Question on Cone Cutter for BAT

[INTJ]

I have been cutting cones for the last year using the compound for the BAT barrels I have chambered. However, I just finished cutting a cone with the PTG 96 degree tool for a CRF M-70, and I am NEVER going to use the compound again for cones.

I went to the PTG website and they show what I think to be the correct tool, called 65 degree Breech Tool. 65 degrees is what BAT calls for many of their actions. That one is a special order.

There is another cutter called 64 Degree BAT Breech Tool and there are a bunch in stock, leading me to believe that with a cone reamer that 64 degrees might be the right call.

So which one do I get? I just called PTG and no one there knew.

 

[Dusty Stevens]

Get the 64. Even if it was 63 youd never know

 

[gunsandgunsmithing]

1° over 1.000= .0174"

 

[INTJ]

I am wondering if there is a advantage to a 65 degree bolt in a 64 degree cone?

 

[hoz53]

1° over 1.000= .0174"

doing the math it does seem like 1 degree over 1" = a bit over 17 thou. the tapered part on the bolt i have may be a tenth of an inch so thats 1.7 thou right. if its 2 tenths of an inch thats 3.4 . Id rather have a parallel crack. I can measure this with my protractor cant I? Im gonna try it after bit.

 

[Dusty Stevens]

doing the math it does seem like 1 degree over 1" = a bit over 17 thou. the tapered part on the bolt i have may be a tenth of an inch so thats 1.7 thou right. if its 2 tenths of an inch thats 3.4 . Id rather have a parallel crack. I can measure this with my protractor cant I? Im gonna try it after bit.

Thats over 1” not a tenth so your gap would be not parallel by less than .0174. Your lathe compound will most likely be off that far. Its of no concern in the end because your gap needs to be what .007-.010 or so? What happens if its more? I do the solder test quite often and my compond cut cones are within .001 across the lug. What if it was .003? What if it was .010- would the case still be supported good enough since the web is solid?

 

[hoz53]

Thats over 1” not a tenth so your gap would be not parallel by less than .0174. Your lathe compound will most likely be off that far. Its of no concern in the end because your gap needs to be what .007-.010 or so? What happens if its more? I do the solder test quite often and my compond cut cones are within .001 across the lug. What if it was .003? What if it was .010- would the case still be supported good enough since the web is solid?

well thats what i put in my post, that its over mabie a tenth or at most 2 tenths of an inch not the full inch. The rest of your post is what i was hoping for. I do believe most set the gap between 005 and 010 at best.
Thanks for your help.

 

[Walt Krafft]

I don't understand the big deal about using the compound to cut the cone. Been doing it that way for years.

 

[GenePoole]

Cosine of 1° is 0.99985 so that's the error factor between 64 and 65°.

 

[gunsandgunsmithing]

I wasn't stating an opinion, just a fact that can be considered when cutting a cone. Not telling anyone how it should or shouldn't be done but just a consideration when you do it. That's all.

 

[wwbrown]

Cosine of 1° is 0.99985 so that's the error factor between 64 and 65°.

The correct comparison would be the difference between cos(65°) and cos(64°)

 

[GenePoole]

Got my trig functions messed up. Should be sine(1°) which is indeed 0.0175. cosine is adjacent over hypotenuse which would mean that with a hypotenuse of 1 inch, the adjacent would be 0.99985. The opposite is the sine and would be 0.0175.

 

[gunsandgunsmithing]

Got my trig functions messed up. Should be sine(1°) which is indeed 0.0175. cosine is adjacent over hypotenuse which would mean that with a hypotenuse of 1 inch, the adjacent would be 0.99985. The opposite is the sine and would be 0.0175.

Math is great but this is easier.
https://www.mathwarehouse.com/trigonometry/sine-cosine-tangent-chart.php

 

[Lucky Shooter]

Easy shortcut.

For sine and tangent of small angles-----convert the degrees angle to radians by multiplying by
pi/180------this number will be your sine or tangent-----you have to carry this out to many decimal
places to get a difference.

The .01745 factor comes from pi/180. You can do this on a 4-function calculator----no trig stuff needed.

A. Weldy

 

[gunsandgunsmithing]

My point was how fast actual bolt clearance and the amount of unsupported case can change with simply being off a small amount on the compound. Dusty brought up a good point in that the scale on the lathe compound can very well be off to some degree.

I use an indicator set up axially with the chuck or work piece to set it accurately. I simply put the indicator tip against the tool holder or post and move the compound exactly 1.000". I adjust until the indicator agrees with the sine of the angle in the link I just posted above.

JMHO, but I'd err to the side of the cone of the bbl being a tad too flat as opposed to too steep but if you set the compound like I just described, you don't have to worry about it..it's right.

 

[INTJ]

Let me ask it this way. Why would PTG make a tool called the "64 Degree BAT Breech Tool" when BAT says it's cones are 65 degrees?

 

[gunsandgunsmithing]

Let me ask it this way. Why would PTG make a tool called the "64 Degree BAT Breech Tool" when BAT says it's cones are 65 degrees?

Likely a good question for PTG. It may be correct or may be as simple as a typo. I pulled it up on their site and zoomed in on the pic of the tool itself. The one in the pic is marked 65° BAT but the desription say 64°. I dunno.

 

[Lucky Shooter]

When considering difference in 1 degree of taper------could this possibly be a way to
guarantee a bit more clearance ?

If I remember correctly, the Panda actions called for 30 degree cone and the old Stiller Viper
called for 29 degrees.

Again if I remember correctly, the rest of the tenon dimensions were alike.

Possibly to err on the side of more, rather than less clearance ?

A. Weldy

 

[gunsandgunsmithing]

When considering difference in 1 degree of taper------could this possibly be a way to
guarantee a bit more clearance ?

If I remember correctly, the Panda actions called for 30 degree cone and the old Stiller Viper
called for 29 degrees.

Again if I remember correctly, the rest of the tenon dimensions were alike.

Possibly to err on the side of more, rather than less clearance ?

A. Weldy

I may be wrong but I don't recall a 29° cone on any Stiller actions..but he did have a 14° on some drop ports series. That cone didn't go all the way to the chamber. There was a I think, .580 od flat at the chamber that then transitioned to a 14° cone. I had one and did bunches of them.

And JMO, but I think if anything, many smiths use more clearance than I prefer. The std seems to be .010. BAT calls for .007 +/-.003 and they have less unsupported case than say a Panda, for example. I prefer about .005 but as this thread has brought up, a 1° difference in cone angle can use that up. There's roughly .250 between the chamber edge and the thread minor. So, we're talking about 1/4th of .01745, with is .00436. Mighty close, there and slightly more than BAT's minimum.

Again, not telling anyone how to do what here. Just something to consider when cutting cones.

 

[geo.ulrich]

Mike, The vipers where coned at least mine was.I believe they changed when the drop port came around....