Re: Denford Orac and Tailstock Tools

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "John Heritage" <johnhe-
uk@s...> wrote:

> Hello everyone!

<SNIP>

> One thing, I noticed just recently while I was turning down the
> outside of a Soda Stream bottle; yes it was empty, it had an entire
> end cut off. It's valve end was used to hold it secure in the live
> centre and it was clamped real tight on the chuck. About half way
> down it's length there was a strange sort of wave like (Sine wave
> shaped I guess) pattern in the grooves the tool had left. This
> pattern was going from chuck to tailstock in the middle for about

2"

> (Only noticable under bright light). Other than that it cut
> perfectly. Any clues as to what it might be?
>
> Sorry it's long guys and thanks for any help,
> John H.

John,

What you are seeing is a vibration pattern - think of the work as
being a violin string - the lathe tool will set up vibrations as it
cuts. These are minimal except when the work is in resonance with the
vibrations that are exciting it, so will magnified at the node points
of the work. If it is supported between chuck and live centre, you
can set up a half wavelength pattern at the mid point, or multiples
of half wavelengths.

On the ORAC you have an infinately adjustable spindle speed (using
the up & down buttons) so you should be able to slightly alter your
speed to get out of the resonance condition - it shouldn't need much
of a change, and you may well find you can shift the position on the
work where it occurs. Another trick is to 'deaden' thin tubes by
putting modelling clay inside to alter their natural resonance
frequency (lower it) and also damp out the vibrations.

'Live chucks' to fit in the tailstock are available, but are very
expensive, however recently there has been a chap on the UK ebay site
selling 2MT (which you need) and 3MT ones at around £90

Having an ORAC myself, which I have stripped and put in a PC based
controller, I am interested to know what was supplied with yours. I
know that some that went to the states had a rotating tool turret
(which I have obtained) and an automatic bar feeder (which I would
love to get)

Regards,

Andrew Mawson,
Bromley, Kent, UK