Using spider in lathe issues

[KY DAN]

Barrel : Winchester 69 22 lr

Goal : 11 degree target crown

22 LR PTG range rod is being used for indicator surface.

So I have never used a spider before so this is all Greek.

I can make one indicator run perfectly 0 while the the other indicator runs .030 to .050 inch out.

When I adjust the second set of bolts the zeroed indicator loses its 0.

So I go back and forth and nothing is done.

How do I do this and what am I doing wrong?

When I get this figured out I will use test indicators

 

[Blue68f100]

Your over correcting. You only want to adj 1/2 of your deviation out at a time. When you adj full you move it 180 to the other side.

 

[4v50 Gary]

You don't need that much of the barrel protruding.

 

[12Bravo20]

@Blue68f100 and @4v50 Gary are both correct.

Only adjust half of what you need. So if you are 0.030" out, adjust it by 0.015". And the more material you have sticking out of the chuck or spider, the more deflection you can get. Deflection is when the material pushes away from the cutting tool.

@KY DAN I don't know how much machining experience you have. So I will apologize if I am giving you information you already know. You definitely can use 1" dial indicators to dial your work in. I use to use them all the time without any issues. And I worked on everything from precision metal punches to big babbitt bearing out of hydroelectric damns.

 

[beag_nut]

If you have a four-jaw chuck (lathe) the jaws are independent of each other and have enough bearing surface to keep the barrel "straight". Then when you adjust the jaws do half of the indicator reading for the opposing jaws. Once you get close or "right on", spin the lathe at low speed to see if there is any "slap" of the barrel in the headstock. If the back of the barrel wobbles, wrap a shop towel over the back of the barrel and cram it into the headstock. I have done numerous similar jobs over 40 years in machine shops (and in my own).

 

[mcb]

If you have a four-jaw chuck (lathe) the jaws are independent of each other and have enough bearing surface to keep the barrel "straight". Then when you adjust the jaws do half of the indicator reading for the opposing jaws. Once you get close or "right on", spin the lathe at low speed to see if there is any "slap" of the barrel in the headstock. If the back of the barrel wobbles, wrap a shop towel over the back of the barrel and cram it into the headstock. I have done numerous similar jobs over 40 years in machine shops (and in my own).

The tapper to the barrel can make that a challenge even with a four jaw chuck.

I would setup the barrel in the four jaw but hold close to the muzzle with soft jaws. Put the spider on the back size of the head stock and true the barrel through the head stock.

 

[a5werkes]

I'm just a amateur simpleton. I know how to use a lathe, however, I have used Dave Manson's efficiently precise 11 degree crown cutting kit that works great. KISS principle.

Gunsmith Dave Manson Muzzle Crowning Tool Kit copy.mov

Shared with Dropbox

www.dropbox.com

 

[NMexJim]

The tapper to the barrel can make that a challenge even with a four jaw chuck.

I would setup the barrel in the four jaw but hold close to the muzzle with soft jaws. Put the spider on the back size of the head stock and true the barrel through the head stock.

And this is a good point. I’ve been scratching my head over your set-up. I see what you’re trying to do, but what’s on the outboard (left) side of the lathe to hold the barrel true there? Gun lathes usually have the spider on the left side of the lathe head. If your hole-through is big enough or outboard is threaded ….

Spider something p like this:

Gunsmith D1-6 Back Plate at Grizzly.com

Your 4-jaw chuck for holding barrels while you thread and chamber them. The main advantage of this plate is that it reduces the distance through the headstock, thus allowing you the ability to thread shorter barrels.

www.grizzly.com

Rather than a 3 or 4 jaw chuck, there should be collet system on the right.

Baring such a system to hold the barrel in rigid alignment, I’d vote for the Mason muzzle crowning tool too.