Hemispherical breach made easy.

[Doc Brown.]

I don't know if anyone out theres looking into simple and easy ways to make a hemispherical breach but heres a pretty simple method. I took a 1.25" Ball nosed end mill cutter with a 1.25" shank and welded it to a piece of 1018 round bar.

[Double D]

Uncle! 

So what am I looking at here?

[de_lok]

Uncle! 

So what am I looking at here?

Douglas,
The piece on the left is the shank end of a 1.25" ball end-mill, the piece on the right is a piece of 1018 round stock  turned and chamfered to butt up and center to the end-mill for welding..............................................................................
Similar to welding on a homemade extension to a drill bit.
 
Dewayne

[Doc Brown.]

Yep. Chuck on the end mill cutter and turn the rod to run true and to the size you need.  Used 7018 rods to weld it up.  That size only comes with a 1.25" shank. At least that's all I could find. Be A good idea to preheat and wrap in insulation after welded. Do this at your own risk though. I don't know if it will snap off and kill you or not. The reason for the 1.25" ball nose end mill cutter only coming with a 1.25" shank is because of the amount of stress the tool is normally under. For a barrel I think its safe but for other applications beware your a dead man.
 
Per my consciences rules and regulations perform at your own risk.
 
 Anyone out there rounding drill bits over can do this and its way better. No creating a special radius cutter. no fancy program. No college degree required.  All you needs about 85 bucks and a 7018 rod.
 
 

[Double D]

Actually without something to give it scale and definition I was guessing and I'll bet a lot of other were also.

A great idea in need of explanation.

[de_lok]

Actually without something to give it scale and definition I was guessing and I'll bet a lot of other were also.

A great idea in need of explanation.

Douglas,
I agree, I had to read the explanation and look at the pic a few times myself before I realized what it was, and I have made dozens of tool extensions like this in the past. The pic should have included all of the endmill (before) and another after it was welded togather (after)...........
Dewayne

[cannonmn]

There may still be some info missing for some, I am struggling here.  Is the extended ball end mill a tool to make that hemispherical breech from stock not shown in the photo?  If so then what do you do, OR does the ball end mill BECOME the hemispherical breech?  If latter is true, then does one use abrasives to remove those nasty cutting flutes from the mill?  Or?  If?

[GGaskill]

This is to make a tool that will cut a hemisphere at the bottom of the bore to replace the cone of a normal twist drill.

At first, I thought the subject was turning the outside of a barrel but soon determined otherwise.

[seacoastartillery]

     

There may still be some info missing for some, I am struggling here.  Is the extended ball end mill a tool to make that hemispherical breech from stock not shown in the photo?  If so then what do you do, OR does the ball end mill BECOME the hemispherical breech?  If latter is true, then does one use abrasives to remove those nasty cutting flutes from the mill?  Or?  If?   

     Gee John, not even a part-time machinist like me was that confused!     However I don't mind being somewhat confused.  Once I got past my confusion over what was pictured, I began to have some very creative thoughts as how to use the extended, welded, ball end-mill tool to perform exterior surface, breech surface, shaping of the round of steel he must have for constructing the mortar tube.  Although I thought a lathe would be ideal machine-tool for the job, I just couldn't figure out how to hold the ball end mill onto it so it would cut the hemispherical outer surface smoothly.  Then a light bulb went on in my brain, (this rarely happens, but did this time).

     I thought, forget the lathe, it's just too hard to use that way, but the milling machine was made for this job.  So, I made a list of procedure steps:

1.   Remove Kurt vise from Mill.
2.   Place Rotary Table on Mill.
3.   Secure 3-jaw chuck to Rotary table.
4.   Clamp workpiece in 3-jaw and attach rotary table hand crank extension.
5.   Crank Bridgeport table down to floor position to make room for the ball end mill extension.
6.   Create Microsoft Excell spreadsheet of -x- and -z- numbers for ____ Radius hemisphere.
7.   Machine stock at appropriate RPM for size of ball end mill used.

     I did a preliminary set-up just to see what it looked like.  I had just finished by taping the ball end mill to the 18" extension.  All of a sudden, Mike was behind me and he Bellowed out,  "What you doin, FOOL?!!"  With his resounding emphasis on the word "Fool", he sounded just like Mr. 'T' (of "A-Team" fame).  Kinda made me cringe.  When he calmed down, I ventured a question, why do you suppose he didn't just clamp the round in the lathe chuck, put a steady rest on it and cut it with a left hand turning tool??  Then Mike says the only thing that made any sense, "Maybe it's a mental health thing?"  I said, "What do you mean?"  Then he says, "When this jerk-water set-up gets to chatterin, shakin and shimmyin, he can give it a kick and it will make him feel better!!"

[cannonmn]

This is to make a tool that will cut a hemisphere at the bottom of the bore to replace the cone of a normal twist drill.

Thanks, I never would have guessed it was for inside the bore.

[Doc Brown.]

There may still be some info missing for some, I am struggling here.  Is the extended ball end mill a tool to make that hemispherical breech from stock not shown in the photo?  If so then what do you do, OR does the ball end mill BECOME the hemispherical breech?  If latter is true, then does one use abrasives to remove those nasty cutting flutes from the mill?  Or?  If?

I see how every ones confused. Sorry I should have said breach wall or something.  You all remember my quest for the hemispherical breach for cohorns. 
 
The nasty cutting flutes really aren't that nasty in the breaches Ive finished with this method. Theres visible flute marks but they are very smooth and not gouging at all. I use this after I already go in with a regular 1.25" drill bit so its only the ball nose scraping the breach wall really and it shaves it, not cuts. So its very smooth. Still a modified sand stick with 80 grit should do the trick to make it perfect. 

Our jerk water set up. Its a no brainier. It doesn't chatter, shimmy and shake at least not if you follow my steps exactly to the T    
Should I have mentioned the round bar is just a few inch long shank extension? For a drill rod that can get you in deep.
 
The flute marks may seem ruff but I went in with my bionic feelers and they are pretty smooth.


 

[Doc Brown.]

Seacoast.  The round bar is only a few inches long that gets welded on. It has to be over sized to start with so you can chuck on the end mill cutter and  machine the extension down in your lathe to be in plane with the end mill cuter.  Then you can use it in a drill rod. I think you know that and made that story up to make a point on how my vague description could lead people down a dark and gloomy path to self destruction. Lesson learned. My apologize.