Re: Rolled vs. Ground ballscrews or other screws!

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "turbulatordude"
<dave_mucha@y...> wrote:

> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Lance Hopper"
> <snaggletto@c...> wrote:
> > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "turbulatordude"
> > <dave_mucha@y...> wrote:
> > > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Lance Hopper"
> > > <snaggletto@c...> wrote:
> > > > I've run a Bridgeport with ballscrews for a couple years. It

was

> > a
> > > > beautiful experience in all situations. Climb milling is
> > possible
> > > > with smaller cutters and lighter cuts, but any backlash or

slop

> > will
> > > > be violently taken up if the cutter digs in. Save climb

milling

> > with
> > > > 2" face mills and heavier cuts for the machining centers. I
> > don't
> > > > doubt that anything is impossible, but to throw the table off

of

> > the
> > > > machine means that the operator is a dumba** and has no sense
> > > > or 'feel' for how to machine.
> > > >
> > >
> > > I figure it this way, he has been a repairman for over 20 years

in

> > the
> > > phila area for Bridgeport, so has seen more machines and been

in

> > more
> > > shops than most tool salesmen.
> > >
> > > 2 over that time is not too bad as I have personally met more

than 2

> > > dumba**'s in shops running machines myself.
> > >
> > > But as we know a ball screw nut will run it self the length of

the

> > > screw if the screw is standing vertical. an ACME won't do

that.

> > the
> > > ball screw also does not have the same TPI so it offers MUCH

less

> > > resistance when smacked.
> > >
> > > Dave
> >
> > Dave,
> > I don't disagree, and my post wasn't aimed at you personally,

or

> > saying that the repairman was a liar. Ballscrews do have much

less

> > resistance, and thus very efficient with little backlash, that's

why

> > they are used. As you said yourself, in a period of 20+ years,

the

> > repairman has seen it happen twice. This is the exception rather
> > than the norm. I would bet that if we had the details of 'how'

it

> > happened on those 2 occasions, we would see that the machine

operator

> > was doing something inappropriate for the job/machine. My point,
> > ballscrews on a manual machine is not a bad thing.
>
> I would fully accept that ONLY twice in 20 years is a very rare
> occurance. probably a novice who ran the rapid the wrong way at the
> wrong time with the cutter perfectly aligned for the disaster.
>
> But, I sorta assume that there are people on here who are also
> novices. : )
>
> Knowing the potential exists gives fair warning. I would not
> re-design a machine or do anything differently. but hopefully that
> warning will have the guys drop the table to get the tool bit to the
> other side.
>
> Dave

Fair enough, I'll buy that. Machining is one of those things that
you never get to be an expert at. After 30 years or so you can call
yourself 'good.' I've got a LONG time to go before I'm even
half 'good.'

I just didn't like the statement "NEVER use ballscrews on a manual
machine." That can really turn off novices to the idea. As I
mentioned before, ballscrews on a manual machine really adds alot to
accuracy due to the minimal backlash. You are correct though, you do
lose alot of that 'self locking' resistance, so be ready to use your
gib locks when preparing for a cut.