Homebrew PCBs

I tend to use resharpend drills (as they are cheaper and so am I !)
but 
use a collar to set the length to a standard so changing mid way 
through a board is less hassel.

The 1/8" drill shank has a 3mm collar forced over it so is a very
tight 
fit. 

Actually adjusting the collar to sit so that the drill tip (or more 
critically a fishtail cutter tip)is exactly where it should be is a
bit 
hit or miss and I wondered if anyone else uses this method and if so 
has a magic way to adjust them.

I sat down to design a screw device to force the drill through the 
collar until it touches a contact and lights an led, but then
realised 
that the collars vary in thickness and the critical reference is from 
the TOP of the collar to drill tip.

AWEM

that the collars vary in thickness and the critical reference is from

>the TOP of the collar to drill tip.
>
>AWEM
>  
>
  Don't see much need for this manually, so I'm guessing you're using a 
CNC of some type.  Just move your contact's reference point to the back 
side of the collar.  You still need the front to push against, but 
instead of connecting your contact plate to that mechanically, have a 
seperate plate that just rests against the other side of the collar and 
attach the contact to it..

  Easier to not worry about the collars, and have the CNC move the bit 
down until it touches a contact plate, and figure the offset for the 
bit.  Use a piece of scrap flat leaf spring (often a guide for the 
printhead conductor cable for older dot matrix printers or similar), so 
it won't break bits if it doesn't sense contact the moment it touches.  
Not as good for just 'pause' and replace bit though.

Alan

On Sun, 02 Oct 2005 16:14:15 +0200, Andrew Mawson <andrew@...>  
wrote:

> I tend to use resharpend drills (as they are cheaper and so am I !)
> but
> use a collar to set the length to a standard so changing mid way
> through a board is less hassel.
> The 1/8" drill shank has a 3mm collar forced over it so is a very
> tight
> fit.
> Actually adjusting the collar to sit so that the drill tip (or more
> critically a fishtail cutter tip)is exactly where it should be is a
> bit
> hit or miss and I wondered if anyone else uses this method and if so
> has a magic way to adjust them.
> I sat down to design a screw device to force the drill through the
> collar until it touches a contact and lights an led, but then
> realised
> that the collars vary in thickness and the critical reference is from
> the TOP of the collar to drill tip.
> AWEM


I have a screw device too, i didn't sit down to design much though....

It's just a large nut with a short piece of copper tubing soldered to it,  
and a washer soldered on the end of that.
There are also two large screws, one with a small indentation and one with  
a small stud. the first one is used to move the ring around and the second  
one can push the drill out all the way if i need the ring for another one.

All the rings i have are same thickness, and i manually set them (maybe  
0.2mm tolerance). If the rings are not the same one could build a similar  
screw adjuster that uses the top side as reference.

ST

How much do the collars vary in thickness? Might it be workable to
add shims to make all of the collars the same thickness? Alternately, 
could the thicker ones be lightly sanded to make them the same height 
as the thin ones?

Regards, Bob

--- In Homebrew_PCBs@yahoogroups.com, "Andrew Mawson" <andrew@m...> 
wrote:
<snip> 

>I sat down to design a screw device to force the drill through the 
> collar until it touches a contact and lights an led, but then
> realised 
> that the collars vary in thickness and the critical reference is 
from 

> the TOP of the collar to drill tip.
> 
> AWEM

--- In Homebrew_PCBs@yahoogroups.com, "Bob_xyz" <bob_barr@h...> wrote:
> How much do the collars vary in thickness? Might it be workable to
> add shims to make all of the collars the same thickness?
Alternately, 
> could the thicker ones be lightly sanded to make them the same
height 
> as the thin ones?
> 
> Regards, Bob
> 
> --- In Homebrew_PCBs@yahoogroups.com, "Andrew Mawson" <andrew@m...> 
> wrote:
> <snip> 
> 
> >I sat down to design a screw device to force the drill through the 
> > collar until it touches a contact and lights an led, but then
> > realised 
> > that the collars vary in thickness and the critical reference is 
> from 
> > the TOP of the collar to drill tip.
> > 
> > AWEM

The top HAS to be the reference as in fact it rests against a
shoulder 
on the collet to set the position in the spindle. Settting the Z
height 
for each tool isn't an option as I'm using a Heidenhain controller on 
a 
Bridgeport Interact 1 CNC mill, and although tool lengths can be set 
individually when called this is not the case in the event of a 
breakage. Variation in collar thickness isn't much - maybe 0.1mm max 
but enough to spoil your day if you are isolation milling pcbs ! If 
it were just drilling holes it could be ignored and allowed for in 
the sacrificial underpad.

AWEM

--- In Homebrew_PCBs@yahoogroups.com, "Stefan Trethan" 
<stefan_trethan@g...> wrote:
> On Sun, 02 Oct 2005 16:14:15 +0200, Andrew Mawson <andrew@m...>  
> wrote:
> 
> > I tend to use resharpend drills (as they are cheaper and so am 
I !)
> > but
> > use a collar to set the length to a standard so changing mid way
> > through a board is less hassel.
> > The 1/8" drill shank has a 3mm collar forced over it so is a very
> > tight
> > fit.
> > Actually adjusting the collar to sit so that the drill tip (or 
more
> > critically a fishtail cutter tip)is exactly where it should be is 
a
> > bit
> > hit or miss and I wondered if anyone else uses this method and if 
so
> > has a magic way to adjust them.
> > I sat down to design a screw device to force the drill through the
> > collar until it touches a contact and lights an led, but then
> > realised
> > that the collars vary in thickness and the critical reference is 
from
> > the TOP of the collar to drill tip.
> > AWEM
> 
> 
> I have a screw device too, i didn't sit down to design much 
though....
> 
> It's just a large nut with a short piece of copper tubing soldered 
to it,  
> and a washer soldered on the end of that.
> There are also two large screws, one with a small indentation and 
one with  
> a small stud. the first one is used to move the ring around and the 
second  
> one can push the drill out all the way if i need the ring for 
another one.
> 
> All the rings i have are same thickness, and i manually set them 
(maybe  
> 0.2mm tolerance). If the rings are not the same one could build a 
similar  
> screw adjuster that uses the top side as reference.
> 
> ST

Stephan,

Can you pop a picture in the photos section?

Cheers,

AWEM

--- In Homebrew_PCBs@yahoogroups.com, "Andrew Mawson" <andrew@m...> 
wrote:
<snip>
> 
> The top HAS to be the reference as in fact it rests against a
> shoulder 
> on the collet to set the position in the spindle. Settting the Z
> height 
> for each tool isn't an option as I'm using a Heidenhain controller 
on 
> a 
> Bridgeport Interact 1 CNC mill, and although tool lengths can be 
set 
> individually when called this is not the case in the event of a 
> breakage. Variation in collar thickness isn't much - maybe 0.1mm 
max 
> but enough to spoil your day if you are isolation milling pcbs ! 
If 
> it were just drilling holes it could be ignored and allowed for in 
> the sacrificial underpad.
> 
> AWEM

My thought was that, as long as the collars were all the same 
thickness, there's a fixed distance from the bottom face of the 
collar to the top of it. That fixed distance could be taken into 
account in your collar setting device.

Regards, Bob

On Sun, 02 Oct 2005 18:41:06 +0200, Andrew Mawson <andrew@...>  
wrote:

> Stephan,
> Can you pop a picture in the photos section?
> Cheers,
> AWEM


maybe tomorrow.

To reference it to the top of the ring you could press the drill against  
the outside of the mechanism with a nut.
I don't mill isolation so 0.2mm tolerance is plenty.

ST