GTA
All Springer/NP/PCP Air Gun Discussion General => Machine Shop Talk & AG Parts Machining => Share Your Simple Home Projects (TRICKS-N-TIPS) => Topic started by: 0351_Vet on December 17, 2011, 05:16:38 PM
-
Is there a good tutorial on Cutting Barrels and properly crowning the muzzle and breeches?
Or any REALLY experienced person here who could lend some guidance?
Thanks in Advance
-
if you don't know what you doing you better leave it to someone who does JMO! but theirs plenty of info on this subject if you want to give it a go! :P
-
Midway USA and Larry Potterfield posted a great video here.
http://www.youtube.com/watch?v=b43odFm0mrI#ws (http://www.youtube.com/watch?v=b43odFm0mrI#ws)
Keep us informed on your progress Walt if you attempt it.
Happy Shooting!!!!
Dave
8)
-
Thanks guys, keep them coming. I have the tools (Power), I am more looking for the "Tips of the Trade" secrets.
Also found this post: http://www.gatewaytoairguns.org/GTA/index.php/topic,1831.msg14616.html#msg14616 (http://www.gatewaytoairguns.org/GTA/index.php/topic,1831.msg14616.html#msg14616)
-
What I would do is buy the longest barrel cut offs you can get cheap, and practice.
Crowning is a tactile thing. You feel it more than see it when everything is right it just happens. After a 1000 crown jobs it will become a skill you'll have confidence doing.
For the first 100 or so it is a get used to it thing and trying to be gentle and let the abrasive do its job over time.
My technique is fast as fast is Profitable. The Brass screw thing was NRA published decades ago. Ld showed me the technique he employed and over time I've developed my own twist as every Smith will. You go with what has worked for you.
The Stone file thing is the expedient I added so the screw doesn't need to do a lot of work.
I use a Fine Stone File from McMaster Carr. The Stone file is tapered 5/16" on one end and ~.125" on the other 3" long. Shape a 90 degree included angle on the back of the stone file. Shape the front so it can do lead ins @ about 15 degree included angle. Shaping stones is about jigging and tayloring with belt sander or jigged Dremel to your needs. Like all thing mechanical the clever guys figure out clever ways of making/maintaining tools.
Face off the barrel from inside out and final cut very small with fresh tool face. I don't use inserts I just Cut my lathe tools back as they wear. I learned from old school tool makers who make & modify most of what they need/use.
Deburr inside edge of Breech & Muzzle (high speed lathe/hand held stone) with 90 degree incuded angle end and oil (both directions) till it goes smooth. Clean and remove abrasives and clean barrel aggressively (I like Gumout Carb and choke cleaner then Rem oil)
Put brass round head machine screw (Head Diam=125% of Bore)in drill press. Apply JB bore past to screwhead. Turn on Drill press.
Lightly push muzzle against screw head as the barrel is spun and swung left right to average out the cut. After doing this a dozen or so times you will start to get a feel for the screw being rough at first and then after about 15-45 seconds it will go dead smooth and this is when the lapping has been completed and the screw has shaped the barrel enuf to mate the radius of the screw to the muzzle crown.
Push patches and clean the abrasives out and push a pellet thru the barrel to see if there is a smooth release at the crown.
If there is a burr you go back and do the screw thing again till the pellet has no resistance at exit.
Smooth entry and exit from rifling is part and parcel to getting the most from any rifled tube.
At the end of the day the experience you get doing or practicing this particular skill will make you better everytimne ytou do it.
You can't screw up a barrel doing a hand crown job correctly. You can make a big gain in accuracy. Done right it will never get worse accuracy unless you cut off the tight end.
Practice Practice Practice. Cutting barrels back .050" at a time till you run out of barrel is the best way to learn something this feel oriented.
There are many ways to skin a fish but the faster fish skinners make more money per fish.
When you crown nearly every barrel that will sit still long enuf you get fast and it makes no sense to let anything get past you without giving it a few minutes to see what it Can Do.
-
Timmy....Great info Brotha. Exactly what I was looking for.
Just out of curiosity. What does a Smith charge to: cut, crown, and drill the transfer port on a owner supplied barrel, per the owners spec's? (excluding S/H/I etc.)
And who provides this service on a regular basis?
Thanks Timmy, Walt
-
For the crown, I like using the Cratex rubberized abrasive cones. Preshape the cone to the desired crown angle and use it with gentle pressure on your Dremel. remember to put a pellet in the end to keep junk from getting into the barrel. I bought a couple 24 inch Crosman barrels cheap and practiced on them. Go slow and check your progress often with a magnifying glass.
-
..............
Put brass round head machine screw (Head Diam=125% of Bore)in drill press. Apply JB bore past to screwhead. Turn on Drill press.
..............
Whoops, as I was writing this, I see Sci Guy posted something similar. Now I am really curious.
Lloyd
....................................
Tim,
Thanks for the very detailed information, and in particular the line of yours that I quoted above.
I have an additional question but I think I know what the answer will be. I use Craytex sticks for various cosmetic deburing and polishing jobs and find them to be fast and efficient. I am assuming that even a hard Craytex stick, of fine grit would not be suitable for performing the job that the brass screw and JB paste do. You are trying to achieve a crisp, but clean and burr free edge, whereas the Craytex would round the edges slightly. Is that correct?
Thanks very much,
Lloyd
-
What is the most common angle used on airguns? Do different calibers require different angles?
-
m i under the wrong impression that its more inportant for the crown to be perfectly square with the bore then the angle of the crown
-
What is the most common angle used on airguns? Do different calibers require different angles?
This is my understanding:
Put brass round head machine screw (Head Diam=125% of Bore)in drill press. Apply JB bore past to screwhead. Turn on Drill press.
Lightly push muzzle against screw head as the barrel is spun and swung left right to average out the cut. After doing this a dozen or so times you will start to get a feel for the screw being rough at first and then after about 15-45 seconds it will go dead smooth and this is when the lapping has been completed and the screw has shaped the barrel enuf to mate the radius of the screw to the muzzle crown.
-
Mr Potterfield is using a 11 degree included and Mr Tim is saying a 15 degree included. I was just wondering if there is a preferred angle for airguns. Getting the face and angle/radius square is very important to accuracy.
-
Mr Potterfield is using a 11 degree included and Mr Tim is saying a 15 degree included. I was just wondering if there is a preferred angle for airguns. Getting the face and angle/radius square is very important to accuracy.
The firearm technique employed may have a 11 degree angle for the piloted cutter. We don't use piloted cutters and the angle of tool I use is 45 degree to the muzzle fase just to break the edge. The 15 degree INCLUDED angle relates to leade in work I have not discussed at all.
I've never seen an airgun done with a piloted reamer and the angle is pretty meaning less as the ege break is critical and square is what you are looking for.
People try to apply firearm info to airguns but you didn't see Mr Potterfield do a crown job in my mind. What he did should not be done to an airgun. FVi9rarms will burn any burr off with a couple of jacketed bullets but airguns are far more delicate and need some hand work. Potterfield used hand tools but he did not do a Crown job on an airgun he cut a firearm off.
-
Tim,
"The 15 degree INCLUDED angle relates to lead-in work I have not discussed at all".
Does this refer to the Breech Face side of the barrel? I would be interested on your expansion of that side of the barrel too. As, when fab'in a new barrel, both ends would have to be "faced" and addressed.
Thank's for all you input, I am beginning to think, with some practice, I would be able to perform this with good outcomes.
"Shape the front so it can do lead ins @ about 15 degree included angle"?
-
Keep it going.....I think I am just about getting the idea.
Thanks everyone....
-
Not that anything I say should be considered correct in this conversation but if I had a need to cut a barrel id ponder using a small tube cutter. I'm sure that's not the correct name for the tool. Its small with a cutting wheel placed between 2 rollers.. mainly used for cutting brake lines and stuff like that.. you turn a handle to move the cutting wheel, get pressed against the barrel and then spin it around 3 or 4 times and you will feel it get loose. Then you tighten the handle down a little more and spin it around the barrel a few more times.. you repeat this untill it cuts the barrel..
Idk if it can be used on a barrel considering how much harder the metal is then a brake line or other tubing.. but id deff ask if it was ok to use, everytime I've used one for brake lines or copper tubing its always given me very clean cuts.. just a thought walt if it will work for cutting barrels
Btw I recrowned my bigcat barrel using a brass screw in my electric drill a few weeks after first joining this forum.. its not perfect but when I finished I had no burrs and a much better looking crown
-
I have chopped and crowned all my airguns using very basic tools with excellent results. I use the same method as SciGuy, and finish off with a hard felt dremel polishing tip with polishing compound.
-
I have chopped and crowned all my airguns using very basic tools with excellent results. I use the same method as SciGuy, and finish off with a hard felt dremel polishing tip with polishing compound.
Would it be safe to cut to length with a metal (carbide) chop saw?
-
I used an angle grinder with a cutting wheel on it. Just make sure you stuff a pellet down past the cut off point so as to keep the grit and shavings out of the bbl. And far enough past the cut point that the heat from cutting doesn't weld the pellet in place, like 2 inches.
-
I used an angle grinder with a cutting wheel on it. Just make sure you stuff a pellet down past the cut off point so as to keep the grit and shavings out of the bbl. And far enough past the cut point that the heat from cutting doesn't weld the pellet in place, like 2 inches.
In a .25, could I shove a 1/4" dowel in and cut through it?
-
on american guns they use a hack saw to cut their barrels down..
-
on american guns they use a hack saw to cut their barrels down..
??? ??? ??? ???
Mike, (http://i1141.photobucket.com/albums/n589/USMC7579/Airguns/tiger_walk-1.gif) Step away from the beer...... :D :D :D :D
(http://i1141.photobucket.com/albums/n589/USMC7579/Airguns/Recon762003b2.jpg)
-
HA HA, he said American Guns......
-
If it's snug, sure, you could even leave it over the cut point and just cut it and the BBL at the same time.
-
Thanks Mike... :)
-
HA HA, he said American Guns......
American Guns. Is that the one where they were trying to cast some bullets, and one guy was holding a cast iron ladle with chunks of lead, and the other guy was holding an acetylene torch on it?
-
HA HA, he said American Guns......
American Guns. Is that the one where they were trying to cast some bullets, and one guy was holding a cast iron ladle with chunks of lead, and the other guy was holding an acetylene torch on it?
:) :) :) :)
-
on american guns they use a hack saw to cut their barrels down..
yeah but it was a shotgun +1 on mike stepping away from the beer
-
You could, but a pellet would work as well or better. This to keep your filings out of the barrel.
pv