Barrel Crown
- Thread starter Louis.J
- Start date
Are you cutting from the inside out, towards yourself?
High speed, cutting edge above center and what I call "neutral rake" results in all the metal being worked away from the bore....
works for me
al
X
xs hedspace
Guest
Y'all are picking fly poop out of black pepper! Just do a square face, break the edge of the bore with a round ball,2x bore diameter, and 220 grit. I have some long shank round head rivets, that I use in a battery drill. About 5 seconds on slow speed, rotating the drill a bit, so a groove is not cut into the rivet head. Barrel face up, tissue plug to keep grit from dripping down, just gravity as the feed.
Al
I cut inside out. My tool is dead level though. My barrels always shoot really well but i cant seem to get that lint free patch some folks talk about. A shot or two and all is well. I will try and set my tool just a bit above center.
I have used HHS and i also have some really sharp carbide incerts that i use from time to time. With the carbide i have to take at least .010 of a cut of it just wont work.
I have ofter though of using a lapping ball and some sandding paper, but i was under the impression it wasnt a good idea? Lee
I cut inside out. My tool is dead level though. My barrels always shoot really well but i cant seem to get that lint free patch some folks talk about. A shot or two and all is well. I will try and set my tool just a bit above center.
I have used HHS and i also have some really sharp carbide incerts that i use from time to time. With the carbide i have to take at least .010 of a cut of it just wont work.
I have ofter though of using a lapping ball and some sandding paper, but i was under the impression it wasnt a good idea? Lee
Skeet,
I would think that not getting a few fuzzies after cutting a straight 90 degree crown would be nigh on impossible when one considers the nice, sharp points/edges you just put on the top corners of the lands. Your couple of shots probably serve to soften that edge up a bit, allowing your crown to then pass the fuzzy test. And if your barrels shoot good...
FWIW, I indicate the bore to ZPS and cut recessed crowns on my barrels using dead sharp HSS, feeding in to out as Al suggested. I then turn my compound to 45 degrees and cut a little bevel (approx. 1/32), feeding in to out. I've never had one not pass the Q-Tip test. My bevel is probably not necessary, but it makes me feel warm and fuzzy.
Justin
I would think that not getting a few fuzzies after cutting a straight 90 degree crown would be nigh on impossible when one considers the nice, sharp points/edges you just put on the top corners of the lands. Your couple of shots probably serve to soften that edge up a bit, allowing your crown to then pass the fuzzy test. And if your barrels shoot good...
FWIW, I indicate the bore to ZPS and cut recessed crowns on my barrels using dead sharp HSS, feeding in to out as Al suggested. I then turn my compound to 45 degrees and cut a little bevel (approx. 1/32), feeding in to out. I've never had one not pass the Q-Tip test. My bevel is probably not necessary, but it makes me feel warm and fuzzy.
Justin
I crowned one of my buddies barrels just tonight. One shot through the bore and no fuzzies. I like everything to be perfect, but i am not to worried about this really. Like i say, the barrels shoot fantastic. Heck last ppc barrel i did for my buddy last week is showing a .150 agg potential. Needless to say he is saving that barrel for the right match! Thanks men! Lee
JerrySharrett
Senile Member
Skeet, run the barrel forward then backward using a Q-tip stem (the round handle part). Stick the handle in at about 45 degrees. Run it a few revolutions each way under power. After that if you still have some frizzies you may have problems if you try to shoot them out!
If you are having frizzies after using the Q-tip handle, resharpen your crowning tool and make sure it has a sharp positive lip on it and an about 0.005" or so nose radius that you put on it with a hone.
JerrySharrett
Senile Member
Any of these will work for crowning but I think the rightmost one works best.
Note that the leftmost one has zero leade, the center one about 20 degree positive leade and the right one is about 15 degrees negative lead.
The leade angle determines whether the material being machined is pulled away or pushed away.
Note that the leftmost one has zero leade, the center one about 20 degree positive leade and the right one is about 15 degrees negative lead.
The leade angle determines whether the material being machined is pulled away or pushed away.
jerry
i wish i had a grinder or the knowledge to grind my own tools. If you will remember Jerry you made me a crowning tool a few years back. that tool worked great but unfortunatly the 1/4" tool wont work on my big grizzly. i wish i had one in 1/2", hint hint!!! lol. thanks jerry. lee
i wish i had a grinder or the knowledge to grind my own tools. If you will remember Jerry you made me a crowning tool a few years back. that tool worked great but unfortunatly the 1/4" tool wont work on my big grizzly. i wish i had one in 1/2", hint hint!!! lol. thanks jerry. lee
Skeet,
As far as your 1/4" tool not working on your big Grizzly, I think you're referring to your tool holder being too big to hold a 1/4" tool. If so, just take another piece of 1/4" HSS and put it under your crowning tool to make it work. You are, in effect, making a 1/2" tool. Obviously, you'll have to adjust your cutting edge to center height.
Works just fine. I do it all the time.
Justin
Skeet,
It will be plenty strong, especially for the crowning operation. Just make sure the bottom tool bit is as close to the cutting bits leading edge as possible and practical, i.e., giving maximum support possible.
I've taken hogging cuts with such a set-up and never had a problem.
Justin
I use my 3/16 or 1/4 circle bar inside out sharp edge. A fresh insert works great but I get better results if I sharpen the insert on the acu finish. A diamond lap would work to sharpen also. I touch the top and sharpen the edges to leave a sharp tip without any radius its a great way to get some life out of the old inserts.
B
bigngreen
Guest
The best results I've been getting with a bur free crown are with a Carbide mini boring bar with the lathe cranked up around 900 rpm, passes the q-tip test every time and it's like a mirror!!
Boyd Allen
Active member
Interesting.
JerrySharrett
Senile Member
Skeet, Justin is correct. It is common practice to "stack" cutting bits like that. What holders are you using? Aloris type or what? With Aloris type holders you still should be able to bring a 1/4" bit on center even with a DA size.