Botched chamber reaming

[Flyinfool]

Check things over on the lathe in general, I also notice chatter on the chamfer at the end of the threads. Maybe something on the machine is loose.

Once you have the chatter you need to go back in super slow so that the reamer is only able to cut the tops of the chatter off. The issue with the floating reamer is that while the cutting edges are over the valleys of the chatter the reamer can move forward and back and even sideways since it is no longer held tight on the point of the center. The wrench can also put a side load on the reamer causing a deflection.

 

[cdhknives]

Good eye. The chamfer at the end of the threads was a quick and dirty swipe with a big file, just enough to deburr and allow the threading bit to start cleanly. So, single cut file plus low RPM plus quick gives an ugly chamfer.

Not to say something else couldn't be loose...but I'm taking a day or 3 off and getting my head wrapped around this problem before I go back and make more chips.

 

[LVLAaron]

If this is a 5R barrel, I'm not surprised.
Did you pre-drill and bore the chamber?
Between centers isn't the best, and if the bore is misaligned much I can see the reamer wanting to go all over the place... again, especially if it's 5R - If it is, you need to bore out as much of the lands as you can up to where the front of the case mouth will be.

And check your runout all the time. After your first 100 thou, check for runout, if there are problems, it's not too late to correct it.

You've got your chamber end of the barrel floating? Coupled with a reamer that's free to point in any direction? I'm surprised you got as far as you did.

 

[xr650rRider]

I've done a couple 5R barrels and never noticed any difference. I use a thru-barrel coolant flush and barely notice the reamer cutting. I drill and pre-bore but only for the body. And I'm not taper boring.

 

[LVLAaron]

I've done a couple 5R barrels and never noticed any difference. I use a thru-barrel coolant flush and barely notice the reamer cutting. I drill and pre-bore but only for the body. And I'm not taper boring.

They can get rowdy pretty quickly... when they decide to. I drill and pre-bore everything, and on a 5R I take 10 extra minutes and bore out the lands. Towards the end of the chamber I have been pulling the pilot off and upping the feed pressure a bit. Leaves me with 1-2 tenths of runout on the chamber body.

 

[xr650rRider]

Seems Gordy Gritters teaches this but seems a lot don't seem to have the problem.

 

[LVLAaron]

Run a 6 flute carbide reamer in a 5R barrel and you'll sing a different tune.
Honest question though.... Those same lot of people that dont have a problem... are they measuring for it? are they checking with indicators? Or are they knocking out quick jobs between centers and calling it good?

 

[cdhknives]

Mine is not a 5R barrel...standard plain old stainless Douglas XX barrel, 6 land rifling, 8 twist.

 

[LVLAaron]

Mine is not a 5R barrel...standard plain old stainless Douglas XX barrel, 6 land rifling, 8 twist.

Got it. You've got too much "loose" I think.. or not dialed in so your reamer is flapping around like a wacky waving inflatable arm flailing tube guy.
If you have the means, I'd pick up a JGS floating holder... They're cheap (for a quality tool) and work beautifully.

 

[cdhknives]

Got it. You've got too much "loose" I think.. or not dialed in so your reamer is flapping around like a wacky waving inflatable arm flailing tube guy.
If you have the means, I'd pick up a JGS floating holder... They're cheap (for a quality tool) and work beautifully.

It was a Manson Precision floating reamer in the mix when this mess started. I had no such trouble on my first 3 using the Hinnant book's method directly. I am thinking I may not try floating reamer holders again until I have a lathe big enough to chamber through the headstock...