Only two opposing stones in one hone - unacceptable for me at this size, mistrust in roundness from bad examples. As for surface finish, a quality piloted reamer with good blades , uneven spaced, does the job perfectly well and a lot quicker. For real roller bearing quality I´d take the lapping tools , unbeatable.
I thought others might be interested in knowing more about a Sunnen hone in case there is general misunderstanding on the above points. Sunnen makes several types of hones for various purposes, but for honing individual holes or line honing of separated ones on everything I can think of on a motorcycle, their model MBB is the one to use.
This hone uses a range of interchangeable mandrels for holes of every size on every motorcycle ever made, from the 0.106" of a main jet on up. As the photo I posted yesterday shows, the stones are on one side of the mandrel,
not opposing each other, with shoes that ride against the bore on the other side. The angular extent of the shoes and stones is large so contact is far from being two points.
As already noted, the angular extent of the shoes and stones is large in their mandrels, ensuring roundness. There's also the circumstantial evidence that Sunnen hones have been in wide use in precision industries for over 80 years, which wouldn't seem likely if the holes they produced weren't round. But, I have direct evidence of roundness from my 2-point and 3-point bore gauges, together capable of determining any out-of-roundness greater than 0.0001".
I can state from my own measurements, a Sunnen produces holes round to no worse than 0.0001".
As the next table from a Sunnen catalog shows, the right stones can achieve a surface roughness of as little as 1 µinch rms on hard steel, if desired, although for proper lubrication bearing manufacturers recommend 6–10 μinches for races. As this shows, lapping a bearing race to a finer finish than easily achievable with a Sunnen is neither necessary nor wise.
As for whether or not reaming is faster, that depends on the amount material to be removed. If a hole is drilled, say, 1/64" undersize and then reamed then, yes, a reamer will remove that 0.016" somewhat faster than a hone will. Still, the difference in time isn't significant in the non-production environment of someone's garage.
As an example, with a purpose-made jig to clamp the inner race to the outer, it didn't take very long with the the Sunnen to resize a 25 mm metric roller bearing by the necessary 0.0158" for a snug clearance fit on the 1" drive-side of my 1928 Ariel's crankshaft.
However, although marginally faster to produce a hole, and whether or not a reamer is sized to 0.0002", good luck achieving a reamed hole whose diameter has that level of precision, whereas it's easily possible with a Sunnen. Further, a reamer will leave a roughness of 30–60 μinches in steel (up to 80 μinches in cast iron), whereas the above table shows a hone will do a lot better than that. It's relevant to note that Kibblewhite recommends reaming cast iron guides to get them close to the correct ID, but followed by honing to achieve the recommended 32 μinches roughness. Similarly, they recommend honing bronze guides as well.
Reamers certainly are very useful, which is why I have a lot of them. Often the holes they produce are good enough for the task at hand. When I make valve guides I get them close to the final ID using reamers. But, when I need to achieve a precision ID, excellent roundness, and a proper surface finish, a Sunnen, not a reamer, is the right tool for the job.
