Movement of reamer in chamber and die

[LVLAaron]

I've not experienced any issues in nearly 40 years of machining. There are reamer designs based on that kinda thing actually. Why would it create an issue and what issue have you seen?

It could be something else, and I'm open to any interpretation of the issue...

I have a particular reamer that seems to always give me an oval chamber. It always has one fluted loaded with chips more than the others.. I can rotate the reamer 180 or 90 degrees and the chips pack in the same flute.

The end result is maybe half a thou out of round. Barrels still shoot a clean target, but I assume the issue is a tall flute and uneven cutting pressure that moves the reamer around in the floating reamer holder as it cuts.

 

[gunsandgunsmithing]

It could be something else, and I'm open to any interpretation of the issue...

I have a particular reamer that seems to always give me an oval chamber. It always has one fluted loaded with chips more than the others.. I can rotate the reamer 180 or 90 degrees and the chips pack in the same flute.

The end result is maybe half a thou out of round. Barrels still shoot a clean target, but I assume the issue is a tall flute and uneven cutting pressure that moves the reamer around in the floating reamer holder as it cuts.

I'd come nearer to saying it's likely the reamer holder but not sure. Half thou isn't as much as people seem to think but still. I still can't imagine the reamer causing an oval hole, in a ĺathe, turning the bbl against the rreamer.Seems like something has to be moving, like a reamer holder. Of course this is also dependent on how you're measuring as well as the lathe

 

[LVLAaron]

I'd come nearer to saying it's likely the reamer holder but not sure. Half thou isn't as much as people seem to think but still. I still can't imagine the reamer causing an oval hole, in a ĺathe, turning the bbl against the rreamer.Seems like something has to be moving, like a reamer holder. Of course this is also dependent on how you're measuring as well as the lathe

It's just that one reamer.

 

[gunsandgunsmithing]

It's just that one reamer.

View attachment 1577522

IDK but if it were the reamer creating the oval, shouldn't turning the reamer 90° cure it? Lol! I don't see how the reamer can be the cause of an oval chamber.

 

[LVLAaron]

IDK but if it were the reamer creating the oval, shouldn't turning the reamer 90° cure it? Lol! I don't see how the reamer can be the cause of an oval chamber.

I think I can imagine a reamer cutting with uneven pressure, in conjunction with a floating holder causing issues

 

[DShortt]

I think I can imagine a reamer cutting with uneven pressure, in conjunction with a floating holder causing issues

I would add that the fact that it's possible to advance the tail stock is evidence that there is clearance there. Extrapolate that out over several inches and there's definitely room for movement.
So once again I'd propose that a dull or incorrectly ground reamer is a possible/likely culprit of wonky chambers. Particularly if you're meticulous with your initial set-up.

 

[Sniperhandle]

This just works!

And Dave Tooley uses a similar system and has given the advice to use a PUSHER many times. He has done thousands of barrels, I tend to to listen to his advice. I know that there are lots of other great smiths on here and each has their own way of doing things and what ever works for each person and produces good results for you personally is what you should use.

 

[DShortt]

This just works!
View attachment 1577995
And Dave Tooley uses a similar system and has given the advice to use a PUSHER many times. He has done thousands of barrels, I tend to to listen to his advice. I know that there are lots of other great smiths on here and each has their own way of doing things and what ever works for each person and produces good results for you personally is what you should use.

That system is capable of correcting for misalignment in all 3 axis, which not all 'floating' holders can accomplish.

That said, a floating holder is only as good as the cutting tool (reamer) that it's feeding.

Biggest difference in a floating set-up and a rigid one is what inaccuracy you're most concerned with, in my opinion.

 

[LVLAaron]

This just works!
View attachment 1577995
And Dave Tooley uses a similar system and has given the advice to use a PUSHER many times. He has done thousands of barrels, I tend to to listen to his advice. I know that there are lots of other great smiths on here and each has their own way of doing things and what ever works for each person and produces good results for you personally is what you should use.

I will use one at some point. I promise.

 

[gunsandgunsmithing]

This just works!
View attachment 1577995
And Dave Tooley uses a similar system and has given the advice to use a PUSHER many times. He has done thousands of barrels, I tend to to listen to his advice. I know that there are lots of other great smiths on here and each has their own way of doing things and what ever works for each person and produces good results for you personally is what you should use.

That's a good design. It's based around the very true premise that the reamer will follow the hole unless forced not to and that tool does about as little as possible to influence it from doing anything else. The ball pushes against a flat surface on the reamer handle.

 

[Sniperhandle]

That's a good design. It's based around the very true premise that the reamer will follow the hole unless forced not to and that tool does about as little as possible to influence it from doing anything else. The ball pushes against a flat surface on the reamer handle.

I have been using one for many years. Always works great as long as I dial the bore in dead nuts. I had to replace the handle because It got caught once and bent, That was my fault. But it's been a great tool that I have confidence in. And it's such a simple tool.

I have a piece of half inch pvc pipe that is about ten inches long that I slide over the handle to hold it while I'm reaming and once my tailstock dial gets to where I want to stop, I quickly remove the pvc. I have my hand directly under the pvc and can feel the pressure on the tool as it's reaming. Some people are scared to use this system, But I have never been hurt using it.

Richard Franklin also used the same setup and I have some very old dvd's of his showing the technique.

My friend made his own, And that's what I would do these days. It wouldn't take long at all and you can get a morse taper chuck mount and use your ball turning attachment to round the end.

 

[Will Henry]

An oval chamber is the result of a reamer being deflected at the pilot while not being able to move at the rear. So, if you support the reamer on the center, and the barrel is running out a little at the pilot location, the chamber will be oval, and this will be more pronounced at the rear.
A reamer which cuts mostly on one edge, generally has a center which is not quite concentric with the body. You can check this by setting the reamer up between centers and indicating on the shank and on the cutting edges. Lock the headstock in place and let the reamer turn on the dead centers. If the shank runs true but the flutes do not, the centers are OK and you can hone the offending edge until it indicates true. To really do this properly, you will want to offset the tailstock center so the edge is parallel to the ways. When honing, don't forget to maintain clearance for the edge. Otherwise, the reamer won't cut. WH

 

[LVLAaron]

result of a reamer being deflected at the pilot

I am a rebel and generally do not use a pilot.

Setting the reamer up between centers and indicating on the shank and on the cutting edges.

I'll give that a try with this problem reamer. I wont hone it, but it'll be interesting to see where it is.

 

[Will Henry]

What do you mean you won't hone it?! In the immortal words of my late friend, Bob Forslund, "It's no effing good now. You might as well try to fix the effing thing!" (Bob's language tended toward colorful).
Seriously, the oval chamber is due to deflection at the front whilst being stationary at the rear. If not due to contact at the pilot, it could be a failure to cut at the neck, by an edge opposite the one which does most of the cutting. WH

 

[Jonnyofalltrades]

You can check this by setting the reamer up between centers and indicating on the shank and on the cutting edges.

Setting up between dead centers is extremely educational. Stuff you assumed was straight isn't, and sometimes a tool you assumed was crooked is actually perfect. I still have vivid memories of my machining instructor checking our second year projects between centers. First time I saw it done, and it was an eye opener.

Yeah, my project was crooked.

 

[DaveTooley]

Nothing and I mean nothing can mitigate all the problems from an improperly setup barrel. A reamer, any reamer will try it's best to follow the hole. A hole that is concentric/ running true on either end (the front being the bore) and you can't screw it up.

I did a 300 WM barrel this week. I was to the point of running the finish reamer in. Bushing was a bit tight. I just took it off. Upon inspection a nice concentric throat.