Noob- Interesting observations using a range rod - Page 2
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  1. #21
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    Quote Originally Posted by john.k View Post
    (a)You worry too much,(b) All barrels are bent.(c) Some are more or less straight on the OD ,but the bore wanders about (d) refer a.......Therefore ,dial in the muzzle end ,and forget about it,then dial in the chamber end to the nearest 001,which is good enough IMHO.....Then rough out the chamber .Having roughed out the chamber better than 80% of material removal,then set up with your rod.This will ensure the throat is concentric,which is what is important.
    .001 IS NOT "GOOD ENOUGH" unless hit a barn is your version of accuracy.

    competition shooter, and i an stuck not being able to get better than .00025 or so.
    some do .0001

  2. #22
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    Quote Originally Posted by ShelbyG View Post
    Thanks for the info. I'm getting another rod for comparison purposes. It just seems odd that there is essentially no deflection in the rod showing on the test indicator until I get to the exact spot that I marked on the rod and for about 1/2" in length. If I traverse the rod length away from this point, I can get to where I have essentially no deflection showing on the test indicator as I spin the chuck.
    Traversing the dti on the rod means you are exposed to any blips in carriage movement on the ways.
    Thats why the two dti approach is more reliable cause the carriage stays put.

  3. #23
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    I don´t know about range rods, but the better linear-motion stuff has about 2 microns TIR in a high spot, and no flats at all.

    So my experience/opinion is that no flats are needed to make exceptionally round rods.

    Fwiw, i´m (still, slowly) working on rigid lapping the 2 microns off in a production setting (my custom automation stuff) to supply somewhat "zero-micron" TGP shafts.

  4. #24
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    OP,
    A lot is made of runout while setting up, but you can still hit a barn if it isn’t perfect

    Example: I strive for perfection like everyone else here because it’s how we are, but out of curiosity we threw a blank from across the room into a 3 jaw and spider with .007 runout. We cut a 300rum chamber with an eBay reamer holder and put it all together with a lightly touched up 700 action. Took it to the range and shot the 215 Berger and 225 eldm very well. We weren’t trying for 1s and zeroes, but got many 5 shot groups under 3/4 moa at 500 yds. Take into account, we don’t test at 100. We start at 300 for initial zero and test at 500 and beyond. Try it sometime with a rechamber for fun.

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  6. #25
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    A classmate from gunsmithing school worked at GA Precision for a couple years after graduation. At GA they hold the barrel in a collet for chambering and strive for no visible run-out. Stress the word visible, an eyeball is all that is used.

    Now I know from mounting sights that you can typically do better than .005 by eye, but I'm sure nearly everyone here gets their barrel running straighter than GA Precision does. GA guns do shoot very well though. We live in a time where we can get wonderfully accurate barrels, much better than our predecessors. Good quality parts can hide a multitude of sins.

    Sent from my Pixel 2 using Tapatalk

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  8. #26
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    Quote Originally Posted by john.k View Post
    (a)You worry too much,(b) All barrels are bent.(c) Some are more or less straight on the OD ,but the bore wanders about (d) refer a.......Therefore ,dial in the muzzle end ,and forget about it,then dial in the chamber end to the nearest 001,which is good enough IMHO.....Then rough out the chamber .Having roughed out the chamber better than 80% of material removal,then set up with your rod.This will ensure the throat is concentric,which is what is important.
    A lot of what you say here rings true but I don't like the idea of using the reamer to rough in the chamber. The reason being that the reamer will center itself on things that aren't concentric to the throat. The best method I've come across for extreme precision is similar to your method - you start out by dialing in your barrel fairly close using whatever method you like. Then you drill out most of the chamber with a drill bit. This step is only to give you access to the throat area. After drilling you can then use a range rod or even better a long arm indicator to precisely align the throat area with the axis of your lathe. Once aligned properly you use a boring bar to true up the drilled hole so your reamer will follow a concentric, parallel path that's dead on square with the throat. Now you can thread and chamber.

    Truth be told I think a good barrel, match grade reamer, and reasonable attention to detail will give you a very accurate rifle. Most factory guns don't use any of the above and still get you enough accuracy for hunting.

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    Quote Originally Posted by ShelbyG View Post
    Thanks John. I think my ignorance in this area is what creates my worry.
    Shelby,
    A training school had a hand-out that said;"Stupid is forever"
    "Ignorance can be fixed"
    You are doing the correct thing, finding reliable information from qualified people. Best wishes, and keep on trying.

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    Thank you for all of the input. I did receive a new range rod and the "flat" spot has gone away in my setup, I think the first rod has some defect. I ignored any variance observed when the test indicator traversed the rod from bore to tip based on all of the comments and was able to get to only .0002" of run out on the test indicator when running the lathe.

    Now all I have to do is perfect cutting threads to move on.

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    Post pics of targets when done. That’s the real test

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    All barrels are not bent!! What you have is a gundrill taking off in another direction, but very slightly. They ain't banana shaped either as some post. I have long wondered how you could bore a banana shaped bore. Could someone enlighten me.

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    Quote Originally Posted by ShelbyG View Post
    Thank you for all of the input. I did receive a new range rod and the "flat" spot has gone away in my setup, I think the first rod has some defect. I ignored any variance observed when the test indicator traversed the rod from bore to tip based on all of the comments and was able to get to only .0002" of run out on the test indicator when running the lathe.

    Now all I have to do is perfect cutting threads to move on.
    So yo can measure to .0002 but you can't cut a thread? How the hell does that happen?
    S

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    Ignore the negative comments. Take any steel you can get and practice. You’ll get it down quickly. I even practiced with pipe when I ran out of barrel stubs. Hopefully you have someone to watch or watch you.

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    Quote Originally Posted by mike in co View Post
    .001 IS NOT "GOOD ENOUGH" unless hit a barn is your version of accuracy.

    competition shooter, and i an stuck not being able to get better than .00025 or so.
    some do .0001
    This is popular opinion...But it's simply hog wash. Ever seen an inspection sheet on a new lathe? Unless you're running a true tool room lathe or VERY expensive high precision lathe....the spindle can't even run within .00015 - .0002" of true. Don't take my word for it, look at the inspection sheet that came with your lathe in the spindle run out section. Oh sure, I know you can dial a bore into .0001" total run out, turning the spindle by hand with no torque or thrust on it, but soon as you throw the power to the spindle it "wallows" around to the error value shown on the inspection sheet, or worse, over time. I dial a barrel in to running less than ,0005 run out, and ream it with a floater. and I have created rifles that would shoot zeros at 100 yards and many 1/4 moa rifles at range. I'm not saying don't be precise as you can. But I'm saying the majority of gunsmiths that make a big deal about dialing a bore into a gazillionth-inch are either ignorant of the mechanics of a lathe spindle under torque and stress as well as spindle bearings, or talking crap to try to win work. And I worked as a machinist/ Tool man at a roller bearing plant. ALL...bearing races are egg shaped if you have fine enough inspection equipment to see it. Some bearings ($$$) just less than others.($)

    - MG

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  20. #34
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    Both agree .. and not.
    Avg auto std ac bearings tend to do about 5 microns tir or 0.0002".
    Lots of asian lathes do the same, or a bit better.
    0.002 mm is common in tir on better 12-13" lathes.

    So what.
    I have no idea how much 1 micron barrel chamber bores help or not.
    Large numbers of premium barrels tend to indicate they are not the required ingredient.


    Quote Originally Posted by MonCeret Gunsmit View Post
    This is popular opinion...But it's simply hog wash. Ever seen an inspection sheet on a new lathe? Unless you're running a true tool room lathe or VERY expensive high precision lathe....the spindle can't even run within .00015 - .0002" of true. Don't take my word for it, look at the inspection sheet that came with your lathe in the spindle run out section. Oh sure, I know you can dial a bore into .0001" total run out, turning the spindle by hand with no torque or thrust on it, but soon as you throw the power to the spindle it "wallows" around to the error value shown on the inspection sheet, or worse, over time. I dial a barrel in to running less than ,0005 run out, and ream it with a floater. and I have created rifles that would shoot zeros at 100 yards and many 1/4 moa rifles at range. I'm not saying don't be precise as you can. But I'm saying the majority of gunsmiths that make a big deal about dialing a bore into a gazillionth-inch are either ignorant of the mechanics of a lathe spindle under torque and stress as well as spindle bearings, or talking crap to try to win work. And I worked as a machinist/ Tool man at a roller bearing plant. ALL...bearing races are egg shaped if you have fine enough inspection equipment to see it. Some bearings ($$$) just less than others.($)

    - MG


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