Chamber reaming question

C

colchester

Member
I chambered a 22-250 ai yesterday in a new benchmark barrel. I set this up like I normally do, thru the HS, indicate with spiders on both ends, drill, taper bore and ream the chamber. I have done many barrels this way and the reamer always cuts like a knife through butter. This barrel was a different story. I hold the reamer with my hand while while pushing it with the tailstock. The reamer felt like it had a lot of torque on it after advancing only.020". Ive never felt this much resistance before when reaming. I can usually feel the torque on the reamer handle drop when I stop advancing the reamer, not the case with this barrel. I chambered at 90 rpm and fed the reamer slowly, I was using moly d and atf mix for lubricant. It cut with the reamer from the start, I went slowly kept the tooling and barrel cool and made my way through it but I was surprised at how difficult it was. So what do you guys think? Are the Benchmarks harder to ream, the other machining on the barrel went just fine. The reamer I used was new from PTG, I may send it back and let them look it over or try it in another barrel to see if there is a difference. The whole thing had me a bit perplexed. Good news I checked the chamber in 3 places for runout when I was done and my .0001" indicator barely wiggled in all 3 locations.
 
Had a similar problem recently cambering a 220 Swift AI. I think I finally figured out I was not getting enough coolant to the reamer. Sent it back to PTG, they re-sharpened for me. I had let the barrel work-harden. Reamed with the re-sharpened reamer and lots of lubricant and no other problems. Not sure the problems are related.
 
right...what material were your other bbls, and what material is the curretn bbl ??

why not just straight pipe thread cutting oil ?? designed for cutting...

mike in co
 
mike in co said:
right...what material were your other bbls, and what material is the curretn bbl ??

why not just straight pipe thread cutting oil ?? designed for cutting...

mike in co
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Mike this barrel was stainless I have used stainless and CM from several of the popular mfgs in the past but nothing as tough as this one. I have a 14 twist Shilen I may chamber up with this reamer and use it for a forming barrel, if it cuts the way Im used to then Ill have the problem isolated.
 
Dennis thanks for the link, the description does sound like what I encountered. I will return the reamer for inspection before I cut anymore with it
 
I was talking to Dave Kiff today, he called about a past inquiry I had made. It seems in the last few years barrel makers have been sourcing different suppliers of steel... some of these steels have different characteristics and require reamers ground with less margin on the body. In effect sharper than previously ground for the older steels.

PTG will regrind their reamers with a finer margin, all the reamers they are now manufacturing are being ground with a very small margin... about 1 thou instead of about 5 thou if I remember correctly.

In the past reamers were not ground with this small margin, as they would tend to chatter easily with the older barrel steels...
 
Try a proper cutting fluid. What led you to that concoction?
 
B.Johnson said:
Try a proper cutting fluid. What led you to that concoction?
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I agree. Moly D and ATF may be fine for to lube the arbor on a neck turner, but not as a cutting fluid for drilling, reaming, etc.
Get a good high sulfur cutting oil, lard oil if you can find it or good too is Rigid pipe threading lube...at Lowes or whatever.
 
Just a thought, there have been many recent posts about reamer grinds giving problems. Seems the margin is too thick or the final hone is somewhat flat. I wonder if this is an effort by the reamer grinder folks to try to eliminate chatter on some of these flimsy lathes being used today??
 
JerrySharrett said:
Just a thought, there have been many recent posts about reamer grinds giving problems. Seems the margin is too thick or the final hone is somewhat flat. I wonder if this is an effort by the reamer grinder folks to try to eliminate chatter on some of these flimsy lathes being used today??
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I think there may be a lot of truth to this.

It amazes me how much difference the right cutting oil can make. I use my regular sulfur oil for about 90% and then switch to mostly Tap Magic for the last 5 or 6 plunges. I can see a difference in surface finish and feel a torque difference on my fingers. It sure would be nice to have a flush system set up! All those chips would come out all by themselves!!
 
JerrySharrett said:
Just a thought, there have been many recent posts about reamer grinds giving problems. Seems the margin is too thick or the final hone is somewhat flat. I wonder if this is an effort by the reamer grinder folks to try to eliminate chatter on some of these flimsy lathes being used today??
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As it was explained to me the old steel was hardest in the center and softer as you moved out the diameter... the new steel is the opposite - softer in the center and harder as you move out the diameter. I don't think 'chatter' has as much to do with the lathe as it has with the steel and the reamer. Just my thoughts...
 
Dennis Sorensen said:
. I don't think 'chatter' has as much to do with the lathe as it has with the steel and the reamer. Just my thoughts...
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Machine rigidity has a lot to do with it too Dennis. If the lathe spindle has no axial stability you will get chatter with even a twist drill. Some of these ChiCom lathes I have seen barely have radial stability in the headstock let alone axial stability.

Think of it this way, take a dull pencil and poke a hole in the end of a shoe box (axial stability), then, take that same pencil and try to poke a hole in the end of that same shoe box at the box edge (radial stability).
 
I`ve run into the same problem.....had a 7mm barrel (Rock) that took me 6 hrs...to ream ....(thru headstock oiler with Ridgid oil)....after drill/pre-bore.... reamer was dull ...3rd. chamber I cut with it......Sent it back to Kiff.... they touched it up and it cuts great... 3 more chambers ( obermeyer/shilen/mcgowan) with no problems.
Last barrel I did was a..Shilen.....took it from a .22 VarTarg. to .223... it was like butter....also with a Kiff reamer...
I`ve heard Lothar Walther barrels are also VERY hard.... never done one...Have contacted them though and cutting speeds reccommended were way above what we use (125 rpm)....they suggested much faster....
not opinion actual personal expierience....
Bill Larson
 
The final tempering of a bar of steel, can result in a "different" type of material, even with the same batch of steel. Some years ago, I ran into a 4' bar of 5"dia. 420 ss, that was supposed to be 34-36Rc. One side was 32Rc, while the other side was 44Rc! The replacement was fine. Nearly all of my years, in a shop were spent with heavy 15"-17" toolroom lathes, which tend to reduce chatter, due to the larger bearings, and heavier weight, which absorbs the small vibrations, before they grow to a frequency, that causes chatter. If a reamer, is too sharp, it can tend to gouge into the stock, and break free, which can create an uneven surface and chatter. One that is not sharp enough, can be broken by the increased torque.
Regards,
Bob
 
Chip Soles said:
The final tempering of a bar of steel, can result in a "different" type of material, even with the same batch of steel. Some years ago, I ran into a 4' bar of 5"dia. 420 ss, that was supposed to be 34-36Rc. One side was 32Rc, while the other side was 44Rc! The replacement was fine. Nearly all of my years, in a shop were spent with heavy 15"-17" toolroom lathes, which tend to reduce chatter, due to the larger bearings, and heavier weight, which absorbs the small vibrations, before they grow to a frequency, that causes chatter. If a reamer, is too sharp, it can tend to gouge into the stock, and break free, which can create an uneven surface and chatter. One that is not sharp enough, can be broken by the increased torque.
Regards,
Bob
Click to expand...

good post
 
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