Stoning a reamer?

I just run the small face of the stone (the 3/4x3/4" square face, rather than the 6x3/4" of a "standard" toolmaker's orange stone) along each flute, such that the face of the stone is perpendicular to cutting lip. You're basically dulling the edge (or changing its rake).

I find new reamers cut too large for a good dowel pin fit, so this is virtually always required. Frequently, intentionally dulling cutting edges (just slightly) in a controlled manner prolongs their life so you get a double bonus.

Remember that chucking reamers only cut in the first couple of millimeters from the end. Everything else is just there for alignment, rigidity, chip flow, etc.

Don't expect to reliably reduce your cutting diameter too much. Perhaps .0003" or so at that diameter. Certainly enough to adjust the fit of a pin through the hole.

Regards,

Robin

What's that Lassie? You say that snipped-for-privacy@newsguy.com fell down the old alt.machines.cnc mine and will die if we don't mount a rescue by Fri, 5 Sep 2008 20:12:52 -0700 (PDT):

take some super fine sandpaper and draw it along the flutes. Or you can turn the reamer backwards and use the sandpaper.

You received some good advise and one that makes the hair on the back of my neck stand up if I understood it correctly.

If the reamer is new check the diameter to make sure you received the right tool, doesn't happen often but you might have received an misidentified or oversized tool.

Simple answer to your direct question as stated by earlier poster very lightly stone the side of the reamer flutes to remove any burs or dings (keeping a positive rake) then the lead chamfers. As a last resort you may wish to stone the OD edge but only as a last resort since it will likely take a new tool and make it an old one.

If you must stone an edge to change the cutting characteristics put the reamer on a v-block & comparator. Put a radius on the leading edge where the champher meets the OD of the flutes. Make sure all flutes the same radius and keep a positive rake as you are stoning the edge.

95%+ problems with new reamers have nothing to do with the reamer and are caused by setup, run out, hole preparation, coolant, feed & speed (unless you bought a cheep one).

So if you need more help we would need to know a lot more about your process like material, tool holder, hole preparation, how much material you are leaving for the reamer, coolant, feed & speed as well as reamer size, style & material for instance.

Tom