Next point of logic: with any multi fluted reamer, each flute is "offset" in a certain manner from a true TDC orientation in order to help prevent chatter. Each offset is slightly different from the others. I am not a tool maker or tool grinder so I'm not familiar with the actual dimensions involved here. I surmise that for the most part these offsets are minor in nature ( a few thousandths either way probably at most) so if the same "angle" setting is used for each flute differences will be minor enough that the overall setting will still result in a reamer that cuts correctly No all reamers do not have offset flutes this is used in form reamers correct terminology is eccentric , con eccentric and concentric fluting this is where flutes line to centerline and determines rake angles.
Since the amount of flute "offset" geometry can vary between makers and even between different grinds from the same maker, it follows that if the offset is "advanced" that is moved clockwise from TDC when looking from rear to front of the reamer, and the face is set vertical relative to the fixture base, and the stoning angle set according to the above, this will result in a greater relief angle at the actual cut (assuming that the actual cut occurs at TDC). Likewise if the offset is "reversed" or moved counter clockwise from TDC, the above setting method will result in a decreased relief angle. yes it will increase back relief angle but will move face to a more negative cutting relief. and if reversed it will reduce side relief and increase face angle.
Now if the relief angle on the margin is reduced enough, the edge will begin to cut extremely small chips (or "dust") and may actually cut very slowly or not at all. A small further reduction in angle and the chamber surface may actually take on a burnished appearance as little or no cutting is taking place. Somewhere within this parameter, the reamer will likely squeak or grab.yes not enough side clearance
Now for my own anecdotal evidence.... I received a reamer from "a well known maker" in a caliber that doesn't make any difference here. I cut one chamber with it and everything was fine. On the second chamber the surface looked a little rougher, and the reamer grabbed a couple of times, so I decided to stone the reamer. First thing I noticed was that with the pointer stop of the fixture set from a previous job, the flute looked to be tilted visibly to the right... in other words, the "offset" was quite a bit different. Anyway, I adjusted the stop so the flute face was vertical and stoned away. Back in the lathe, I was horrified to see that the chamber surface was burnished, the reamer was barely cutting, and it would grab like crazy. Obviously I had changed the margin geometry significantly in the wrong direction.
Back to the stoning fixture.... I adjusted the stop to where the flutes were at their original angle and re-stoned things. And the reamer cut perfectly... no binding, no burnishing, very nice surface, and seemed to go in and pull out effortlessly.
So my tentative conclusions... and please chime on this, guys... A too small back relief (margin cutting angle) can really play games with how a reamer cuts. Flute offset will play a large role in what the actual margin cutting angle (relative to the flute face) needs to be. And if a reamer cuts "dust" or squeals or binds, it might be a good idea to stone or grind(if you've got the capability) a slightly larger margin angle on the reamer flutes. Also note that these observations only pertain to the major diameter body section of the reamer. Neck, throat, and shoulder don't seem to have the same effects imho. to wide of a margin will cause back side of relief to rub, to small relief angle will cause backside to rub, rotating face will either increase or decrease side relief but move front face either to pos. or neg. relief. after all this we can address to much side clearance this will cause reamer to grab ,chatter and prematurely wear .....
