My first attempt on chambering and turning a barrel

[andremajic]

Well, I got a few wwII cutoffs from numrich that were too inexpensive to pass up. I figured it would give me practice on threading and chambering. That way if I screwed up, I wouldn't be ruining a 200.00 blank!

Because it's pretty hard to take pics while I'm working on a lathe I am limited to describing what I did and link the pics that I did take while the lathe was turned off.

http://www.flickr.com/photos/24940707@N07/with/5396940452/

First thing I did was use pin gauges that fit snug in the barrel and used an indicator, my spider, and a 4 jaw chuck to get it running true with approx .0005" runout on the chamber end and muzzle end. Sorry, not perfect, but I'm a newbie!

Faced off each end square and re-centered it. Turned down all the rust and gunk on the chamber end until I got steel with no interruptions on the cut and measured. Best thing about these super heavy barrels is there is a lot of meat left.

Reinserted gauge pins to make sure it hadn't moved out of line after the turning and it was still true. "whew"

Finally figured out why I was turning 20 tpi on the lowest setting! I was using power feed and not the half-nut! After using the right levers, the threading was correct. Using a thread mic I used the same measurements from a takeoff 700 barrel and cut the threads to depth.

Drilled out approx 1/2 the depth of the chamber out and bored the recess for the bolt face. Used the reamer to (for the next 3 hours) with a lot of cutting, cleaning chips, reoiling, and recutting until the go gauge sat just a little short of what my takeoff barrel read. I used a feeler gauge with the original barrel to get an original reading on how deep to ream the chamber, as I don't currently have an action to use it with yet.

Set it up between centers and with a lathe dog and used a homemade aluminum center for the chamber, as I did not want to have to clean up any damage that a steel center might leave in the chamber. Turned down all the extra metal and rust off the barrel until the profile seemed about right.

Using a coarse file to finish blending the contours and a lot of carding between passes, I used succeedingly finer files until I could take over with sandpaper. After going to about 180 grit, I stopped sanding, because the finish was nice I will probably be sandblasting and using a bake on finish. I get those free newspapers to use to cover the bed and ways of my lathe to keep grit off.

I won't know how much more fitting I have to go until the reciever I have on layaway is paid off, but I'll keep you guys posted!

Andy.

[leftiye]

I enjoyed reading this! Good work. As for 20tpi., I suspect that you're in the wrong setting elsewhere. My lathe has a high and a low field for each gear/thread setting range. Also, there is probly a high, medium, and low setting that corresponds to the horizontal lines on your threading chart (within each range). On mine they are on a lever with A, B, C marked on it (A1 ring a bell?). These also affect the feed while you are turning, but they therefore do differentiate your threading feeds. You don't want to go changing gears if you don't need to! - BIG MESS!

[andremajic]

Well, I set it to setting A 1 on the chart, which would cut (according to the chart) 4 tpi, but it didn't. Turns out that if you use the power feed lever, it will cut too fine a thread.

Being a newbie I just figured that the same lever to feed the carraige forward would do the same for cutting threads. (In theory it did)
NOT SO, there's a reason they have different levers on a lathe to do different functions. After reading more information about how to operate a lathe, which showed what each lever did I was able to figure it out.

All threads (on my lathe) need to have the power feed lever in neutral and engage the half-nut lever to start threading. After I did that the threads turned out beeutiful!

Andy.

[nanuk]

got to love the success stories with self taught craftsmen!

[x101airborne]

Congrats!!! I just recently purchased a 1970's Monarch tool room lathe for chambering work and counterboring mauser muzzles. Basically I will do everything BUT re-taper barrels on it. What book did you read on how to run yours? The 80.00 Monarch book (pamphlet) doesn't say anything about setting up the lathe, running it, or anything. Obviously I dont know c#$p about running a lathe, but it looks good in my shop!

[andremajic]

Lots of books out there, but the internet is a good place to start for free. There are a couple army manuals for free download on how to run a lathe. Scribd is a good place for free info. practicalmachinist.com is a good source, lots of free information on the internet.

Andy.

[deltaenterprizes]

The Home Shop Machinist is a good place for new users, Practical Machinist does not like answering questions from hobby shops.

[David2011]

Andy,

Are you using the back gear? That increases power in a major way and puts everything in slow motion. Brownell's sells a book, "How to Run a Lathe" for about $8.00 that is written for the South Bends but should apply very closely to your Logan. Nice machine. The spider is a nice touch.

David

[dragonrider]

+1 for Home Shop Machinist,

[andremajic]

Andy,

Are you using the back gear? That increases power in a major way and puts everything in slow motion. Brownell's sells a book, "How to Run a Lathe" for about $8.00 that is written for the South Bends but should apply very closely to your Logan. Nice machine. The spider is a nice touch.

David

Yep, back gear and a variable frequency drive make threading really slow easy as pie.

Deltaenterprise, I've found that as long as I approach the forum members with the appropriate amount of humility and ask the right questions at practicalmachinist forums that they are quite willing to help a newbie like me out.

I had a back and forth conversation where one of the members taught me a little trigenometry because I was having problems finding the correct taper for my headstock insert. (I've never taken trig, but I can do basic math and a little algebra.)

After a lot of coaching, I was able to figure out - Long distance - with another forum member if the insert he was selling was a match for my lathe. Turned out it wouldn't work and it saved me some money by not buying the wrong part, even though the pics looked like it would fit.

[andremajic]

+1 on homeshop machinist too.

[Willbird]

One possible problem, when you pre drilled the chamber, was the reamer pilot able to enter the bore BEFORE the reamer started cutting ? I do not pre drill, if I DID pre drill, I would be forced to single point bore to the same taper as the cartridge in question.

One older smith I respect quite a bit told me the few times he got a bad reamer chatter was trying to step drill or some such, so he cut it out :-).

I'm never in a big hurry to chamber a barrel, so running the reamer in the whole way does not bother me a bit :-).

One way to gauge how good your setup was is to mark the reamer flute with a sharp pencil where it exits the chamber, then measure the reamer there carefully with a micrometer...and compare that to the chamber dia right at exit as close as you can measure. Typically without a setup trick or two, it will be bigger...overall not good.

Now for the setup trick...once you get the barrel in place, and threaded..take a hose clamp, and clamp your test indicator to the threaded stub,put a dead center in the tailstock, then move your tailstock up close enough to touch the indicator needle to the angle on the dead center, tighten the tailstock down...then rotate the barrel so the indicator needle is indicating the dead center in the tailstock. Get the runout down to .000..what you find may may make your jaw drop. If you chamber using a steady rest you can "cheat" and just move the steady until the indicator says .000 runout. if you have the barrel up in the headstock you can adjust the tailstock right/left, but if there is an up/down issue your in for some rough hoeing to correct it, luckily my Grizzly was dead on up/down, and also very nice right/left.

If I had a lot of up/down going on I would make a dead center that could be adj...or you could use a boring head that had a morse taper (they do exist) and mark it for index. Technically the tailstock should be fixed so that it is level, some say older lathes were built .001 or so high to compensate for wear...if I found one much off I would take it clear apart first and check where it slides to adjust taper to make sure everything was in good order there.

This is a fairly quick check I do on every chamber....AFTER I cut my first one big at the back end and had to take 2" off the breech end and start over.

Another trick I like to do when cutting a chamber is screwing the action on the barrel, put the go gauge in, put the bolt in, and then get the indicator in there and actually measure the end play...this means you are hitting a value YOU decide, not just "a go goes and a no go does not".

.002" is my value for general purpose rifles, 0 for precision rifles.

Also work on hitting the headspace dead on by measuring as you go, the headspace gage for a good craftsman is just the final proof you have it right. You will need a depth micrometer to do the measurements needed. With a 700 and it's separate recoil lug things are easier...you can use a cheap set of chinese gage blocks (good ones if you want to throw down the $$) or even calipers to measure between the end of the reciever and the barrel shoulder when you are quite a ways away yet. if the gap is .300, and the recoil lug is .200 you have exactly .100" to go. I stick the mag base on the carriage, you can then move the indicator as you go deeper, and even use the carriage stop to move it in a controlled fashion if you need to. Generally when I get in there a ways I only go .05" at a time, then pull the reamer, blow out chips, re oil, then in for another .05. You will get a feel for when it is getting clogged with chips.

Then you can get that test indicator in there so that it hits the end of the tailstock quill with the reamer all the way in, zero it, and thus measure your advance of the reamer. It IS possible to hit that headspace RIGHT where you want it to the .001" with careful work

ANOTHER important thing to check for in any action, is that the recoil lugs are actually bearing, not the bolt handle(or secondary ie safety lug)...should never happen but I did see it in a mauser I did for a guy....he admitted after the fact that he got a box of actions and bolts, and just picked the two that fit well and looked nice....well the secondary "safety" lug was bearing not the locking lugs.

Also some speak of building in "crush" for when the barrel is tightened up.....I have always checked for it when doing the work, but never have I found it to be needed....if the math supports .002" end play on the bolt on a "go" gauge...that is what I end up with.

On rem bolt counterbores...I always true up the bolt nose first, and the front end of the bolt nose too, then plan on .010" in every direction clearance, that means .010" on the end, .010" at the front of the lugs, and .020" in dia.



Bill

[PatMarlin]

Great thread.

[deltaenterprizes]

A floating reamer holder solves many problems.

[Four Fingers of Death]

I found the US Army shop manuals on the net once, great stuff, lost them when the computer got fried.

[andremajic]

Thanks for the tips willbird. I will try the indicator and center trick next setup!

Next best thing I was able to do was insert the reamer and turn the barrel slowly, using the reamer body to indicate off of. (The indicator didn't move from zero)

Since I don't remove the barrel since the initial setup, the threads are perfectly concentric with the chamber.

From everything I've read in books and on the web, there certainly is more than one way to skin a cat. :D

[JIMinPHX]

Whatever you do, stay away from the videos that are put out by AGI. The guys that "teach" "gunsmithing" in those videos don't know the first thing about proper machining methods. They give bad information & they do hack work as they demonstrate "what you should do". The way that they undersize the PD on a single pointed thread on a brand new barrel just about made me sick. Those guys ruin a lot of nice gun parts when they "teach you how to accurize".

[PatMarlin]

PD- point dimension?

I don't speak all the fancy lingo.. .:\

[Bulldogger]

Well done. Always like to see folks pull off chambering and threading.

When did you get the blanks from GPC and if you don't mind saying how much? Any more left, etc., etc.?

Bulldogger

[JIMinPHX]

PD- point dimension?

I don't speak all the fancy lingo.. .:\


PD = pitch diameter, also called "E" sometimes. It's the diameter at which the threads are measured for proper clearance to qualify for a particular class of fit (e.g. class 3a). Normally you either measure over wires of a specified diameter for a given pitch, like I do, or else you use a thread mic, like Andy did. Either way works.

[nanuk]

Now for the setup trick...once you get the barrel in place, and threaded..take a hose clamp, and clamp your test indicator to the threaded stub,put a dead center in the tailstock, then move your tailstock up close enough to touch the indicator needle to the angle on the dead center, tighten the tailstock down...then rotate the barrel so the indicator needle is indicating the dead center in the tailstock. Get the runout down to .000..what you find may may make your jaw drop.

Bill


Just a question Bill, I have read where some lathe's tailstocks actually come in a bit high, not true centered to the headstock. (to allow for wear??) I believe I have read this on "Practical Machinist" site.

anyways, if this difference could be measured, I assume it could be added/subtracted to the indicator reading to ensure a true bore?

[JIMinPHX]

It's been my experience that the tailstock on every lathe is a little different. Also, you sometimes need to indicate them & tap them in to center if you are doing precision work. They often have front to back adjustments on them, but seldom have up & down adjustments on them. Each lathe is a little different though. I have recut & shimmed tailstock housings before to bring them back to where they need to be. A little rust under them or a little swarf on the bed will cause them to rise a little sometimes.

[jim147]

I'm confused on your tpi. I understand you had problems with the lathe setup to start. I've had things not work out right myself.

Was this a Rem 700? What tpi did you wind up with on the barrel?

20 was the wrong lever, I get that. But I saw 4 and 8 listed. Isn't a 700 16 tpi?

I mean no offense and think I'm missing something. I would just like to learn a little more about barrels.

jim

[andremajic]

I'm confused on your tpi. I understand you had problems with the lathe setup to start. I've had things not work out right myself.

Was this a Rem 700? What tpi did you wind up with on the barrel?
Once I was finished, it was 16 TPI. It started out at 20 TPI because I was using the power feed lever instead of the half-nut.

20 was the wrong lever, I get that. But I saw 4 and 8 listed. Isn't a 700 16 tpi? I tend to write a bunch of stuff that might be irrelevant to the post, mainly for my own info to reference later. 4 and 8 were the lowest settings that I could go while using the power feed and 20 TPI was the lowest result I was getting. (Hope that makes sense.)

I mean no offense and think I'm missing something. I would just like to learn a little more about barrels.

I'm not offended by questions or even critisism. The correct setting that cut 16tpi with my particular lathes quick change gearbox turned out to be B-4, using the half-nut to engage the carraige. Once the thread depth was correct, I am able to now screw the action on with a slight amount of resistance. AAA thread fit!

jim

I hope what I wrote helps make sense.
Andy.

[jim147]

I got you now.

Thank you

jim

[MBTcustom]

Hey fellas, I'm just a machinist so I don't know a whole lot about gunsmithing:twisted: but I do know this: three wires is the most accurate way to measure threads, it does not make accurate threads. A thread is a way to fit two things together and as such its best to cut the threads to match the threads you are trying to mate, either inner or outer. This is how I thread a barrel. I could cut threads perfectly according to the wires, but depending on what some other yay-who (god knows where and god knows when) did, the threads may be loose or tight (loose is far more common). By custom cutting the threads to the action you can insure a perfect fit on even the most beat-up old military actions.
One other thing I will say is that a thread file is pretty cheap and it is very useful for creating accurate threads. So many times I have been sneaking up on the perfect PD and all of a sudden, my tool decides to bite the thread and then you have a real problem. The thread file does three things,
1 it cleans all the burs off the threads so you don't get false readings from the mating part when checking for fit.
2 it changes the finish on the surface so that your tool will remove a few ten-thousandths without riding and creating push-off that will bite you later. 3 when it gets down to the last couple ten-thousandths of an inch, you can polish that PD right in with the file.

[Cap'n Morgan]

As Goodsteel says, three wire measurement is the correct way to measure the pitch diameter of a thread. That said, there's no need to worry about the fit being a little too loose. A 60 or 55 degree thread is pretty much self-centering once the barrel is pulled tight. If anything, a loose fit may actually improve concentricity, and strength-wise it hardly matters at all.