Gunsmithing 4-Jaw vs. Spider on the Spindle

[Wannashootit]

I use a 4-jaw when chambering through the spindle, I'm thinking about changing to a spider.

"Pro's" would seem to be, closer to the spindle means shorter barrels no problem (vs. depth of chuck and backplate), plus being closer to the headstock always means less runout. Probably faster to indicate as well.

"Minus" would be concern of barrel slippage with small brass-tipped screws. Especially on the shank end with little or no taper, the 4-jaw is going to provide more surface area contact and clamping force. I always work "light" when it comes to barrels- especially when chambering in a steady- but I have concerns that facing/chambering forces could cause the barrel to slide to the rear using two spiders. When I chamber with a steady, I always put a shoulder on the muzzle end after truing it so it locks against the face of the chuck jaws and can't move, period. I plan to use 3/8" -24 screws, same as on the outboard spider.

I know a lot of you use a front spider, are my concerns unfounded?

 

[Danny1788]

I use a spider on the front, I took out the brass pads in the screws and machined the ends with a ball end mill, I use ball bearings and Steel feet so that the barrel will pivot and not bend. Once you lock those down tight it’s rock solid never had a barrel spin using this setup.

 

[Quickshot]

I’m running a TBAS now. But I started with spiders. Danny’s rig is the way to go. I don’t have a mill. So, I turned custom barrel collar bushings for the front spider. Never had one slip.

 

[Wannashootit]

^^^^
Now that's the shit right there...
I was trying to figure out a way to pin a pivoting "shoe" to a screw and somehow be able to index it to the spindle axis and gave up.

 

[Danny1788]

Dab of grease on the ball bearings keeps the pads on the Ball bearings

 

[Wannashootit]

^^^
Yep, guessed that was what you did there. Epoxy to hold the ball bearing ends on the screw tips?

I've got a threaded spindle, debating whether to machine a fixture just like the Grizzly one (wish I'd bought one for fifty bucks when they had them on closeout) and screw it to a backplate, or turn and (female) thread a round "pipe" type to screw right onto the spindle.

Thanks for the great idea.

 

[LRI]

Get a C16 indicatable collet chuck and be done with scroll chucks and spiders. Way safer and much, much more rigid.

 

[Danny1788]

Cheapest I could find a set tru 16c collet chuck was a TMX 6” 16c set tru chuck for $970.

I doubt hobby guys are gonna want to spend that much on the chuck, then a back plate and collets for it.

 

[Rubicon Precision]

Cheapest I could find a set tru 16c collet chuck was a TMX 6” 16c set tru chuck for $970.

I doubt hobby guys are gonna want to spend that much on the chuck, then a back plate and collets for it.

I use an adjustable 16C on the turning center for barrel work. I use a 6 jaw set-tru type chuck on the manual. The 6 jaw set-tru is way easier to dial in than an independent 4 jaw. You are not changing the pressure on the jaws when dialing it in.

 

[Danny1788]

I have a 6 jaw set tru chuck now, that’s all I use on my lathe now. Makes things so much faster. Hardly ever have to change chucks for different projects and then just put a copper ring on the barrel and slide it on for chambering.

 

[Quickshot]

This is lowest cost 16C chuck I found
https://www.smalltools.com/tmx-6-16c-tru-length-collet-chuck-plain-back-mount-3-862-0601p/

If you don’t have a way to gimble the chuck; your only gonna get the barrel bore close to the lathe bore center line. The spiders will allow you to match the bore center lines.

Cheers,

 

[Wannashootit]

Chad,
Ya lost me with collets for this application.
I've never used collets in an application where the stock (or barrel) is tapered.
How can correct grip in a collet be established here? Fine if working on a shank with no taper- but some do have taper (even slight) and certainly when flipped around to work the muzzle end.

I don't mind dropping coin on tooling (not a hobbyist-07- but keeping the 6 figure "day job" a few more years until I retire to do it full-time) when it makes sense.

 

[spitfire_er]

Find an aluminum plate and make your own. I made this one for a shorter barrel I had to do. Not finished in the photo with the screws, but it works great and never slipped a barrel in it. If you don't have a mill, you need a decent size drill press and holding fixtures to hold it straight.

I normally use a buck adjust tru with everything over 24" long with my lathe.

Last barrel I did was an AR 15 barrel in 20 tac. Whipped out the steady for that one.

 

[Wannashootit]

^^^
No rotary table on my mill.
I suppose I could blue up the plate, and scribe some lines that would be "close enough" as it doesn't need to be precise.

I have a 6-jaw Buck that I use for everything else, I'm just not inclined to want to fuck up the two-tenths runout it's dialed in at every time I want to chamber a barrel, and then have to dial it back in. Sounds like a lot more work to me that way.

 

[LRI]

Chad,
Ya lost me with collets for this application.
I've never used collets in an application where the stock (or barrel) is tapered.
How can correct grip in a collet be established here? Fine if working on a shank with no taper- but some do have taper (even slight) and certainly when flipped around to work the muzzle end.

I don't mind dropping coin on tooling (not a hobbyist-07- but keeping the 6 figure "day job" a few more years until I retire to do it full-time) when it makes sense.

First, don't overthink it.

If you can successfully machine a barrel with 4 little tangent points of contact, you can do the same thing with a collet. If the barrel is tapered and the collet isn't, the thing is basically behaving like a hula hoop in a cereal bowl. Tangent contact across the periphery.

I wondered the same thing 15 years ago till after I tried it. I haven't looked back since.

 

[Praeger]

First, don't overthink it.

If you can successfully machine a barrel with 4 little tangent points of contact, you can do the same thing with a collet. If the barrel is tapered and the collet isn't, the thing is basically behaving like a hula hoop in a cereal bowl. Tangent contact across the periphery.

I wondered the same thing 15 years ago till after I tried it. I haven't looked back since.

If a collet centers the barrel based on the OD, how would you adjust to center it to the bore (radially)? I've cut a few barrels using the 4 Jaw & Spider method (Gordy Gritters, et al . . . ) and am trying to picture your process indicating the radial and axial alignment. Any photos you saved from pre-CNC days you can share?

 

[LRI]

If a collet centers the barrel based on the OD, how would you adjust to center it to the bore (radially)? I've cut a few barrels using the 4 Jaw & Spider method (Gordy Gritters, et al . . . ) and am trying to picture your process indicating the radial and axial alignment. Any photos you saved from pre-CNC days you can share?

With an indicatable collet chuck. They aren't cheap, but they do exist.

 

[Praeger]

With an indicatable collet chuck. They aren't cheap, but they do exist.

Can you post a link to one - I've tried searching "indicatable collet chuck" without success.

 

[LRI]

Can you post a link to one - I've tried searching "indicatable collet chuck" without success.

Dunham makes one.

 

[coontz74]

LRI, could one of these be used in its place? Maybe in a 4 jaw or such to dial in as necessary? Just thinking outloud here??

 

[coontz74]

After looking further, it appears a 5c collet would not be big enough to do BR barrels thru but would it work for sporter contours?

 

[Wannashootit]

After looking further, it appears a 5c collet would not be big enough to do BR barrels thru but would it work for sporter contours?

Shars has a set-tru ER-40 collet chuck, and I have a set of ER40 collets, they're available up to 1-3/16"- which still isn't large enough.

You'd likely still have an issue with any contour at the chambering end unless you chuck it up with a lot of stickout, which defeats the whole purpose of the exercise IMO. Even sporter contours are going to be 1.20-1.25 at the breech cylinder.

For me, it's about getting the business end closer to the spindle and not have all the depth of a chuck setup. Otherwise no advantage gained over the 4 jaw.

 

[Danny1788]

Here’s the one I found that is a set tru style.

TMX 6" 16C Tru Length Collet Chuck Set Tru Mount 3-862-0605P-T965

TMX 6 16C Tru Length Collet Chuck Set Tru Mount 3-862-0605P-T965

www.smalltools.com

 

[Rprecision]

I use a spider on the front, I took out the brass pads in the screws and machined the ends with a ball end mill, I use ball bearings and Steel feet so that the barrel will pivot and not bend. Once you lock those down tight it’s rock solid never had a barrel spin using this setup.

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That's a pretty slick idea. It's been added to my to do list!

 

[spitfire_er]

^^^
No rotary table on my mill.
I suppose I could blue up the plate, and scribe some lines that would be "close enough" as it doesn't need to be precise.

I have a 6-jaw Buck that I use for everything else, I'm just not inclined to want to fuck up the two-tenths runout it's dialed in at every time I want to chamber a barrel, and then have to dial it back in. Sounds like a lot more work to me that way.

If you look closely you can see the scribe lines on mine. I was between milling machines when I made this. So a bunch of careful measuring, and my sturdy old 1951 delta 17" drill press got my holes drilled to within a thou in every direction. Could have whipped it out in half the time on a mill with a rotary table or super indexer though.

Only reason mine is a larger diameter is because that was the size of the back plate I used. Works well because all the cap head screws are recessed and I have about 2/3rd the hole depth that is threaded.

 

[Wannashootit]

In case anyone else wants to save some time...
Didn't know Grizzly made this fixture, for under $25 cheaper than my time to machine one.
Simple to slap it on a backplate.

Aluminum Spider Plate - 5" Diameter

Made specially for gunsmithing operations, particularly when chambering barrels, these spider plates are used so that shorter barrels can be chambered through the headstock of the lathe. The brass tipped screws prevent damage to the barrels and allow for fine adjustments very similar to a 4-jaw...

www.grizzly.com

I'm going to remove the brass tips, put in ball bearings/shoes per Danny1788 above.

 

[Danny1788]

In case anyone else wants to save some time...
Didn't know Grizzly made this fixture, for under $25 cheaper than my time to machine one.
Simple to slap it on a backplate.

Aluminum Spider Plate - 5" Diameter

Made specially for gunsmithing operations, particularly when chambering barrels, these spider plates are used so that shorter barrels can be chambered through the headstock of the lathe. The brass tipped screws prevent damage to the barrels and allow for fine adjustments very similar to a 4-jaw...

www.grizzly.com

I'm going to remove the brass tips, put in ball bearings/shoes per Danny1788 above.

That’s where I got mine from many years ago. Good price on those might want to grab two just in case.

 

[81STFACP]

Here is what I did back in 2015 with the Grizzly spider, bolted it to a faceplate. I used 3/8x16 unistruts nuts that straddle the slots on the faceplate

 

[Rubicon Precision]

Chad,
Ya lost me with collets for this application.
I've never used collets in an application where the stock (or barrel) is tapered.
How can correct grip in a collet be established here? Fine if working on a shank with no taper- but some do have taper (even slight) and certainly when flipped around to work the muzzle end.

I don't mind dropping coin on tooling (not a hobbyist-07- but keeping the 6 figure "day job" a few more years until I retire to do it full-time) when it makes sense.

I make diameter/taper specific collet “adapters” when working on the muzzle end. This really isn’t practical on a manual lathe. I still use a set-tru style 6J chuck/#4 solid copper wire when doing muzzle work on the manual machine (which is something I really try to avoid...)