Critique my Crown, now with NEW QUESTION! - Page 1

[ARCHIVED THREAD] - Critique my Crown, now with NEW QUESTION!

Posted: 4/9/2015 7:10:33 PM EDT

I'm a veteran gun tinkerer, but a beginning machinist.

My buddy sent me his Arisaka to blue for him, he wanted me to crown it before bluing.

I'm sure he was hoping my neighbor would crown it,

but I've been watching and practicing, the old Arisaka seemed like a good candidate for my first time without supervision.

So tell me what I screwed up and what I can do better.

I know it's not pretty, and the potato photo isn't great.

Fire away.

Posted: 4/9/2015 8:36:00 PM EDT

[#1]

I like your post's on blueing/browninig

Posted: 4/9/2015 10:25:42 PM EDT

[#2]

Quote History

Quoted:
I like your post's on blueing/browninig

View Quote

Thanks, I'm going to do a start to finish on this rifle in another thread. lot's of time consuming work to do on the small parts, so I'm waiting until it's finished to post.

Posted: 4/10/2015 7:48:40 AM EDT

[#3]

In all honesty it looks pretty rough. Way too many tooling marks. What did you use for a cutting tool?
I am gonna guess you set the compound at 11 degrees and backed out the compound?
I use a small carbide boring bar for crowning, sharpened to a very crisp edge. If I have to do an 11 degree I take a few light cuts to get to my depth. My final cut is just a shave, backing out the compound very slowly and evenly.

Posted: 4/10/2015 8:26:02 AM EDT

[#4]

Quote History

Quoted:
In all honesty it looks pretty rough. Way too many tooling marks. What did you use for a cutting tool?
I am gonna guess you set the compound at 11 degrees and backed out the compound?
I use a small carbide boring bar for crowning, sharpened to a very crisp edge. If I have to do an 11 degree I take a few light cuts to get to my depth. My final cut is just a shave, backing out the compound very slowly and evenly.

View Quote

I agree; I will bet that surface finish is more-so due to tool choice and cutting edge than anything else.

Posted: 4/10/2015 10:13:29 AM EDT

[#5]

Quote History

Quoted:
In all honesty it looks pretty rough. Way too many tooling marks. What did you use for a cutting tool?
I am gonna guess you set the compound at 11 degrees and backed out the compound?
I use a small carbide boring bar for crowning, sharpened to a very crisp edge. If I have to do an 11 degree I take a few light cuts to get to my depth. My final cut is just a shave, backing out the compound very slowly and evenly.

View Quote

Yes

I used a carbide bit, but it was one of my neighbors from his bench, so it probably wasn't the sharpest. I should probably buy a new bit dedicated for such work.

Would slowing the machine down make any difference or is it more about the tool sharpness and compound movement?

I broke the edge with a screw and clover and polished it up a bit before bluing it.

School me.

Posted: 4/10/2015 12:01:26 PM EDT

[#6]

Higher speed, slower feed.

Posted: 4/10/2015 12:10:52 PM EDT

[#7]

I use the crowning tools from Brownells. I square off the end with the 180 degree (90 degree) cutter, then the 11 degree cutter or the 45 degree cutter, then lap in with brass lap and 600 grit lap compound. Check for burrs on inside of crown with a fresh Q tip. If fuzz is present, lap more till Q tip come out clean.

Posted: 4/10/2015 1:24:18 PM EDT

[#8]

Quote History

Quoted:
Higher speed, slower feed.

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This, I crank mine up and ultra slow on the feed.
The hardest part using the compound is turning it out at an even, smooth rate.
I never liked the crowning tools, too easy to drag a chip.

Posted: 4/10/2015 2:38:33 PM EDT

[#9]

Well, You guys were right of course, it did look pretty rough, so I had another go at it this morning. I did it before reading the recommendations for higher speed, so I actually slowed the machine down. I'll try high speed on the next one.

I did hunt down a very sharp carbide threading tool and went with a 90 degree recessed crown this time.

Turned out much better, it was so clean I didn't even feel like I needed to break the edge.

Crappy potatoe photo, flame away.

ETA: Passed the q-tip test with flying colors, thanks for the tips.

Posted: 4/10/2015 3:31:20 PM EDT

[#10]

^^^Much nicer!
Practice makes perfect.

Posted: 4/11/2015 10:37:29 AM EDT

[#11]

Now a new question; My eyes aren't as good as they used to be, seeing it in shop light is hard, but studying the photo below, it looks to me that the old Arisaka may be victim of cleaning rod erosion.

My buddy reports that the one time he shot the old girl before starting on refinishing, the groups were decidedly unspectacular, which is why he asked me to re-crown it.

I'm thinking it might need more; maybe an inch off the muzzle?

Opinions?

Sorry for the crappy photo.

Posted: 4/11/2015 1:53:16 PM EDT

[#12]

For crown work, you want a HSS cutter instead.
A carbine insert will last a lot longer due to the hardness of the metal insert, but is can not be sharpened to a sharp tip without the tip shattering off on the first cut.

Also for light passes, insert does not need a chip breaker on the tip of the cutter.
So on that note, figure out what inserts your friend is using on his lathe insert holders, and pick up some HSS inserts without chip breaker for future work on his lathe.

Posted: 4/11/2015 2:08:44 PM EDT

[#13]

Quote History

Quoted:
For crown work, you want a HSS cutter instead.
A carbine insert will last a lot longer due to the hardness of the metal insert, but is can not be sharpened to a sharp tip without the tip shattering off on the first cut.

Also for light passes, insert does not need a chip breaker on the tip of the cutter.
So on that note, figure out what inserts your friend is using on his lathe insert holders, and pick up some HSS inserts without chip breaker for future work on his lathe.

View Quote

Thanks

Posted: 4/11/2015 2:14:27 PM EDT

[#14]

If you have some gauge pins, you can use them to check muzzle wear, and then cut past that.

Posted: 4/11/2015 6:26:54 PM EDT

[#15]

Quote History

Quoted:
If you have some gauge pins, you can use them to check muzzle wear, and then cut past that.

View Quote

^^^What he said
I've never had the chipping issue on my boring bar.

Posted: 4/12/2015 10:09:37 PM EDT

[#16]

I spoke to my friend, who reported that six inches had been removed from the barrel by the smith who drilled and tapped it prior to the refinishing starting.

I don't have gauge pins, but a fat AMAX fits tighter than a nats ass an everything looks concentric and true with it stuck in the muzzle, so I think it's GTG.

The photo must have been an optical delusion.

So Onward with the bluing!