Re: [CAD_CAM_EDM_DRO] Re: Modifying an X-Y table

>
>
> I modified a very similar X-Y vice. On mine one nut was cast in, I
>

This could very well be the same vise, actually. I understand that only
2 or 3 manufacturers make all the castings, for almost all the tool
manufacturers -- that's why Grizzly tools are virtually identical
(except for level of finish) to Harbor Freight, which is virtually
identical to Jet, which is virtually identical to Homier, and so on and
so forth...

>drilled, counter bored and taped for a clamping screw then slit that side
>of the nut. The lead screw thread was off centre in the cast lug... almost
>like it was designed for the modification.
>

Like I said, it may very well have been. A different manufacturer might
want that capability, and it was just put into the generic casting used
by everyone.

So, you took out the screw, "sliced" the lug down the side, and
"clamped" it around the lead screw, to adjust for backlash. Makes sense
-- I did something similar on my larger wooden table...but I did it with
nylon, not with cast iron. My fear in doing something like this with
cast iron, would be cracking the casting.

>The other screw had a removable
>nut on which I used Sven Peter's Hamburger-Hotdog design (posted sometime
>in may 2001).
>

I found a description of it.
http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/message/24936?source=1

Basically it consists of dividing a nut in half, and clamping the halves
on "top and bottom" of the screw. Again, it's "squeezing" the nut
around the leadscrew, and compensating for backlash in that manner. Am
I reading it correctly?

>While it
>was apart I did a bit of filing/scraping and lapping which was well worth
>the effort.
>

Any hints? I don't have a background in machining, so this is "black
magic" to me. Seems simple enough, but then I go to do it, and that's
where the details come in. Since this is related to the conversion of a
table to CNC, I wonder if *this* part of the discussion should be done
on list, or off?

>With less than optimal 100 in/oz motors I get rapids of
>600mm/min. (12v steppers and a 30 volt driver based on allegro 3977 chip -
>same as Xylotex)
>

I have a few Allegro chips around -- I may try building something from
them. Regardless, I have some boards coming back to me, relatively
soon...they can be used to test it out. I'll just use the same
connectors on both machine, and "swap" the driver module.

The only "extra" steppers I have lying around are 60oz-in and 75 oz-in.
Hardly ideal, but hey, they're free! ;-)

-- Chuck Knight