? chucking up a barrel ?

[frwillia]

Questions from the inexperienced:
If one uses a 12" Grizzly rod, that is held at its end in a tail stock chuck, to indicate a spot that is 2" down the breech end of the bore, and the indicator is as close as it can be to the end of the barrel, and there is a small weight hanging from the rod to take the slack out of the assembly, would the actual amount of runout be approximately 10/12ths of what the indicator showed, and if the tip of the rod was advanced into the bore to a point that was 6" from the end, would it be 6/12ths?

You are almost there but it's the inverse. In your example the actual runout (bushing movement) would be 12/10 of what the indicator shows (or .00012" per division on a 0.0001" DTI).

To see this visualize the radial movement: set a pencil on the table with the point against your thumb. The point on your thumb is the end in the tail stock. The eraser is the bushing. Pick a point on the pencil, then move it through an angle my moving the eraser and leaving the point against the thumb. You can see the eraser moves a longer distance than the point on the pencil. So the runout, eraser movement, is greater than the indicator movement.

The rod pivots through an angle. The bushing, being farther from the pivot point (at the tail stock chuck), moves farther than the point the indicator touches which is closer to the pivot point. So in your example the indicator shows 10/12 of the actual runout, or the runout is 12/10 bigger than the indicator shows.

Said differently, arc length at a constant angle is directly proportional to radius.

I realize that these ratios ignore the length of engagement in the tail stock chuck, and the distance from the end of the barrel to the closest position that the indicator tip can be positioned, but I am talking round numbers, to see if I have a grasp on the concept. Beyond this, if I have the ratios right, why would the information thus generated not be useful?

You have the ratios upside down but you are on the right track. The information thus generated is definitely useful. One is centering, correcting for small deltas from a constant. The "sensitivity" of the measurement in your example is reduced from 0.0001"/div to 0.00012"/division, which I submit is not a significant degredation.

Also, of a longer whisker is fitted to a test best type of indicator, does it not reduce the resolution in a similar way, unless it was originally manufactured and calibrated that way?

Yes. If the length of the whisker is doubled, the resolution of the indicator is reduced by a factor of 2. This is the same as the resolution that happens if a 12" Grizzly rod is inserted 5-1/2" into the barrel and the DTI presses against it about a half inch outside the breech.

Fitch

 

[frwillia]

Wonderful life wasn't it.

It was. Watching the rubberheads in HR chase the latest fads was a circus.

About 1965 or so Kodak joined the Gimmick of The Month Club, and we did it all. The first one and probably the best was MBWA. Kind of like this divining rod thing that is the rage in chambering. MBWA, walk around it long enough and it will die on its own, which I hope the wiggledy-rod....NO... No, I hope everyone discovers this marvelous new technology and that everyone shoots wiggldy-rod barrels in 2011!!

The temp is now up to 24F and sunny. I'm gonn' go shoot.

MBWA and its predecessor MBO. MBO died after three years - they had to give up on it or fire everybody.

It's sunny here, but I'm not going shooting today. Later in the week it's supposed to get to almost 50F. I "will" be making some noise then.

Fitch

 

[Boyd Allen]

Good catch! I really do understand how it works, I just didn't proof it as well as you did. Thanks (How does that go? Never enough time to do it right, but always enough time to fix it)

 

[JerrySharrett]

MBWA and its predecessor MBO. MBO died after three years - they had to give up on it or fire everybody.


Fitch

I totally forgot MBO, Management By Objective. You know, had we not had all those gimmicks, we may have still had US Steel, et. al.

Do you guys realize that chucking up the next barrel that it may be ChiCom steel? Will it have a slant eyed bore? Will it be a rice burner? How would we wiggldy rod a slant eyed hole??

 

[JerrySharrett]

I remember the 80's when The Enemy was Japan. They were "taking us over."

al

And I remember the '40's when the Japs were our enemy. Want to know something? The Japs were going West to head off Mao. The Germans were going East tohead off Stalin. Neither of them were "heading" here!! FACT!!!!

 

[pdog]

really new here

This is one of those threads you just can't stop reading, excellent job gentleman...In my pea brain i cant see where there's alot of difference between an indicator or a rod for TRO of the bore...Gordy speaks of watching the rhythm of the indicator..would you not be looking at the same thing with a test indicator? Ive learned alot from this post and have never chambered, but now its starting to make sense to me what the procedures are and the fear is subsiding

 

[JerrySharrett]

....watching the rhythm of the indicator..would you not be looking at the same thing with a test indicator? ...

... Ive learned alot from this post and have never chambered, but now its starting to make sense to me what the procedures are and the fear is subsiding

Watching the rhythm of the indicator? Now that would un-subside my fears!!

 

[pdog]

sorry if i insulted your intelligence, wont happen again..

 

[JerrySharrett]

sorry if i insulted your intelligence, wont happen again..

I'll vote for that!!!

You don't even know where I'm coming from about that "rhythm of the indicator" statement do you??

 

[alinwa]

Well, OK, sorry pdog..... maybe he IS being a prick.

I dunno.

Hang in there, not everybody's gonna' get all up in your face.

al

 

[pdog]

al

think i'll just go back to reading the forum's and not get into any p---- contest's...thanks for the welcome..
pdog

 

[JerrySharrett]

al

think i'll just go back to reading the forum's and not get into any p---- contest's...thanks for the welcome..
pdog

pdog, read back up, you're the one who remarked about insulting my intelligence.

The rhythm remark, a machinist would understand as a joke.

As to al, I don't read his crap so I can't remark about a pi$$ing contest. Life is too short.

Anyhow I'm off to the Shamrock and will be off the forum till next Monday.

Stick around, there is always something to learn.

 

[alinwa]

Maybe some "machinists" will come on and 'splain the joke for us retards

Obviously it won't be Gordy Gritters..... no "machinist" there......

lol


al

 

[Ken Worth]

pdog, relax.

I sometimes think Jerry makes a point of mis-reading or mis-interpreting posts. I don't know how to avoid it and I've been posting on this board for 15yrs. I dunno how long Sharrett's been here but we perty much misinterpret each other every twice't in a while. I can currently write this with impunity because Jerry has me "blocked" for offending him I'm not sure how I offended him.

That said, WE ALL live in our own heads!

WE ALL have only our own viewpoint to draw from.

So when we enter the public arena of the BRC forum we never know how we'll be received nor how we'll receive others' input.

Watching actions/reactions on this board is a fascinating character study.

But this I can say with utter sincerity. I DO NOT believe Jerry's trying to shut you out or shut you up. I don't know what he's saying either. I don't get it......... in fact I agree with your verbal description, I'm glad your fears are subsiding and if you're thinking of trying it I say "go for it." My suggestion is to ask Jerry what he means.

MIGHT work?

Meantime, relax, have fun and don't get too close to anything said here.

be welcome

al

I don't think this forum has existed for 15 years??? I know it crashed one time and we all reregistered apparently 2003?? But 15 years?

I thought calling some other user a PRICK was against the rules too??? Wouldn't it take a PRICK to call someone else a PRICK????====takes one to know one===

 

[Dennis Sorensen]

Maybe some "machinists" will come on and 'splain the joke for us retards

Obviously it won't be Gordy Gritters..... no "machinist" there......

lol


al

I must be a retard with you too Al...I don't understand what's funny about indicator rhythm.

 

[Ken Worth]

I must be a retard with you too Al...I don't understand what's funny about indicator rhythm.

I'm not a machinist either but I can answer that. An indicator is not supposed to have rythm, its supposed to be zero. If it is rythming back and fourth, you aren't there yet. What is so hard about that???

 

[JerrySharrett]

I'm not a machinist either but I can answer that. An indicator is not supposed to have rythm, its supposed to be zero. If it is rythming back and fourth, you aren't there yet. What is so hard about that???

Thanks Ken. I didn't think that "rhythm of the indicator" would upset any self professed "retards". (Where did this PRICK business come in?)

 

[Gordy Gritters]

I had to chuckle when I read about the "rhythm" thing. I'll have to go back and watch the video to see what I was doing if I said that. I can guess what it's about, though.

When dialing in bores using extremely sensitive indicators, the needle hardly sits still when you're measuring moving things. When initially dialing in the bore with a range rod, there is a little clearance between the bushing and rod, and the bushing and the bore. This gives you some rod movement which the indicator picks up, and there is a definite "rhythm" to this movement when the rotating bore still has some runout. Then when fine-tuning it while direct reading in the bore with the long reach indicator, the needle really jumps when going over the lands and into the grooves.

All this needle movement can be quite disconcerting to folks until they get used to it, but then it becomes quite easy to see when things are dialed-in where you want them. I've seen this with guys taking my classes, but once they see and experience what's going on, they get used to it quickly!

Gordy Gritters
www.ExtremeAccuracyInstitute.com

 

[pbike]

I'm not a machinist either but I can answer that. An indicator is not supposed to have rythm, its supposed to be zero. If it is rythming back and fourth, you aren't there yet. What is so hard about that???

Wait a minute. How can it possibly be zero? Sherrett has it inside the bore where the rifling is.... Oh he must be useing smooth bore? Sherrett is against using the wiggly slant eyed rods right?

 

[pbike]

Hey Jerry Sherrett,

Do you only use 4 and 6 groove barrels? What or how would you indicate a 3 or 5 groove barrel? When the lands and grooves are opposite each other the way they are in one of those barrels. I can see where it would be easy to see the highs and lows and indicate where the lands and grooves are and to adjust for that when they are opposite each other, but with a 4 screw spider or a 4 or 6 jaw chuck? What am I missing here?

Paul