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

I'm curious why there is so much interest in hobbyists who make no more
than couple of PCBs per week would need a CNC drilling machine to drill
the holes. I found hand drilling is not that big a deal when you have a
good drill press. There is a prototype place near my area and I noticed
they hand drill the holes even though they have a small CNC drilling
machine. The owner of the shop told me by time they setup the machine
its quicker to hand drill. So, anyone thought about building a really
good drill press ?

The drill press I made couple of years ago is still working very well
and I'm happy with it. The basic design uses a straight grinder mounted
to the end of a long arm (400mm) which pivots at the opposite end. This
is mounted on a wooden base.


___
| |
o__________|_| straight grinder
| |
_|____________________ wooden base (18 mm MDF)


The arm is made from a piece of 50 x 50 mm aluminum square. The pivot is
made from two thrust bearings (from car clutch) that clamp on opposite
sides of the square aluminum arm. This is then fixed to the wooden base
with two pieces of aluminum right angles. In the diagram, thrust
bearings are "2", the arm is "3". Threaded bar, "4", goes through the
right angles , the thrust bearings and square arm so everything is
tightly clamped.


_ ____ _
| || | | || |
4=== | |2 | 3 | 2| | ===4
| || |____| || |
|----- | | -----|
-----------------------------------
----------------------------------- <-- wooden base


This setup gives stable and extremely smooth vertical movement of the
drill. There is of course an inherent arc movement of the drill bit.
This does not cause a problem when the drilling depth is only a few
millimeters. The most difficult part for me was mounting the straight
grinder to the end of the arm. This fixture needs to be adjustable to
allow slight alignment of the drill so it has perfect vertical feed. I
choose a straight grinder (BOSCH GGS27) because it was the only thing
around that came with a precision hardened steel ground collet and also
in my price range. The roundout is acceptable for carbide bits, (haven't
broken my 0.45 mm bit yet). The Dremel I first tried was useless because
of the sever round out. Luckily I got my money back. Major problem with
this machine is it can take up a bit of space. It compromises low
complexity for size. One improvement to the design would be to add a
stepper motor control for the down feed. That way both hands can be used
to position the PCB and a food pedal to operate the drill feed. Any
thoughts ?