Homebrew PCBs

On 13 Sep 2014 11:56:44 -0700, you wrote:

>Thank you, James.
>
>I don't have a drill press yet, no, but I do have a Proxxon IB/E high speed electric rotary milling tool.   I was thinking of getting a Proxxon Micromot MB 140/S drillstand for it, unless I find a regular drill press cheaper.    Even then,  a cheap drillstand might be a gamble as to how well it drills PCB material.

You don't want it to wobble from side to side at all.  You may
consider doing the following:

1) elevate the board on a platform with a 1/4 inch hole in it.
2) light the board from above
3) have an optical crosshair and eyepiece focused on the bottom of the
board.   I'd suggest using a 45 degree mirror.
4) have some sort of dust collector on the top
5) use a BB gun sight with the little red dot for the bottom sight
alignment if it works.  The dot can be adjusted to match the exact
location of the hole you'll drill.

This way, you position the board over the cross hairs, then just
drill.  If you ever have to align top and bottom boards, this makes
the alignment easy when you do the patterns first and glue the boards
together.

Harvey

Generally you go by the size of the leads on the components. You want 
a drill that is about 5 to 10 percent larger. But at least a minimum 
of 0.002" to 0.004" larger in any case.

Specific sizes: Many components, including DIP packages, will be OK 
with a #65 - #72, or a 1/32" or a 0.8mm. Half Watt and larger 
resistors will need larger sizes. Capacitors are all over the map so 
a 3/64", #55 - #60, or a 1.2mm would be a good second size. Beyond 
that, you just have to measure your component leads. And do it BEFORE 
making the board unless you want to make it twice.

Carbide may not be the best choice for your first efforts. Carbide 
will break very easily so if you are using a hand drill or a drill 
press with any amount of play, you may snap the small diameter ones 
quickly. I would start with HSS (High Speed Steel) bits and work my 
way into carbide after some experience. A good HSS bit can last for 
many dozens, even hundreds of holes, even in fiberglass epoxy. And 
you can buy several HSS bits for the price of one carbide one.

How does one resharpen bits this small?  Or do you?

Thank you.

Jim Pruitt

----- Original Message ----- 
From: Paul Alciatore palciatore@... [Homebrew_PCBs] 
To: Homebrew_PCBs@yahoogroups.com 
Sent: Saturday, September 13, 2014 8:30 PM
Subject: [Homebrew_PCBs] Re: What size drill bits ?

Generally you go by the size of the leads on the components. You want 
a drill that is about 5 to 10 percent larger. But at least a minimum 
of 0.002" to 0.004" larger in any case.

Specific sizes: Many components, including DIP packages, will be OK 
with a #65 - #72, or a 1/32" or a 0.8mm. Half Watt and larger 
resistors will need larger sizes. Capacitors are all over the map so 
a 3/64", #55 - #60, or a 1.2mm would be a good second size. Beyond 
that, you just have to measure your component leads. And do it BEFORE 
making the board unless you want to make it twice.

Carbide may not be the best choice for your first efforts. Carbide 
will break very easily so if you are using a hand drill or a drill 
press with any amount of play, you may snap the small diameter ones 
quickly. I would start with HSS (High Speed Steel) bits and work my 
way into carbide after some experience. A good HSS bit can last for 
many dozens, even hundreds of holes, even in fiberglass epoxy. And 
you can buy several HSS bits for the price of one carbide one.

Paul,
I will disagree with your statement of 2 to 4 mils above lead diameter. For the past 40 years, the standard play for through hole has been a minimum of 7 mils in order to have tin/lead solder flow easily and make a good solder joint. Lead-free solder flow less easily than tin-lead, so I would use at least 8 mils over the lead diameter.

But that is just what the industry is saying (check IPC recomendations), you might know better.

Jean-Paul
AC9GH

On Sep 13, 2014, at 11:30 PM, Paul Alciatore palciatore@... [Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:

> Generally you go by the size of the leads on the components. You want 
> a drill that is about 5 to 10 percent larger. But at least a minimum 
> of 0.002" to 0.004" larger in any case.
> 
> Specific sizes: Many components, including DIP packages, will be OK 
> with a #65 - #72, or a 1/32" or a 0.8mm. Half Watt and larger 
> resistors will need larger sizes. Capacitors are all over the map so 
> a 3/64", #55 - #60, or a 1.2mm would be a good second size. Beyond 
> that, you just have to measure your component leads. And do it BEFORE 
> making the board unless you want to make it twice.
> 
> Carbide may not be the best choice for your first efforts. Carbide 
> will break very easily so if you are using a hand drill or a drill 
> press with any amount of play, you may snap the small diameter ones 
> quickly. I would start with HSS (High Speed Steel) bits and work my 
> way into carbide after some experience. A good HSS bit can last for 
> many dozens, even hundreds of holes, even in fiberglass epoxy. And 
> you can buy several HSS bits for the price of one carbide one. 
> 
> 
>

Proxxon rotary tool and proxxon drill stand are perfectly adequate for drilling pcbs with carbide bits. The runout of the tool is small enough not to break the bits.

Generally people don't resharpen small drills. However I have seen several comments on the internet claiming that new, good quality, bits from reliable suppliers are not as sharp as they could or should be. If you want to try resharpening bits of this size do a Google search for "wishbone sharpener"

Craig

On 14/09/2014 18:36, craigl2@... [Homebrew_PCBs] wrote:
> Generally people don't resharpen small drills. However I have seen
> several comments on the internet claiming that new, good quality, bits
> from reliable suppliers are not as sharp as they could or should be. If
> you want to try resharpening bits of this size do a Google search for
> "wishbone sharpener"

Mega Electronics supplies resharpened carbide drills. They work just as 
well as brand new ones, and are quite a lot cheaper.

Resharpening carbide drills is difficult at home.

Leon
-- 
Leon Heller
G1HSM

I have a box each of 13, 26, 35, and 43 mil (I think those are the right
numbers) carbide PCB drills.  That plus a set of standard twist-drills
in letter/number/fraction sizes for weird holes.

The 13s are for vias (28 gauge brass wire is perfect for hand-soldering
these)

The 26s are for small parts (1/4w resistors, through-hole ICs, etc)

The 35s are for larger parts and sockets

The 43s are for soldering wires to the board (22ga etc).

As for drilling, I use a dremel on a custom stand for small boards:
  http://www.delorie.com/pcb/dremel-stand/
or my CNC machine for big ones:
  http://www.delorie.com/photos/cnc/

Hi,


I found that Dremmel sell this set (see photo) that has all the standards
size drill bits of PCB for through-hole parts, including connectors and

headers ...


best regards,


TheRojecas


2014-09-12 18:10 GMT-05:00 alan00463@... [Homebrew_PCBs] <
Homebrew_PCBs@yahoogroups.com>:


>
>
> Getting ready to make my first PCB with through-hole parts.    What
> diameter s of carbide drill bits do I need for drilling holes and how many?
>
> Thanks, Allan
>
>




[Non-text portions of this message have been removed]

On 15. 09. 2014 20:43, DJ Delorie dj@... [Homebrew_PCBs] wrote:
> I have a box each of 13, 26, 35, and 43 mil (I think those are the right
> numbers) carbide PCB drills.  That plus a set of standard twist-drills
> in letter/number/fraction sizes for weird holes.
>
> The 13s are for vias (28 gauge brass wire is perfect for hand-soldering
> these)
>
> The 26s are for small parts (1/4w resistors, through-hole ICs, etc)
>
> The 35s are for larger parts and sockets
>
> The 43s are for soldering wires to the board (22ga etc).
>
> As for drilling, I use a dremel on a custom stand for small boards:
>    http://www.delorie.com/pcb/dremel-stand/
> or my CNC machine for big ones:
>    http://www.delorie.com/photos/cnc/
>
>
> ------------------------------------
> Posted by: DJ Delorie <dj@...>
> -------------------------------
That's nice stand, but by design they have side motion too. The tool 
doesn't go straight down but in radius (12") of a circle. But of course 
that's 100% beter than a dremel in hand. This kind of drills (at least 
chinese copy) come badly balanced some time. that's a reaon why you have 
vibrations...

Slavko.

Even if it were a perfect circle, a 0.25" plunge (about twice my normal)
on a 12" radius means it's offset by only 2-3 mil.  I think the amount
of slop in the whole system is more than that, esp in the runout of the
bit itself.  A normal plunge would be way less than the runout.

Plus, because there's two beams, at least the dremel is still vertical
as it plunges - it's not itself rotating about a point 12 inches away.

But either way, the results are good - I rarely break drill bits, and
usually when I do it's because of something stupid I did (like drop
them) and not the drill press.

On 17 Sep 2014 10:17:32 -0700, you wrote:

>Thank you, Craig, and DJ, and Harvey, for showing me your setup's.    Now I realize that addressing the ergonomics of drilling holes will be worth my while if I decide to make more than one board.    Since my Proxxon rotary tool is AC powered, I will probably hook it up to a solid-state relay controlled by a footswitch so I can rapidly switch it
>on/off.

Hmmm, don't.   <grin>  I tried the solid state relay approach, and it
works mostly.  The tool does not completely stop, but vibrates just a
little.  I'd picked up a transformer run 12 volt tool, and that works
with a solid state relay.  I think you need a minimum load on a solid
state relay, and what the controller in the AC proxxon presents is not
load enough.  I'd go with a simple old relay.  

You could easily get  a heavier duty footswitch and just run the tool
directly without even a relay.

Mine is controlled by the processor that does the drilling cycle.

The main thing is that if you want to do accurate double sided boards,
the accuracy of your alignment holes is absolutely critical.

Harvey