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Before I do anything on my lathe that requires precision, I will install a center in the chuck, set my compound to 30 degrees and recut the center. I will then install the live center on a short quill, in the tail stock, and mount a pre-drilled, 30" bar on the centers. I will take a truing cut next to the chuck and set the feed wheel collar to zero. Then I will traverse the carriage to the far end of the bar nearest the tail stock, and with the feed wheel set to the same "zero" mark, take a cut. Using a micrometer that measures down to .0001, I will measure both cuts. If the turned "bosses" on each end of the bar do not measure "exactly" the same, then I will place a dial indicator against the bearing collar of the live center, and adjust the tail stock right or left and repeat the cutting process until they do. You can leave the dial indicator in place, unclamp and move the tail stock back and forth to verify that it will maintain it's zero, which on a good machine is does. With practice, the above alignment check can be done rather fast and it provides peace of mind when you're charging customers good money to wear your name on their firearms... | |||
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I have question on "spiders", Well more of comment really, based on many years of professional manufacturing expirience making everything from machine tools themselves through aerospace, automotive and gun parts. The jaws on most chucks of the size we (here in this board) use to make gun barrels have about 3" of bearing surface on the gripping part of the jaw. If you use a four jaw chuck and align the bore dead nuts; then put a spider on the back of the head sotck and align the bore dead nuts out there by adjusting the jack screws,(Remember that 3" of bearing surface acting on the barrel 18" away?), all the spider is doing is bending the barrel to make the center of the bore appear to line up. The chuck would have to have point contact on the barrel and not linear contact on the barrel. What the four jaw is doing is no different than if you were to machine a matching taper on the barrel that matched the Morse Taper in the spindle and stuck the barrel into the spindle taper; just like a dead center. There is no way that a spider is going to do anything other than bend the barrel, it can't overcome the linear clamping load imparted by the chuck to make a true straight line out of the bore. It is phyisically impossable. I know, I know, I have all (well most) of the books writen by all the "masters" too, most of them advocate the use of a spider. Hell I almost made one myself till I sat down and thought about why I have never seen a spider used in acctual industry to line up a bore. Unless you have a chuck with spherically ground jaws (perpendicular to the axis of the spindle centerline, giving point contact) the spider will do nothing but fight the chuck; and because the chuck has far more holding power than the spider, the barrel will bend. Now just slapping a barrel in a four jaw and indicating center isn't going to be the most accurate either. How do you know the bore is parrallel with the OD? You don't. The most accurate method is to place the barrel between centers, and create a known parrallel, and zero runout diameter, this known parrallel and runout free surface goes in the four jaw, then the chamber can be reamed. Now the use of a spider to control barrel whip and kill vibration; that is a totally different animal; not to be confused with axial alignment. Asbestos underwear is on, extigisher at he ready. Flame away all you want. Rusty's Action Works Montross VA. Action work for Cowboy Shooters & Manufacturer of Stylized Rigby rifle sights. http://i61.photobucket.com/alb.../th_isofrontleft.jpg | |||
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Rusty I use 2 spiders. One on each side of the headstock. I do this because I have a headstock that is too long for a 4 jaw and a spider. I agree with you on bending a barrel. I proved it to myself a long time ago. I think Pat B. suggested that I use soft copper or soft aluminum wire between the barrel and jaws or spider. It lets the barrel to pivot without bending it. For those that indicate on both ends of the headstock, after you are done put one of Dave Kiff's 4" rods with the appropiate bushing on it into the chamber end. Now set up 2 indicators 3" apart on your rod and check your reading. You will see how crooked the bore runs out. Rusty you can do the same and you will have runnout on the rod. Don't take my word, try it. Butch | |||
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One thing that seems to be missing in this discussion is the axial alignment of the spindle with the lathe ways. That's the first check to make. Then, if you are chambering off of the tailstock center. Does it have the same alignment with the spindle? Simply dialing in the chuck to the tailstock doesn't really tell you much. It does tell you that you are dead on at that particular point. What happens when you advance the tailstock quill? Is it still dialed in? Probably not to the kind of top level accuracy we are striving for. One other method that I have always questioned was pre-drilling, boring or reaming with a roughing reamer. That's all done to save the reamer, not produce the best chamber. I want the reamer to follow the bore not a hole that is hopefully aligned with the bore. It's false economy anyway. How much does a reamer cost? How many chambers can you ream with it? I've never counted exactly, but it's quite a few. Now, how much time to ream, bore or drill prior to engaging the finish reamer. It's not worth the time to do it, plus it setting up the finished chamber to be slightly off. Even if you do everything exactly right, the chamber isn't ever going to be exactly true. So you are only exaggerating the problem when you do it twice. Not trying to step on toes, but think about it. Roger Kehr Kehr Engraving Company (360)456-0831 | |||
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This is getting funny. A few months ago on this very forum a long discussion took place where guys (with lots of practical experience) were describing how they had chambered barrels using a drill press. Let’s get real for a moment and get out of the twilight theoretical world and back into the shop. Number one...there has never been a barrel made that had a “perfectly†straight bore. Neither has there ever been a lathe made that had “perfectly†concentric and square alignment and movement in all its parts. Now lets add in the fact that there has also never been a “perfectly†sized and concentric reamer or drill bit made. How often does everyone take their measuring and lay-out tools in and have them checked and calibrated for “perfect†accuracy? The damned ammunition that is going to go in these chambers that will propel a bullet down that bore is not “perfectly†sized and concentric. I’m all for striving for precision, but there comes a point when “close-enough’ is totally acceptable, and about as good as its gonna get. | |||
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You are correct. But there is an easy way around this. Obtain a spare set of jaws and weld a piece of flat bar stock to each jaw. Turn yourself a "collar" that you can place around the I.D. steps of the jaws. Open the jaws against the collar to remove the slack. Take a boring bar and recut the jaws making them true to the axis of the machine, and then apply the spider. Personally I prefer using these "soft" jaws with my roller bearing steady rest when threading and chambering rifle length barrels. It keeps things so uncomplicated.  | |||
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Rough and finishing with different tools is the norm in industry. Let the rougher take the abuse, get nicked, chipped what ever. Then the finish tool (which stays sharp and true much longer) comes in it cleans up the "mess" made by the rougher. Quite often when the finish tool is worn, it gets resharpeded into a rougher. This way you get alot of economy out of one purchase; you want to get every last nickle out of that reamer because your barrels are only about $55-75 bucks a peice completly finished. There isn't enough profit margin on them to waste time goig slow and easy with a finish tool to do the job complete. For custom guns where the cost of the barrel is several hundred dollars and there are relativly few chambers cut in any one caliber per year, you are absolutly correct about roughing being a false sence of economy. However when a company is making thousands of barrels a year the manufacturing technique has to be different. A rougher can run at twice the feed rate of the finisher. It is cut differently and breaks the chips up for better swarf clearing. So you pound out the chamber with a rougher, then tickle away the last .01-.02" with a finish tool. Its a matter of time/chamber. And most production barrels shoot fairly well. Granted they aren't BR ready, but 99% of shooters aren't BR accuracy freaks either. When you spend $500-700 for a factory mass produced gun you excpect a certain level accuracy. When you spend $2000-to-the-moon on a custom one-off gun you excpect a whole lot more. Malm, you are so close, but... haveing the chuck jaws clamp parrallel with the spindel center is only half the problem. Even if the jaws are parrallel how do you know if the bore is parrallel to the OD of the barrel. Notice I didn't say "runout". The bore can have runout and be parrallel to the C'line of the OD, or it can have ruout and be out of parrallel. Trueing the OD between centers cures these ills. If you true only one end and place it in a trued up four jaw, then support the other end in a steady then you are golden.  The accurace attainable is only limited by tooling and the machine; most of which is completly out of our controll.Rusty's Action Works Montross VA. Action work for Cowboy Shooters & Manufacturer of Stylized Rigby rifle sights. http://i61.photobucket.com/alb.../th_isofrontleft.jpg | |||
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Rick, Since you replied to my post I assume you meant that "it's funny". You are absolutely correct that it's never going to be perfect, but the more varibles that are removed the better the chamber will be. It's up to every gunsmith to decide when it's good enough and what method of chambering works best in each shop. To each his own. Roger Kehr Kehr Engraving Company (360)456-0831 | |||
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Rusty, Agreed! I don't work at the production level so I don't think in those terms. I also think that most customers are striving for a higher level of work than is being produced in factories. That's what I was referring to. If I can get 15-20 chamberings off of a reamer that's 8-10 bucks per job. I factor that into the cost of the job. BTW, I'm not denigrating anyone's methods. Just putting my .02 cents worth. Like I said, "To each his own". Roger Kehr Kehr Engraving Company (360)456-0831 | |||
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Roger, I'm not trying to be argumentitive but I can set up a barrel, thread it, drill the chamber to with .1 deep, run a boring bar in to true the hole and then chamber with the finishing reamer in short order... To rough drill and run in a boring bar takes 3-5 minutes I'd guess. Then, since there is little metal to be removed I can run the finish reamer in probably 15 minutes. Let me clarify, I am speaking of a ppc chamber right now, 1.5" long. I have chambered pretty much everything up to .375H&H. Of course the the mags take longer. Since my main interest is the ppc and being able to use a proven reamer as long as possible I try to take care of it.. At the moment my ppc reamer has chambered well over 100 barrels and is still going. BTW, when I indicate a barrel in I use a .0001 indicater with a long stem so I can indicate where the throat is going to be, after all, that is the first place the bullet makes contact. You can use a piece of heavy copper wire in your 4 jaw between the jaws and the barrel. Then the barrel will pivit when inidcating the muzzle end.. Many ways to skin this kitty. | |||
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This is a valuable discussion. I plan to save this thread for when I'm able to start doing my own machine work. Thanks for all the posts...................DJ ....Remember that this is all supposed to be for fun!.................. | |||
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Pat, I'm not trying to stir the pot either. I've not tried to set up to drill and bore prior to finish reaming. It just seemed to be counter intuitive to me to do the extra work. It also seems that every operation detracts from the final goal of a concentric chamber. Perhaps I am living in a theoretical world, but why add variables to the setup? Roger Kehr Kehr Engraving Company (360)456-0831 | |||
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Rick, I have to agree with you on your last post. Things are getting a little sticky when the runout between the lathe ways and the spindle axis is taken into consideration. Soon someone will bring up keeping the shop at a constant temp. to compensate for expansion of material. You are certainly correct in your enough is enough theory. I have made up a set of alum. soft jaws to hold barrels, run a boring bar down them a thou. or two under the diameter of your barrel and your home free. Bob | |||
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And don’t forget to only chamber when Jupiter is aligned with Mars, and your juju is in the seventh house...or something like that! | |||
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Rick, you are correct, most of the stuff we (in industry too) worry about doesn't amount to enough error to be conserned about. Two of the most accurate rifles I have ever shot were both chambered on a Bridgeport mill. The guy hangs the barrels off the back side of the table in a v-block and then trams in the bore by using a location fit pin in the bore. He trams it high on the pin (about 2" off the barrel) and then right at the enterance. If the indicator readings are different he shims the v-bloc (8X8 squre x 1.5 thk with the V running along the 1.5") till the readings are the same. All the chips and cutting oil run out the barrel and into a bucket. Very little fuss and zero mess. Best of all it works great. So to hear of people using a drill press... yup a ridgid press with a floating holder and rugged fixture should work just fine. The only reason I got involved in this post was the comment on using a four jaw and a spider set off my  alarm. Too many years making parts in industry I guess.Rusty's Action Works Montross VA. Action work for Cowboy Shooters & Manufacturer of Stylized Rigby rifle sights. http://i61.photobucket.com/alb.../th_isofrontleft.jpg | |||
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Rusty, Mark Stratton shows a neat set up to replace using a spider in his book. He turns and fits a piece of delrin to fit his spindle taper and bores it to fit the barrel and uses that to support the barrel sticking out of the back of the head stock. | |||
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Wow! I'm a little taken aback. Gotta start making fun when others don't slop the work together the way you do, huh! Well, flame away! Roger Kehr Kehr Engraving Company (360)456-0831 | |||
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That's what a spider is supposed to do, control whip and vibration. In every tool room I've been in we used a strip of cardboard box and/or duct tape to build up the diameter of a long rod. The built up section works just like Mr. Stratton's peice of delrin. Just alot less high tech. My bitch was with another gentelman's use of a spider to jack the barrel around till the bore ran true on the back side of the head stock. Scrollcutter, if your post was directed at me, So be it. The guy's setup is incorrect. If somebody doesn't make it clear that useing a spider to fight the chuck is wrong he will just keep doing it and never know any better. There are half a dozen or more very accurate and fantastic methods to chamber a barrel. They are all in this thread. TRUST ME, I have made my fair share of embarrasing total F*&K up's, I am not God's gift to machinist's, and I am constantly learning new and better ways of doing things. Rusty's Action Works Montross VA. Action work for Cowboy Shooters & Manufacturer of Stylized Rigby rifle sights. http://i61.photobucket.com/alb.../th_isofrontleft.jpg | |||
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Rusty, with the soft jaws that I have made up I can dial in the chamber end loosley and then indicate the muzzle end with a spider, go back and make sure the chamber end is still O.K. and tighten the chuck. There is a guy at a club I belong to in Mass. that chambered both ends of a streight profile barrel. One end was 30x47 the other 30BR. gotta clean the opposite chamber a lot but it shot and not too bad. Bob | |||
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But you're not fighting the chuck. You are working with it. Totally different. Rusty's Action Works Montross VA. Action work for Cowboy Shooters & Manufacturer of Stylized Rigby rifle sights. http://i61.photobucket.com/alb.../th_isofrontleft.jpg | |||
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Rusty, My post is absolutely not directed at you. I haven't read anything you have posted that has tried to denigrate my methods. Hell, I even agree with you. I jost don't like people denigrating me or slighting my methods. I also don't like speculating about things and when I suggest that people might think about checking to see if the spindle is on the money a couple of wise asses start in with the flames. I shouldn't let it bother me. I'm sure any potential customers reading this thread are going to be chomping the bit at sending their new Kreiger off to somebody that wants to just slap it on the receiver and collect their check. Roger Kehr Kehr Engraving Company (360)456-0831 | |||
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There seem to be quite a few "My method is the best and all others are inferior" posts in this thread. I think (I'm not sure, though) that a finished chamber can have a zero TIR and still be oversize. So nothing is really gained by indicating a finished chamber. Measure chamber diameter with pin gages. IMO (read OPINION) the best way to check the finished chamber alignment is to put the reamer in the hole and indicate the tail end of the reamer for indicator movement. If you are within a thou or so, you have a very straight chamber. How you got it is not as important as the result. So there........ | |||
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LOL you know better than that and so do I. I love posts like this one, there are so many ways of doing a job that return the desired results. The accumlated knowledge that gets shared on this entire web site is phenominal. Take B beyers post above. If sombody suggested cutting a muzzle crown that has the characteristics of a chamber, I'd be the fist one to raise my eybrows (real high too). But hey, apparently it works; gives the added benni of being able to thread a compensator on to protect the threads too. Throws a big o'l mud pie at the 11 degree crown doesn't it?  Rusty's Action Works Montross VA. Action work for Cowboy Shooters & Manufacturer of Stylized Rigby rifle sights. http://i61.photobucket.com/alb.../th_isofrontleft.jpg | |||
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Roger, I hope that you don't think that anything that I said was a put down of you or anyone else. Obviously the way that anyone does something is the way it should be done in their mind, they would not do it that way if that were not the case. In a way you are probebly right in regards to the center line of the headstock spildle varying in relation to the c/l of the tailstock, and that is the reason that I always chamber with my tailstock locked at a particular spot on the ways that I have determined that the two do line up. I think in a lathe with very little wear on the ways that would not be necessary, but that is not the case with my machine. Bob | |||
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Hay guys this is a great thread. Everyone is happy with their setup or they would do it differently. One example impressed me the most but bits and pieces from the different post leave something to think about. I will be chambering a barrel in about 2 weeks. Thanks for all the good information. bglenn | |||
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Do it the way that you are happy with or every time you throw a shot you will be blaming it on the way you chambered the barrel. Bob | |||
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