NEWS FROM THE TUNNEL, Barrel Indexing

I think - -

Bob Kingsbury said:
Gene,
It was implied that , all that was needed was an action wrench
and barrel vise.
A bushing with similiar threads in and out would advance at the same
rate. Moving the bushing would have no more affect than removing
the first thread .0138( 1/4 turn) back . The shoulder still stops at the same
place. Another 1/4 turn deeper, and the only thing that has changed
is the position of the bushing. The stop point is the same.
A set screw can impose an axial force on the bushing , much the same
as a sight base screw which is to long can on a barrel tenon. I would
think a set of spacers would be much better
Click to expand...

If one uses spacers behind the shoulder of the barrel for any reason, the headspacing of the chamber is going to change. The hole must change it's index point where the shoulder of the barrel abutts the action face. This is why the insert must be free to move and why there needs to be a restraining device; the set screw.
 
Stephen B Moore said:
If you have 18 tpi =.0555" gain or loss per revolution, it does'n change inside versus outside.

Each "hour" of the clock is valued @ .0046".


"Timing IS Everything" Steve Moore
Click to expand...

Actually 0.0556" per turn. With four shims [(1) 0.0046", (2) 0.0093", (1) .0278"], you can index at all 12 clock hours without modifying the action, as Boyd suggested.

Cheers,
Keith
 
Ok,-

Make the bushing 18 tpi outside, 28 tpi inside. make the bushing .111" shorter than the bbl tenon. Counter bore if
needed for unthreaded portion of bbl tenon. You could notch the front of the bushing for a spanner wrench or make a tool threaded same as bbl, only longer to accept a jamb nut / sleeve. Screw the bushing in the action .055" outside face of bushing to out side face of action. Snug/lock the bushing in the action with a screw in a sight base hole.[front] Keep in mind what ever you put in the hole to protect the threads may have to come out later. You now have one revoultion of the bushing adjustment, in or out. Screw the bbl in the action noteing where the index mark is. If the index mark is between 12 & 6 o'clock screw the bushing IN .0046" for each hour of timeing. If the index mark is between 6 & 12 o'clock, screw the bushing out .0046" for each hour of clocking.[not to be confussed with how long this is gonna take you] DO remove or release the screw retaining the bushing before adjusting the bushing. The screw doesn't need to be there after the bbl is torqued up.
To switch bbls, they would have to be head spaced off the shoulder of the bbl the same.

Dammit Gene, now I gotta go out to the shop!

I havn't stayed at a Holliday Inn, as my wife worked for Marriott over 25 yrs.

But I do own a 6913 Clausing lathe!!
Steve Moore
 
Compound thread

Picture, if you will, the compound thread arraingment on a K&M neck turner. The knob is one thread and threads into the body, but the cutter is a different thread (finer) and threads into the knob. SOOOOOOOOO...turning the adjustment knob advances the cutter by a smaller amount.
Same reasoning on Gene's setup.

I still have to wonder about the strength factor.
Bryan
 
Keith

the bbl shoulder still mates up the action face. Any shims between these "faces" will change head spacing. I think we are trying to rotate the bbl to change the angle of the dangle of the bbl without changing the head space. I don't know where you could put shims to change one without changing the other.

Don't forget, obammy promises change-- You will be lucky if you have ANY change left after he takes all of YOUR dollars.
Steve Moore
 
The shims that I proposed would be between the end of the bushing and the barrel shoulder (and of a diameter that would clear the inside of the action threads), not the action face. Tightening the bushing against the barrel shoulder, with a shim in between the two, would change the clocking of the bushing's external thread relative to the barrel depending on the thickness of shim used. At that point the barrel with the bushing tightened in place would be screwed into the action and tightened. (Obviously,for this to work, the bushing would have to be shorter than the barrel tenon.) If slots were on both ends of the bushing it could be tightened on the barrel, or removed from the action if it hung up and stayed there as the barrel was being removed.
 
Slave action

Gene:
Are you using one specific action to preform this procedure ? After indexing the barrel, how much extra work is required to fit it to another action? I have a hard time visualizing this without pictures. I've been a believer in Indexing for years, but most smiths don't want to admit, they don't know how.
 
This entire indexing exercise may be for naught. If the barrel was chambered and the tenon shoulder were machined with the barrel muzzle "flopping" like as if the breech end was aligned with a range rod in the tailstock, there may be need for indexing. But if the muzzle bore and the chamber neck were aligned together there would be no need for indexing.

Any way you index a barrel, that is trying to get a a particular part of the barrel pointing in a particular direction, it is going to be time consuming, a pain, and an unnecessary step.
 
Fred J said:
Gene:
Are you using one specific action to preform this procedure ? After indexing the barrel, how much extra work is required to fit it to another action? I have a hard time visualizing this without pictures. I've been a believer in Indexing for years, but most smiths don't want to admit, they don't know how.
Click to expand...


Fred, this is SO MUCH COOLER than that!! You could take the barrel and sleeve right out of one say Panda or Viper action and walk over to another Panda or Viper and just screw it together....... AND walk the barrel into ANY position of the clock you want on EITHER action! If you didn't like the clock position you could move the barrel 20 or 90 or 276degrees, whatever you want....


You just ....

shoot, I'll just let Gene explain it..... ;) I'm just kinda' excitable! :eek:

al
 
JerrySharrett said:
This entire indexing exercise may be for naught. If the barrel was chambered and the tenon shoulder were machined with the barrel muzzle "flopping" like as if the breech end was aligned with a range rod in the tailstock, there may be need for indexing. But if the muzzle bore and the chamber neck were aligned together there would be no need for indexing.

Any way you index a barrel, that is trying to get a a particular part of the barrel pointing in a particular direction, it is going to be time consuming, a pain, and an unnecessary step.
Click to expand...


Jerry,

hiding the curve doesn't make it go away ;)

al
 
It would seem to me - -

Boyd Allen said:
The shims that I proposed would be between the end of the bushing and the barrel shoulder (and of a diameter that would clear the inside of the action threads), not the action face. Tightening the bushing against the barrel shoulder, with a shim in between the two, would change the clocking of the bushing's external thread relative to the barrel depending on the thickness of shim used. At that point the barrel with the bushing tightened in place would be screwed into the action and tightened. (Obviously,for this to work, the bushing would have to be shorter than the barrel tenon.) If slots were on both ends of the bushing it could be tightened on the barrel, or removed from the action if it hung up and stayed there as the barrel was being removed.
Click to expand...

That the shims you proppse would be a B word to make and a set screw is very simple. No doubt the shims would work but Why not go the easy route? If damaging the threads is a concern, use a Brass set screw.
 
Yeah, what you said Al-

Either you think it's worth it, or you don't. I'm retired now, over 30 years service as a Union Carpenter. [almost got "20 years" when younger though] I have the time and patiece and inclination, and it beats doing honeydoos for the wife.
Moments-20 minutes [real time] ago, I was posting how I index a bbl. I was almost done when Poof, it disappeared into cyber space. I'll try again after dinner.

"Good enough" usually isn't. Steve Moore
 
I have trouble believing that the bushing retains full strength
in shear. Visualize two bushings , both with the same TPI inside
and out. Now visualize one with the threads in phase inside and
out. Picture the other 180 degrees out of phase. One cannot have the same strength in shear as the other. To some degree a differential
thread must share that problem. That this must also have a thin
cross section is not in its favor
 
Perhaps - - - -

Bob Kingsbury said:
I have trouble believing that the bushing retains full strength
in shear. Visualize two bushings , both with the same TPI inside
and out. Now visualize one with the threads in phase inside and
out. Picture the other 180 degrees out of phase. One cannot have the same strength in shear as the other. To some degree a differential
thread must share that problem. That this must also have a thin
cross section is not in its favor
Click to expand...

Shear is not an issue in this case. Perhaps all that is required is say, 100 FP of torque to secure the barrel to the shoulder firmly in the correct position and all else is not in jeprody. So, why complicate things?
 
al

alinwa said:
Jerry,

hiding the curve doesn't make it go away ;)

al
Click to expand...
What you are saying means the bullet traveling down a curved barrel continues its flight in that curved path. It does not!!

Discounting the bullets curved path caused by gravity, the bullet travels straight ahead from its exit directing.
 
Gene,
and others , help me out here. What we seem to be working with here is the difference in advancement between 18 and 26 TPI, which should amount to about .020 per turn...right? Now if you face off a 28 TPI hole enough to have a shouldered barrel advance one full turn ( ignoring tenon length and headspace for the moment)the amount would have to be .038. So..in order to get this (as the difference of pitch advancement per turn) by turning the bushing we would divide .020 by .038 to find that one turn of the bushing in the action would give 53% of a full turn of barrel index. To get all the way around we would have to devide 360 by 53 multiply the answer by 100 to get total degrees and then divide that by 360 to get turns which turns out to be 1.89. 1.89 times the rate of advancement per turn of 18 TPI (.056) gives .105. One would need to add to this something for thread clearance, so something like a difference of .120 between and action threads and bushing length should allow one to comfortably explore the full circle of barrel indexing, and 3/4 of that if one only wants to look at 90 degree intervals. Or Gene could just tell us how far he had to advance his bushing (fraction of a turn, or degrees) to advance the barrel index one quarter turn relative to the action.
 
barrel index one quarter turn

Barrel moves out .056 per turn of bushing.
Barrel moves in .037 per turn of barrel.
Quarter turn of barrel = .009
How much to turn bushing for .009??? (.009/.056)
===> .16 of turn ===> 60 degrees

PS. All numbers approx due to round off error.
 
What a day this has been ! !

Wow! Where to start? :eek:

Jerry Stiller, you're a genius!

Stephen Moore, your posts were also right on the money and very well written.

Many thanks also to Alinwa, Boyd Allen, Don Jackson, Pete Wass, Bryan Armatys, Fred Jamison, Jerry Sharrett, and all the others who joined in the discussion.

After twenty years in benchrest, I must say the past week and especially the past three days, have been the most exciting and rewarding thus far. What a breakthrough! :D :D :D

As stated earlier, I have experimented with barrel indexing for several years, searching for a way to re-index centerfire barrels without altering headspace. Last Sunday morning during the drive home from Phoenix, the solution finally came to me. I couldn't wait to get to work! :D

The first prototype worked well but I was not completely happy with adjustments. Quite by chance, I had used 28 tpi for the inner threads of the bushing and barrel tenon. At the time I did not realize that this difference in threads was the key to making the system work. Sometimes you just get lucky; huh? :D

Yes, the system worked but I wanted to move the adjustable bushing a certain number of degrees and have the barrel rotate the same. I had already discovered that the bushing and barrel rotate in opposite directions. I could live with that but I wanted a one to one ratio between the bushing and barrel. I theorized that if I used 18 tpi threads throughout, I would have the perfect setup. Wrong! :mad:

Jerry Stiller, bless his heart, was the first to point out that my same thread idea would not work. At the time, I thought,

"Well,,Jerry just doesn't understand; he'll 'get it' after he sees the system work." :cool:

Boy, was I ever wrong. :eek: Jerry was absolutely right! In the future, I'll think twice before questioning his wisdom. Thank you Jerry. :) THANK YOU THANK YOU !

Well guys I'm tired; it's been a long but wonderful day. Seven hours of machine work and about two hours testing in the tunnel but I would not take a million bucks for what I learned today. :)

Later,

Gene Beggs
 
and to think i was

gonna offer you a cool $750k and figured you would take it. Oh well, I guess I am back to the original idea of blondes, bikes and booze with the money. :eek:
 
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