"Larry Jaques" wrote in message
...
On Sat, 17 Mar 2012 12:43:40 -0500, Ignoramus13020
wrote:

On 2012-03-17, Dennis wrote:
I've just test run a little CNC router / mill I've put together.

At the moment I'm using M10 x 1.5mm pitch allthread for the lead screws
and
PVC blocks for the nuts.


I've calibrated the axes (Mach3) using the 1.5mm leadscrew pitch and the
known motor steps/rev.


With a dial gauge on an axis, when I do a 1mm move sometimes I see
0.90mm or
0.95, sometimes 1.0. It seems repeatable, ie if I reverse the steps I
see
the same values.

What do people think? I guess this is typical for cheap bit of allthread
from the local hardware store?


ACME leadscrews are on the drawing board when finances are willing....



I would look for problems elsewhere.

Ditto. Sounds like there might be some play in the leadscrew mounts.

Dennis, I have a spare (unmachined ends) RM1204 (12mm) x 300mm
leadscrew for sale fairly cheap, if you're interested. I also have 4
extra SBR12UU linear bearing blocks. (from a misunderstanding with a
Chinese supplier.)


Thanks for the offer Larry, unfortunately I'm in Oz so the shipping etc
would likely be a killer.

There's an eBayer in Eastern Australia who has Chinese ballscrews cheap, but
I'm even cheaper so I'm looking at some ACME leadscrews.

I'm using the SBR16UU bearing blocks, the quality is not the best, but
probably good enough for my needs.


I jst had a play in the shed, still a long way to go but it's working.....

http://www.youtube.com/watch?v=FwrWbG7wZnA

http://www.youtube.com/watch?v=4eumURX6S9w

www.youtube.com/watch?v=byYxS12dy5w