Homebrew PCBs

Adam,

The Nawide delt driven machine has a maximum speed of 30,000 rpm. 
Speed is important but feed rate is more important. Higher speeds 
allow higher feed rates. Do some research on "chip load" which will 
give you an idea of what speeds and feed rates to use. I just adjust 
the scope drills until it "feels right" with highest speeds for small 
bits and slow speeds for big bits. Feed rates are adjusted for 
minimum drill wander in a scrap of material as viewed in the scope. 
That's another benefit of these machines, you can actually watch the 
bit come through the board and check for drill wander which is 
minimal to begin with.

The Excellon Uni-Drill uses a Precise #65 spindle that will go to 
45,000 rpm and the Aetna Acrodrill uses their own Aetna spindle that 
runs up to 40,000 rpm. The optical scope on the Nawide uses a small 
prism that projects the image onto a screen that has a bombsite 
reticle. Aetna uses a small microscope lens in the scope that 
projects onto two "first surface" mirrors and then to the ground 
glass screen. These mirrors are at 90 degrees to each other for image 
correction (left-right movement)and that assembly is at a 45 degree 
angle between the lens near the drill bit and the screen. Aetna uses 
a focused lamp and Nawide uses fiber optics for illumination.

Excellon had two scope systems, the small one used a lens at the 
table and and a small mirror (looks like a dentit's mirror)to reflect 
the image to a paper screen in the back of the scope housing. It 
worked but was a cheap looking device. Another optional scope was 
offered that was much larger and better with mirrors and a big ground 
glass screen. I have one of these scopes laying around and can 
provide a photo of it as well.

The best way is to use the right lens with a cheap video camera and 
monitor. Many of these machines were converted to this setup over the 
years. The Excellon scope drills are the easiest to convert to video 
and the Nawide would be most difficult.

BTW, I got one of my Nawide machines for free because no one wanted 
it. My Aetna Acrodrill was purchased for $200 after it sat in a 
surplus shop for almost five years. They said no one knew what it was.
A guy on eBay had a brand new Electro-Mechano scope drill (just out 
of the crate) and he couldn't get a $500 bid for this $7500 new 
machine! He asked me to make an offer but I didn't need another one 
and the shipping would be way too high for me. These machines can be 
had for next to nothing now days. They can't be beat for prototypes 
and small volume hobby boards. Just keep looking and you will find 
one for the right price.

Tom

--- In Homebrew_PCBs@yahoogroups.com, Adam Seychell 
<adam_seychell@y...> wrote:
> Thanks Tom , that makes it more clear. If its not too much 
> effort, I would like to see a few basic pics of the machine you 
> own. With Nawide machine having belt drive, what RPM did this run 
> at ? I'm curious, what do you think is a "good" RPM for manual 
> drilling  around the 0.6mm - 1.5mm diameter range ?
> 
> I know your talking 100k RPM and above for the very large and 
> expensive Excellon CNC production drill machines.
> 
> Was it quick to change drill bits on these machines ? My guessing 
> is the spindle would feed far upwards so the collet pops up 
> through the flat panel giving you access to it.
> 
> Adam