Running needle rollers between cast iron plates

Bearing races and internals are generally hardened.

Any ideas on how long a needle bearing running cast iron races would last?

What failure mode should I expect?

Dave

Rather than the classic ‘Brinelling’ … I would expect the failure mode to be the creation of Cast Iron ‘dust’ which would then abrade the rollers.

This might actually take a long time … presumably depending upon loads, quality of material, surface finish, lubrication etc etc

[ all the ‘unknowns’ ]

MichaelG.

I have read that some (all?) surface and cylindrical grinding machines have steel tape to take the surface load. I can't think of an engineering application that has hardened steel rollers in contact with hardened rollers, but I would suggest a larger diameter might reduce the effects that Michael has highlighted.

Bill

Depends on the loading on the rollers, surface finish, lubrication, speed, etc. Steel is the usual contact face, a smooth surface allows the roller to stay separated from it by an oil film.

Interesting question, not an expert but I was surprised what Google search had to say...
This is a bit off the topic ....
1-high-nickel cast iron...Not all cast iron created equal......
2-Low load continious running with not much stop starts....

Youtube:
"Machining a Cast Iron Bearing"....I see ABOM79 machined a cast iron bearing, look at this.

Maybe someone has 1st hand experience of aplications-?

Edited By Chris Mate on 17/01/2022 20:25:26

Edited By Chris Mate on 17/01/2022 20:26:49

If you buy needle roller races from Arc, they come with a pair of hard steel washers so they don't have a hard surface to roll on.

I have a Boxford T & C grinder that doubles as a surface grinder, the top table which is of course cast iron runs on linear needle roller bearings nested in plastic cages so its clear this type of bearing is well suited to use with cast iron --- deepening of course on the grade of the material.

See the link below for a photo -- I hope !

John

https://www.ntnglobal.com/en/products/rollingbearing/linear_motion.html

edit -- keep in mind the load on these bearings is low, they serve only to allow easy back and forth movement of the table.

Edited By JohnF on 17/01/2022 21:09:11

This is the sort of thing I was thinking about. I wonder how you figure out the allowable loading.

I'm considering way methods for a small CNC mill, rather than bolting on linear rails given my base is a surface plate could a bunch of rollers give satisfactory Y axis for the saddle? It can be 'gibbed' under the overhang with rollers, much like my CVA is.

Dave

Dave,

In MEW 293 and 294 [May and June 2020 respectively] Alan Jackson describes his conversion of the remains of the lower end of his Dore Westbury milling machine into a surface grinder.

He faced rather similar problems and solved them by rolling the table on its under surface slides on a series of fixed position ball bearings. It seemed to be a good solution.

Another possibility occurs to me and that is to flank the needle rollers with tracks of cut down hard point saw blades that have done their time. I made a very successful 3.5 inch diameter thrust bearing from 1/4 inch diameter caged balls rolling between two flat washers of this material which showed polishing only of the contact surfaces after 10 years of service under high load conditions.

Regards Brian

Edited By Brian Wood on 18/01/2022 10:51:59