Re: [CAD_CAM_EDM_DRO] (unknown)

catboat15@... wrote:

> In a message dated 2/17/2002 1:53:04 PM Pacific Standard Time,
> whollid1@... writes:
>
> > What I do
> > not understand is the functional difference between a gear head
> > machine, versus a belt driven machine.
>
> Gear heads are smoother in operation on lathe or mills. We don't often think
> about it but any belt (except specials) are joined at some spot and they
> create vibration when running. Some people on our lists have replaces
> regular V belts with a joint by using "Link Belts" These don't have any one
> joint, but each link acts as a joint and the users claim smoother running and
> cutting. Plus on some machines such as many of our older hobby lathes to
> change a V belt you must remove the spindle and it is a chore to get it out
> and replaced correctly, with the link belts you can just thread it through
> the openings and link it together.

I'm not sure this is true. Both the large Sheldon and the Hardinge
lathes use belt drive to the spindle because it doesn't cause
gear vibrations. They use some pretty fancy segmented Vee belts,
though. The Sheldon uses 3 matched 5L belts to provide adequate
torque. The only gears in the head are for backgear, where the speed
may prevent gear vibrations from being a problem. The Monarch
10EE uses a similar setup. The belts isolate gearbox vibrations
from the spindle.

Large V-belts and timing belts have no joint. They are molded in one
piece, like a car tire.

The large Sheldons have a neat design. the spindle runs on 2 bearings.
The input shaft runs on 2 separate bearings, with the pulley overhanging
outside the headstock. The input shaft is larger and coaxial to the spindle
(a little like the Atlas cone pulley) but the input shaft doesn't touch the
spindle at any point. It has a balanced set of drive teeth to make the
direct drive connection (equivalent to the Atlas direct-drive pin).
So, the belts can be replaced without disassembling anything.

The usual difference between belt and geared-head lathes is said to
be driving torque. This may not be such a good thing for the hobbyist
learning the art of turning, as mistakes might be more expensive or
injurious.

Jon