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Gunsmithing 3 chuck vs 4 chuck lathe for barrel threading?

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p3ripperfw

Private
Minuteman
Aug 5, 2012
89
0
41
Fort Worth, TX
I called a local gunsmith the other day to talk to him about bedding my rifle, doing some cerakote work on it, and also cutting the barrel down and indexing it with a bastard brake. I also mentioned I was possibly using another local smith to do the barrel work and then have him do the bedding and coating. He replied that he wasnt trying to scare me away from the other guys work because he was giving me a good price but that he heard the other smith was using a 3 chuck lathe. (I believe thats what its called) He mentioned that he only used a 4 chuck lathe and that he didnt advise the use of the 3 chuck because of issues with accuracy and possibly not getting the brake on exactly strait because of this.

The other smith seemed very knowledgable and everything he told me seemed very accurate. He said he measured off the inner bore and did not use the outer portion of the muzzle because it would not be concentric to the bore.

My question is: Is this a case of one smith trying to keep all the work in his shop or is there really some issues with using a 3 chuck lathe? I havent verified that the original smith is using a 3 chuck lathe but I wanted to know the answer to this before I decided who to use.
 
Re: 3 chuck vs 4 chuck lathe for barrel threading?

a 3 jaw "set-tru" style chuck, provided the jaws are parallel with the spindle axis would probably produce a rifle more accurate than any "tactical" type rifle needs to be, if the bore where the throat will be is where it is indicated/dialed in to near dead-nuts.
 
Re: 3 chuck vs 4 chuck lathe for barrel threading?

Ask the smith what he uses. A plain jane 3jaw scroll chuck doesn't have the ability to adjust it to remove runout like a 4jaw chuck does, unless like mentioned it's some type of set tru chuck, or some type of adjustable backplate.

Ask him, and see what he says.

Onyx
 
Re: 3 chuck vs 4 chuck lathe for barrel threading?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: p3ripperfw</div><div class="ubbcode-body">I called a local gunsmith the other day to talk to him about bedding my rifle, doing some cerakote work on it, and also cutting the barrel down and indexing it with a bastard brake. I also mentioned I was possibly using another local smith to do the barrel work and then have him do the bedding and coating. He replied that he wasnt trying to scare me away from the other guys work because he was giving me a good price but that he heard the other smith was using a 3 chuck lathe. (I believe thats what its called) He mentioned that he only used a 4 chuck lathe and that he didnt advise the use of the 3 chuck because of issues with accuracy and possibly not getting the brake on exactly strait because of this.

The other smith seemed very knowledgable and everything he told me seemed very accurate. He said he measured off the inner bore and did not use the outer portion of the muzzle because it would not be concentric to the bore.

My question is: Is this a case of one smith trying to keep all the work in his shop or is there really some issues with using a 3 chuck lathe? I havent verified that the original smith is using a 3 chuck lathe but I wanted to know the answer to this before I decided who to use. </div></div>

Just to get the nomenclature correct here - it is the JAWS on the CHUCK that are 3 or 4 NOT the lathe itself. So it is a 3 JAW CHUCK or a 4 JAW CHUCK (there are chucks with more jaws as well).

As mentioned above there are more than one way to adjust both.

Almost anybody with a decent lathe normally has several chucks as well as collets. For one smith to say that another only has "such and such" tooling - sounds like gossip until you check for yourself. No harm in asking and then you will have it from the horses mouth.

Ancient Chinese proverb says: "They say" is often times proved a great liar.
 
Re: 3 chuck vs 4 chuck lathe for barrel threading?

"believe none of what you hear, and half of what you see."

There's something to that, right there.
 
Re: 3 chuck vs 4 chuck lathe for barrel threading?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 300sniper</div><div class="ubbcode-body">a 3 jaw "set-tru" style chuck, provided the jaws are parallel with the spindle axis would probably produce a rifle more accurate than any "tactical" type rifle needs to be, if the bore where the throat will be is where it is indicated/dialed in to near dead-nuts. </div></div>

Correct, again. A 3 jaw set true/adjust tru will provide even clamping pressure on the barrel. The whole chuck can be manipulated with it's jacking screws to align the barrels bore. On a four jaw, you will always have uneven pressure on all four sides of the barrel while trying to align the bore. Does it matter?? I don't really know, but I've found it a lot easier to use a 3 jaw adjust tru chuck. BTW, have done it both ways with great results either way.
 
Re: 3 chuck vs 4 chuck lathe for barrel threading?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: STR</div><div class="ubbcode-body"> BTW, have done it both ways with great results either way. </div></div>

errrr....., well...... ya but please take into account you didn't just fall off a turnip truck yesterday so things come a bit easier for you. With your past experience, knowledge and abilities I am betting you can do chit in a comma me and others can't/couldn't do with a dose of Ritalin, a couple of weeks of time and a narcassistic ego inflated engineer!!
wink.gif
 
Re: 3 chuck vs 4 chuck lathe for barrel threading?

4 jaw independent chuck is better.

A 3 jaw chuch "assumes" that the bore and barrel are in cylindrical alignment.

You could chuck up the barrel and find that the bore is running off center . . . no way of truting it.

A 4 jaw chuck lets the machinist/gunsmith center the barrel by using the bore of the rifle as the primary datum. Once the bore is established as the datum, then you can thread the barrel accurately to accept a brake/suppressor with confidence that the bore of the host and guest are in alignment.

Good machinists/gunsmiths have no issue with uneven pressure from the jaws. Pressure is equal. Kind of like cracking a nut with your fingers, one finger may be kept in place and the other moving, but the pressure exerted on each side of the nut is the same.
 
Re: 3 chuck vs 4 chuck lathe for barrel threading?

Killer, they are talking about a set-tru type 3 jaw. It is a little different than a scroll type 3 jaw, in that after you secure the workpiece in the jaws, you may adjust the entire chuck to run true to the bore of the workpiece.

They are made for production type use, but are also very convenient for running chambers. As STR said, they are pretty quick to dial in, no loosen this side, tighten that side BS. I have spent many years aligning large rotating equipment, sometimes I get backwards, and it seems like it is when I am almost "there". The Set-tru ( there are several brands, that is best known) helps keep that straight.
 
Re: 3 chuck vs 4 chuck lathe for barrel threading?

Learned something new!! I only knew about "standard" 3-jaws and was immediately gonna say don't go to that guy since no way to dial in! Glad I held my tongue for the experts!!
 
Re: 3 chuck vs 4 chuck lathe for barrel threading?

Man thanks for all the informative responses. Yall taught me a ton and Im better off knowing it. Thanks again for all your knowledge. I emailed the smith today to see what type chuck he was using so now all I have to do is wait and see!
 
Re: 3 chuck vs 4 chuck lathe for barrel threading?

it doesnt even realy matter how accurate the chuck is , their are some very very good 3 and 6 jaw scroll chucks that are very precise , that is a moot point since they are biting on the OD of the barrel and you need to be dialing in on the ID of the barrel and those are rarely close as they should be.

a "set-tru" style scroll chuck is great as is regualr 4 jaw
 
Re: 3 chuck vs 4 chuck lathe for barrel threading?

3 or 4 jaw both work equally well IF the work can be indicated in properly. You can clamp a ring in the rear of a 3 jaw and bore the jaws and if your headstock bearings and chuck is still fairly tight is will run true. Ideally the ring will be close to your clamping diameter. It can be done with hard or soft jaws.

The 4 jaw give you the ability to dial in about any workpiece round or square.

Its the experience of the operator that makes a huge difference.

(Toolmaker by trade and bias opinion)
 
Re: 3 chuck vs 4 chuck lathe for barrel threading?

There are plenty of ways to skin this cat in my opinion, and people that can consistently get their guns to shoot have their head in the game and think about what works with the equipment on the floor.
 
Re: 3 chuck vs 4 chuck lathe for barrel threading?

Well heres the response I got so far. Sounds like hes got the set up and knowledge to do this properly. What do yall think?

I asked what type chuck he used:

"I use a variety of chucks depending on the job. 3 jaw, 4 jaw and a spider/cat head."



to Morgan
Which do you use for threading and indexing a brake?


Morgan :
Just depends on the gun. Most guns won't benefit from the cathead, it might get it .0001 more concentric. I didn't use it on my own 300 accuracy international and its dead nuts to 1500 plus yards. Most will be threaded between centers using a live center thats brass tipped to not damage the bore. The cathead is an additional 1 hour of work for dialing it in, on those who request it, the price is $80 to thread.
 
Re: 3 chuck vs 4 chuck lathe for barrel threading?

I use soft jaws for threading the muzzle I rebore them

I use four jaws for chambering.. I dial in both ends of the barrel .0001

Every smith has their own method
 
Re: 3 chuck vs 4 chuck lathe for barrel threading?

Whether its 3,4,5,6 . . . Jaws the nuts n bolts of this is whether or not the operator of the machine can accurately aline the bore of the barrel to the common axis of the machine spindle. If you/i/anyone were to approach an enginner and present them with your parts they'd tell you that the bore is the datum. Everything about a gun is based upon where the center of the bore is. ignoring that fact doesn't make it magically change just because you don't want it to. (I'm not saying this to anyone in particular, its a blanket response)

The success/failure of the setup is then dependent upon it being able to retain this alignment throughout the barrel fitting operation. A basic fundemental rule of any machine op is rigid work holding. Meaning fixturing a part so that it does not move/vibrate/distort while you are cutting on it.

Its a pass or fail exercise.

Good luck.
 
Re: 3 chuck vs 4 chuck lathe for barrel threading?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: C. Dixon</div><div class="ubbcode-body">Whether its 3,4,5,6 . . . Jaws the nuts n bolts of this is whether or not the operator of the machine can accurately aline the bore of the barrel to the common axis of the machine spindle. If you/i/anyone were to approach an enginner and present them with your parts they'd tell you that the bore is the datum. Everything about a gun is based upon where the center of the bore is. ignoring that fact doesn't make it magically change just because you don't want it to. (I'm not saying this to anyone in particular, its a blanket response)

The success/failure of the setup is then dependent upon it being able to retain this alignment throughout the barrel fitting operation. A basic fundemental rule of any machine op is rigid work holding. Meaning fixturing a part so that it does not move/vibrate/distort while you are cutting on it.

Its a pass or fail exercise.

Good luck. </div></div>


This is probably the best answer. While tooling and workholding play a role in the work the man spinning the dials is the critical variable.
The entire magic to machine work is in the set up. If that is not correct it doesn't matter what else happens after that.
 
Re: 3 chuck vs 4 chuck lathe for barrel threading?

Hey P3Ripper,

I can tell you this, DallasShootingSupplies (morgan) seems like a knowledgeable guy and boy the price is right.

but

Based on location to Ft Worth, Im North of you near TMS, I went with THEBBC (Chad) and for a bit more money but a lot less driving he took care of the job.

Later THF'er

wink.gif
 
Re: 3 chuck vs 4 chuck lathe for barrel threading?

Yeah I hear ya....Ill probably have him just do it because I was going to have him do the cerakoting so that will save me a trip as well.

Thanks man.

Where do you shoot at by the way?
 
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