Question re: boring bushings for Atlas 6 inch lathe

[Woodsman 22]

Thank Ken, it was his link, and a good one!

Well then, my thanks to Ken, and yes it is a good link!

 

[RandyM]

Sizing balls would ruin most oil impregnated bushings.

Yeah Bob, we had always heard that comment, but have never seen any actual facts to back it up. I myself can not condone or disrespect the practice. Just giving Woodsman an option to his problem. I myself would have no problem doing it. I think it is one of those issues that is over evaluated. My two cents is that Woodsman can use regular bronze bushings and never know the difference. One last note, the sizing balls would not ruin the bushings, it would possibly make the oil in them less effective.

PS. The sizing balls were just common gage balls.

 

[RandyM]

Here is an excerpt right from Boston Gear's website.

Bost-Bronz® is Boston Gear's all-purpose, oil-impregnated, porous bronze bearing material. It is manufactured using the powdered metal process with the purest metal powders. This process ensures the uniform distribution of pores between the bronze particles which absorb the oil by capillary action. In addition, Bost-Bronz® has a self-contained oil supply (approximately 20% by volume) which provides a uniform protective film over the entire bearing surface. As a result, Bost-Bronz® bearings are one of the most effective bearings available for precision performance.

I think with their formula alone I would not hesitate to machine or modify their product for my applications.

Here is a link if you want more info.

Boston Gear Bronze Bearing Info

Also from their website.

Product Features

• Bost-Bronz® bearings' tight tolerances allow for reduced shaft clearances and better press fits.
• Their long-lasting lubrication offers several benefits:
  • An oil film for smooth start-ups
  • No oil hole or groove requirements
  • The option to be re-oiled, if required
• Many different in-stock styles accommodate a wide array of applications on an immediate basis:
  • Sleeve
  • Flanged
  • Thrust bearings
  • Cored bars
  • Solid Bars
  • Plate stock
• They can be machined to your precise specifications.
• The Bost-Bronz® Emergency Bearing Bank, which stocks popular sizes and offers refills, minimizes downtime and costs.

 

[4GSR]

........
PS. The sizing balls were just common gage balls.

That's interested that they were common gage balls. We sure got jipped on the one's we bought. A ball for a 2.000" ID was around $175!!! This was about three years ago. Plus, you have to order the size slightly larger than the hole size. I think the ones we bought were around 2.012/2.015" in size to create a 2.000"-2.003" hole size in cast iron. This part did not make any sense at first. It did work!

Ken

 

[RandyM]

That's interested that they were common gage balls. We sure got jipped on the one's we bought. A ball for a 2.000" ID was around $175!!! This was about three years ago. Plus, you have to order the size slightly larger than the hole size. I think the ones we bought were around 2.012/2.015" in size to create a 2.000"-2.003" hole size in cast iron. This part did not make any sense at first. It did work!

Ken

Ken, I think being cast iron is where the difference is coming into play here. I would tend to think that you would have to go a little more oversize with the cast iron than the bronze. I think our shop may have had to push the balls through 2 or 3 times to get them to size correctly. This is all so long ago my memory is foggy.

 

[Bob Korves]

https://www.oilite.com/bmp.asp (they think ball sizing is OK)

Quoted text:
Best Machining Practices
There are a few basic machining practices required to optimize retaining surface micro-porosity and the self lubricating properties of Oilite® bearing materials.

Cutting tools must be sharp. For this reason, carbide inserts are highly recommended since they hold a cutting edge much longer. This preserves the open-pore structure from which oil can flow freely. A dull tool will smear the pores, greatly reducing the self-lubricating qualities of the material.

Turning: Cutting Feed Rate: 0.002-0.006 IPM
Speed: Oilite® Bronze 375-500 SFM
Speed: Super-Oilite® 250-500 SFM

Roller Burnishing is an excellent choice to modify an ID slightly. Ball sizing can also be used on the ID effectively for final sizing.

Honing and grinding are never recommended on Oilite® bearing materials. Using these methods on any surface which will become the bearing surface will introduce grinding media and could easily smear the bronze pores sealing the micro-porosity.

After extensive machining, bearings should be re-impregnated with appropriate / specified oils. Vacuumed impregnation is recommended. If bearings were not lubricated prior to machining and if cutting fluids were used, that medium must be removed prior to any impregnation of the oil selected for the application. Your authorized distributor can provide oils for re-impregnation after machining.

 

[Bob Korves]

Oilite bearings are used in many applications where they will never be re-lubricated. At certain speeds and loads, that works fine. On a lathe, where we have to lube stuff often anyway, I think it is best to think of the oil storage capacity of oil impregnated bearings as a safety backup feature, and also include provision for easy manual oiling of them on a regular basis. Then they will last about forever with good maintenance. I think the oil should be delivered to the O.D. of the bearing, which would hold a small reserve of oil in the drilled hole and Gits oil hole cover and keep the bearing saturated. That is how I would do it on a lathe counter shaft.

 

[Woodsman 22]

Yeah Bob, we had always heard that comment, but have never seen any actual facts to back it up. I myself can not condone or disrespect the practice. Just giving Woodsman an option to his problem. I myself would have no problem doing it. I think it is one of those issues that is over evaluated. My two cents is that Woodsman can use regular bronze bushings and never know the difference. One last note, the sizing balls would not ruin the bushings, it would possibly make the oil in them less effective.

PS. The sizing balls were just common gage balls.

- The original bushings that I removed looked to me to be normal bronze bushings- they did not look at all like oilite bushings to me (had that solid bronze look, like a couple of pieces of bronze stock that I picked up), and that might go some distance to explaining why the original spindle looked so scored and worn. There were no oil holes drilled into the bushings that I removed. Maybe these bushings were replacements for the real originals at some point? Who knows.