Jerry Sharrett?

L

Lynn

Registered User
Jerry
I have been reading these posts for quite some time now and have a very strange question.
Why do gunsmiths dial in the barrel for hours on end then use a floting reamer holder?
As you can tell I am not a gunsmith and have never done any work like this.

I would think one would want a death grip on the barrel once it is running true and a like situation on the reamer/holder.What am I not understanding?
Lynn aka Waterboy
 
Lynn, given the fact that no barrel is perfectly straight all one can do is to dial the barrels existing bore in at two points. The important points to be aligned is where the bullet enters the rifled bore and the place where the bullet exits that rifled bore.

I pre determine the length of the finished barrel based on a number of factors, desired length, finished weight, etc. First I cut off the muzzle end to within a fraction of the finished point. Then I dial in this point and at the same time I dial in where the chamber neck leade/freebore intersect.

Then follows rough drilling, pre boring for the reamer, threading, etc.

I have a dial indicator mounted on a bracket at the left end of the headstock and another dial indicator that is used to reach up in the breech bore to where this chamber neck leade/freebore intersection is.

With most barrels I can insert the barrel in the spindle, secure the outboard end with a spider and the inboard end in a 4-jaw chuck, dial the outboard to less than 0.0005" TIR and the throat area within 0.0002 TIR in less than 5 minutes.

As to why the floating reamer holder/pusher (I use a pusher), the lathe headstock that spins the barrel and tailstock that pushes the reamer are never in perfect alignment so the reamer must "float" to compensate for that inaccuracy.
 
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JerrySharrett said:
Lynn, given the fact that no barrel is perfectly straight all one can do is to dial the barrels existing bore in at two points. The important points to be aligned is where the bullet enters the rifled bore and the place where the bullet exits that rifled bore.

I pre determine the length of the finished barrel based on a number of factors, desired length, finished weight, etc. First I cut off the muzzle end to within a fraction of the finished point. Then I dial in this point and at the same time I dial in where the chamber neck leade/freebore intersect.

Then follows rough drilling, pre boring for the reamer, threading, etc.

I have a dial indicator mounted on a bracket at the left end of the headstock and another dial indicator that is used to reach up in the breech bore to where this chamber neck leade/freebore intersection is.

With most barrels I can insert the barrel in the spindle, secure the outboard end with a spider and the inboard end in a 4-jaw chuck, dial the outboard to less than 0.0005" TIR and the throat area within 0.0002 TIR in less than 5 minutes.

As to why the floating reamer holder/pusher (I use a pusher), the lathe headstock that spins the barrel and tailstock that pushes the reamer are never in perfect alignment so the reamer must "float" to compensate for that inaccuracy.
Click to expand...

Jerry i'm not a machinist but why not use a 4 jaw chuck in the tail stock with the reamer indicated off the spindle center line? There must be a problem with that method i'm not thinking of. I guess the ways could be off or cranking out the reamer would be off??? just wondering, thanks
 
Jack,
You are really confusing me!! If the barrel is in a chuck in the tailstock, how do you get to it with a reamer?
Butch
 
If I may be so bold, tail stocks are rarely perfectly centered on headstocks, and if a reamer is pushed by a dead center in a misaligned tail stock, the back of the chamber will be enlarged in diameter by twice the distance that the point of the center is from the headstock's axis of rotation. There are other ways of dealing with this problem, but a floating reamer holder, or simple pusher work, if the floating reamer holder is properly designed for chambering. Generally there are two schools of thought on setting up a barrel through the headstock. One is to indicate the muzzle and where the reamer pilot will end up as the chamber is finished, and and the other is to use a sort of reflected measurement off of something like a deltronic pin, and indicating next to the breach end of the barrel, and back out on the pin a distance equal to the depth that the pilot will be inside the barrel. Gordy Gritters' method is a variant on the latter. In those cases, the muzzle will probably not be secured on center, but will be where it has to be so that the two references at the chamber end can be centered. Excellent work has been done both ways.
 
Butch Lambert said:
Jack,
You are really confusing me!! If the barrel is in a chuck in the tailstock, how do you get to it with a reamer?
Butch
Click to expand...



My mistake, what i was trying to say was hold the barrel in the head stock centered in a 4 jaw chuck and hold the reamer in the tail stock centered by holding with a 4 jaw chuck. That would be using two 4 jaw chucks for this operation, barrel and reamer centered off the same center line using two 4 jaw chucks. Jack
 
The purpose of the floating reamer holder is that it will not force the reamer in any direction... if you have dialled your barrel as close as you can and pre bored the body diameter under size, the reamer will follow that chamber and not be forced off by any inaccuracies of the tail stock...

at least that is my belief...
 
What Dennis says is true Jack. If the Bore were perfect[it never is] and the tailstock and lathe bearings were perfect it might work. Bores are not straight.
Butch
 
Not to play the devils advocate, but I'm aware of several benchrest gunsmiths that push the reamer with a dead center in the t/s... I suppose there's many ways to skin the kitty..
 
Jack, I was thinking along the lines of a tail stock 4 jaw at one point also. What that would do though, would only correct the center line coincidence (offset) and not correct any angular misalignment. You would need 2 adj. points on the tail stock to hold the reamer. This of course would not take care of issues with the tail stock tenon moving in and out off center line. Then there ways to contend with and then, as Butch said, no bores are perfect. There in lies the question of which two points are best to indicate. Answers vary.
I have my own opinions, not enough experience to confirm or deny, but I'm gaining on it.

Butch, what is your take on barrel clocking? I have some interesting findings.
Jim
 
Jim Mc said:
Jack, I was thinking along the lines of a tail stock 4 jaw
Butch, what is your take on barrel clocking? I have some interesting findings.
Jim
Click to expand...

Hanging even a small. light weight 4-jaw to the tailstock will just add to the problem of tailstock deflection. As the tailstock quill extends the 4-jaw weight will just pull it down further.

As to aligning a reamer in that tailstock, how do you propose to indicate the reamer to align it with the headstocks rotational center, like where is the dial indicator going to be mounted, what surfaces on the reamer do you intend to indicate, etc???
 
Jerry, I was saying that I was thinking along those lines "at one point" also.
After some thought, I realised that would not do all that what I wanted it to do with out being more elaborate if not possible or at least not feasible. Anyway with all the other things involved, it is probably just as well to use a floating reamer holder.
I have only chambered about a dozen barrels to this point. I have been using a Gretan pusher, so the quill being coincident to the bore is important to me. I was really interested to hear what any recommendations would be for a floating reamer holder.
I plan to chamber a barrel with a hand drill and a die micrometer top opened up to go on the reamer for a depth gage just to see how it shoots.
Many of you already know what to bother with or what is wasting time. I still have a lot to learn.
What is your take on clocking?
I was trying to meet you at the shoot in Hickory, but with that being my first time and feeling pressured for time, I missed getting to your relays.

Oh, I'm not sure exactly how to indicate two points on a tail stock chuck as I was thinking hypothetically. But maybe setting the test indicator in the tool holder and reading the bore ID devided by 2 to get to CL then same at end of reamer?? Maybe something along those lines? Just thinking briefly out loud.
I don't mean to occupy too much time trying to figure that one out, as I believe a floating reamer holder will be all that's necessary.
Jim
 
Jim Mc said:
Jerry, I was saying that I was thinking along those lines "at one point" also.


I plan to chamber a barrel with a hand drill and a die micrometer top opened up to go on the reamer for a depth gage just to see how it shoots.
Many of you already know what to bother with or what is wasting time. I still have a lot to learn.

For heaven sake why?? Sounds like a plan for disaster to me!!

What is your take on clocking?

The method I use for chambering doesn't require clocking. Clocking is only needed if the muzzle is pointing some direction other than where the rest of the gun is pointing.


I was trying to meet you at the shoot in Hickory, but with that being my first time and feeling pressured for time, I missed getting to your relays.

, as I believe a floating reamer holder will be all that's necessary.
Jim
Click to expand...

Were you at the Egg Shoot?
 
I was there mostly hanging out with Greg Culpepper, he was kind enough to let me use his equipment. I asked him to introduce me to you. For what ever reason, he didn't see you when I was with him.
Maybe next time.
Do you ever come to Piedmont?
Got a couple more people I'd like to meet some time.
Jim
 
Jim Mc said:
I was there mostly hanging out with Greg Culpepper, he was kind enough to let me use his equipment. I asked him to introduce me to you. For what ever reason, he didn't see you when I was with him.
Maybe next time.
Do you ever come to Piedmont?
Got a couple more people I'd like to meet some time.
Jim
Click to expand...
Haven't made Piedmont yet this year. Get with Greg and come to Oak Ridge in June. We'll be at the Super Shoot in May when Oak Ridge shoots.
 
Barrels & bores

I have been following this thread. I dont know much at all about the things you guys are talking about. But I do have a question. With all the advances in precision machining techniques & machines, why are barrels and bores never straight?????
 
Big G said:
I have been following this thread. I dont know much at all about the things you guys are talking about. But I do have a question. With all the advances in precision machining techniques & machines, why are barrels and bores never straight?????
Click to expand...

Big G,

Well for all intents and purposes they are straight, ONLY AS STRAIGHT AS THE MANUFACTURERS CAN GET THEM, which isn't perfect yet. So we have to assume that they are not straight at all when chambering!!! That is when everyone has their way of aligning the center of the bore or the center of the portion of the bore they are going to be cutting to a point where they want it for chambering. Then feeding a reamer into that hole in hopes of cutting a straight chamber.

Another thought is, What is "straight"? Is straight "zero" runnout from center for entire length of the barrel, What then is zero, .000 or .0000, or .00000 or .000000? these figures all represent zero runnout, but some represent it more accurately, by tens, hundreds, or thousands of times. A barrel that is straight to .00006 is not straight, but if only measured to .000 it's well within the idea of what straight is.
 
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