Need Advice on Rebuilding the Niles Spindle

Not my field at all, but I would try to stick to the original arrangement.
The problem with changing it, is the problems will only apparent after you have run it for a while and by then it may be too late to reinstate the original. Whereas if you stick to the original you can see how it performs and maybe modify later when you have a better feel for the beastie.
Changing to the Timken roller should satisfy you urges to improve it.
Del
(pics pics, we want pics)

_{Terms and conditions apply, this advice may be completely worthless}

Niles had the option to use a tapered roller bearing but there is a reason not to and Niles chose to avoid those pressure issues, you should follow their lead too.

Use submerged arc welding or thermal metal spray to build up the bearing surface then re-machine to spec's, this will enable a 50 - 60 year turn around before R&R again.

Bill,

I hang out here also,

I did not suggest sumerged arc welding any kind or weld build up because of your spindle being made of cast iron. It could be very difficult to do. Now the molglass metioned may hold up. I wouldn't use it. Why not remake the sleeve looking piece you show on your VBM in the pics on the PM site? Doesn't the spindle ride on that? Wouldnt that be easier than trying to make a thin sleeve?

Ken

Thermal spray has been used very successfully possibly due the plethora of coatings available to build up bearing surfaces. May it be we are not each on the same page

Common materials Sprayed:

• Zinc and aluminium for anti-corrosion cathodic coatings on steel
• Nickel/aluminium composite wire for bond coats and self-bonding coatings
• Molybdenum for bond coats
• Molybdenum for hard bearing applications, excellent resistance to adhesive wear, used on piston rings, syncromesh cones and journals.
• High Chromium steel for many applications requiring hard and wear resistant coating
• Bronzes, babbitt for bearing applications
• Stainless steels, nickel and monel for anti-corrosion and wear
• Aluminium, nickel/aluminium for heat and oxidation resistance

The Combustion Wire Thermal Spray Process formerly known as Metallizing, Flame Spray and Metal Spray Processes was first invented in 1910 by Schoop in Switzerland

Cast iron no worries mate

Hi,

"Heavy felt strips are fitted into the slots to prevent the lubricating oil from being slung out"

More likely to act as an oil reservoir and let the sliding contact draw some oil onto the shaft and into the bearing gap.

"Warren is very concerned with turning the collapsible bearing"

Use a bolted internal or external ring to stiffen it and - if necessary - use a small grinding spindle in exchange of the cutting tool.

"stick with a cast iron sleeve or should we try to improve the design by adding a bronze sleeve"

Cast iron sleeve is very good if the shaft is steel and hardened, else I would turn to bronze or the above suggested flame-sprayed surfacing. (This will need grinding). Any bronze sleeve will expand relative to the steel/iron shaft if temperature goes up. This may be good as the radial temperature profile tends to shrink the clearance.

Any ground surface should be slightly polished to remove the uppermost parts of the mountain tops. The valleys will store the oil, the flat tops will facilitate gliding.

"Roller Thrust bearing"

Needs a lot more dynamic load capability than your estimate.

You will drop the heavy pieces with some small velocity onto the table. This kinetic energy plus the energy from static load and elastic deflection of the bearing will be converted into elastic energy in the bearing's compliance. If no mass in the table and zero velocity at touchdown there will be 3times the static load for some time after touchdown. So I would choose without calculation (or better calculate?) the dynamic load capability to be 12 times the maximum weight of a workpiece plus table.

Diamant Moglice: as suggested in another post is well established in repairing slowly running machines like yours. They have a subsidiary in the US and will be glad to help you.

May be a good idea to install a continuously filtered oil supply.

If you want to have a super-machine then convert all bearings to hydrostatic action.

This is not too complicated as you have big diameters and thus high load capacity at moderate pressure. Any bearing (cylindrical or flat) shall then have minimum 6 or 7 or more restrictors (orifices) where the oil enters and radial grooves in-between to let the oil out. Clearance should be near 100ppm or 0.01% of diameter. Pressure drop shall be 45% of supply pressure at "no workpiece load"-condition.

If you don't like the orifices as these need a lot of manual work to insert there is another possibility of hydrostatic bearing the "fluted bearing" invented by Harold Arneson in the 1970ies. The company "Professional Instruments" he founded (earlier) is still thriving, see www.airbearings.com.

These may need a smaller gap (if oil-flow is too high) and will provide higher stiffness at the same load capacity.

The oil-film in both designs will provide nearly indefinite load capacity at impact loading so these machines with hydrostatic bearings will withstand more severe crash situations than machines equipped with sliding bearings.

Surfaces that are turned on hydrostatic machines can have near optical quality, so you will see in your machine the action of the gears that transmit some force-variations.

Best success wished

RHABE