Re: Bridgeport ballscrew retrofit kits and prices

Hi Roy, thanks for reply.

I worked at a place were we used taper lock pullys for cut to lenght
applications. I have to say i personally didnt like them for the
following reasons.

1. The O.D. on the taper is usally off center a little. How much is
luck of the draw...

2. The random locking factor...taper locks tighten up to a different
point every time...If you take the pulley off and reinstall it you
have to tighten it up further up the hub every time. This causes
your belt to be out of line...In the type of arrangement you are
talking about, the hub can't be moved since it is part of the bearing
holding assembly...Now you have to adjust the other pulley on its
shaft except you can't if it is pinned like i would like to do...

I can see were you are a special case with your custom hub, and you
were able to make it work for yourself with your setup...But for all
the aggravation taper locks have caused me over the years, i would
like to throw them all in the lake.....


Wally



--- In CAD_CAM_EDM_DRO@yahoogroups.com, R Rogers <rogersmach@y...>
wrote:

> Mine uses a special hub that is keyed and set-screwed on the end of

the ballscrew. On this hub is a taper that the timing pulley with a
standard tapered bore is drawn on to with bolts through a flange on
the same hub. Then there is a shoulder where the handwheel/dial
resides and beyond that, threads for the standard Bridgeport serrated
ring nut to lock the handwheel. The shaft then has room for a
handcrank which I didnt use and were substituted with a sleeve spacer
then the nut on the very end secures everything tightly. Keys don't
chuck. If they do they need to be replaced. Or the keyway in the
shaft or the sheave is damaged or was never machined properly to
begin with. In this arrangement the hub cannot be secured until the
preload on the bearings has been achieved because it needs to be able
to slide so the nut on the end of the screw can pre-load the whole
assembly. Then the setscrew is secured. The Z axis knee uses the same
hub however it is threaded inside to screw on the shaft

> and is then roll-pinned to secure. I'll answer this before it's

asked: I don't have any drawings or dims of that hub. I'm going to
disassemble one and get the dims eventually, just haven't had time.

>
> Ron
>
> cnc_4_me <cnc4me@g...> wrote:
>
>
> > You don't need any extra threads. You just make spacers so that
> the end
> > nut holds everything.
> > >
> > - Steve
>
>
> Well, that is the problem... The end nut has to hold

everything...It

> has to tighten up the bearing pair thru the pulley...This means

that

> the pulley now cannot be pinned and probally not even
> taperlocked...This leaves only setscrewing the pulley to the shaft
> after the nut is tightened...For the kind of torque we are talking
> about i am not sure setscrewing will hold up...
>
>
> Also using the standard end does not address how to put a encoder

on

> the end of the ballscrew or if you want to put a handle on after

the

> pulley like you would like to do...This is why a custom end is so
> desirable.
>
> Wally
>
>
>
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, Stephen Wille Padnos
> wrote:
> > cnc_4_me wrote:
> >
> > >>So what do you think is the best bet?
> > >>
> > >>Scott
> > >>
> > >>
> > >Same question i have been asking myself...
> > >
> > >For myself there are 2 clear choices, Rockford ballscrew with
> rolled
> > >ballscrew with .002 or .003" error and made with custom
> ends...This
> > >would give you a very nice installation...I could have one end
> > >machined for a handwheel for manual operation and the other end
> > >machined for bearing support, motor drive pully and encoder...
> > >
> > >
> > I wouldn't bother with rolled ballscrews, especially since the
> ground
> > ones are so close in price. The ones I mentioned from Machine
> Tools
> > Direct are ground, and cost $600. The maximum lead error on my
> screws
> > was 0.000466 for the long one, and 0.000233 for the short one.
> (yes,
> > that's just under 1/2 of a thousandth, and 1/4 of a thoudsandth)
> >
> > You don't need custom ends to use a handwheel on one side. The
> standard
> > ends have a long shoulder on which a handle OR a pulley can be
> mounted.
> > I'm trying to figure out how to get both on one end (I would like
> both X
> > handles, and a Y handle), but that probably won't happen. There

is

> a
> > bearing journal on both sides, and it's needed on both sides. You
> > should have dual angular contact bearings on one side (the motor
> side),
> > and one double-row angular contact bearing on the other side. The
> > single bearing on the "far" end doesn't fill the space inside the
> > bearing bracket, to allow for thermal expansion without bending

the

> > screw. The thread on the end of the ballscrew is used on both
> ends.
> > I'm still designing, but I think this will be the stack-up on my
> machine:
> > nut | washer | spacer | pulley | spacer | bearing pair |

ballscrew

> shoulder
> > On the other side, just replace the pulley with a handwheel, and
> the
> > bearing pair with a single wide bearing, and you're all set.
> > These screws are just a little long for my 9x42 table - though

they

> > might not be if I had official Bridgeport bearing brackets. (My
> machine
> > had a power feed on X, which isn't compatible with the ballscrew,
> so I
> > bought a clone mill bearing bracket off ebay)
> >
> > The only thing I had to do was to bore out the pulleys to 0.625.

I

> had
> > a hard time finding small pulleys that already had a wide bore. I
> did
> > find one company that can customize the pulleys, but they wanted
> $75
> > minimum for the job - it didn't seem worth it for 4 pulleys.
> >
> > >Second choise would be ground ballscrew from hiwin...For a

couple

> of
> > >hundred dollars more than rolled screw you get a .0005" error
> > >screw... And the bragging rights that go with it...But you have

to

> > >live with the standard ends...
> > >
> > >
> > See above - standard ends are fine. The ground screw is still way
> less
> > accurate than the control resolution - my machine will have 40000
> steps
> > per inch - the screw will be 20 counts of error. (though this is
> > correctable with EMC and others)
> >
> > >What i would like to know is how everyone else has made do with
> the
> > >standard ballscrew ends...How did you work out the opposed

bearing

> > >mounts...You need a thread on the shaft between the pully and
> > >bearings to tighten up the bearing assembly, but standard screws
> do
> > >not have this thread...They only have the end of shaft threaded

to

> > >hold handle on...
> > >
> > >
> > You don't need any extra threads. You just make spacers so that
> the end
> > nut holds everything.
> >
> > >Wally
> > >
> > >
> > - Steve
>
>
>
>
>
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