RPMs while chambering

Woodhunter,

Thanks for that formula! I was rootin' around in the Machinist Handbook the other day trying convert SFPM to RPM's. That formula will make things a bit easier.

Butch,

What type of reamer holder set-up are you using?

I use a Bald Eagle and have some concerns about 400-500 rpm's tearing my fingers off. Your thoughts?


All,

Is it possible to run the barrel too slow or feed so slow as to negatively affect the chambering or reamer? I'm thinking work hardening the material, dulling the reamer, etc.

Justin
 
Superman said:
4mesh, it doesn't matter what kind of barrel I'm using, I asked what YOU guys were doing. You still don't get that. Butch was able to offer exactly what I was asking for. HSS reamer in a chrome molly barrel at 500 rpms. He also mentioned his holding method, the caliber, and the cartridge he was chambering. I'd venture that Butch probably wouldn't run that fast with a 416SS barrel.
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I run similar speeds to Butch. 416 barrel steel chambers easier than 4140, as Butch says, "Like Butter". With a pumped sustem, a good reamer holder, a sturdy setup, sharp tooling, I have to really watch the last .025" or so as it is real easy to run the reamer in too far, they really cut at 400 to 600 RPM!!!
 
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Zebra13 said:
I Is it possible to run the barrel too slow or feed so slow as to negatively affect the chambering or reamer? I'm thinking work hardening the material, dulling the reamer, etc.

Justin
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You can dwell too long while the spindle and the reamer is not cutting but still engaging the workpiece and work harden the material. That is something to be careful of running a chambering reamer over about 200 rpm is dwelling and work hardening. Doesn't take long at 250-450 rpm, just a few revolutions. Being that a reamer is a form cutter I'd suggest not running over 100 rpm.
 
do not take it down just because some none or all dissagree with you...its an open forum , most of us are willing to listen to other methods.

i do fewer than you but i don't use bushings..i prebore, taper bore and ream.....i dial in at the throat......
only one br bbl so far..it shoots in the low 3's at 200 yds..i'm happy.....

mike in co
 
Your big floating reamer holder looks like a Scully-Jones or similar. commonly used on turret lathes, vertical spindle drilling machines and screw machines (back when we made stuff here). That would be the only design tailstock held/tailstock driven reamer holder I'd use, otherwise I'll stick with my floating pusher.

Good pictures.
 
let me ask you a simple question...
are you a gunsmith that learned machineshop skills as part of being a gunsmith, or were you a machinist that took up gunsmithing ?



mike in co
Superman said:
After a recent conversation with Kiff at PT&G, I've been curious about the process others are using. When discussing the HSS vs Carbide reamers we got on the discussion of rpm's used while chambering. Dave said a carbide reamer needed to be going twice as fast as a HSS reamer for good surface finish at about 400 rpm's. I was taught to chamber as slow as your lathe would run but Kiff told me I should be running my HSS finish reamers around 200 rpm's. Are you guys going turning this fast? A freind told me Kiff was a "tool and die maker, not a rifle builder". Your thoughts please and please include a brief description of your chambering method (IE reamer with pilot the entire time, drill and prebore etc.).
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Mike,
I had machining experience before becoming a gunsmith but I would not consider myself a full blown master machinist. I understand basic machine shop practices but I also understand certain circumstances supersede those practices. The comments posted about Kiff being a tool maker and not a gunsmith were not my thoughts. I came here because of the knowledge base to get more opinions. I've been chambering at 70 rpms and get a satisfactory surface finish but if there was a way to do it better, I wanted to advance my skills.
 
ok who taught you to chamber ? you said you were taught to chamber slow...
my comment is that most gunssmiths learn machines to do thier job, and little more. a machinist makes his living off his machines, and learns how to get the job done based on experience, not what a gunsmith said to do....yep sorta slamming gunsmiths and instructors, but they get set in a way and thats what they teach. go read jackie's thread on chambering. here is a machinist the decided to chamber his own rifles. approached the job as an experienced machinest, not a gunsmith, and does it a bit different.....and he can do one quick.

mike in co
 
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I have lots of experienced rifle building friends, some that have spent time in my shop showing me different methods. I am primarily a pistol builder, but I did spend a week with Gordy Gritters. Everyone I know building rifles is chambering at a slow rpm.
 
What was the value of this thread. 2 different opinions and the OP ain't changing his mind. Doesn't really matter to me which way you guys do it.
My reamer holder is a little larger copy of the Bald Eagle. The handle is short enough that nothing will stop it if I let it loose. Don't want it to catch on the ways. If you drill and taper bore to within .020 I have little pressure on my reamer and I feel very little torque.
Butch
 
i tend to agree with you butch,
sounds like someone that was trying to get backing for his method, with no intentions of changing how he does his chambering.
or to disapprove of what dave reccommends....
mike in co
Butch Lambert said:
What was the value of this thread. 2 different opinions and the OP ain't changing his mind. Doesn't really matter to me which way you guys do it.
My reamer holder is a little larger copy of the Bald Eagle. The handle is short enough that nothing will stop it if I let it loose. Don't want it to catch on the ways. If you drill and taper bore to within .020 I have little pressure on my reamer and I feel very little torque.
Butch
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Butch Lambert said:
What was the value of this thread. 2 different opinions and the OP ain't changing his mind. Doesn't really matter to me which way you guys do it.
My reamer holder is a little larger copy of the Bald Eagle. The handle is short enough that nothing will stop it if I let it loose. Don't want it to catch on the ways. If you drill and taper bore to within .020 I have little pressure on my reamer and I feel very little torque.
Butch
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Butch, I don't know what makes you think I'm not changing my mind. Two opinions don't outweigh the other 6 or 8 I have. I'll have to call George and ask him how he's doing it. I would imagine at 1200+ rifles a year he's building more custom rifles than everyone else here combined. I'm sure the method used will have some effect on how many rpms is suitable. If you're pre drilling and boring it might be possible to turn the bbl faster and still have an acceptable finish without any chatter. For the record, I'd consider anything less than 200 rpms on the slower side of the scale.
 
Depending on the lathe I have always chambered at a slow rpm (in a steady rest) and it has always worked for me. Now I dial the barrel in the head stock and chamber anywhere from 45 to 100 rpm. The reamer is hand held on a 'push'. I have no carbide reamers.
 
Thanks for the input DS. I too am chambering through the headstock while running 70 rpm. If there was a way to do as good or better job I am all ears.
 
Before I switched methods I could do about 1 to 1 and half barrels per day.

I now chamber with a high presure flush system and chamber most barrels from 100 to 200 RPMS. I use a Micrometer Adjustable Reamer stop and a floating reamer holder. It takes me about 20-25 minutes to dial in a barrel in the headstock and spider. It takes me another 20 minutes to turn and cut the threads. Another 10 minutes to counter bore or cone a tenon. The chamber and headspacing takes another 10-25 minutes. I usually spend another 5-10 minutes polishing the chamber for easy extraction. If I have to cut a custom throat that ususally takes me 10 minutes to setup and cut. From start to finish I can complete most chamber jobs in 2 hours if the stars and planets line up and I have no interruptions. In the old days I would do1 chamber per day and 1-2 chambers in a weekend. Then after going to a flush system, I was busting my buns and doing 1 to 4 chambers a day and maybe 5 in a weekend until a year ago. Now I am doing about 2 -3 per week. No, it is not the ecconomy, there is plenty of work out there. I was killing myself and realized it. Spending time with my girlfriend is much better than standing behind a lathe and paying Obama 50% of everything I made.

I chambered a barrel with Bob Pastors Vipers Veneom the old way (70 RPMs) about 2 months ago. It felt so odd reaming and cleaning every .050" and taking 2 hours to ream and headspace the chamber. I would hate to go back and doing a chamber center to center again.

Nat Lambeth
 
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nate,
since i'm stil new at the chambering biz, would you care to elaborate on the chamber polishing??...
i know others that say the reamer give a good enough finish, but i'd like to hear your side too...
you could start another thread...
thanks
mike in co
 
Thanks for sharing Nate. I too just purchased the chamber flush system and have installed it but I haven't yet used it while chambering a barrel. I plan to very soon. One of the last steps I do before removing the barrel is using some 320 grit sand paper to polish the chamber and shoulder area then I go over the recess with a little Flitz.
 
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