butchlambert
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rbertelatto, I agree.
Butch
Butch
Chamber Runout?
- Thread starter Bob3700
- Start date
WOW! I must be some kind of a legacy!.........
Like all gunsmiths......You mix a bit of machining knowledge, a bit of math, a bit of practical experience and then you just build a bunch of rifles and a theme develops over time.........This technic or setup works and this other one, not so good.....But we love to experiment and try different things. That's why we've been on this and other forums for the past ten or twelve years.
But rifle building is really quite understandable......all it is is a series of concentric circles........if we could get than darn hole in the barrel straight, our lives would be so much easier!
Like all gunsmiths......You mix a bit of machining knowledge, a bit of math, a bit of practical experience and then you just build a bunch of rifles and a theme develops over time.........This technic or setup works and this other one, not so good.....But we love to experiment and try different things. That's why we've been on this and other forums for the past ten or twelve years.
But rifle building is really quite understandable......all it is is a series of concentric circles........if we could get than darn hole in the barrel straight, our lives would be so much easier!
rbertalotto,
There are not many people who know something useful, know how to communicate it, are willing to communicate, and are right there when you want them.
I always figured you were financially well off, because you were unafraid to give away gunsmithing secrets.
After you explained how to do it, my brother has done 10 chamberings and I have done 17. And we are still going.
We have only made 3 lathe spiders based on the photo you took for me, and all have 4 screws, not 3.
There are not many people who know something useful, know how to communicate it, are willing to communicate, and are right there when you want them.
I always figured you were financially well off, because you were unafraid to give away gunsmithing secrets.
After you explained how to do it, my brother has done 10 chamberings and I have done 17. And we are still going.
We have only made 3 lathe spiders based on the photo you took for me, and all have 4 screws, not 3.
I WISH!
I don't do gunsmithing for a living. Only my own guns and I also make prototype parts for motorcycles. All as a hobby. My real job is a Real Estate executive for a chain of retail stores........go figure!
I have no reason not to share anything I might have picked up along the way.
Level 1) There is an independent jawed big chuck on the right side of the headstock and on the left is another small chuck, called a spider. Both ends are dialed in with a test indicator, locating on the grooves or the lands.
Level 2) If the bore is dialed in on both ends, the barrel may be bending to conform with the big chuck jaw edges not being parallel to the lathe axis.
To compensate for this, the big chuck jaws bite through a piece of Copper wire wrapped the barrel, the barrel can make a gimbal like movement to point at the dialed in spider, without flexing the barrel. Again, both ends are dialed in with a test indicator, locating on the grooves or the lands.
Level 3) If the bore is already bent, then just the gimbal does not assure that the throat is concentric and parallel to the lathe axis just by dialing in both ends. This can be compensated by dialing in over a length of spud protruding from the bore near where the chamber will be cut. The spider is then adjusted, not to dial in, but to change the angle the barrel as it sits in the gimbal so that the spud is concentric with the lathe over some length, in order to compensate for a bent barrel.
Level 2) If the bore is dialed in on both ends, the barrel may be bending to conform with the big chuck jaw edges not being parallel to the lathe axis.
To compensate for this, the big chuck jaws bite through a piece of Copper wire wrapped the barrel, the barrel can make a gimbal like movement to point at the dialed in spider, without flexing the barrel. Again, both ends are dialed in with a test indicator, locating on the grooves or the lands.
Level 3) If the bore is already bent, then just the gimbal does not assure that the throat is concentric and parallel to the lathe axis just by dialing in both ends. This can be compensated by dialing in over a length of spud protruding from the bore near where the chamber will be cut. The spider is then adjusted, not to dial in, but to change the angle the barrel as it sits in the gimbal so that the spud is concentric with the lathe over some length, in order to compensate for a bent barrel.
butchlambert
Site $$ Sponsor
alanfuge, now how will a boring bar cut a cam shaped hole? Is the cross slide going in and out as it is boring the hole? As I said to Rustystud early on, you can bore it out of concentricity with the bore, but how can you induce a out of round bored hole? Oversize maybe.
Butch
Butch
Butch,
Getting away from the original runout post and I hate to do this but you CAN cut an elliptical hole with a boring bar without moving the xx or yy. You can also cut one with an end mill. It can happren only when the operator is a screw up and the head is not in tram on a vertical. This will happen when he raises the knee up and down and leaves the quill locked. It'll will happen when the operator is generally new . If the head is in perfect tram, this will not happen. Yes, I pulled my hair out trying to find out how this happened to one of my students in a modelmaker's course. Now I teach them how to tram the head correctly. He trammed using a square and it had burrs under it. Iv'e been through it and share this fiasco with all. LOL
John
Getting away from the original runout post and I hate to do this but you CAN cut an elliptical hole with a boring bar without moving the xx or yy. You can also cut one with an end mill. It can happren only when the operator is a screw up and the head is not in tram on a vertical. This will happen when he raises the knee up and down and leaves the quill locked. It'll will happen when the operator is generally new . If the head is in perfect tram, this will not happen. Yes, I pulled my hair out trying to find out how this happened to one of my students in a modelmaker's course. Now I teach them how to tram the head correctly. He trammed using a square and it had burrs under it. Iv'e been through it and share this fiasco with all. LOL
John
butchlambert
Site $$ Sponsor
John,
My lathe doesn't have a quill or a knee.
Butch
My lathe doesn't have a quill or a knee.
Butch
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