ASSRA Forum › General › Gunsmithing Single Shot Rifles › Inscribed Octagon Dimensions
(Moderator Group: Moderator)
‹ No Topic | Next Topic ›
Page Index Toggle Pages: [1]  Send TopicPrint
Hot Topic (More than 10 Replies) Inscribed Octagon Dimensions (Read 28383 times)
SSShooter
Frequent Elocutionist
*****
Offline



Posts: 2932
Location: Southern NJ
Joined: Aug 1st, 2010
Inscribed Octagon Dimensions
Sep 29th, 2016 at 6:56am
Print Post  
Have my new barrel and have done the math on making the 1.200" round section (5" at the breech end) full octagon to make it similar to the original Hepburn Creedmoor rifles. Any of you math wizards want to post the width of the octagon section dimension to double-check my work before I put this on the mill and start removing metal. I'll be 'internet challenged for the next several days, but will post my math next week to compare (don't want to influence anyone's work ahead of time).
Thanks.
  
Glenn - Stevens 044 1/2, Bartlein SS 5R barrel in 22LR
Back to top
GTalk  
IP Logged
 
old7groove
Junior Member
**
Offline



Posts: 81
Location: San Diego
Joined: Jul 6th, 2016
Re: Inscribed Octagon Dimensions
Reply #1 - Sep 29th, 2016 at 7:19am
Print Post  
To determine octagon dimension across flats - divide 1.200 by 1.08 = 1.111.
7~
  
Back to top
 
IP Logged
 
nuclearcricket
Oldtimer
*****
Offline



Posts: 780
Joined: Oct 15th, 2008
Re: Inscribed Octagon Dimensions
Reply #2 - Sep 29th, 2016 at 7:38am
Print Post  
My cad program came up with 1.109. 
Sam
  
Back to top
 
IP Logged
 
SSShooter
Frequent Elocutionist
*****
Offline



Posts: 2932
Location: Southern NJ
Joined: Aug 1st, 2010
Re: Inscribed Octagon Dimensions
Reply #3 - Sep 29th, 2016 at 7:41am
Print Post  
Thanks. Rule-of-thumb close, but not good enough for precision machine work. I'm using some trig to be exact (mill with indexing head is good to 0.005").
  
Glenn - Stevens 044 1/2, Bartlein SS 5R barrel in 22LR
Back to top
GTalk  
IP Logged
 
Deadeye Bly
Frequent Elocutionist
*****
Offline



Posts: 1080
Location: Stephens City
Joined: Feb 25th, 2011
Re: Inscribed Octagon Dimensions
Reply #4 - Sep 29th, 2016 at 8:23am
Print Post  
My MORSE Machinist Practical Guide booklet says diameter X .9239. Your barrel measures 1.250" at the breech end so you can mill an octagon 1.154" across the flats or anything smaller.

Check with Klinger to see what size his barrel is.
  
Back to top
 
IP Logged
 
marlinguy
Frequent Elocutionist
*****
Online


Ballards may be weaker,
but they sure are neater!

Posts: 16585
Location: Oregon
Joined: Feb 2nd, 2009
Re: Inscribed Octagon Dimensions
Reply #5 - Sep 29th, 2016 at 11:31am
Print Post  
Glenn, would it help if I measured my original Hepburn Creedmoor barrel and posted the dimensions? I'm not a machinist, so can't begin to calculate the measurements you need.
  
(You need to Login or Register to view media files and links)
Back to top
 
IP Logged
 
frnkeore
Frequent Elocutionist
*****
Online



Posts: 7372
Location: Central Point, OR 97502
Joined: Jun 16th, 2010
Re: Inscribed Octagon Dimensions
Reply #6 - Sep 29th, 2016 at 12:25pm
Print Post  
I either divide the diameter by 1.082 or multiply by .924 to get the across the flat size. To get the width of one flat, multiply diameter by .3826

Frank
  
ASSRA Member #696, ISSA Member #339
Back to top
YIMAIM  
IP Logged
 
Chuckster
Frequent Elocutionist
*****
Online



Posts: 2251
Location: Colorado
Joined: May 15th, 2008
Re: Inscribed Octagon Dimensions
Reply #7 - Sep 29th, 2016 at 12:36pm
Print Post  
Frank and DB are correct.
Multiply the round diameter times the Cosine of 22.5° (.9239) to get the maximum distance across the flats for an octagon.
Chuck
  
Back to top
 
IP Logged
 
uscra112
Frequent Elocutionist
*****
Offline



Posts: 4079
Location: Switzerland of Ohio
Joined: May 7th, 2007
Re: Inscribed Octagon Dimensions
Reply #8 - Sep 29th, 2016 at 4:20pm
Print Post  
nuclearcricket wrote on Sep 29th, 2016 at 7:38am:
My cad program came up with 1.109. 
Sam


I cheated too.  My CAD says 1.10866 flat to flat.
  
<div class=
Back to top
 
IP Logged
 
SSShooter
Frequent Elocutionist
*****
Offline



Posts: 2932
Location: Southern NJ
Joined: Aug 1st, 2010
Re: Inscribed Octagon Dimensions
Reply #9 - Sep 29th, 2016 at 8:54pm
Print Post  
marlinguy wrote on Sep 29th, 2016 at 11:31am:
Glenn, would it help if I measured my original Hepburn Creedmoor barrel and posted the dimensions? I'm not a machinist, so can't begin to calculate the measurements you need.

Vall - that would be great. I've got dimensions from Tom Klinger's barrel which I'll post when I get home next week, but would be interesting to compare them. Could you let me know just in front of the receiver and at the end of the octagon and also the length of the octagon portion? Tom's rifle is a 34" long 44-100. Is yours the same? Thanks.

And, yes...... That cosine of 22.5 x the diameter is correct. Thanks to all.
« Last Edit: Oct 3rd, 2016 at 8:18am by SSShooter »  
Glenn - Stevens 044 1/2, Bartlein SS 5R barrel in 22LR
Back to top
GTalk  
IP Logged
 
marlinguy
Frequent Elocutionist
*****
Online


Ballards may be weaker,
but they sure are neater!

Posts: 16585
Location: Oregon
Joined: Feb 2nd, 2009
Re: Inscribed Octagon Dimensions
Reply #10 - Sep 30th, 2016 at 10:27am
Print Post  
Glenn,
My Hepburn is not in what is considered a "Creedmoor caliber". Mine is a Match B with Creedmoor barrel marked "32 40 B&M" which is the standard .32-40 Ballard & Marlin cartridge.
My barrel is exactly 34", nothing slightly over. The octagon portion is exactly 12", and forearm cap ends even with the octagon portion. The octagon is .998" at the receiver, and .925" at the end of thhe octagon. Round is .984" at the start, and .737" at the crown. Front sight dovetail is @15/16" on center from the crown.
  
(You need to Login or Register to view media files and links)
Back to top
 
IP Logged
 
SSShooter
Frequent Elocutionist
*****
Offline



Posts: 2932
Location: Southern NJ
Joined: Aug 1st, 2010
Re: Inscribed Octagon Dimensions
Reply #11 - Oct 3rd, 2016 at 5:41pm
Print Post  
Vall - here are the measurements from Tom's original 44-100 Hepburn Creedmoor rifle, which I'm going to copy as best I can. 

At the receiver the barrel measures 1.185 across the flats. At the front end of the octagonal section the flats measure 1.167. Then starts round at 1.162 and tapers to .870 at the muzzle. The octagonal section is 2.3 long.

As you can see, the octagonal section is only 2.3" in length. The 1.154" I can use will be close to the 1.185" of the original. The 0.018" of taper may be tricky. Will see next month when I get started on it.
« Last Edit: Oct 3rd, 2016 at 7:14pm by SSShooter »  
Glenn - Stevens 044 1/2, Bartlein SS 5R barrel in 22LR
Back to top
GTalk  
IP Logged
 
marlinguy
Frequent Elocutionist
*****
Online


Ballards may be weaker,
but they sure are neater!

Posts: 16585
Location: Oregon
Joined: Feb 2nd, 2009
Re: Inscribed Octagon Dimensions
Reply #12 - Oct 3rd, 2016 at 6:57pm
Print Post  
I'm guessing the big differences in barrel diameters between the .44-100 and my .32-40 are due to bore sizes, and weight restrictions. The smaller bore requires more metal be removed or it wouldn't fall within the 10 lb. limit. 
Just out of curiosity I measured my Ballard #7 Longrange in .44-100 to see how it compared to Tom's Hepburn. The Ballard is 1.160" at receiver and octagon is 11.375" long. End of octagon is 1.090" Round is .920" at the muzzle. Also 34" long Creedmoor length.

In looking at Tom Rowe's Hepburn book I see quite a variety of Creedmoor barrel shapes! A few with the short octagon section of Tom's gun. Some with half octagon barrels. And a few with Rigby flats also. And the military Creedmoor barrels in full round with all the military bands.
  
(You need to Login or Register to view media files and links)
Back to top
 
IP Logged
 
shovel80
Oldtimer
*****
Offline



Posts: 896
Location: Sonora,CA
Joined: Jun 6th, 2011
Re: Inscribed Octagon Dimensions
Reply #13 - Mar 25th, 2017 at 12:27pm
Print Post  
SSShooter wrote on Sep 29th, 2016 at 7:41am:
Thanks. Rule-of-thumb close, but not good enough for precision machine work. I'm using some trig to be exact (mill with indexing head is good to 0.005").


Going to loose some diameter to draw filing.

Terry
  
ASSRA Member # 11021
Back to top
Facebook  
IP Logged
 
SchwarzStock
Frequent Elocutionist
*****
Offline



Posts: 1231
Location: SchwarzWald
Joined: Mar 23rd, 2010
Re: Inscribed Octagon Dimensions
Reply #14 - Feb 8th, 2021 at 3:01am
Print Post  
Don't take one side off all at once. Make several passes on alternating sides to prevent stressing/bending the tube. Dividing head makes this easy. Smiley

SS
  
If your rifle is not in 7.62 and you can't hit what you are aiming at with de-linked machinegun ammo you are a pretender.
Back to top
 
IP Logged
 
wesg
Senior Forum Member
****
Offline



Posts: 307
Joined: Sep 13th, 2004
Re: Inscribed Octagon Dimensions
Reply #15 - Dec 21st, 2024 at 11:44pm
Print Post  
SSShooter wrote on Sep 29th, 2016 at 7:41am:
... not good enough for precision machine work ... mill with indexing head is good to 0.005").


.005 is 'precision? Wink
  
Back to top
 
IP Logged
 
Page Index Toggle Pages: [1] 
Send TopicPrint
‹ No Topic | Next Topic ›
 
  « Board Index ‹ Board Top  

ASSRA Forum » Powered by YaBB 2.6.12!
YaBB Forum Software © 2000-2025. All Rights Reserved.

Valid RSS Valid XHTML Valid CSS Powered by Perl Source Forge

Page completed in 1.3120 seconds.