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

Regarding 2 or 3 manufacturers make all castings. Do you mean they make the molds? or actually
cast the metal. Also, do you know if they use the same alloy.

I have experienced what we lovingly call chinese joke steel with Harbor Freight products (screw
drivers that twist 70 degrees without loosening the screw, wrenches that bend before loosening
bolts and sockets that strip).

A friend who is a metallugist said that if they are in a hurry or have a really tight contract
they will for go tempering the steel or use unknown allows.


--- Chuck Knight <chuckknight@...> wrote:

> >
> >
> > 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
>
>
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