hoz53
Gold $$ Contributor
Isn’t it hard to hold everything in place while tightening the spider screws with the other pieces
Chambering Through Headstock - Shims
- Thread starter GSPV
- Start date
Not really. I initially lightly hold the barrel with the outboard spider, then run a center with tailstock to hold the barrel up front, sliding the finger clamps and running the screws to the bearings is effortless. With the center holding one end of the barrel, while the outboard is holding the other end, the finger clamps are close enough to center the barrel like running your 4J to the same ring reference on the chuck to start.
hoz53
Gold $$ Contributor
Ok Thanks for that.
Cloudrepair
Silver $$ Contributor
I use a dab of grease and when needed some spring close tweezers.
butchlambert
Site $$ Sponsor
I understand a few chamber with the muzzle flopping on the outboard side. I did that a couple times and found it not to be any advantage.
To each is own.
Alex Wheeler
Site $$ Sponsor
I didnt say not to use a spider, just HOW it should be used. I like them but like you said they can be used in a way that will not produce the best possible job.
I can see how most of the clamping designs shown could introduce a bend in the barrel when used with a similar support at the opposite end of the headstock if the technique is poor. And I can see how the line between good and poor technique is so fine that the average though educated observer may not notice the difference.
What would change this would be if the chuck side clamp system employed a spherical bearing-like structure that would put the center of off-axis rotation at the bore centerline. As these designs are now each support's 'pivot' is at the outer surface of the block in contact with the barrel. As soon as the barrel is at an angle to the headstock those supports are effectively offset and then they become the fulcrum point and the stop.
I'm not saying to use a spherical bearing because for the application those have too much play in them, but a similar design with no play (slotted external "race"?) would eliminate the rear support's ability to bend the barrel since the point of rotation would be centered in the bore. Could still manage to get the barrel's bore at an angle relative to the headstock, but that should be a simple chore to dial out.
I think this design, once sorted out, wouldn't change anything except to reduce the total time involved in getting the barrel into the right place.
Just an idea that popped into my head and I doubt that I'm the first to think of it.
What would change this would be if the chuck side clamp system employed a spherical bearing-like structure that would put the center of off-axis rotation at the bore centerline. As these designs are now each support's 'pivot' is at the outer surface of the block in contact with the barrel. As soon as the barrel is at an angle to the headstock those supports are effectively offset and then they become the fulcrum point and the stop.
I'm not saying to use a spherical bearing because for the application those have too much play in them, but a similar design with no play (slotted external "race"?) would eliminate the rear support's ability to bend the barrel since the point of rotation would be centered in the bore. Could still manage to get the barrel's bore at an angle relative to the headstock, but that should be a simple chore to dial out.
I think this design, once sorted out, wouldn't change anything except to reduce the total time involved in getting the barrel into the right place.
Just an idea that popped into my head and I doubt that I'm the first to think of it.
My spider has brass tip screws. When I unsnug them barrel stays put until I loosen the chuck jaws.
I think I’m missing something. I use the spider and chuck jaws to dial a barrel in. When I’m on the far end of the range rod with test indicator I loosen spider screw acording to which way the barrel needs to go. Then once satisfied with concentricity at that end of range rod I move it to the breach side and do the same but with the chuck jaws. Back and forth until I have the rod concentric at both ends. For short barrels I use a jig similar to many posted on this thread. What is the difference if you use chuck jaws with brass rod for rotation and spider screws with rounded brass tips vs a jig with two sets of jacking screws? I’m not arguing or anything. Obviously I’m missing something.
GSPV
A failure to plan is a plan for failure.
The point about this whole thread is how you get the critical part of the bore running concentric with the spindle bore without flexing the barrel in the process.
There is a tad of not marring the surface Of the barrel, but the gist is the first paragraph.
Lots of ways to skin the cat.
There is a tad of not marring the surface Of the barrel, but the gist is the first paragraph.
Lots of ways to skin the cat.
. Obviously I’m missing something.[/QUOTE]
We just talking around each other. I like the idea of the round stock you use with your 4 jaw. I have a cathead on a backplate i use instead of a Chuck on my sb13 to do shorter barrels with a spider on the outboard end. Was really just thinking out loud how I could rig something to hold that round in my cathead instead of my brass tipped screws. Probably work the same. On my 4jaw i just bend about a third of a copper penny over the end of the jaws.
We just talking around each other. I like the idea of the round stock you use with your 4 jaw. I have a cathead on a backplate i use instead of a Chuck on my sb13 to do shorter barrels with a spider on the outboard end. Was really just thinking out loud how I could rig something to hold that round in my cathead instead of my brass tipped screws. Probably work the same. On my 4jaw i just bend about a third of a copper penny over the end of the jaws.
Alex Wheeler
Site $$ Sponsor
Stan, I think the biggest difference in opinion when it comes to chambering is whether or not having the section of bore in front of the chamber concentric to the chamber plays a role in accuracy or not.
this is friggin' brilliant!
I've got a rollaround full of different copper shims/rings/pennies/clips/tips/rollers and I'm constantly looking for a better system to follow the chuck jaws.
I've been latestly doing this
Altho this isn't completely typical since it's a MUZZLE not a chamber shank and it's on a carbon fiber blank so I added even more shimmage for dispersion..... but I've got 30-50 of those rings in all different sizes and they work OK
BUT..... like I said. A setup which follows the jaws id easier not to screw up.
Thank you for your idea!
(I could never bring myself to drive with a spider setup...... I use them as Alex describes, as a support for the outboard end AND, in my case for jacking the chuck end around. I build the entire rifle around that 1" section of the bore that the bullet sees......)
spitfire_er
Silver $$ Contributor
I've seen these being used by several people, and I don't knock anyone, but here's my honest question about this setup.
Wouldn't you need the back of the shim to be an "oval" slot which would allow shear forces of the barrel to move between the ball bearing and the shim when adjusting each individual screw, and straightening the barrel within the fixture. Otherwise I would think the shim would need to slide on the barrel, otherwise you are putting a shear force between the shim and the barrel.
I'm not oppose to trying this out, I've done it just about every other way, but that's my line of thinking. Am I missing something?
Last edited:
Cloudrepair
Silver $$ Contributor
With the type I showed in earlier post I came to with lots of experience with shims and holding stock in many ways. And looking for better answers.
If you try this kind you will see for yourself how well it works.
When the barrel is held in the spiders front and outboard they become the pivot points.
You don't want the shim to move on the barrel it can pivot at the balls in the shim all it needs to if the shim radius matches the screws ball.
The center line of barrel can be dialed in quickly and be stress free.
If you think about this
If the barrel has a bend in it at all it has stress and the force of machining may cause it to move because the barrel will try to straiten out unless you have a lot of clamping force holding it.
With this ball ended screws it takes less holding force and stays put because it is held in a free state.
I have parted barrel off and re checked the alignment and have no movement while I have dialed in a barrel with brass tipped screwd and brass ring or steel ring and done less stressful machining and still had them move even when I think they shouldn't have.
If you try this you will see.
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