Poor reamed hole finish

Pete Wass

Pete Wass

Well-known member
I just spent a lot of time chambering a barrel and no matter what I did, I kept getting a rough finish in the chamber. I tried reaming by hand, slow, fast and touching up, none of them worked for me. I tried the reamer in some stubs from other barrels and it seemed to cut fine. The chips I got from the rough one were more granular vs smooth shavings. Could it be the steel of the blank itself causing this?

Thanks,

Pete
 
Pete Wass said:
The chips I got from the rough one were more granular vs smooth shavings. Could it be the steel of the blank itself causing this?

Thanks,

Pete
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Yes, some barrels with a higher chromium content require a much higher feed rate in order to cut instead of grind out the barrel material.

Review the cutting procedures for Walther barrels in order to prevent work hardening and poor chamber finishes.
 
If it was a walther they recommend such a high feed rate you need a very large cnc to chamber one. Hence why you never hardly see any used. Instead of using a more believable steel like every other barrel mfr they use a "very high grade" chrome steel that our chambering methods wont work on. Most smiths have chambered one. Then they buy a new reamer and keep goin with the other "less quality" barrels we all know.
 
Pete, first check your reamer. Start by taking the edge of a fingernail and run it along the full length of each cutting edge of each flute feeling for irregularities. Then take a loupe or magnifying glass of about 10X or so and inspect each cutting edge. If the reamer checks out, look elsewhere in the setup and methodology.
 
What brand of reamer? New? Or how many chambers on it? What brand of barrel? SS or CM? what brand were the stubs you used? Did you ream them to full depth too or just past the shoulder? Does it seem that the reamer is binding or "catching" and trying to rotate? Have you or someone else ever stoned the flutes? These will all help to sort out what is happening.
Also, you could have gotten ahold of a blank with "gummy" stainless steel. it happens, and if so it can be really difficult to get a good finish. Or your blank could be work hardening as you ream in which case the cutting edges on the shoulder particularly will be getting dull and pulling out "grains" instead of chips... until finally you have to get it resharpened..
A lot of things can be happening and the details may tell.
 
stool said:
did any of you read his entire post ??
he states he has cut stubs with good results WITH THIS reamer.
yes he could have ruined it on the last stub..but not likely.


so what is the bbl material ? and what lube ? what speed ??
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I dont think you read it- he went back on some stubs and it cut fine
 
Now Children - - -

I cut chambers in stubs both before and after the barrel in question. I would rather not say the blank maker on here. I used the Black cutting oil with lard oil in it. I think the brand is Rigid??? Cut the stubs smoothly but not the barrel I have tried to save. Guess I will do the best I can lapping the chatter marks out. What else can I do? (rhetorical question) I tried using the reamer by hand, gently and that didn't work either. The barrel in question acts more like cast iron than steel when machining it. The inside finish of the barrel looks and feel smooth and I was able to get a good crown without burrs, after a few attempts. It machined the same as the chamber, granular chips.

Pete
 
I went as fast as I could

Dusty Stevens said:
try using alot more speed. this comes up quite often on those barrels
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considering the low gripping force I had on the barrel in the 4 jaw. I think next time I will indicate the barrel in dead nuts, turn the outside to be concentric, then hold the barrel in a collet. Then I can juice the speed up some without shaking the headstock off the machine :).

Pete
 
Pete Wass said:
considering the low gripping force I had on the barrel in the 4 jaw. I think next time I will indicate the barrel in dead nuts, turn the outside to be concentric, then hold the barrel in a collet. Then I can juice the speed up some without shaking the headstock off the machine :).

Pete
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Increase the feed rate not the speed rate until you get a continuous chip instead of grainulour grind, you may need to re-bore or drill the chamber area if the chamber is already work hardened from your previous cuts.
 
How much of a bite are you taking on each plunge? Could be swarf marks. Also some steels do cut differently. For me Bartlein cuts real nice compared to Krieger. " at least on the last few I have cut on" Both shoot just fine, but I can see the difference in the metals. Lee
 
Pete Wass said:
considering the low gripping force I had on the barrel in the 4 jaw. I think next time I will indicate the barrel in dead nuts, turn the outside to be concentric, then hold the barrel in a collet. Then I can juice the speed up some without shaking the headstock off the machine :).

Pete
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Pete, if you are running enough RPM reaming to cause your lathe to shake, you've got real problems!!
 
As it turned out - - -

I finally gave up on trying to get a great looking finish and completed the chamber. I installed the barrel and had a chance to shoot it yesterday. It shot dern good so I will shoot it in a match this weekend. We'll see. A couple of things I did notice : 1. there was no carbon deposit @ the leade after the first box of 50 down the tube, unlike the other three RF barrels I have been using and it cleans up nicely. I did pre-treat it with a mixture of Kroil and Marvel Mystery Oil before shooting round one. Hopefully it will prove o be a good one, I need a break after the barrel I have been using on this rifle :).

Pete
 
Well - - -

JerrySharrett said:
Pete, if you are running enough RPM reaming to cause your lathe to shake, you've got real problems!!
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folks were advising not tightening the 4 jaw a lot and I only held the spider end finger tight. The chamber end showed zero runout on the indicator pin under power @ the recommended reaming speed.

Pete
 
Pete Wass said:
folks were advising not tightening the 4 jaw a lot and I only held the spider end finger tight. The chamber end showed zero runout on the indicator pin under power @ the recommended reaming speed.

Pete
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You were reaming a rimfire chamber? I guess I didn't notice . Big difference in the SFM of a PPC and a 22rf at that RPM>
 
Here's my 2 cents and you may already be doing this...
I almost never get that perfect shiny finish in my chambers. So i buff out all my chambers in the lathe at about 400rpm with a small piece of sandpaper to get rid of the reamer marks/chatter, then touch it up with scotch brite to give it a satin finish.

Honestly i think it has no effect on accuracy or function as long as the chamber isnt ribbed or full of bad chatter.

good luck

MMG
 
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