Re: Advice on small mill table conversion

I've converted a KT-150 table using the original nuts.
Just like you described, I made a fine cut and used 2 M3 bolts to
adjust the backlash.

You also might want to reinforce the casting of y-axis (the upper
axis). Since it's fixed with two M5 bolts above center of the
spindle, the power of the motor will move it up and down.
There is room for two brackets wich connect to the casting and the
top of the table.
The x-axis doesn't have this problem.

I used 2 axial and 2 radial bearings per ax, all mounted on the motor
side.
Futher I used timing belt and pulleys for the connection between the
steppers and the spindles.

I lost about a inch of travel by doing so but it was already limited
by using the proxxon stand.

There are some pictures in my gallery at cnczone (username jerber).

Jeroen

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Graham Stabler" <eexgs@...>
wrote:

>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "turbulatordude"
> <dave_mucha@> wrote:
> >
> > You need to put thrust washers on the handles to make sure the

screw

> > does not move axially. that is the easy part with your design.
> >
> > The nuts can be made pretty easily, I think. you did not show the
> > drawing, but it might be possible to add a second nut, and bolt

it to

> > the first with some tiny screws on the perimiter.
> >
> > The more you tighten these, the less backlash and the more

friction.

>
> It has thrust washers (i.e. plain washers) but I was thinking thrust
> bearings to prevent the axial movement. I am a little limited in

terms

> of space, anything of greater diameter than that collar will catch

on

> the bed, however I think I would probably be OK, there would still
> need to be something to prevent radial movement though, there is
> nothing at the moment, a needle roller would be compact enough or a
> flanged radial mounted in the end of the extrusion.
>
> One thing I am a little bothered about is the fact that since the
> castings already stick out about 3" from the bed once I add space

for

> a coupling or a motor Everything sticks out a long way, this is a
> niggle really but I prefer to make it more compact if I can.

Perhaps

> I could use a belt drive putting the motor above the casting. I

also

> wondered about fixing the leadscrew rigidly to the stepper motor

using

> the motor as the thrust bearing, these motors seem to have massive
> bearings but I worry about long term reliability. It would allow a
> compact direct drive installation though and the motors are so

cheap.

>
> In terms of the nuts, I'm trying to find a ACME tap of the right

size.

> I know people have made these but I don't have any acme rod either,
> I'll keep searching. Perhaps if I use the self forming method
> described in another post I can make the starting threads using

just a

> normal metric tap before "cold forming" the rest of the threads. A
> long delrin nut had been my first thought, I don't think there is
> quite enough meat in the current nut to make it antibacklash but I
> will look into it, I might be able to make a fine cut and add screws
> to allow it to sprring.
>
> thanks all
>
> Graham
>