chamber run out?

J

JDR

Guest
Hello when i chamber i seem to always have .001 to .0015 run out in the chamber area. I use a four jaw chuck and spider. I use a chamber rod with a good fitting pilot to dial in the barrel i set the pilot in the area of the bullet. Then I drill out some of the chamber not to drill deaper than the pilot will reach rifling and about .030 under . I use a boring bar to true the first part or the barrel.I hold the reamer witha floating holder [manson] and start the reamer slow I hold the reamer and do not feel any movment.With the reamer pilot in the rifling I chamber the area I have drillled I check and aways have the run out . what is causing this thanks Jdr
 
yes i will check after drilling could uneven flutes on reamer cause some run out or the fact that the bore is not perfect cause a.001 or so . thanks JDR
 
On the next one you do, try drilling out almost all of the chamber and then stopping your boring bar about .050 from the end of the drilled hole. After you run the boring bar, check your bored hole for runout. Your runout on the bored hole should be zero or very close to zero within a few tenths. Bore out the start of the hole to where the front shoulder of the reamer will just start in the hole. Then support the rear of the reamer with a dead center. As you ream farther down the chamber and get more support into the reamer you can switch to a floating pusher if you want. The reamer will follow the bored hole even if the pilot isn't in the bore. I had a floating reamer holder that was made with two screws in rear of the reamer holder. I used it one time and cut the largest oversize chamber that I've ever cut. The reamer holder would torque over against the screws and push the rear of the reamer away from the centerline of the barrel. If your reamer holder is made the same as the one in the photo below, don't use it and that will probably solve a lot of your problem.

floatingreamerholder.jpg


A reamer pusher like the one in the photo below will work better and will cut a chamber closer to reamer size. The pusher is just a tube bored out to a few thousandths over reamer shank diameter and doesn't touch the reamer at all. It pushes against the Sinclair case holder that is shown in the photo. It has clearance on the reamer shank and bottom.


reamerholder.jpg
 
Mike Bryant said:
On the next one you do, try drilling out almost all of the chamber and then stopping your boring bar about .050 from the end of the drilled hole. Bore out the start of the hole to where the front shoulder of the reamer will just start in the hole. Then support the rear of the reamer with a dead center. As you ream farther down the chamber and get more support into the reamer you can switch to a floating pusher if you want. The reamer will follow the bored hole even if the pilot isn't in the bore.
Click to expand...

Mike,

If the tail stock isn’t in vertical alignment will the dead center method help produce an enlarged chamber or not? I've seen machines that had tail stocks +.004" high or more when checked for vertical alignment.

Thanks, just curious as to your take on this.
 
Mike thank you for the reply.The reamer holder I use has three screws as you say I cant tell from the picture , are you holding the tube pusher with a drill chuck thanks JDR
 
The tube is held with a drill chuck. When you start with the dead center, the center needs to be in line. Even if the reamer is cutting slightly oversize when you are pushing with the dead center, when you switch to the pusher it will take care of the oversize with the taper of the reamer. If the tailstock is .004 out if line, I doubt if it would take care of that much misalignment.
 
Mike,
I have often wondered, could someone make a split dead center that had provision for the point to be shifted so that it would be on axis with the headstock. I know that for this to really work well the travel would have to be parallel to the headstock axis. Also, I have heard of a center being rigged up on the tool post and adjusted to center with a dial indicator and magnetic base on the chuck. Have you seen, or do you have any experience with this setup?
Boyd
 
Boyd Allen said:
Mike,
I have often wondered, could someone make a split dead center that had provision for the point to be shifted so that it would be on axis with the headstock. I know that for this to really work well the travel would have to be parallel to the headstock axis. Also, I have heard of a center being rigged up on the tool post and adjusted to center with a dial indicator and magnetic base on the chuck. Have you seen, or do you have any experience with this setup?
Boyd
Click to expand...

Boyd, I think Jim Farley made an adjustable dead center for doing his barrels. I believe Rex Reneau uses one as well. Even then, it would have to be indicated in every time you use it. If it's not centered in the tailstock, then it's not going back into the tailstock the same every time you put it back. An adjustable dead center should be easy to indicate. My guess it would have four set screws like everything else and move it back and forth and up and down in the taper adapter.

I personally don't think that it's a good thing to drive the reamer with the carriage. Every time you set up the center in the carriage, you would have to indicate it in because it's not something you set once and leave. The compound is being moved around all the time and I guarantee it wouldn't be in the same place as it was for the last barrel you chambered. Too much cutting threads, shoulders, cones and everything else that goes with setting up a barrel and all that involves moving the compound.
 
IMO the pusher shown in bottom pic where the reamer holder is driven off a tube bearing against the reamer holder will account for a misaligned tailstock well beyond .004 runout provided it's set up correctly.

'Correctly' means that the reamer holder is machined to a close fit on the reamer shank and the driving surface is machined to be perpendicular to this shank. If this is not done carefully misalignment will occur, in fact if the reamer driver isn't well made, the driver, the method itself, will LEAD TO misalignment.... will CAUSE misalignment and oversized chambers. Misalignments are accounted for and corrected because if the reamer goes off of centerline axis the driving surface transfers the the 'high side' forcing the reamer tail back to center.

It is my opinion that driving a reamer using a generic holder like the Sinclair caseholder is asking for trouble. It's still better than other methods but hard to make identical chambers with it.

opinionsby


al
 
Concern over use of Sinclair holder

Al,

I also had similar concerns over the use of the 2-piece Sinclair holder but quickly found out I could hold the faces of the holder flush up against the face of the pusher when tightening the holder on the reamer shank.

I'm convinced this method is about as close to fool-proof as possible.

I've done eight (8) consecutive 223 chambers-----3 Rem and 1 Sako action--with 100%interchangeability of neck sized brass. I don't claim all the chambers to be exactly the same size but they are close enough to allow this interchangeability of fired brass.

The guys here have put us onto a good method.

A. Weldy
 
A.,

hmmmmm, as my buddy Jesse sez, "you cain't argue with results!"

BUT, "tightening against the pusher" isn't foolproof IMO. Let's just say that you have the quoted 4 thou of misalignment in the system, wouldn't setting it up this way just insure that the 4 thou stays in? I'm not saying that it would show up as "four thousandths of error" in anything... just that it's THERE isn't it? Wouldn't this setup ensure that the working center would be right where you set it??

puzzling the picture

al
 
I have asways felt a barrel set up through the head stock of the lath using a four jaw chuck and a four screw spider on the back could be dialed in on both ends and still ont be running true the full lenght of the barrel to the center line of the lath am I wrong here I also felt the way most tail stocks are made thay are not adjustable enought thanks JDR
 
JDR said:
I have asways felt a barrel set up through the head stock of the lath using a four jaw chuck and a four screw spider on the back could be dialed in on both ends and still ont be running true the full lenght of the barrel to the center line of the lath am I wrong here I also felt the way most tail stocks are made thay are not adjustable enought thanks JDR
Click to expand...

Unless a barrel bore is perfectly straight, which we know none of them are-its impossible, and you dial it in in any two spots, the remainder will be running out. Any method, headstock, steadyrest, wiggle rod, whatever, the most of the barrel will be running out-FACT.

Now, the decision is, what two spots do you want running true? IMO, it is where the bullet enters the bore and where the bullet exits the bore.
 
JerrySharrett said:
Unless a barrel bore is perfectly straight, which we know none of them are-its impossible, and you dial it in in any two spots, the remainder will be running out. Any method, headstock, steadyrest, wiggle rod, whatever, the most of the barrel will be running out-FACT.

Now, the decision is, what two spots do you want running true? IMO, it is where the bullet enters the bore and where the bullet exits the bore.
Click to expand...

Running true to what Jerry? Since the bore IS arc'd, dialing it between centers leaves you no choice but to intersect the arc with the chamber and the crown cut, you can't get parallel to the bore between centers.

al
 
Ahhh, I think I gotcha'....... you want the muzzle to be directly in line with the chamber and on the centerline of the barreled action assembly, not off to the side somewhere's. And you do parallel the section at the muzzle when you cut the crown. So really, you've got the crown cocked to the centerline while the chamber's straight to centerline, cocked to the bore.

al
 
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