"Gunner Asch" wrote in message
...
On Sat, 17 Mar 2012 18:16:46 -0700, Larry Jaques
wrote:

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.)


Ive got some used but ok double angular contact thrust bearings and
housings. Hole is about 10 mm.

Gunner



Many thanks for the offers Gunner - I'm in Oz so shipping etc would likely
outweigh benefit. Offer is much appreciated anyway.

Just had a play in the shed:

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

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

www.youtube.com/watch?v=byYxS12dy5w