Chattering chamber reamer

[elk hunter]

New problem to me. I started chambering a barrel in 405 Winchester and after the reamer was about 1/4 of the way in it started to chatter. I tried the old trick described in "Gunsmith Kinks" of filling the flutes with bees wax or in this case, thick machining lube wax, and increased the feed rate, it still chattered. I tried hand reaming, chatter again.

I'm wondering if the chamber has work hardened, but the reamer still seems to cut.

I'm considering making a lap and trying to lap the chamber round but I'm worried that even with a properly charged lap, I might leave some abrasive imbedded in the steel and ruin my brand new reamer when I go back in.

Never having had this problem before, I'm running out of ideas or at least good ideas. Any suggestions?

[leftiye]

Maybe not work hardened, but the chattering could have created a series of flute marks in the chamber - a series of high and low places that catch the flutes and then release them after the high spot has been passed. I'd try hand reaming very carefully and slowly. You may have to resharpen the reamer (magnifying visor and FINE diamond hone, don't ferget back rake). If all else fails, you could single point it (the chamber) lightly along its surface to make it round again. When you start again, slow and easy with lots of lubricating oil. Floating reamer holder if the chamber isn't perfectly centered in the barrel or lathe.

[Cap'n Morgan]

+1 what leftiye said. Your reamer has left chatter marks. Once this happens the process is pretty much "self-sustaining".

Try mounting the reamer in a chuck holder or similar to get as solid a setup as possible. Tighten the lock on the tailstock spindle slightly to take up any slack, run the lathe as slowly as possible and eeeaaassseee the reamer into contact. If possible, you may try varying the speed by using the clutch, or starting and stopping the lathe. Once all traces of chatter marks are gone you can proceed in normal fashion.

Oh, I almost forgot... If the suggestion above doesn't work, try wrapping a few loops of thread or string around the pilot in front of the flutes. The idea is to form a cushion under the flutes to prevent the cutting edge to "bite" too deep.

[Willbird]

I have also heard of wrapping paper around the cutting flutes of the reamer, if you are only 1/4 of the way in you may be able to carefully bore the chamber round. if you trig out the angle and set your compound to that you should be able to bore out the chatter with a small boring bar. Just use a ctg case as a depth gauge to ensure you are not going too far. With that case being nothing but a long taper you will probably need to run a very slow rpm and careful feed to ream it without chatter once you get rid of it.

If you have a section of barrel blank laying around it might be worth running a chamber in it to break the reamer in a bit, I'd just drill a hole clear through just a hair bigger than the pilot on the reamer.

[deltaenterprizes]

Try taking the lathe out of gear so you can turn the chuck by hand. Insert the well oiled reamer into the partial cut chamber and turn chuck by hand while applying a light feed with the quill on the tailstock.
If you fill the flutes with grease where are the chips going to go?

[waksupi]

You should never cut over .100 without withdrawing, and cleaning the cut, preferably less when cutting a chamber. If you were pushing more than this, it may have caused the chatter.

[Willbird]

You should never cut over .100 without withdrawing, and cleaning the cut, preferably less when cutting a chamber. If you were pushing more than this, it may have caused the chatter.

I have not done a 405 yet waksupi but from the drawing I found it is a looooong tapered guy, I can see why it might want to get a chatter going. Without a muzzle flush I only go .1" max I agree, and I went .06 with my older lathes that were graduated in 1/16" on the tailstock quill, new lathe is .100. that is pushing it with some ctg.

[elk hunter]

SUCCESS!!!!!

After thinking about the problem for a time, I indicated the compound to the same angle as the chamber, put a new insert in my 1/4" shank carbide boring bar, dialed in a .005 cut, crossed my fingers, said a few mystical incantations, which I dare not repeat, and made the cut. I stopped the lathe and withdrew the boring bar, no visible chatter marks. I put the back plunger indicator ID finger in, turned the chuck by hand, no more bump, bump, bump, no more chatter marks. The reamer took right off cutting properly and the job was finished.

Thanks for all the ideas.

[Willbird]

Alright . In shops I have worked in before we called that pulling it out of your _____ <---insert bad word there . I would rather be lucky than good any time .

Bill