5R runout demonstrated

[Alan Warner]

The stylus on the interapid is 2.75” and it reads in .0005 graduations….I can easily break that down into .0001 or finer with the gap that is between the marks.

If you are preboring to the shoulder, I don’t see how the little bit of reamer deflection in the throat will cause the body to have runout…the throat is the only part cutting the lands and that’s the most flexible part of the reamer….I’m not buying it.

The reamer wants to go to the middle. The only way it doesn’t if we do something to cause not to.

If you are getting runout or out of round chambers, I’m guessing you need to look at your machine and/or setup.

"I’m guessing you need to look at your machine. "


Head stock bearings in particular.
Alan

 

[Alan Warner]

The reason I do it does not translate well because I do not chamber my barrels the way the vast majority do.

basically, it allows me to insert the reamer well over 1/2 way into the bore before it starts to cut.

I am a proponent of doing what works best for you with the tools at your disposal, letting the rifles function and target being the final judge.

Jackie
I'm with you on this. I step bore to -.005/.006 under finish @ the shoulder /neck junction and carry the taper (steps) rearward in either .200 or .400 lengths in Z then use the finish reamer. Pilot is well supported in the bore before any cutting takes place. Typically about a half inch travel to finish depth.
Alan

 

[LVLAaron]

"I’m guessing you need to look at your machine. "


Head stock bearings in particular.
Alan

It's not a headstock issue. It wasn't cut on my machine and I can promise you, it wasn't the headstock. The phenomenon has been described but I hacked together a visual.



Red line through the middle is one opposite set of flues on a 6 flute reamer.

One flute hits point A to make a cut. The ramp in the flute, coupled with an unsupported oppsite side (B) can flex/push/force the reamer into the B section. The further along you get, the more gets eaten away where B is, making it easier to push the cutting further into B. Another impact to the mess, is the ramped nature of the lead. You're pushing the reamer into and up that ramp... more force on the unsupported side.

On a standard 4/6 land barrel, the reamer is always equally cutting and supported on opposite sides.

 

[Adam in WI]

Does this problem present on 3 groove barrels?

 

[LVLAaron]

On a 3 groove you'd have a land every 120 degrees, and on a 6 flute cutter you have a flute every 60 degrees... So, no. You'll always be cutting each land at the same time.

 

[WSnyder]

Jackie
I'm with you on this. I step bore to -.005/.006 under finish @ the shoulder /neck junction and carry the taper (steps) rearward in either .200 or .400 lengths in Z then use the finish reamer. Pilot is well supported in the bore before any cutting takes place. Typically about a half inch travel to finish depth.
Alan

I step bore as well. Reamer is supported by multiple points of contact and starts easy with a light cutting load. Takes a little extra time penciling out my target dimensions but once done it goes in the book for next time.

 

[xr650rRider]

On a 3 groove you'd have a land every 120 degrees, and on a 6 flute cutter you have a flute every 60 degrees... So, no. You'll always be cutting each land at the same time.

If you were trying to lop that entire land off if 1 revolution then you'd have a problem. But if reamer has been cutting in a trued hole, it has support for 360 degrees on the body, you' be taking a very light cut on a land and unless your running so slow, your rubbing, then I don't see deflection being a problem. Now if your start with the tailstock out of alignment and your cutting an eccentric the entire time, then I could see a problem. I run the reamer at least 200 RPM per JGS recommendations and using a barrel flush, I never really feel the reamer cutting at all. Maybe see the reamer holder torque a little.

 

[LVLAaron]

If you were trying to lop that entire land off if 1 revolution then you'd have a problem. But if reamer has been cutting in a trued hole, it has support for 360 degrees on the body, you' be taking a very light cut on a land and unless your running so slow, your rubbing, then I don't see deflection being a problem. Now if your start with the tailstock out of alignment and your cutting an eccentric the entire time, then I could see a problem. I run the reamer at least 200 RPM per JGS recommendations and using a barrel flush, I never really feel the reamer cutting at all. Maybe see the reamer holder torque a little.

Assuming your machine is right and you're dialed in correctly... the reamer is supported as long as the reamer is also correct... It cutting on one flute will give you an oblong chamber...

Same applies with the diagram I made... It's not fully supported if you're cutting on one flute and not the rest. If you prebore the lands as far up as you can it's really not a problem. I imagine reamers with short freebore/lead are less prone to the problem, but I'm speculating.

 

[WSnyder]

It cutting on one flute will “could” give you an oblong chamber...

You should stop stating this as a given in that it will happen but should maybe state it could happen. It’s obvious it doesn’t happen for many but does happen for some. The reasons why? Don’t know. Maybe technique, pre-bore style, reamer maker, cutting fluids, reamer holder, etc… could be discussed to see if one could identify what works and what doesn’t. We know Gordy says he (and you) pre-bore the lands. That’s great but many haven’t had to do that and they don’t get any anomalies whatsoever on a 5R.

 

[xr650rRider]

You'd think if it was such a wide-spread problem that barrel makers would never sell a 5 groove barrel. They would have naturally weeded themselves off the market.

 

[LVLAaron]

Fair, it COULD.

All I wanted to do with this thread was demonstrate a barrel that walked into the shop, that I know was not given the proper attention.

So far zero people who say "I don't have any problems" have shown a video of an indicator running, or provide details about how they got there. I thought it would be interesting to show an actual outcome and discuss it.

 

[LVLAaron]

You'd think if it was such a wide-spread problem that barrel makers would never sell a 5 groove barrel. They would have naturally weeded themselves off the market.

To be fair... the barrel in my first post shot a 600-42x the weekend prior. So would the owner or smith who turned it say there was a problem? Doubtful. Does the chamber have 5 sides? Yes.

 

[Tucker65]

You'd think if it was such a wide-spread problem that barrel makers would never sell a 5 groove barrel. They would have naturally weeded themselves off the market.

Or maybe reamer makers could make 5 flute reamers for those that want to use them with 5r rifling. I've never had this issue but it appears some do for some reason.

 

[Edd]

Assuming your machine is right and you're dialed in correctly... the reamer is supported as long as the reamer is also correct... It cutting on one flute will give you an oblong chamber...

Same applies with the diagram I made... It's not fully supported if you're cutting on one flute and not the rest. If you prebore the lands as far up as you can it's really not a problem. I imagine reamers with short freebore/lead are less prone to the problem, but I'm speculating.

If the reamer is cutting the chamber body with one flute, is that same single flute going to be cutting the neck and throat?

 

[LVLAaron]

Or maybe reamer makers could make 5 flute reamers for those that want to use them with 5r rifling. I've never had this issue but it appears some do for some reason.

I believe you can get them. but it's hard to measure dimensions on something with an odd number of flutes.

 

[LVLAaron]

If the reamer is cutting the chamber body with one flute, is that same single flute going to be cutting the neck and throat?

I dont want to confuse anyone here - talking about two different things.

1) There are some reamers from a place we all know that "cut on one flute" because they aren't ground very well.
2) One land at a time being cut, because geometry.


To answer your question... depends how out of whack the reamer is I suppose. It's possible the reamer is correct above the neck but has one long flute on the body.

I have 1 PTG reamer and it's a one-flute-cutter. Based on where the chips pack, it's a problem all the way to the tip. Just one reamer, and one guys experience with it. It still cuts a round chamber.

 

[INTJ]

The little "U" shapes at the end of the rifling don't seem to affect anything.

Reasons why some see this and some don't?

Chambering at a higher RPM often fixes the U. Different barrels types seem to cut differently. Not every one is super fussy about their chambering jobs.

 

[GenePoole]

Fair, it COULD.

All I wanted to do with this thread was demonstrate a barrel that walked into the shop, that I know was not given the proper attention.

So far zero people who say "I don't have any problems" have shown a video of an indicator running, or provide details about how they got there. I thought it would be interesting to show an actual outcome and discuss it.

I don't normally make videos of every chamber job. In fact, I can only think of one chambering video I've ever done (and I believe it is in this thread somewhere, or in the chamber flush thread). Next time I get a 5R job, I may think about it if time permits.

In my mind, for 95% of the chambering process, the "reamer" (1) is cutting on a non-interrupted surface. Unless your setup is way off, the 5% or less of the tool cutting an interrupted surface is going to be dampened by the smooth surface the rest of the tool "sees."

1. What gunsmiths call reamers we machinists call form tools.

 

[WSnyder]

So far zero people who say "I don't have any problems" have shown a video of an indicator running

Probably because they don't have time to film, haven't had a chance to take the time and or lack the skills or time to figure out how to post a video

Is my word not good enough for you that I say I do not have and have not had this issue? I do know how to use my indicators and I do check my work after so......

 

[Ksracer]

In my mind, for 95% of the chambering process, the "reamer" (1) is cutting on a non-interrupted surface. Unless your setup is way off, the 5% or less of the tool cutting an interrupted surface is going to be dampened by the smooth surface the rest of the tool "sees."

1. What gunsmiths call reamers we machinists call form tools.

I mentioned reamer support in my earlier post. If I can get the neck of the tool supported as well as the body before I hit lands, I have far fewer issues.

If you're a machinists by trade, then you've probably heard the rule of thumb that 2 flute end-mills cut slots truer to size in 1 pass than a 4 flute. And you also probably know that there are exceptions to that rule based on many variables, but the theory is the same.