Power Transmission? was: Does this make sense?

----- Original Message -----
From: "Jon Elson" <elson@...>

> That is not a power transmission grade screw. The Saginaw, Nook and other
> low-cost screws (new cost runs around $12/foot for 1/2 or 3/4" screws, and
> $40 or so for single nuts) is often black with a very grainy (nitrided?)
> surface, and the company's catalog lists them as "power transmission
> grade". Thay are used for elevating pieces of machinery, anything like
> the hand-cranked wheels that support the front end of semi-trailers
> when not attached to a tractor, to moving boxes around in packing
> machines.
>
> That black, grainy coating is a giveaway that these screws can't
accurately
> position a machine tool.

Ok, yes. I've seen the short versions of these on Ebay going for about $30
each. (2 or 3 foot)
I think they are Kiln hardened Chinese Utility Screws. I'm not sure of how
accurate they are but I am sure of one thing.
You might get one year of use from them, if that...


> You can (barely) see such a screw on my photoplotter
> http://jelinux.pico-systems.com/photoplot.html
> attached to the stepper motor at the right. (The silver thing below it
> is a Thompson guide rod.) This was a proof of concept setup, I
> have later replaced that arrangement with a BSA plastic-nut and
> screw that has a backlash compensator. it works MUCH better,
> but wouldn't be suitable for a machine tool.
>
> Here's the EXACT same thing on eBay right now, black screw and
> I recognize the nut as a Saginaw, exactly the same as was in my
> photoplotter:
> <
>
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2549546354&category=25276
>
<http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2549546354&category=2527
6>
> >

Heck, I'd be happy with a few of these to make a PCB router but I think that
would be as far as it went.

On an off-topic note: There is a pretty neat program out there if you havent
already come acrossed it yet, called "NMAP". Would be great to double check
your site for any holes.
Check it out. http://www.insecure.org/ . I'm still working on mine.

Thanks again for the info.

Vince