Re: Conversion of 12 x 24 lathe

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "sbsmwj" <mwjones99@m...>
wrote:

>
> Hello,
>
> A friend of mine, having seen my conversion of a Sherline lathe and
> the parts it makes, has decided that he really needs to convert his
> much bigger lathe. It's a Chinese made, gear head lathe (less than

a

> year old), which can swing parts 12 inches in diameter. He wants to
> turn model locomotive wheels on it which are cast iron and 10

inches

> or 7 inches diameter. The lathe can be seen here

http://www.warco.co

> uk/lathes/gh1224.htm
>
> Backlash has already been considered and various modifications have
> been either made or planned to correct problems.
>
> How do we determine the right size stepper motor for this two-axis
> conversion?
>
> Presumably, the best choice would be to run the steppers through a
> belt-reduction drive to increase the torque available?
>
> I can't convince him that once he's converted his machine to CNC he
> might not want to run it manually, but if he insists, are there any
> strategies that might permit this?
>
> Thanks for your advice,
>
> Mike Jones
> Cardiff, Wales

Hi Mike,

Mariss posted a great list of points on post 77354

What he did was to use a Bridgeport as the basis of design.

I have cut 1/4" deep (1/2 OD) cuts on steel in my other life. No
way I could maintain the cutting forces, but I have no idea what they
were either. AND, since it was not MY machine and my boss wanted the
parts FAST, we did what we could.

Next, considder the screw pitches. I would think the Y axis (cross
slide) would be just like the table on a bridgeport.

On the Z axis (carriage) you can either drive it with the leadscrew,
or with the keyed shaft. I assume the lathe can thread with the
leadscrew, but uses the keyed shaft for turning.

My thoughts are that you use the leadsccrew and replace the half nuts
with beefier ones that are Moglice matched to the screw.

I would think gears in the carriage will have way too much slop to be
used for CNC to get any precision.

Also, halfnuts will allow the manual use of the machine latter, and
yes, he will want manual. There are a lot of lathe project that are
best done manual.

As for motors ? I would assume you would really want a DRO and
servos with encoders can be used on the cross slide, but I think a
carriage needs a seperate wire encoder or linear scale.

Many choices on the display, there are a few good choices at decent
prices. I know of two low cost ones, but I'd have to dig to get the
URL's and I'm too lazy. There is also the Sumatech (sp?) from a guy
who used to be on this list till his DRO started selling like
hotcakes.

Hope that helps

Dave