Botched chamber reaming

[seasicksteve]

That chatter is nasty!!!. As mentioned I would try to bore out the chatter but without knowing how you set this up it might cause chamber misalignment or not cleanup with the reamer. You can try wrapping the reamer with wax paper and go back at it. You can also take some cotton cleaning patches cut small xx s in them and pack them with grease Put the x cut over the reamer and continue reaming with the cotton and grease packed around the reamer flutes. Play with your speed and feed and try to get in past the chatter I think you need to speed up the spindle some. You can also rub the edges of the reamer flutes with an old copper penny sometimes helps on a new reamer. Is this a 5r barrel? Hows the fit between the reamer bushing and the bore?

 

[seasicksteve]

I copied this explanation from another forum
GT, this happened to me a few years ago. I never figured out why it started to chatter, but I figured the barrel was ruined. It was a #4 stainless Shilen,,not much shank), so I knew I couldn't set back enough to start over. I talked to David Kaiser at Brownell's and then to Dave Manson. Dave K had some good suggestions, but Mr. Manson was specific about what to try. On his recommendation, I took a .30 cal cotton cleaning patch and punched a hole in the center just big enough to slide over the reamer pilot and back to the shoulder, then lubed everything and fed the reamer in .010" and then pulled it out to clean it. Repeated this 3 times with a fresh patch every time. It worked like magic. The reamer flutes cut right through the patch, but it damped the reamer enough to stop it from just deepening the chatter marks. Once the chamber cleaned up, I depth miked it and determined exactly how much I had to set the shoulder and breech back.

I have used this method it works but in my case I caught the chatter very early before it got ugly.

 

[Earl]

I dont envy you working on such a nasty problem. I dont have a solution to fix the chamber but I do have a suggestion for your next chamber. I would suggest that you run your steady rest on the threads. The reason being that the outside diameter of the barrel is almost never concentric to the bore. If you indicated the bore before you cut the stub and then the threads, the od of the threads is concentric with the bore. Running the steady on the threads (light but positive contact) will help to insure that the bore is running true to the axis of the lathe and reduce the runout of the barrel when you are running the reamer in.

 

[cdhknives]

I dont envy you working on such a nasty problem. I dont have a solution to fix the chamber but I do have a suggestion for your next chamber. I would suggest that you run your steady rest on the threads. The reason being that the outside diameter of the barrel is almost never concentric to the bore. If you indicated the bore before you cut the stub and then the threads, the od of the threads is concentric with the bore. Running the steady on the threads (light but positive contact) will help to insure that the bore is running true to the axis of the lathe and reduce the runout of the barrel when you are running the reamer in.

I hear you and have read arguments each way. My setup for the tenon is to set a live center in the bore, skim cut the outside of the shank to true it, and cut-n-thread the rest of the tenon in one setup. That should have the shank OD, threads, and bore very close to parallel, at least to the accuracy of the counterbore from the barrel factory that shaped it. At that point I can't see how running the steady on threads vs shank will make a measurable difference, and it hopefully allows a little tighter setup on the steady without damaging the thread tops. At least that is my logic...I'm obviously still trying to figure a lot of this out as I go! If I had a bigger lathe where I could do this through the headstock I would change a lot of things!

 

[cdhknives]

Mr. Manson was specific about what to try. On his recommendation, I took a .30 cal cotton cleaning patch and punched a hole in the center just big enough to slide over the reamer pilot and back to the shoulder, then lubed everything and fed the reamer in .010" and then pulled it out to clean it.

This method is outlined in the chatter PDF file on Manson's website. Read it. Haven't tried yet. I contacted Ray at Manson and he said to expect a call from Dave himself...

 

[pontiac428]

At the point you are at with this barrel, can you still do a set back and re-cut the tenon and threads? How stuck are you? It would be a bummer if you can't , to the end that you may well end up with a 270 WSSM. I wouldn't be happy about that, the WSSM are powder hogs. I also personally think PRC is better with a 6mm, but that's just my experience.

I also support how you turned the fat end of the barrel on centers. A barrel turned that way will chamber on the steady very nicely, and should be concentric beyond your ability to measure. No worries there.

 

[cdhknives]

How are you driving a reamer from a dead center. I’m sure I’m missing something. Can you post a photo of your setup.
Chuck

Tip of the (live or dead doesn't matter, reamer is not rotating) center seats in the dimple at the back of every reamer which holds base of reamer on centerline of lathe (to the accuracy of your tailstock). Once it starts cutting pressure holds it all in place. Wrench prevents reamer from spinning. Pilot aligns reamer tip with bore. When cutting the reamer is actually acting as the center pin for the bore and holding the barrel in line (if steady fingers are loose). With tight steady and this setup the chamber can be oversize due to misalignment, hence the floating reamer holder (as I understand it). This setup worked great on my first 3 barrels. Not so much #4 when I swapped the wrench and center for the floating reamer holder.

 

[cdhknives]

At the point you are at with this barrel, can you still do a set back and re-cut the tenon and threads? How stuck are you? It would be a bummer if you can't , to the end that you may well end up

I have about 3/4" of depth to cut and there appears to be just barely enough chamber diameter to clean up the grooves...IF I don't make it any worse. Otherwise a WSM may be the next order. 6.5WSM is a well known wildcat.

Otherwise, a full cutoff of the tenon would put the shoulder in front of the start of taper, but barely. I could partially cut back and put the thread relief groove at the receiver action screw hole and lose maybe 2 threads out of 30...(Browning 32 TPI).

 

[mickri]

When you have time you should make a micrometer reamer stop. Not hard to make. I made one. https://www.hobby-machinist.com/threads/micrometer-reamer-stop-build.89937/

 

[cdhknives]

When you have time you should make a micrometer reamer stop. Not hard to make. I made one. https://www.hobby-machinist.com/threads/micrometer-reamer-stop-build.89937/

Great, *another* project on my list to do!