Re: bearings or bushes - lathe backgear design
Two problems to beaware of when using solid bearings. One the spindle shaft will need to be micro-polished to get any time out of it. Two the top speed is reduced. A 9" SB with solid bearings should not be run over 1000 rpm. And it has to have a constant oil supply, you keep adding it as it leaks out the ends of the spindle and wipe it off the walls and floor and ceiling.
There is no magic bullet.. trade speed... needed for carbide insert cutters or better finish at slower speeds.
I have a 7x10 and a 9" SB so I am covered.
--- In email@example.com, "James Early" <j.w.early@...> wrote:
> David I am becoming very disenchanted with ball bearing spindles on small
> lathes. I am in the process of cutting back to just my South Bend and one
> 7x10 for light work. I will be posting all the other lathes and at least one
> mill for sale in the next few months because of this difference in quality
> between a sleeve bearing lathe and a ball bearing one. With sleeve bearings
> on the spindle the surface finish of the parts is so much superior it is
> unreal and dimensionally the sleeve bearing lathe is also far superior to
> any ball bearing spindle lathe I have ever used. The one 7x machine that I
> will be keeping I will be experimenting with fitting it for sleeve bearings
> also in place of the ball bearing ones in there now.
> Long Beach, CA
> ----- Original Message -----
> From: "David Halfpenny gmail" <davidhalfpenny@...>
> To: <firstname.lastname@example.org>
> Sent: Thursday, June 24, 2010 1:09 PM
> Subject: Re: [mlathemods] bearings or bushes - lathe backgear design
> > --------------------------------------------------
> > From: "James Early" <j.w.early@...>
> > Sent: Thursday, June 24, 2010 2:11 PM
> > To: <email@example.com>
> > Subject: Re: [mlathemods] bearings or bushes - lathe backgear design
> >> Back gears should always use bronze sleeve bearings as ball or needle
> >> bearings do not have the strength to take the side loads present there!
> >> JWE
> >> Long Beach, CA
> > That's a fair point James, reinforced by the fact that the intermittent
> > load from the gears could damage the races if it exceeded their yield
> > point* but surely exactly the same side loads act on the lathe spindle?
> > (* It's often called Brinelling after the guy who invented a test in which
> > you force a ball bearing into the metal and measure the width of the dent
> > caused to check yield strength.)
> > The traditional back-geared lathes of my youth all had plain bearings on
> > the spindle too.
> > David 1/2d