chamber runout issues

I do appreciate all the replies. Keep in mind that I do pre bore every chamber. I have tried pushing entirely with my deAd center in the tAil stock, which is set up properly. I indicate in the grooves and use a snug fitting bushing. I use a cheap Chinese machine and I have done a LOT of work on it in the last few years. I am inclined to think its a mechanical issue with the lathe. If I put some pressure against the chuck with an indicator on it, I can make it move several thousandths out (sideways) with medium pressure. Is this normal or would tightening up the headstock bearings take that movement out?

Chuck
 
You say SEVERAL thousands sideways. How much and how far from the headstock face are you measuring?

Do you know if your headstock bearings are adjustable? Some cheap machines use ball bearings which are not adjustable. Of mechanical bearing types, for lathes tapered roller bearings are best.
 
From a machinist standpoint, a off center tail stock will not cause run out, it will cause the reamer to bind and cut oversize.

If you start a reamer in hole that is truly straight, the one major thing that will induce run out is if the reamer encounters a place that is not straight.

I agree with Dave. Most of these barrels are no where near straight, you can find .001 runnout in as little as 1 inch difference in length. Also, if you are set up for a specific spot in the barrel, (we all shoot for the throat), and the pilot encounters a spot somewhere in there that is not that true, something has to give.

Chambering has, and always will be a compromise. If barrels were dead straight, this would all be a moot point, but since they are not, you do the best you can within the requirements of the job.

The OP did say that he is seeing no difference in the way they shoot. That right there says a lot about the whole subject......jackie
 
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Worrying 'bout thangs that don't make no difference!

chuck williams said:
i used to be able to keep runout under .0005 easily. my setup has not changed but now i see runout as much as .001 regularly. the rifles still shoot fine but this is driving me crazy! any ideas? could it be that my headstock bearings need to be adjusted?

chuck
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Chuck, I don't post much anymore because many others with more experience and knowledge do a better job, but I just wanted to make a couple of points and pass along a little advice that I think will help you.

Benchresters, especially those that do their own machine work, tend to be very detail oriented and analytical; many are brilliant in the extreme. It's easy to become obsessed with insignificant details that simply don't matter but waste a great deal of time that could be spent on things that do.

In my opinion, you are wasting time worrying about excessive runout in your chambers. If you are getting as much as .001 runout (Oh heavans:eek:) in your chambers, you are doing very well indeed. Jackie Schmidt in his post above said it very well. In other words, quit worrying 'bout it!

I don't know how long you have been in the game or what your level of experience with machining is but it sounds as if you are expecting unrealistic performance from yourself and equipment. In our efforts to achieve perfection and match winning accuracy we sometimes get lost in details that don't mattter.

Have you ever heard the old saying that goes like this;,

"Measure it with a micrometer, mark it with a grease pencil and cut it with an axe."

That's what you're doing when you worry about .001 runout in your chambers. Like Jackie Schmidt said above, "The barrels are not straight."

Hope this helps.

Gene Beggs
 
If runout is not a problem, why even buy a lathe and a good dial indicator. Sears sells a 1/2" 5-amp drill will easily propel a 6PPC reamer.
 
JerrySharrett said:
If runout is not a problem, why even buy a lathe and a good dial indicator. Sears sells a 1/2" 5-amp drill will easily propel a 6PPC reamer.
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:mad: Oh man Jerry, you let the cat outta' the bag. I was planning on applying for a patent on that. That's the way I chamber but I must confess; I use a Harbor Freight drill, not a Craftsman. :cool:

Seriously, in my post to Chuck, I was not suggesting that chamber runout is of no concern; of course it is. We all want everything to be as near perfect as possible but we have to keep things in perspective. I was just saying that if Chuck is consistently getting .001 TIR or less at the aft end of his chambers, he is doing very well indeed. In my opinion, that is well within tolerances for that specific job.

When someone speaks of chamber runout the first question that comes to mind is; how are they measuring it? Runout relative to what? If they are chambering through the headstock on an 'O'-ring, are they threading and finishing the tenon, THEN measuring runout without rechecking after every operation? If so, I assure you things will move around during all that machining. If they are chambering in a steady rest, are they running the steady rest fingers on the threads; on a concentrically turned journal right in front of the tenon shoulder, where? What kind of indicator is being used? A plunger type, angled in at the aft end of the chamber, or a finger type indicator? Lots of room for miscommunication here.

I have chambered many barrels through the headstock but I prefer the steady rest for a number of reasons. I'm confident that one method is as good as the other. It just depends on the gunsmith, his equipment and what he is most comfortable with.

Jerry, thanks for the input. It's always good to hear from you.

Gene Beggs
 
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