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bea175
Guest
Which do you guys prefer for barrel crowning three jaw and steady rest or four jaw from the Head Stock? What is the best setup for a 11 degree crown?
JerrySharrett
Senile Member
If you are doing a straight crown, and want it close use a 3-jaw, if you want it right use a 4-jaw.
If you are doing an 11-degree, you must use a 4-jaw and indicate it to within about 0.0002" or better or really screw it up.
If you are doing an 11-degree, you must use a 4-jaw and indicate it to within about 0.0002" or better or really screw it up.
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wnroscoe
Guest
Use a Four Jaw Chuck for all Barrel & Receiver work. Use a Three Jaw for Non-Precision Work.
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Dennis Sorensen
Guest
It would depend on how accurate your 3 jar chuck is and how concentric the bore of the barrel is with the diameter.
If you are cutting an angle you should be centered or extremely close to being centered on the bore or it may look wonky.
I know the majority of precision gunsmithing gets carried to extremes, whether it always pays off in accuracy is not known. I think this is because we want to eliminate any possible detriment whether it is a theory or fact.
I don't think the accuracy difference (if any) can be measured between a barrel that is crowned with the bore off center by 5 thou over one where the bore is centered dead on... but dead on eliminates the chance there is a difference.
.
If you are cutting an angle you should be centered or extremely close to being centered on the bore or it may look wonky.
I know the majority of precision gunsmithing gets carried to extremes, whether it always pays off in accuracy is not known. I think this is because we want to eliminate any possible detriment whether it is a theory or fact.
I don't think the accuracy difference (if any) can be measured between a barrel that is crowned with the bore off center by 5 thou over one where the bore is centered dead on... but dead on eliminates the chance there is a difference.
.
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jGEE
Guest
4 jaw! 
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bea175
Guest
I use the four jaw and was just wondering what everyone else was using.
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coopshooter
Guest
wellllllllllllll kids
been doing machining for 30 odd years and yes 4 jaw is more accurate most the time but if you invest time into a set of soft jaws for your three jaw chucks then bore to desired size and these are the most accurate foe normal use they arent the best for hogging cuts but for bug nuts accuracy its only way to go
been doing machining for 30 odd years and yes 4 jaw is more accurate most the time but if you invest time into a set of soft jaws for your three jaw chucks then bore to desired size and these are the most accurate foe normal use they arent the best for hogging cuts but for bug nuts accuracy its only way to go
Butch Lambert
Active member
Coopshooter, Have you indicated the bore after chucking with your 3jaw with bored softjaws?
Butch
Butch
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Big Al
Guest
It only matters if you are using the chuck to hold the end of the barrel to crown. Then I use my three jaw, the TIR on my chuck is .0003 and repeats to .0003. Most of the time I crown off of the steady and the chuck doesn't mean squat.
Butch Lambert
Active member
Al,
It does matter to me. How many people turn the OD of the barrel on both ends to be concentric or coaxial to the bore?
Butch
It does matter to me. How many people turn the OD of the barrel on both ends to be concentric or coaxial to the bore?
Butch
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wnroscoe
Guest
I quess I missed something along the way. I thought the bullet had to enter the throat straight and leave the muzzle straight. If your gonna crown in a three jaw you might as well chamber in a steady rest after you set it up between centers.
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NesikaChad
Guest
If given my choice in the matter.
Set the machine up for 5-C collets in a spindle chuck that is able to be indicated. These aren't real cheap, but they do exist.
Make a set of rings out of soft iron wire so that the barrel is basically "gimbled" int he collet.
Support the rear end through the bore using a spider.
Indicate and then go for it. I'd do the same minus the ring for threading/chambering. The advantage being lots of surface contact to mitigate tools "singing" to you while working. (chatter)
That's how I wanna do it when I'm set up.
Set the machine up for 5-C collets in a spindle chuck that is able to be indicated. These aren't real cheap, but they do exist.
Make a set of rings out of soft iron wire so that the barrel is basically "gimbled" int he collet.
Support the rear end through the bore using a spider.
Indicate and then go for it. I'd do the same minus the ring for threading/chambering. The advantage being lots of surface contact to mitigate tools "singing" to you while working. (chatter)
That's how I wanna do it when I'm set up.
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Bnhpr
Guest
Coopshooter,
The hardest part after so many years as a machinist is when you realize you don't know everything about gunsmithing....or the science of the barrel.
I thought I knew something about running a lathe a few years ago too.
what Butch is trying to tell you is that the bore of a barrel is rarely in the center of the barrel, so soft jaws are USELESS in indicating the bore.
Some people believe that a flat crown is the best way to crown a bbl, but I now chamfer the crown slighly, so it must be indicated very accurately at the muzzle edge....I believe this to be true....who knows.
Ben
The hardest part after so many years as a machinist is when you realize you don't know everything about gunsmithing....or the science of the barrel.
I thought I knew something about running a lathe a few years ago too.
what Butch is trying to tell you is that the bore of a barrel is rarely in the center of the barrel, so soft jaws are USELESS in indicating the bore.
Some people believe that a flat crown is the best way to crown a bbl, but I now chamfer the crown slighly, so it must be indicated very accurately at the muzzle edge....I believe this to be true....who knows.
Ben
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jackie schmidt
New member
Chucks
The best is to get a set true 3-jaw, commonly called a "Buck Chuck". As a Machinist, I believe the man that came up with this concept deserves a special place in Heaven.
On our Pratt & Whitney, which I do all of my Rifle work on, the 3-jaw buck chuck has not been off of it in years. That is how versitile it is.
We also have a 4 jaw independent, and a 6 jaw set true, (very expensive). Never use them.........jackie
The best is to get a set true 3-jaw, commonly called a "Buck Chuck". As a Machinist, I believe the man that came up with this concept deserves a special place in Heaven.
On our Pratt & Whitney, which I do all of my Rifle work on, the 3-jaw buck chuck has not been off of it in years. That is how versitile it is.
We also have a 4 jaw independent, and a 6 jaw set true, (very expensive). Never use them.........jackie
varminthunter1
Club Coordinator
Barrel Crowning
Jeff
Jackie, I believe you and a few others who post here regularly, really deserve a special place in Heaven. Thank you all for the great advice you give for all to see. Some of us want to be better than just good enough! We strive to produce benchrest quality. Posts like these are a great place to go to school.
Jeff
JUST to elaborate for those who don't know what a "Buck Chuck" is....... note that it's NOT just a "very precise three-jaw" but instead a 3-jaw that's FAST but can be dialed in like a 4-jaw.
Precision of the 3-jaw is not the issue, it's meaningless for crowning.
Crowning without indicating the bore for both center and perpendicularity is hack-work IMO.
FIVE THOUSANDTH'S Dennis??? C'mon. I can do better than that by eyeball, watching the bore lope. I recently crowned a factory gun by indexing with the initial cut in the grooves and can guarantee you that it was within a half thou. Painfully slow to index using the tool bit but certainly accurate.
Buck Chuck
http://www.buckchuckusa.com/userfiles/How to Mount and Operate(2).pdf
hth
al
Precision of the 3-jaw is not the issue, it's meaningless for crowning.
Crowning without indicating the bore for both center and perpendicularity is hack-work IMO.
FIVE THOUSANDTH'S Dennis??? C'mon. I can do better than that by eyeball, watching the bore lope. I recently crowned a factory gun by indexing with the initial cut in the grooves and can guarantee you that it was within a half thou. Painfully slow to index using the tool bit but certainly accurate.
Buck Chuck
http://www.buckchuckusa.com/userfiles/How to Mount and Operate(2).pdf
hth
al
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Dennis Sorensen
Guest
Al
I wasn't suggesting you try to get it 5 thou off...
I said, "I don't think the accuracy difference (if any) can be measured between a barrel that is crowned with the bore off center by 5 thou over one where the bore is centered dead on... but dead on eliminates the chance there is a difference."
try it and see...
Dennis
Hey, I just couldn't let FIVE THOU go! That's a LOT man...... kinda like using a crescent wrench for a caliper and measuring with a tape.... using "the little lines"....
And YES I still think there's a difference, a big difference. The lead in cut on a piece is never the same as the loaded cut, there's no freaking WAY you can get a consistent lead-in burr when you're flopping in and out 5 thou.... 90degrees or no.
just MY opinion...
But then I'm completely bugged to see sanding marks on my lands after having someone else do my crown too, even though most gunsmiths scoff at the idea... This is why I've settled on using Borden's Accuracy for stuff I can't do myself. You can SHAVE with Jim's crown cut.......
AND why I finally bought a lathe, tired of fighting it.
al
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coopshooter
Guest
if u turned the tennon
on center to the bore of barrel and u are lining barrel up straight and on center with a steady rest to cut off end and crown then its much easier and more accurate using a soft jaw set-up plus if as oft happens you need to put it back on to do some dang thing u overlooked the soft jaws will repeat time after time as long as u follow proper machine setup numbered jaws on a numbered chuck and same chuck alignment onto headstock
on center to the bore of barrel and u are lining barrel up straight and on center with a steady rest to cut off end and crown then its much easier and more accurate using a soft jaw set-up plus if as oft happens you need to put it back on to do some dang thing u overlooked the soft jaws will repeat time after time as long as u follow proper machine setup numbered jaws on a numbered chuck and same chuck alignment onto headstock
Butch Lambert
Active member
So you are going to grip a threaded tenon with soft jaws and it will be perfect??
Butch
Butch