What I have Recently Learned About Chambering

[INTJ]

So far I like my simple 4-Jaw at home with aluminum shims. It holds well, gimbals well, dials well; but the potential downside is uneven force on the jaws. Then again, if x amount of pressure is applied to one jaw, the barrel is pushed into the opposing jaw and the force on the opposing jaw is similar.

At work I like the inboard spider. I found that the flat tip brass tipped screws on 1/8" aluminum shims hold better than the ball bearing tipped screws. It also dials well and gimbals well. It has the same potential issue of uneven pressure on each screw, which really doesn't seem to be much of a problem. Then again I do try to keep forces even.

Maybe the ultimate is a six-jaw chuck with a six-bolt spider......

 

[Dusty Stevens]

So far I like my simple 4-Jaw at home with aluminum shims. It holds well, gimbals well, dials well; but the potential downside is uneven force on the jaws. Then again, if x amount of pressure is applied to one jaw, the barrel is pushed into the opposing jaw and the force on the opposing jaw is similar.

At work I like the inboard spider. I found that the flat tip brass tipped screws on 1/8" aluminum shims hold better than the ball bearing tipped screws. It also dials well and gimbals well. It has the same potential issue of uneven pressure on each screw, which really doesn't seem to be much of a problem. Then again I do try to keep forces even.

Maybe the ultimate is a six-jaw chuck with a six-bolt spider......

4 bolt spider is fine. The chuck has 4 adjustments as well

 

[tobnpr]

Maybe the ultimate is a six-jaw chuck with a six-bolt spider......

We have a masochist amongst us

 

[BoydAllen]

Although I do not have a lathe I have followed posts on chambering closely for many years, and I have had numerous conversations with top gunsmiths, who do not all follow the same procedures. This is the inboard spider design that I think has the most merit, but if anyone has a different opinion I would like to hear it and know why. Looking at the number of parts that have to be dealt with, I came up with the idea of drilling the tips of the screws and epoxying in strong magnets so that they are just short of the bearing balls. A friend did this and reports that it works well. The magnets are rod shaped.

 

[DaveTooley]

I'm willing to give it a shot. I'd like to use it because it's a much more well balanced chuck on top of everything else. I find the adjust-tru part a bit annoying to fine tune but I probably just need some muscle memory for it.



In my head this looks like a great way to gimbal the barrel. Don't have the tools to get those brass inserts in the jaws though.

View attachment 1360251

Just a suggestion. Get a set of soft jaws and use your imagination. Or better yet get a 3 jaw set tru and a set of soft jaws.

 

[DaveTooley]

We have a masochist amongst us

My head hurts just thinking about that. I know a 6 screw spider for the 3 groove barrels.

 

[shortgrass]

Just a suggestion. Get a set of soft jaws and use your imagination. Or better yet get a 3 jaw set tru and a set of soft jaws.

Too simple!

 

[tobnpr]

I came up with the idea of drilling the tips of the screws and epoxying in strong magnets so that they are just short of the bearing balls. A friend did this and reports that it works well. The magnets are rod shaped.

Not following (?)...
Looks about identical to mine, drilled out the brass spider screw tips with 1/4" ball end mill and epoxied ball bearings into the recesses, which ride in identical recesses in the v-blocks. Magnets wouldn't do me any good as my blocks are aluminum, but I'm not seeing where they're located?

 

[WSnyder]

Not following (?)...
Looks about identical to mine, drilled out the brass spider screw tips with 1/4" ball end mill and epoxied ball bearings into the recesses, which ride in identical recesses in the v-blocks. Magnets wouldn't do me any good as my blocks are aluminum, but I'm not seeing where they're located?

If I read it right and think about it, the only way it would work is they did it opposite from most. I would guess the aluminum blocks have the balls permanently attached to them and the set screw has rod type magnets run in deeper than the circular mating surface machined into the ends of them that mate with the balls???

I suppose you could also add small disk type magnets to the blocks sunk slightly deeper than the ball mating surface to do the same thing if the balls are attached to the set screws.

 

[BoydAllen]

If I read it right and think about it, the only way it would work is they did it opposite from most. I would guess the aluminum blocks have the balls permanently attached to them and the set screw has rod type magnets run in deeper than the circular mating surface machined into the ends of them that mate with the balls???

I suppose you could also add small disk type magnets to the blocks sunk slightly deeper than the ball mating surface to do the same thing if the balls are attached to the set screws.

The balls are not glued to anything.

 

[WSnyder]

The balls are not glued to anything.

So the magnets just hold the balls on the set screws and you still slip the blocks in by hand? If so then it’s not really functionally different than gluing the balls to the set screws correct?

 

[BoydAllen]

So the magnets just hold the balls on the set screws and you still slip the blocks in by hand? If so then it’s not really functionally different than gluing the balls to the set screws correct?

That would be a guess on my part. If it works it works. I guess that my main point is that the overall design is the best that I have seen, however you handle the details.

 

[LVLAaron]

I tried the 6 jaw today. Meh. Real pain in the ass to get centered up vs the 4 jaw. The small set screws and tight fit of the chuck to the set tru back plate is super annoying to move around for a barrel thats out a couple thou...

 

[LVLAaron]

That's my setup. The inserts are rounded so the barrel gimbals easily enough. I get things aligned and then loosen the jaws a tiny bit to relieve any binding that happened and re-adjust. Quick enough for the girls I go out with.

Btw, I'd like to thank Defiance to having brought enough thread engagement for the whole classroom.

 

[tobnpr]

The small set screws and tight fit of the chuck to the set tru back plate is super annoying to move around for a barrel thats out a couple thou...

Exactly my take.
You need to loosen the opposite axis screws, just to move the two you're working on. I know many use them, but I've found it to be more difficult, not easier.

 

[Dusty Stevens]

That's my setup. The inserts are rounded so the barrel gimbals easily enough. I get things aligned and then loosen the jaws a tiny bit to relieve any binding that happened and re-adjust. Quick enough for the girls I go out with.

Btw, I'd like to thank Defiance to having brought enough thread engagement for the whole classroom.

View attachment 1360931

That tenon is rediculous

 

[LVLAaron]

I refused to thread the whole thing just out of spite and hate.

 

[Dusty Stevens]

I refused to thread the whole thing just out of spite and hate.

You could take a break when you start each pass. I have an old dga with about a 3” long thread maybe 4”

 

[Alex Wheeler]

That's my setup. The inserts are rounded so the barrel gimbals easily enough. I get things aligned and then loosen the jaws a tiny bit to relieve any binding that happened and re-adjust. Quick enough for the girls I go out with.

Btw, I'd like to thank Defiance to having brought enough thread engagement for the whole classroom.

That setup will always bind. I will explain. As the the barrel pivots, the contact point changes. They are no longer straight across from each other. Even with the radius on the pads the contact points move off center and naturally want to straighten the barrel again. I dont like the ring but since the radius is smaller it will bind less. I hope you can picture what I am saying. I am not cutting down methods. I am just sharing what I have learned and hopefully its not taken the wrong way.

 

[Walt Krafft]

I tried the 6 jaw today. Meh. Real pain in the ass to get centered up vs the 4 jaw. The small set screws and tight fit of the chuck to the set tru back plate is super annoying to move around for a barrel thats out a couple thou...

I slightly loosen the 3 bolts that hold the chuck to the backplate leaving them just snug. I then indicate in. When I like it, I will tighten the bolts again. Another spin of the chuck to confirm it didn't move and I am done. I was getting some movement while machining the tenon if I didn't tighten the mounting bolts. Doesn't take much time at all and I leave the wrench on the way under the chuck so I know it is still loose.