Discussion in 'Advanced Gunsmithing & Engineering' started by Rustystud, Oct 6, 2017.
Jim Borden was a "Professional Mechanical Engineer", and happens to be a reputable machinist.
Then his actions should have been "PME" instead of "TPE".
I'm grabbing the beer and popcorn for this one
I've had two break in the last two years. Same deal with one flute breaking off. I predrill and bore leaving .015" or so for the reamer to clean up. Pilot is always solidly on the lands and contact at the rear of the chamber to provide alignment. I can say without question there was no overload on the reamer itself. The one flute just popped off. One was within .100" of headspace so I polished the sharp corners at the end of the fractures and finished the chamber while standing on eggshells. Chamber turned out fine. This was a straight 284 so it had pretty deep flutes and thin webs.
As for the reamers not cutting an all flutes, they certainly should. They are ground at less than equal spacing to minimize chatter yes, but they are all the same dimension and should all cut equally if ground properly. If all flutes were spaced evenly they would set up a resonance of sorts, imagine a reamer digging in and every flute hitting the 'hiccup' at the same moment. It would get bad real fast.
My .02, rebranded crap Chinese or other cheap foreign reamer blanks or tool steel.
I've broken one reamer. I knew it wouldn't make it as soon as it touched steel. A 17 Mach IV. Very thin flutes and a small diameter core. It would grab and twist. Nothing I could do but wait for the crash. I worked with Dave Manson when he was still running Clymer to work out some problems I was having. I was having a bitch of time making sizing dies. The issue was every angle on the reamer changed as soon as it touch steel. You could watch the reamer twist from the load. He increased the diameter of the core and made the flutes thicker. Pretty much eliminated my problems. Everything is a compromise so the fix reduced the chip capacity of the reamer.
This is what I was trying to say on my reply way back before the mud slinging started. Thanks Dave for putting it into the correct terms : )
Dammit!! Just broke a flute off a .260 reamer that I've had for 15 years! So it isn't the steel that they're using to make the reamers. Wonder if the barrel makers have changed something in the steels they are using?
Maybe the electricity running the lathe has changed--dammed solar power.
Sorry to hear that. How many barrels on the reamer? was it sharp?
Dunno, maybe 25 barrels. I think it is sharp and the chamber was bored to within 1/4 inch before putting the reamer in it. So I don't think there was undue stress on the reamer flute.
M-2, M-7 and M-42 are the steels used. 62-64 Rc.
I broke a PTG reamer some 15 years a go. A brand new never used HSS 243 Win. Broke one flute off. Called Dave and he overnighted a replacement that he had on the shelf: A spiral flute carbide reamer. No cost to me.
Man, those carbide spiral flute reamers really make the HSS reamers that most of us use seem like they are made from charcoal seared corn cobs. Wow, do they every cut and leave a smooth finish.
I would love to see photos of the original poster's chambering setup, including the reamer holder.
PS, once I switched to pumped coolant and the use of a "real" floating holder I have not had any reamer problems.
Don't fret, This is an old photo. Since the photo was taken I have made a nice 4 screw "cathead type" chuck for the breech end to replace the unwieldy monster 4 Jaw shown.
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