plenty
of material to re-sharpen.

I hope the instructions are clear, feel free to ask.

ST