Gatlinggunforum

General Category => Machining => Topic started by: on February 27, 2011, 01:46:57 PM

Title: Turning barrels
Post by: on February 27, 2011, 01:46:57 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.
(http://i847.photobucket.com/albums/ab36/pmercer1975/gatling%20gun/2ef27485.jpg)

I also machined the hexagon profile on the muzzle end of the barrels at this stage.
(http://i847.photobucket.com/albums/ab36/pmercer1975/gatling%20gun/30418062.jpg)

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
(http://i847.photobucket.com/albums/ab36/pmercer1975/gatling%20gun/f33e20bb.jpg)

I moved the steady to the left \'bearing\' surface and again turned down to within 0.6mm of final taper diameter.
(http://i847.photobucket.com/albums/ab36/pmercer1975/gatling%20gun/a697edc0.jpg)

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.
(http://i847.photobucket.com/albums/ab36/pmercer1975/gatling%20gun/88432d88.jpg)

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)
(http://i847.photobucket.com/albums/ab36/pmercer1975/gatling%20gun/7ed2f3d6.jpg)

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.

Title: Turning barrels
Post by: Dave on March 07, 2011, 11:02:59 AM

Nice write up!

Title: Turning barrels
Post by: maccrazy2 on May 10, 2019, 12:20:47 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.

Title: Turning barrels
Post by: bruski on May 11, 2019, 02:09:24 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

Title: Turning barrels
Post by: Cutter on May 11, 2019, 06:11:45 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

Title: Turning barrels
Post by: bruski on May 13, 2019, 05:06:14 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 

Title: Turning barrels
Post by: maccrazy2 on May 13, 2019, 05:54:03 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.

Title: Turning barrels
Post by: maccrazy2 on May 13, 2019, 08:23:11 PM

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

Title: Turning barrels
Post by: Cutter on May 14, 2019, 05:59:29 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.

Title: Turning barrels
Post by: Cutter on May 16, 2019, 03:31:44 PM

A batch of 60 from 2013