Lets talk crowns

[Danny1788]

I know this has been covered more times then anyone can count. i just had a few questions.





Here is my crown i just cut on my brothers barrel yesterday morning.

I used a range rod to center the bore to within .00025" run out. knowing that its running true to the bore i just cut a 90 deg. recess and cleaned it up with some 320 emory cloth. I then used a carbide insert and ran the lathe at 680RPM and jsut barely broke the edge on the bore/crown. As you can see no burs or anything.

Lets hear how you guys setup for cutting crowns and how you actually cut them. Lets not get into a measuring competition about which is better lets just talk technique.

 

[billlarson]

I know this has been covered more times then anyone can count. i just had a few questions.





Here is my crown i just cut on my brothers barrel yesterday morning.

I used a range rod to center the bore to within .00025" run out. knowing that its running true to the bore i just cut a 90 deg. recess and cleaned it up with some 320 emory cloth. I then used a carbide insert and ran the lathe at 680RPM and jsut barely broke the edge on the bore/crown. As you can see no burs or anything.

Lets hear how you guys setup for cutting crowns and how you actually cut them. Lets not get into a measuring competition about which is better lets just talk technique.

 

[billlarson]

Good looking work......... several articles and tests have been done on the subject.The ones I recall are Harry Popes findings and another on Long Range Hunting`s site....

 

[ridgeway]

I cut 90 degree square with a sharp bit at high speed, slow feed. Finish is smooth clean and sharp. I follow the same process regardless the crown whether it's recessed, tapered to flat. I never hit with emory or scotchbrite.

 

[riflewoman]

So long as the crown is cut square and concentric to the bore/groove it really doesn't matter on technique. I use a piloted 11deg crowning cutter because it saves me time and gives accurate results.

 

[Steelnecktie]

I use HSS at slow speed, slow feed. Gives great finish. I haven't tried documenting different angle effects, just use 11° angle. Has worked excellent, no need to experiment I guess.

 

[Preacher]

I do it exactly like Ridgeway does it, right down to no abrasives on the crown....

 

[Danny1788]

I do it exactly like Ridgeway does it, right down to no abrasives on the crown....

This was why i was asking is using abrasives on the crown bad? Also jsut to clearify im not actually touching the "crown/bore" with any abrasive or emory clothe. Just the outter recess to clean it up.

 

[riflewoman]

There are no reasons not to use abrasives if you need to polish the crown. It used to be a method to crown using a brass ball smothered in grinding compound. The ball was wobbled around and the crown took on a spherical profile. While maybe not as accurate as the recessed or 11 deg, it certainly worked for many.

 

[Preacher]

Seems too me that after cutting a perfectly flat crown, and then using abrasives on the end of your finger to clean up your last cut is a bubba sort of thing..
A fast speed, and slow cutting makes a perfect edge, why mess that up with abrasives..
As far as using a ball smothered in grinding compound to make the crown, back in the day they made barrels out of flat stock too...
Seems like some of the new ways are lots better.....

 

[akajun]

I leave them sharp, cut them 90* recessed or 11* with a hss bit going about 400rpm, take light cuts of about .005 to finish, basically just enough to make a good curled chip.
I no longer touch it with emory cloth, i just drag a q tip on it, that will tell you if you have a burr. If it does, and it rarely does, I just re cut and try again.

 

[billlarson]

So long as the crown is cut square and concentric to the bore/groove it really doesn't matter on technique. I use a piloted 11deg crowning cutter because it saves me time and gives accurate results.

What crowns that are ground.....???? they are not concentric...???