Three Jaw or Four Jaw for Barrel Crowning

[coopshooter]

its a trued surface

u cut it in alignment with the bore yes . its threaded but it will run true you dont need to reef the daylights out of it threads that are cut on a lathe are alot diff then threads on common bolts where mass production is all that matters ive gripped many parts by the threads to finnish a part or becuz i forgot to do something and only od to use was the threads try a lil test and see what happens

 

[jackie schmidt]

Coopshooter

I see the possibility of a lot of "stacked tolerances" cropping up with what you are doing.

But if you are happy, that is fine.........jackie

 

[Bnhpr]

Sorry, not on my threads....recipe for galling.

 

[alinwa]

OK you threaded tenon grippers

Assuming that the bore is crooked and the barrel's bent AND that the bore isn't centered in the barrel........... when you dial in the crowned end do you just bend the barrel or what?

al

 

[Big Al]

JUST to elaborate for those who don't know what a "Buck Chuck" is....... note that it's NOT just a "very precise three-jaw" but instead a 3-jaw that's FAST but can be dialed in like a 4-jaw.

Precision of the 3-jaw is not the issue, it's meaningless for crowning.

Crowning without indicating the bore for both center and perpendicularity is hack-work IMO.

FIVE THOUSANDTH'S Dennis??? C'mon. I can do better than that by eyeball, watching the bore lope. I recently crowned a factory gun by indexing with the initial cut in the grooves and can guarantee you that it was within a half thou. Painfully slow to index using the tool bit but certainly accurate.

Buck Chuck

http://www.buckchuckusa.com/userfiles/How to Mount and Operate(2).pdf

hth


al

Al this is the chuck I use on my old heavy 10" South Bend.

http://www.yuasa-intl.com/products_indv.aspx?pid=36

As far as Butch's comment, did you know that the jaws on your steady rest move? You can pin the barrel and find center easily, just like the three jaw Accra chuck.

The reason I bought this chuck instead of the BUCK chuck is look at the guaranteed tolerances. The Buck when new is guaranteed to what? .001.

I've used my chuck now for 13 years and the run out still is less than the guarantee.


What part of pinning the barrel and indicating does anybody find to be to hard?

 

[Butch Lambert]

Big Al,
You can pin it and indicate if you have already turned the OD to be coaxial to the bore. I'm with Jackie though on the stacked tolerance.
Butch

 

[alinwa]

The Buck when new is guaranteed to what? .001.

Statements like this make me smile

The Yuasa claims .0005 (May be "per side"??)

The Buck claims .001 (May be "inclusive??")

Either way it's not exactly an order of magnitude.....

And Joe The Average is somehow convinced that .0005 is "WAYYY more accurate!" Somehow "5 ten thousandths" or "five tenths" or even "50 Millionths" is better than "1/2 a thou"...

Now a difference of .001 to .0001 is meaningful.....

And I'm not RATING a Buck Chuck over another, this is a conceptual thing.... I'm just trying to illustrate that "accuracy" of a chuck (or a spindle or the whole freaking lathe) is only as good as the operators understanding of tolerance, runout, loading and lash.... AND where to measure FROM!

al

 

[Big Al]

al,

TIR has as the operative word "Total", that does not mean per side. The test papers that came with my chuck, read .0003" TIR. After setting up the Yuasa back plate and the chuck was mounted, I was surprised to find a TIR of .0003".

Stacking tolerances, well when you adjust each end to read as close to zero as you can get it, where does the stacking start? That is indicated to the tool you are going to do the work with.

 

[alinwa]

al,

TIR has as the operative word "Total", that does not mean per side. The test papers that came with my chuck, read .0003" TIR. After setting up the Yuasa back plate and the chuck was mounted, I was surprised to find a TIR of .0003".

Stacking tolerances, well when you adjust each end to read as close to zero as you can get it, where does the stacking start? That is indicated to the tool you are going to do the work with.

I'm with you on TIR...... but a TIR of .0005 or even .0003 just isn't that much better than .001 and calling it "50 millionths" or "30 millionths" as some are wont to do is REALLY gilding the turd......

And "a thou" or "a half a thou" TIR is still not the whole picture. A headstock bearing is by definition a BEARING and must have some slop.... the real question is, "how does the machine take a load once the lash is taken up"... It's all about setup....

In My Opinion

al


BTW, regarding the last paragraph, I don't "indicate both ends to read as close to zero as you can get it", ever...... I indicate the area to be worked to be as close to zero as possible..... what the other end does is of no note to me.

 

[Dennis Sorensen]

A headstock bearing is by definition a BEARING and must have some slop....

al

I have checked my lathe while cold and again after 20 minutes when the headstock was warm. I could measure no difference using a 10 thou dial. No slop in my headstock. It uses a large adjustable tapered Timken bearing that has some load to it I guess.

 

[jackie schmidt]

Big Al

I think you are confusing chucks. What we are referring to as a "Buck Chuck" is a 3-jaw universal that is mounted on a face plate with a female to male clearance of about .008. The body of the chuck has four set screws that extend all the way down to the male fit on the face plate. You use these screws to move the entire chuck body on the face plate. There are Socket Head Capscrews that hold the chuck firmly against the plate. I normally do not even loosen these when dialing something in, the set screws have enough force to move it.

These chucks are not designed for rough interrupted work, or banging around on, as it will shift on the face plate. But, for operations such as barrel work, they are great. You can dial something in as close as the lathe bearings will turn.

I guess they call it a "Buck Chuck" because that is who came upwith the concept. I think the real term is "set true".......jackie

 

[RoyB]

6 Jaw Tru-Adjust.......Piece of copper wire around barrel. Snug up those six jaws tight, then adjust the whole chuck to get as close to Zero runout as you can get. Indicating off the grooves, not the lands.

Run the breach in a spider, indicating off the chamber if it is already reamed.....

 

[Don]

I think you are confusing chucks. What we are referring to as a "Buck Chuck" is a 3-jaw universal that is mounted on a face plate with a female to male clearance of about .008. The body of the chuck has four set screws that extend all the way down to the male fit on the face plate. You use these screws to move the entire chuck body on the face plate. There are Socket Head Capscrews that hold the chuck firmly against the plate. I normally do not even loosen these when dialing something in, the set screws have enough force to move it.

These chucks are not designed for rough interrupted work, or banging around on, as it will shift on the face plate. But, for operations such as barrel work, they are great. You can dial something in as close as the lathe bearings will turn.

I guess they call it a "Buck Chuck" because that is who came upwith the concept. I think the real term is "set true".......jackie

Thing I do not like about the "Buck Chuck" is the adjusters are not direct opposing, where as the Yasuu does use direct oppose.

Can not understand why "Buck" and some other adjust chucks dont use the direct opposing adjuster design, probably has something to do with size and space, I assume.....................Don

 

[RoyB]

You folks would die if you saw how I adjust my Tru-Adjust.

Those bolts that run through the front of the chuck and into the backplate have Belview (sp?) washers under them. The opposed adjustment set screws are backed out and not used. I simply loosen those three bolts about a half turn, and then using a tiny lead hammer, I tap the chuck into alignment. When aligned, I tighten the three bolts and remeasure. This method works very well and is unbelievably fast. I can indicate a barrel in about 30 seconds.

When you stop rolling on the floor laughing...........I'll race ya.....

 

[Don]

You folks would die if you saw how I adjust my Tru-Adjust.

Those bolts that run through the front of the chuck and into the backplate have Belview (sp?) washers under them. The opposed adjustment set screws are backed out and not used. I simply loosen those three bolts about a half turn, and then using a tiny lead hammer, I tap the chuck into alignment. When aligned, I tighten the three bolts and remeasure. This method works very well and is unbelievably fast. I can indicate a barrel in about 30 seconds.

When you stop rolling on the floor laughing...........I'll race ya.....

I suspected something was going on when I saw those large bolt heads and washers instead of the normal cap screws used in these Set-tru's........................Don

 

[Roger rodbolt]

Thing I do not like about the "Buck Chuck" is the adjusters are not direct opposing, where as the Yasuu does use direct oppose.

Can not understand why "Buck" and some other adjust chucks dont use the direct opposing adjuster design, probably has something to do with size and space, I assume.....................Don

Don,
My 3 jaw and 6 jaw Buck set-true chucks use directly opposing adjusters or I'd say they adjust like a fine pitch four jaw to center the scroll jaws. I'm not sure what you are referring too? I don't own a Yuasa chuck but guess they are very accurate and durable. I can vouch for the quality of their indexing head, rotary table, etc. that I use.

 

[Don]

Don,
My 3 jaw and 6 jaw Buck set-true chucks use directly opposing adjusters or I'd say they adjust like a fine pitch four jaw to center the scroll jaws. I'm not sure what you are referring too? I don't own a Yuasa chuck but guess they are very accurate and durable. I can vouch for the quality of their indexing head, rotary table, etc. that I use.

 

[jackie schmidt]

Roger

Ours have the four opposing screws as well. Dialing someting in is a snap.

I am not sure just what Don is referriing too........jackie

 

[Don]

Ours have the four opposing screws as well. Dialing someting in is a snap.

I am not sure just what Don is referriing too........jackie

Maybe I should have used the terms "90 degrees evenly spaced and direct opposed", would have been more accurate, see the following pic. for "uneven" spaced;

 

[Roger rodbolt]

Ours have the four opposing screws as well. Dialing someting in is a snap.

I am not sure just what Don is referriing too........jackie

Jackie,
I double checked a spare 3 jaw that I have to make sure I'm not loosing it.......it is like the others, 4 adjusters spaced ninety degrees and each adjuster is factory numbered 1 thru 4.