pre boring reaming

[michaelb]

Hello,

I was working and thought about the fact that most of us drill and bore to remove the bulk of meat from the chamber.

Well, at work, the engineers had us change all of our program feed rates for our reamers and all the porting tools. All of them, even the deep hole port tools that port to a depth of 4.875. The rationale was that the increased chip load and increased tool pressure would follow the small gun drill hole and not walk causing out of tolerance port ID's.
Miraculously, the engineering department brought out something that actually has been working well for nearly two months now. Usually their trouble shooting solutions go the other way.

I wonder if there would be any benefit to chambering here with the same concept? We always remove most of the chamber meat prior to reaming. What about the idea of leaving it all there and loading the force on the tailstock quill or compound leadscrew for those who chamber from the toolpost, and increasing greatly the tool pressure on the flutes. Any benefits? Any one ever tried this? Obvious down side, tool wear. Any thoughts?

Thanks, Mike

 

[MColeman]

I'm probably one of the few who never prebore their chambers. I have always used a finish reamer for the entire chamber. Dave Manson told me years ago that a reamer would cut nearly 100 chambers before it need to be sharpened so I just use the finish reamer. Never had a problem.

 

[burtona]

I'm probably one of the few who never prebore their chambers. I have always used a finish reamer for the entire chamber. Dave Manson told me years ago that a reamer would cut nearly 100 chambers before it need to be sharpened so I just use the finish reamer. Never had a problem.

Same with me.

 

[michaelb]

Hi Mickey,

Nice to know. Another thought occurred, usually when I run into chatter problems, (either turning or milling applications) it seems the chatter problem comes on the final finish cut. I get around it by decreasing rotation and increasing feedrate, usually -10% on the spindle rotation and +20% on the table or carriage feed.

You think a chamber reamer is more likely to chatter under light cutting vs heavy cutting?

Mike

 

[mike in co]

just a beginer...but my guess is the light holding pressure we use precludes heavy loading......

mike in co

 

[frwillia]

I'm probably one of the few who never prebore their chambers. I have always used a finish reamer for the entire chamber. Dave Manson told me years ago that a reamer would cut nearly 100 chambers before it need to be sharpened so I just use the finish reamer. Never had a problem.

Both the local guys I know just use the finish reamer as well. That is also what Richard Franklin does in his video.

The Gritter's video was loaned to me so I watched it twice last night. I understand why he does it, but it looks to me like the reamer could get running off line since the pilot doesn't reach the throat till after it has been cutting for a while. It didn't get off line in the video, but it looks like it could.

Fitch

 

[Jay Idaho]

Your engineers changes were done for reasons not found in chambering. We do not have wandering concerns, the pilot follows the bore.
I pre-bore for bigger chambers but not for BRs and Dashers. It allows a higher feed rate. Nothing to be gained from reaming all the way but it doesn't hurt anything, either.
Opinions, we all have them.

 

[ultramagmed]

Is there any notable difference in accuracy between the two chambering methods? I’m getting ready to chamber my first barrel (I actually have two to do). I have been a little nervous about pre-boring for my first chamber; I don’t want to screw it up. It sounds like it might be a little easier to finish ream the whole thing. Any thoughts?

Med.

 

[MColeman]

Hi Mickey,

Nice to know. Another thought occurred, usually when I run into chatter problems, (either turning or milling applications) it seems the chatter problem comes on the final finish cut. I get around it by decreasing rotation and increasing feedrate, usually -10% on the spindle rotation and +20% on the table or carriage feed.

You think a chamber reamer is more likely to chatter under light cutting vs heavy cutting?

Mike

I think some reamer designs are more prone to chatter than others but I'm not a reamer maker so can't prove my 'theory'. I do know that since I've been using PTG reamers chatter is almost non-existant.

The neatest trick to get rid of chatter in a chamber is to use waxed paper. If you see chatter in a chamber stop and get you a piece of waxed paper about 2x3 inches. Wrap it around the reamer tightly and then ream just a few thou. Take that paper off and replace it with a fresh piece. Repeat until chatter is removed. Works like magic!

 

[MColeman]

Both the local guys I know just use the finish reamer as well. That is also what Richard Franklin does in his video.

The Gritter's video was loaned to me so I watched it twice last night. I understand why he does it, but it looks to me like the reamer could get running off line since the pilot doesn't reach the throat till after it has been cutting for a while. It didn't get off line in the video, but it looks like it could.

Fitch

Not really. Since Gordy has bored the chamber after indicating the bore the reamer, being self-centering, will follow the center line and the bushing will pick up the bore as it should.

When I first began to get into chambering several 'old hands' said that chambering between centers was the only way to go. Horse hockey! My steady rests would always develop some slack in them right in the middle of a chamber and there goes your centers. I don't chamber except through the headstock but many people chamber on centers and do a great job. It just ain't for me, though.

 

[Rustystud]

Singing Pilot..

Mickey:

With the cure of chatter behind us now. I have a second issue I would like for you to cure for me. I high speed ream chambers and my pilots like to sing. With 35-125 psi of coolant flushing between the pilot and the reamer I still get singing pilots.

Nat

 

[mike in co]

ask th co-pilot to do the harmony...


mike in co

 

[chris k]

reaming a pre drilled hole

A problem with reaming a predrilled hole is that the chamber is being aligned with the shoulders outer cutting edge of the reamer .So I guess the majority of the chamber being cut is not being aligned with the pilot of the reamer. Hopefully the reamer is as precisely ground at the cutting edge of the flutes .

Chris

I also do not predrill my chambers

 

[Rustystud]

Pre drilling and boring, and irony .

Almost every Bench rest gunsmith I know pre drills and pre bores their chambers before reaming and every reamer maker recomends against the practice. All the premium barrel maker say the amount of drill wander in the first 6 inchs of a barrel is less than the bearing run out on any manual lathe.


Is there too much time on the hands of most benchrest gunsmith? Are we too anal?

Nat Lambeth

 

[mike in co]

A problem with reaming a predrilled hole is that the chamber is being aligned with the shoulders outer cutting edge of the reamer .So I guess the majority of the chamber being cut is not being aligned with the pilot of the reamer. Hopefully the reamer is as precisely ground at the cutting edge of the flutes .

Chris

I also do not predrill my chambers

do you think the pilot is not aligned with the rest of the reamer ?? ( and the inverse). you need to get another source for your reamers....
mike in co

 

[Hal D.]

Almost every Bench rest gunsmith I know pre drills and pre bores their chambers before reaming and every reamer maker recomends against the practice. All the premium barrel maker say the amount of drill wander in the first 6 inchs of a barrel is less than the bearing run out on any manual lathe.


Is there too much time on the hands of most benchrest gunsmith? Are we too anal?

Nat Lambeth

I've never timed the difference between the two methods, but I don't think it adds much (or any) time to a chamber job, by drilling and pre-boring the chamber. The reamer only makes a few passes until I have a finished chamber, so the only real time spent is in the drilling and boring process. As to the "are we too anal" question, no doubt I am...

 

[JerrySharrett]

Almost every Bench rest gunsmith I know pre drills and pre bores their chambers before reaming and every reamer maker recomends against the practice. All the premium barrel maker say the amount of drill wander in the first 6 inches of a barrel is less than the bearing run out on any manual lathe.


Is there too much time on the hands of most benchrest gunsmith? Are we too anal?

Nat Lambeth

Nat, how many reamer grinders do you know that actually try to cut benchrest quality chambers.

As to chatter, IMO, it comes principally from two sources;

1- The reamer-Reamer flute geometry and finish grind clearances. I use Hugh Henriksen reamers and they cut on all flutes as a reamer should.

2-The lathe headstock design and spindle bearing integrity. Ball and roller bearing headstocks that have a 3-bearing design and good tapered roller bearings do best. These cheepie ChiCom shoe-box headstocks with two cheap ball bearings are the worst.

Too much time on our hands? Hell, no. I've been tearing down and hauling off a shed house for the last few days. Then I'm applying for a bailout of about $75 billion to build it back. And yes, the shovels are ready!!!

 

[chris k]

reaming

do you think the pilot is not aligned with the rest of the reamer ?? ( and the inverse). you need to get another source for your reamers....
mike in co

Thas not the idea I am trying to get across. The idea of the pilot is just that.To pilot the reamer with the bore of the barrel.By pre drilling your chamber ,your concentricity becomes only as good as the boring process ,set up , and how well the outer flutes are ground to the rest of the reamer

I am not saying it does not work just adds some other variables .

Chris

 

[Wayne Shaw]

If you poke a .00001" indicator up into a barrel a ways, get it real close, then just set back and watch it while you slowly rotate the barrel, you will see the grooves and the lands aren't perfect. I suppose when the barrel is lapped, maybe some compound gets loaded a little heavy on one side, the grooves aren't perfectly "round" as the indicator comes off one land and rides to the next land. If you watch as the indicator rides up onto each land, it has a different height and profile, so to speak.

Now this is really splitting hairs, when you're talking about seeing a "tenth" or two difference here and there. I think most consider the grooves as the target to indicate to, not the top of the lands. There is much more "groove" profile to the bullet once it expands to the barrel in firing, the lands are minimal and is there to drive it into a spin. So to keep the upset bullet as concentric as possible, it needs to fit the grooves, not the lands.

There can be some differences in the tops of the lands when indicating. To fit a tight bushing to these lands, assuming they are perfectly concentric with the grooves, may not work out concentric every time. Does a "tenth" or two make that much difference? Maybe, maybe not. What we try for is perfection.

I have intentionally used a loose fitting bushing when I have noticed some slight irregularities. But, I drill and bore before I ream, and in doing this I think it really doesn't matter as much, the reamer follows the hole. Once finished, the leade looked very even all around, and it shot well.

That's my take on it.

 

[Bnhpr]

Mickey:

With the cure of chatter behind us now. I have a second issue I would like for you to cure for me. I high speed ream chambers and my pilots like to sing. With 35-125 psi of coolant flushing between the pilot and the reamer I still get singing pilots.

Nat

Nat,

Harmonicscan be difficult to isolate in machines. The best way to determine what is causing the resonance is to change/vary one component at a time in your setup.

I would start with spindle speed then feed rate, reamer holder length etc. until you determine the source.

Ben