RE: [CAD_CAM_EDM_DRO] Home built machine setup, perpendicularity

Hi Scott

I use a large 24" machinist's square and an indicator.

SHARS used to sell these in accuracy class H in a fitted wooden case
for only $99. I have lab grade granite surface plates and granite square to
check
these on and found them quite accurate...within tenths. You have to
carefully control
temperature to measure such things. I bought several.

I checked their site to get a link for you but they seem to be out of stock.
J&L has them but the price is $250 and they are advertised as only workshop
grade...
much poorer perhaps.

You can play games with Pythagorus and such or generate three sets of
precise squares
if you have a very accurate surface plate but it takes a lot of time.

Hmm....no economical large squares out there...I have thoughts of making
some for sale. Perhaps 24x36" or 36x 48"? Class H? I could do that...
but surely not for $100. Not $1000 or something like a Starrett either.

Leslie M.Watts
L M Watts Furniture
Tiger Georgia
(706) 212-0242

Main page:
http://www.lmwatts.com
Engineering:
http://www.lmwatts.com/shop.html
Cnc surplus for sale:
http://www.lmwatts.com/forsale.html
Carved signs:
http://www.lmwatts.com/signwp.html


-----Original Message-----
From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com]On Behalf Of Scott Riddle
Sent: Thursday, July 07, 2005 9:59 AM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] Home built machine setup, perpendicularity


I am looking to put together my own home built CNC machine with
linear rails and ball screws onto a heavy tube frame. I am trying to
figure out how to drive the main X axis which will move a gantry
over the table. I am contemplating using 2 ball screws(smaller ones)
to drive each set of trucks. This way I can assure no racking
problems and have increased machine stiffness. My main questions is
if I go to the 2 screw system and I am using stepper motors how do I
initially when build this machine get my X and Y axis perpendicular?
Assuming that each X and Y rail setup is straight to start with.

Basically can I measure perpendicularity on a 3' x 3' linear rail
setup with something like indicators. I do not have access to any
large right angle plates or things like that. I would think that
there would be some clever way to measure this.

I used to design machine tools for several years so I know all the
basics but when we did this setup part it was all done with a laser.

Thanks
Scott





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