Straight tapered bbl

[Nvreloader]

Guys,
I am having a hard time figuring the correct amount of taper,
to use to make this bbl come out to the right dimensions etc,
I use a boring bar head to offset the bbl, in the tail stock,
with live centers, at both ends.

Bbl as it stands now, will be fitted to a post 64 M-70, 30/06 action,
Straight shank = 1.350" dia, will be fitted to a post 64 M-70 action,
Shank length of 2.50 to 3.00" in length,
At the end of the chamber shank dia,
I want to taper to 1.00" dia, with a length of 18" +/- on the tapered section.

Can I get some help on figuring this out......it would be greatly appreciated,
Trying to finish another SP pistol in 280 AI caliber.

Tia,
Don

 

[Tim Singleton]

I would get a wooden dowel to check anything I did first.
Double check my math it's been a while
.350(the amount of material being removed or one side of a triangle)
divided by 18 the length of the taper (or the second known side of the triangle) equals .0194 the tangent of the angle
.02 is the tangent of a 1.2 degree taper

 

[223Randy]

How long is the barrel in total?

 

[Tim Singleton]

I would get a wooden dowel to check anything I did first.
Double check my math it's been a while
.350(the amount of material being removed or one side of a triangle)
divided by 18 the length of the taper (or the second known side of the triangle) equals .0194 the tangent of the angle
.02 is the tangent of a 1.2 degree taper

Mistake in the above in that the .350 of material removed the tool need only advance half that or .175
the taper is more like .6 degree

 

[WSnyder]

You do realize that when he adds the 2.5-3" straight shank that the .175" number will not be correct? .175" would work only if he was turning the taper with 18" between centers.

 

[Tim Singleton]

You do realize that when he adds the 2.5-3" straight shank that the .175" number will not be correct? .175" would work only if he was turning the taper with 18" between centers.

Hey said at the end of the 2.5 to 3 inch shank he wanted an 18" taper to 1"

 

[billlarson]

Mistake in the above in that the .350 of material removed the tool need only advance half that or .175
the taper is more like .6 degree

.6* is close,to what you want... a bit much I do believe.... however........ set barrel up and use an indicator to set taper attachment.......
bill

 

[boltman223]

.6* is close,to what you want... a bit much I do believe.... however........ set barrel up and use an indicator to set taper attachment.......
bill

6 degrees will give you a taper length of 16.3 inches. .544 degrees will give you your 18 inches.

Since you are using your tail stock I don't think degrees will do you any good. So like Tim mentioned law of cosine is the most useful. Sorry, I'm a little rusty on that.

 

[boltman223]

6 degrees will give you a taper length of 16.3 inches. .5444 degrees will give you your 18 inches.

Since you are using your tail stock I don't think degrees will do you any good. So like Tim mentioned law of cosine is the most useful. Sorry, I'm a little rusty on that.

Hang on... I think this has been over thought. Offset your boring head .175 and you'll end up where you want. You don't want to take off .175 in one pass. So start at an offset of .02 or more if you want( I don't like removing a lot at one time).

Am I right or have I had too many beers?

I just blew out my flip flop.

Disclaimer: this is all assuming your muzzle diameter is 1" which after reading it again I'm not so sure that's what you meant. Let me know.

 

[boltman223]

You do realize that when he adds the 2.5-3" straight shank that the .175" number will not be correct? .175" would work only if he was turning the taper with 18" between centers.

Hmmmm. You may have a good point here.

 

[boltman223]

You do realize that when he adds the 2.5-3" straight shank that the .175" number will not be correct? .175" would work only if he was turning the taper with 18" between centers.

Hmmmm. You may have a good point here.

With the longer distance between centers(than 18") he will need less taper(as in degrees) to get to the desired deminsions right?

So Nvreloader, if you are moving your boring head in increments you will be able to sneak up on your desired diameter and taper length. And see if you're on the right path.

I know after one cut you will be able to see what is going to happen and you can adjust from there.

I'm glad I have a taper attachment.

 

[boltman223]

The boring head in the tailstock is a damn good idea for sure!

 

[Nvreloader]

As I am slightly confused as to the degree info,

So I'll start again, if you will please bear with me,
I can see that I did not include all the info required,
in the first post.

This bbl is 24" in total length overall,
I will cut off approx 3" from the chamber end and approx 2.750" off the muzzle end, after the tapering is finished to my spec's etc,
and will be using the middle section of this bbl,
to be sure I have good ends,
I want to end up with a total bbl length of 18", which includes the chamber/bbl threads etc.

The barrel diameter is 1.335" now,
(this diameter may be reduced as I get to the final dimensions),
not sure just yet.

The chamber shank length is 3.00"
(which includes the action/bbl thread length),
(Win M-70, 30/06 cal, post 64 action),
I would like a straight taper to 1" at the muzzle, to which a 5 gill Ross brake will be threaded on.

This barrel is being turned between centers,
with live centers on both ends.
I am using a boring bar head with live center to off set the muzzle end,
I do not make heavy cuts, .020" per cut max, with sharp tooling etc.

I hope, I have included all the required info.

Tia,
Don

 

[boltman223]

No need to worry about the degree info since you're not using a taper attachment or any device that measures in degrees.

 

[boltman223]

Offset your boring head .02. put your tool at the 2.5-3.0 spot(aka end of your breach)engage feed and let it go.( Feeding from headstock to tail stock). It won't touch the barrel until it gets towards the end.

At this point back out start all over(move back to beach). Move boring head another .02. touch tool off, engage feed and let'er rip.
Repeat until you get to desired deminsions.

 

[Keith Kilby]

Did I read your original post correctly....this barrel is going on a pistol? With 18" barrel?

 

[Nvreloader]

KK

Yep, you read that right,
For more info, go here:
http://specialtypistols.infopop.cc/eve/forums/a/frm/f/4246004005

Here is my first build,
http://specialtypistols.infopop.cc/...46004005/m/4410087466?r=4410087466#4410087466

Lots of fun and will make a shooter out of you,
once you past the learning curve.

Try it, you'll like it.

Tia,
Don

 

[WSnyder]

Essentially you want 15" of tapered barrel from 1.350" dia to 1" dia in that length. That's a half angle of .670°. Your offset at the tail stock on the full 24" blank between centers should be .280" (edit .330"). Your total depth of cut should be ~.210". Put the barrel in the lathe with that offset, run an indicator along side the barrel and see if the dimensions work before you cut. You should see .175" in 15" of travel. Adjust accordingly if needed.

 

[boltman223]

Essentially you want 15" of tapered barrel from 1.350" dia to 1" dia in that length. That's a half angle of .670°. Your offset at the tail stock on the full 24" blank between centers should be .280". Your total depth of cut should be ~.210". Put the barrel in the lathe with that offset, run an indicator along side the barrel and see if the dimensions work before you cut. You should see .175" in 15" of travel. Adjust accordingly if needed.

There you go NV. Wsnyder is on point

Essentially you want 15" of tapered barrel from 1.350" dia to 1" dia in that length. That's a half angle of .670°. Your offset at the tail stock on the full 24" blank between centers should be .280". Your total depth of cut should be ~.210". Put the barrel in the lathe with that offset, run an indicator along side the barrel and see if the dimensions work before you cut. You should see .175" in 15" of travel. Adjust accordingly if needed.

Wsnyder has it fingered, probably the only one on here. Using your indicator will tell you if you have your offset right, like he mentioned. He didn't mention your indicator should read zero from start to finish, Or is that only with the compound? Buhahaha

 

[BoydAllen]

If I were figuring this, I would take half the reduction from the shank diameter as the side opposite which would be .175. Then I would take the length of the tapered portion (parallel with the bore, as the side adjacent. The tangent of an angle is defined as opposite over adjacent, which would be .175/18 = .00972 (with the 2 repeating). To get the angle I would need to take the arctan, which by my inexpensive calculator (pushing the 2nd and then the TAN buttons) results in an angle of .5570 degree.

http://www.coolmath.com/reference/triangles-trigonmetry