Interesting Way to Hold Barrel in the Lathe

[tac284]

The bearing allows axial alignment and the combination independent/scroll chuck allows for radial. Must be using rear jacking bolts for adjustment of axial alignment...?

 

[tobnpr]

I don't see how that could work for someone like myself that usually, uses a Grizzly rod to dial in the chamber end.
With the barrel gimbaled in that bearing, one would need to loosen the chuck jaws- disturbing the location of the barrel there- in order to move the end of the barrel via the outboard spider. I just do not see that as being workable.

I need the barrel where held in the spindle spider to remain undisturbed while I adjust the outboard spider to move the ass end of the barrel.
Can't have both moving. The section of bore held by the inboard spider (the pivot point) can't be disturbed for the purpose of moving the end of the barrel two inches down.

 

[JasonT]

I understand everybody’s point about how it’s adjusted when it’s tight.

It’s a balancing act to be sure, but it’s not impossible if you grease the bearing surfaces beforehand. That way, you need to give it that last go around on the screws to really snug things up.

Yes I am definitely using an outboard spider.

I only bring this up out of interest - I’ve chambered barrels with copper pads, bearing rollers, fancy swiveling soft pads, and an angle/radial-adjustable collet chuck (the easiest by far, but I didn’t buy it, my previous work did to make extra precise submarine parts, I believe). I have never had any issue achieving the required accuracy/precision to achieve a 3/8-1/2moa rifle with any of the methods if the barrel wasn’t a complete banana to start with.

I think this method really shines for barrels that really ARE curved by more than .005-.01” over the length. I think less than that, and it probably doesn’t make much difference if you use a much more rigidly mounted setup, because a 30” barrel that’s curved by 5 thou is only curved by 0.00015”/inch length, so the angular misalignment in the first 2-3” is pretty small.

That said, I chambered a barrel with bearing rollers in my 4jaw for my Barnard rifle and it ran out by at least 0.03”, so I clocked it at 12 and it shoots 1/4 Moa all day long out to 400yd and 3/8-1/2 Moa out to 1000yd when shot from a machine sled.

So maybe it’s way less important how we hold the barrel than we all worry about, maybe I just got lucky, or maybe I’m doing them all in my sleep some other way that I can’t recall when I’m conscious.

I’m betting on a little of each #1 and #2.

 

[Walt Krafft]

Interesting, yes. Better, I am not convinced. Adding moving parts will reduce rigidity of the system. That generally reduces accuracy.

 

[matthias]

Always keep an ear to the ground. And don't be afraid of trying new things. We should resist being stuck in our ways, and should strive to try new things.

This exact method may not work as well for me as my current method, but I am going to try it. the reason is the more experience with different methods may one day lead to a truly new and better way to do things. This is the philosophy that propels humans forward. What can I say , stay curious.

 

[JasonT]

Always keep an ear to the ground. And don't be afraid of trying new things. We should resist being stuck in our ways, and should strive to try new things.

This exact method may not work as well for me as my current method, but I am going to try it. the reason is the more experience with different methods may one day lead to a truly new and better way to do things. This is the philosophy that propels humans forward. What can I say , stay curious.

I love that attitude and I’m always impressed by fellow makers and machinists.

I’ve toyed with the idea of making a spherical bearing with 3D geometry drive keys so that the grip on the barrel for rotation is independent of any clamping load. Kind of like a floating reamer holder but with a rigid bearing fit instead of full float. I’m thinking half round slots in the inner race with bearing balls attached to the outer race. That would give it a drive torque without limiting angular alignment.

Not sure if the idea will pan out into something useful on a larger scale, but I figured it would be worth a try.

 

[skeetlee]

id like to see a little less surface contact myself about half that width would be ideal. i like the concept though

 

[JasonT]

Here’s a quick 3D model I threw together. Note that some of the intricacies are not shown because they’re things like cutting slots for compression and pressuring bearing balls, etc...

Everything is shown as a solid.

 

[WayneShaw]

I usually use a copper wire and a 4 jaw, and spider of course. Regardless, whether you are using range rods or dialing in straight, I don't tighten down on either end, use finger tight pressure until you get it close, to allow the barrel to be stress free, then start snugging things up.

 

[JasonT]

I usually use a copper wire and a 4 jaw, and spider of course. Regardless, whether you are using range rods or dialing in straight, I don't tighten down on either end, use finger tight pressure until you get it close, to allow the barrel to be stress free, then start snugging things up.

So many ways to pet a cat.

 

[Dusty Stevens]

I don't see how that could work for someone like myself that usually, uses a Grizzly rod to dial in the chamber end.
With the barrel gimbaled in that bearing, one would need to loosen the chuck jaws- disturbing the location of the barrel there- in order to move the end of the barrel via the outboard spider. I just do not see that as being workable.

I need the barrel where held in the spindle spider to remain undisturbed while I adjust the outboard spider to move the ass end of the barrel.
Can't have both moving. The section of bore held by the inboard spider (the pivot point) can't be disturbed for the purpose of moving the end of the barrel two inches down.

Using a grizzly rod you have to move both ends. Think of his chuck as your outboard spider and his steady as your chuck. Its the same exact thing

 

[MGMIAM]

Isn't that like a Gimble bearing in the back of a boat outboard ?

 

[MGMIAM]

Gimbal, whoops

 

[JasonT]

Gimbal, whoops

I think it is basically the same.

 

[Bamban]

I thought about buying a TBAS until I visited Mike Bryant, I copied his methodology. These modified shaft collars will have to do for now. Waiting on Jason on what he comes up with up and willing to market them.

 

[butchlambert]

Jason, I understand what you are trying to say.

"I think this method really shines for barrels that really ARE curved by more than .005-.01” over the length. I think less than that, and it probably doesn’t make much difference if you use a much more rigidly mounted setup, because a 30” barrel that’s curved by 5 thou is only curved by 0.00015”/inch length, so the angular misalignment in the first 2-3” is pretty small."

I have never seen a curved bore, only a slight spiral or more on a few. Being a machinist, how could you machine a banana shaped bore. I'm not criticizing your setup though.

 

[JasonT]

Jason, I understand what you are trying to say.

"I think this method really shines for barrels that really ARE curved by more than .005-.01” over the length. I think less than that, and it probably doesn’t make much difference if you use a much more rigidly mounted setup, because a 30” barrel that’s curved by 5 thou is only curved by 0.00015”/inch length, so the angular misalignment in the first 2-3” is pretty small."

I have never seen a curved bore, only a slight spiral or more on a few. Being a machinist, how could you machine a banana shaped bore. I'm not criticizing your setup though.

Butch, I mean that even if the bore is central to the OD of the barrel, the barrel is rarely straight. More often than not, I see that the OD is not concentric to the bore itself, and the difference between the muzzle and breech ends is often not the same. I should probably have said, the bore is rarely concentric and coaxial with the OD of the barrel.

But I do think that the barrel bores tend to curve independent of the barrel OD. Otherwise, there would be no need to clock barrels to 12o’clock once the first few inches has been aligned with the spindle axis.

 

[butchlambert]

Butch, I mean that even if the bore is central to the OD of the barrel, the barrel is rarely straight. More often than not, I see that the OD is not concentric to the bore itself, and the difference between the muzzle and breech ends is often not the same. I should probably have said, the bore is rarely concentric and coaxial with the OD of the barrel.

But I do think that the barrel bores tend to curve independent of the barrel OD. Otherwise, there would be no need to clock barrels to 12o’clock once the first few inches has been aligned with the spindle axis.

I agree that the bore is very seldom straight and concentric with the OD. My point is the bore does not travel in a banana shape in the blank. It travels in a helix.
I think we are on the same plane though.

 

[Dusty Stevens]

But I do think that the barrel bores tend to curve independent of the barrel OD. Otherwise, there would be no need to clock barrels to 12o’clock once the first few inches has been aligned with the spindle axis.

This may be another one of those internet “must haves”

 

[Edd]

Does anyone use one of these?

https://www.straightshotgunsmithing.com/page25