Single point tool profile for crowning

C

Curious

New member
Guys,

I would be interested to see what tool shapes and geometries you use for your crowning tools.

I recently came across these micro boring tools on eBay and they work very well.

Screen Shot 2016-09-09 at 22.39.42.jpg
 
Best insert I have used

is Kyocera TPGH080204R PV 7020 TPGH1.51.51R I have tried so many different ones and this is the best by far.

Richard
 
I do not use inserts for crowning. I grind a positive rake tool out of 883 cemented carbide on my tool grinder.

The easiest way to check for any minute burrs is with a Q-Tip.
 
Curious said:
Guys,

I would be interested to see what tool shapes and geometries you use for your crowning tools.

I recently came across these micro boring tools on eBay and they work very well.

View attachment 18371
Click to expand...

That is the same type I use in the turning center, may even be the same bar. The holder for them is great because it is dead nuts repeatable when changing the bar and it directs coolant to the tip perfectly.

 
jackie schmidt said:
I do not use inserts for crowning. I grind a positive rake tool out of 883 cemented carbide on my tool grinder.

The easiest way to check for any minute burrs is with a Q-Tip.
Click to expand...

Until I found that micro boring bar which is carbide I was just using my own ground HSS bits. Im curious as to why your using 833 Jackie, is it because it was available or do you feel it adds something in some way that HSS HssCo doesn't?
 
The Q-tip test

will tell you if what you are using is good. The insert I'm using was recommended by a shooter that has shot on the WBC several times. I can grind whatever tools I need but why? When you can get something that works just as good.

Richard
 
I have a small carbide boring bar that uses micro inserts made by Circle. These inserts are CDCD . I set my feed at the slowest feed speed, and I run my chuck around 1500rpm. Slow feed, and fast speed cuts a perfect crown every time.

when I first started machining my own barrels, crowns used to give me fits. I tried everything, trying to get that perfect sharp crown. the boring bar I now use I found on ebay for 5 bucks. Id be lost without this tool. My PTG reamer holder, and my 5$ boring are my two favorite tools in my shop!!
 
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Yes,

The Circle carbide bar and inserts are really good. The only thing is that they don't make them any more. I haven't found a replacement that I liked as good as those.

I will have to check out E-Bay for that. I think I have about 20 inserts and that will last quite awhile. It used to be MSC would have a sale on a "package deal" of a bar and 10 inserts.

Richard
 
skeetlee said:
I have a small carbide boring bar that uses micro inserts made by Circle. These inserts are CDCD . I set my feed at the slowest feed speed, and I run my chuck around 1500rpm. Slow feed, and fast speed cuts a perfect crown every time.

when I first started machining my own barrels, crowns used to give me fits. I tried everything, trying to get that perfect sharp crown. the boring bar I now use I found on ebay for 5 bucks. Id be lost without this tool. My PTG reamer holder, and my 5$ boring are my two favorite tools in my shop!!
Click to expand...

Lee,

Do you have a picture of the micro inserts?

Nez
 
skeetlee....
feed is that out or in ?
low angle ??
i use a solid circle small bar
high speed and hand feed out at 45 degrees.
this is the transition from bbl bore to bbl nuzzle face.
 
Nez
I will send you a pic.
I always run my feed from the centerline of the bore out. Im not sure you would want to try this any other way. If I cut an 11 degree crown, then I of course use the compound and turn the dial very slow. Slow feed, and fast speed with carbide. I read this procedure on these forums a few years back. Works well for carbide. Lee
 
so the second part of the question,
the muzzle face is the crown ?
i do a muzzle face, and then go back and
cut what i consider the crown.
from the inside out, 45 degrees,
cut is just slightly more than the height of the lands.
very small very short cut 5 to 7 thou or so.
 
Curious said:
Until I found that micro boring bar which is carbide I was just using my own ground HSS bits. Im curious as to why your using 833 Jackie, is it because it was available or do you feel it adds something in some way that HSS HssCo doesn't?
Click to expand...

883 is a softer Carbide, about C-2 grade, actually intended for machining of Cast Iron and non ferrous metals. But I have found you can put a very sharp edge on it when using a soft green wheel on my Cincinanati Tool Grinder.

Keep in mind, I am talking about a flat Benchrest Crown.

http://benchrest.com/attachment.php?attachmentid=18399&stc=1&d=1473649846
 

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A C-7 or C-8 carbide can be ground with a diamond impregneted wheel to cut a burr free crown edge, but a HSS/Co will be easier to grind and unch more economical.

Take a close look and feel to make SURE there is not a push-over burr in the bore. Even a 0.003"-0.005" burr can make a breakout and ruin the accuracy of a barrel. On a new crown, after a few shots, feel with your fingernail to see if it pushed out any burr. If so you will have a very fragile crown...

.
 

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