21.05.2003 06:29:20, Adam Seychell <
adam_seychell@...> wrote:
>
>
>Stefan Trethan wrote:
>> 20.05.2003 16:00:06, "Steve" <alienrelics@...> wrote:
>>
>
>>
>> thanks for the pictures. now it is much clearer how you operate it.
>>
>> @steve:
>> in my browser the apostrophe was no problem.
>> but tinyurl takes a lot time to redirect. ;-)
>>
>> @markus:
>> ok, i will regard this request.
>> i didn't think about it a lot.
>> normally i answer all emails on top.
>>
>> i find it a little strange to have to scroll down and search the whole email for the reply (which is
in
>> between and not at the bottom because of all of the sponsor advertising etc..
>>
>> but i understand with mailgroups it is then easyer to read old postings because the text is in the
right
>> order. anyways i personally find it more comfortable to write/read the latest thing on top of a mail.
>> (the lower part only being for reference if anyone is not familiar with it).
>>
>> but of course i will join the majority and from now on write on the bottom.
>>
>>
>>
>> i have tested the drill i wanted to put on the new press.
>> it is scrap.
>> the carbide bits will never withstand this.
>> it is out of center....
>>
>>
>> i will go to the tool shop tomorrow, see their minidrill products.
>> the proxxon drill presses are very nice (and ready made) but also much more expensive than the hand
>> tools and making the press your own.
>> i also have a second (dremel-like) minidrill at home which is much better centered..
>> i will maybe use this after closer inspection.
>>
>
>
>The small drill presses I've seen for a few hundred dollars have
>not been very stable compared to the thing I made. As I said, its
>a first design and there are much better ways do go about
>building a pivoting type drill press. I haven't seen a proxxon
>drill spindle but from the web page you gave they look better
>made than a Dremal. You have to check roundout.
>
>The arc radius can be made smaller than 680 mm as I have done.
>I'd say a radius of 400 mm would be ok for drilling few mm deep.
>
>A bit of math's shows the amount the drill moves out of position
>due to the arc is equal to r - sqrt(r^2 - h^2)
>Where r is arc radius and h is the depth the drill enters the
>PCB. So if r = 400 and h = 5 you get 0.031 mm or 1.2 mils.
>
>I'm sure carbide drill bits can survive 0.03mm of movement.
>
>A simpler approach for a pivot is to use two "rod end" bearings
>at the rear of the base. A 16 mm piece of threaded bar can be
>bent into a V or U shape to make up the main arm. Each end of the
>threaded bar is screwed to a female rod end bearing. Two vertical
>posts made from 16 mm bolts are mounted at the rear of the base.
>The opening of each rod end bearing go on these posts, and
>tightened up with nuts on either side. The advantage of using rod
>ends is they do not have to be aligned and you get perfect stable
>rotation along the axis between the two centers of each rod end
>sphere. You can also adjust the height of each rod end which
>allows easy alignment of the drill in that axis.
>
> |---------------------|
> | O O <-|-- 16 mm threaded posts
> | \\ // <-|-- 16 mm female rod ends
> | \ / |
> | \ / <----|-- 16 mm threaded bar
> | \ / |
> | \____/ |
> | |/ \| |
> | |\__/| <-----|-- drill spindle
> | ---- | mounted to bar
> | |
> | |
> | |<- machine base
> |---------------------|
>
>
>For drawings of rod ends see http://www.skf.com
>Rod ends are relativly cheap and should be available from any
>bearing supplier.
>
>
>Adam
>
interesting idea!
but i don't think i have rod end bearings at home.
i also think they have lot of clearance (sure when they are old, maybe new ones haven't).
you sometimes have to change them on the car's steering assembly (to pass security inspection).
they test them by simply pressing the ball in the hull and when there is too much clearance you have to
get new ones.
do you think there is no clearance in rod end bearings when they are new for horizontal movement?
i will maybe construct it this way, but my idea with the needle printer linear rails is not fully off
yet.
the problem: i have no suitable drilling machine found at the tool shop i was today.
they only have dremel and "minitool", each not good quality (dremel has aluminium collars).
they don't have the proxxon tools which i think is better.
i can buy the proxxon drill at a mail order company but so i can't get my hands on it prior to buying to
inspect it closely.
as you see i won't start building before i don't have a suitable drill.
thanks for the information..
regards
stefan