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Turning barrels


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#1 Pmercer

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Posted 27 February 2011 - 06:46 PM

I had a lot of problems with turing my barrels, so thought I'd post a write up on here about how I did them.

I bought my barrels as blanks that were something like 500mm long and 25mm diameter.

The first thing I did was to chop them to slightly over length at about 420mm.

To skin them down to the required OD of 12mm I clamped them in the lathe with just over half hanging out of the chuck. The loose end was held in a revolving center.
I then turned the barrel around and skinned down the other end to 12mm as well.

I wanted to turn the detail on the breach end of the barrel which would eventually be threaded so did this at this stage.
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I also machined the hexagon profile on the muzzle end of the barrels at this stage.
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The next stage was to turn the taper on the barrels. I decided to offset the tailstock to do the tapers. I moved the tailstock towards me which meant when I parrallel turned, I ended up with a tapered barrel. I wrapped two layers of masking tape around area that would eventually be threaded and placed this into the chuck jaws.

At the muzzle end, I'd turned up a brass dowel that was snug fit in the barrel. I placed this in the tailstock chuck and oiled it up before sliding it into the barrel. A rotating center would have been ideal.

When I spun the barrels up in the lathe, I found that they were not perfectly aligned since I had thinned them in two seperate operations previously. Because I was cutting a taper, the fixed steady and the moving steady weren't really ideal.

I found that I could make a cut with no chatter if I had an rpm of 200, a 0.2mm/rev feed and a 0.1mm cut. Each cut along the length of the barrel takes 24 minutes though. I've never had to do such a ridiculous cut!! I managed to get the first taper done on one barrel in 6 hours.

I decided to use the fixed steady from this point on.
I cut two true 'bearing' surfaces for the fixed steady to run on using the 200rpm / 0.2mm/rev / 0.1mm cut.
I then placed the fixed steady in the far right 'bearing' surface and was able to cut the barrel using a 500rpm / 0.8mm/rev / 0.2mm cut to within 0.6mm of final taper diameter
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I moved the steady to the left 'bearing' surface and again turned down to within 0.6mm of final taper diameter.
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I then removed the fixed steady and cut the remainder of the barrel using the 200rpm / 0.2mm/rev / 0.1mm cut. There were only two cuts needed about 100mm long.
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I then did 6 cuts using the 200rpm / 0.2mm/rev / 0.1mm cut for the whole length of the barrel which I'd smeared in oil. (No coolant on my lathe)
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I finished my second barrel in about 3.5 hours which is a large improvement.

Normally I'd be very annoyed at having to stand watching a lathe for 24 minutes at a time, but I've got so many other parts to make, I'm just spending the 24 minutes working on other parts on the bench next to the lathe.

I tried a few different methods of cutting the tapers but all were a nightmare to do. The process listed above worked well. I hope this helps someone.

#2 Dave

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Posted 07 March 2011 - 04:02 PM

Nice write up!

#3 maccrazy2

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Posted 10 May 2019 - 04:20 AM

Am I missing something. The original post talks about a taper on the barrels. I don’t see a taper on my plans. Was this something that changed from older plans?
I just started roughing the barrels tonight. I tried a few finishing cuts but still need to experiment to get the surface finish a little better. The final pass I used the follower rest and it looked good but not spot on yet.

#4 bruski

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Posted 11 May 2019 - 06:09 PM

There is no taper for the barrels on my plans for the RG-G gun. The D & E plans have a taper on the barrels though. I wonder if your plans got mixed up together or something.

 

bruski


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#5 Cutter

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Posted 11 May 2019 - 10:11 PM

Am I missing something. The original post talks about a taper on the barrels. I don’t see a taper on my plans. Was this something that changed from older plans?
I just started roughing the barrels tonight. I tried a few finishing cuts but still need to experiment to get the surface finish a little better. The final pass I used the follower rest and it looked good but not spot on yet.


Pmercer was building a D&E

#6 bruski

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Posted 13 May 2019 - 09:06 PM

Cutter, I didn't realize that pmercer started this topic back in February 2011 when I replied to it thinking that Maccrazy2 started it. What a relief after thinking that all of that turning was for nothing.

 

bruski 


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#7 maccrazy2

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Posted 13 May 2019 - 09:54 PM

It took a bit of experimentation but I think I have them down pretty good. Takes about 15 minutes to rough one down and leave .010 for a final pass. The final is quite slow but leaving a good finish.
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#8 maccrazy2

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Posted 14 May 2019 - 12:23 AM

First 3 roughed. These were all springfield barrels. I’m interested to see how the other brands machine.

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#9 Cutter

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Posted 14 May 2019 - 09:59 PM

First 3 roughed. These were all springfield barrels. I’m interested to see how the other brands machine.

 

For what it’s worth,
 
A standard machining practice would go something like this.
Leave about an inch sticking out of the chuck an indicate the bore in, best
to use a pin with rifled barrels. Face to clean up the end and tool in a 60° center.
Used barrels will require different size pins.
The holding end should also be indicated in with a pin, faced, and a diameter
turned for holding.

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#10 Cutter

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Posted 16 May 2019 - 07:31 PM

A batch of 60 from 2013

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