Homebrew PCBs

John,

thanks, but this is way of what i asked.

i know there are other options, i know there is drill rod.

but i hoped you may tell me which surface your gas pipes have.

the tpi of metric allthreads is about in the range of 20tpi (~1,2mm rough 
guess)
and i hope i find a software which compensates for wacky fractions.
i really think they will work for now.
even if i don't manage to have the software recalculate it i can still 
change my drawings.
and at least i can test the machine, only to see it working it doesn't 
matter if the output
is out of scale. i can still buy better threads later.

stefan



i'm sure going metric (and some day we will convince you guys to do so too 
;-) )

On Sun, 05 Oct 2003 19:44:41 -0000, crankorgan <john@...> wrote:

> Stefan,
> Drill Rod is cheap and very accurate. You will then need a bushing to 
> ride on it. The bushing can be a block of nylon with a hole in it. The 
> problem is you might not be able to find a drill bit that will produce 
> the correct hole. But that would be a first test. You could also hack old 
> printers. You have to test the waters.
> The biggest hurdle is software. Are you going to work in Metric or 
> Inches? Then on to the threaded rod. It needs to be fine not coarse. I 
> use 20 tpi rod. With a 200 step motor that devides and inch by 4000 
> steps. 20 tpi with a 200 step motor gives a nice .00025 inches per step. 
> This makes all IC pin centers and connectors dead on. A Metric rod with a 
> 200 step motor will produce wacky fractions.
>
> John
>
>
>
>
> --- In Homebrew_PCBs@yahoogroups.com, Stefan Trethan 
> <stefan_trethan@g...> wrote:
>> well, john, you said you are willing to discuss pcb mill here.
>> so what i ask you to discuss maybe it the quality of rail surface.
>>
>> i saw some of your designs (and the designs of others) use some sort
>> of common pipes or steel profiles.
>>
>> especially i saw gass pipes at your page... i wonder which surface
> quality
>> they have.
>> I have lots of pipes and sqare stock here, but i have no idea how
> smooth
>> and plain the surface needs to be.
>>
>> obviously professional machines only use precision ground surfaces.
> but how
>> much is needed for accurate milling?
>>
>> it is hard to describe a surface quality, maybe you can find a way.
>> how looks it when you put a straight edge against these pipes? is
> there
>> light shining through?
>> are these welded pipes?
>>
>> the european pipes may differ from your pipes, and there are lots
> of
>> different surfaces available.
>>
>>
>> have you ever had problems with these rails? i mean precision
> problems.
>>
>> thanks
>>
>> st
>>
>> (by the way - don't you use a car for some reason? i mean you write
> a lot
>> about walking here and there and so on..?)
>
>