Hey,

I was thinking of this - I assume that the big mfg's uses CNC lathes for barrel cutting and chambering. I was wondering if it had a place in the custom gunshop.

Now I know CNC is most useful for production work but the idea of chucking up a barrel, bringing up a Rem 700 program for threads and chambering and letting her rip sounds great. Particularly if I had 4 or so rifles to cut and chamber. Time would be saved I think other than writing the program.

CNC lathes are not cheap but they do seem cheaper than say a new pick up. Also a CNC lathe could be used for other things - say choke tubes or firing pins or bolt bodies ect.

Any thoughts? Am I way off base?
Also as to the accuracy question - I have seen some seriously accurate rifles from the big mfgs - they can not obviously be chucking the barrels up individualy and cutting and chamering them one at a time by hand.

I have extensive experience with CNC milling machines both vertical and Horizontal and some experience with turning centers including fourth axis machines with M-spindles.....some of these ran over 1/2 MM bucks.

They still required set up and skilled adjustments to every new run as it never was as good as it should have been. IMO they are not a good investment for a one-at-a-time gun shop.

You hit the nail well...they are expensive, they are production machines.

quote:

Originally posted by Loonie:
Hey,

I was thinking of this - I assume that the big mfg's uses CNC lathes for barrel cutting and chambering. I was wondering if it had a place in the custom gunshop.

Now I know CNC is most useful for production work but the idea of chucking up a barrel, bringing up a Rem 700 program for threads and chambering and letting her rip sounds great. Particularly if I had 4 or so rifles to cut and chamber. Time would be saved I think other than writing the program.

CNC lathes are not cheap but they do seem cheaper than say a new pick up. Also a CNC lathe could be used for other things - say choke tubes or firing pins or bolt bodies ect.

Any thoughts? Am I way off base?
Also as to the accuracy question - I have seen some seriously accurate rifles from the big mfgs - they can not obviously be chucking the barrels up individualy and cutting and chamering them one at a time by hand.

A CNC will alow you to come close to final depth for chambering, but you will still have to carefully set the headspace for each bolt and receiver. I've seen too many variables between actions and components to where "one size fit's all" programing would work.

i did a PC control refit to a hurco cnc some time ago... i was a fair to good machinst before, and now, i am good to some better than good.. because the machine does what I want and tell it to do..

jeffe

CNC technology shines when doing production runs of parts that need to be as dimensionally similar as possible. Threading/fitting/chambering rifle barrels does not fall into that category real well due to the reasons already mentioned by malm.

For building gun parts to sell they may work great...but for “gunsmithing†I believe they would not be all that cost effective or useful.

Okay..

so, we'll all agree there's nothing that you can do with a CNC machine that is impossible to do with a manual machine...

seems to me that we must be talking about apples and BLUE, as cnc is fast and fairly easy to learn. and, if you are willing to take an early machine and refit it, fairly cheap.

though if you haven't ever run a cnc machine, especially not out of a production environment, it might be a hard thing to grasp.

as with most things, there's more ways to get to it than walking into the local supply house and dropping 100k.. in fact, you can do a PC refit to a "bad" control cnc mill for about what a used manual machine would cost, without DROs.. A machine suitable for a PC rebuild, and therefore a low use shop, is nothing but scrap iron to a production shop.



there's a ton of yahoo groups related to PC control refits.. which is THE cost effective way to get to CNC machines in a small shop.

http://groups.yahoo.com/group/mach1mach2cnc/
http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/
http://groups.yahoo.com/group/DIY-CNC/
http://finance.groups.yahoo.com/group/geckodrive/
http://groups.yahoo.com/group/CNC_Toolkit/

I built my cnc mill, with about .0015 .0015 total backlash, for less than a good shape bridgeport with DROs.. and my machine IS a bridgeport series I varispeed j-head. .. but it said HURCO on the control (KM1) and is worthless for anyone wanting a production machine. Production machine today means 200 IPM cuts, with 300PSI flood coolant, and a tool changer .. none of those things matter to a small shop. and for gunsmithing, i know for a fact that they are cost effect and useful.. i use mine all the time!! it's easier than most video games to run.. and the chips on the floor are far cooler!!



For me, at least, finding 2 edges and the top surface takes just as long with either type of machine... then again, i think that the precision of doing it perfect, the first time, is a good thing

Learning amateur gunsmithing along with two machinists over the last 7 years [I am an engineer] started out with some complaining that I was not providing any drawings.

Gunsmithing is allot of custom fit stuff, where you deal with the parts that show up.

So if there are no drawings, there sure is no CNC.

this could be a question of what you are used to.

quote:

Originally posted by tnekkcc:
Learning amateur gunsmithing along with two machinists over the last 7 years [I am an engineer] started out with some complaining that I was not providing any drawings.

Gunsmithing is allot of custom fit stuff, where you deal with the parts that show up.

So if there are no drawings, there sure is no CNC.

that mixes metaphors.. and is not really accurate for the CNC "no drawing no cnc"..

FITTING is generally not do with a drawing, it's done with the control, in conversational mode, or basic gcode. Fitting, something like "the dovetail on this sight is .003 too long" is pretty trival... and all this below takes less time with a QC toolholder and cnc than just the time it takes changing collets on an R8 machine

put a 3/8" edge finder in, touch X, set X axis to .1875, touch y, set Y axis to .1875, get a feeler gauge or a piece of mic'ed paper.. bring Z down to touch, and that .0035 Z ... the dovetail is .065 deep

to make life easy,
g1 x.1875 y.1875 f10

then zero X/Y DROs
g1 z-.068 f2

with X/Y at zero, dovetail cutter a the proper height, assuming you have the sight lined up along the X axis and it's .75 x.75
g1 y-.003
g1 x 1.125 f10

and now you want a set screw in the midddle of it. You swap to a drilling chuck (there's several choices) and touch set Z...

g1 x0, y0, z.003 f5
x.375 y-.375
g1 z-.275 [it's a thick sight] f2 [just to keep it straight]
z.02
x-5 y0

now tap it while in place..

all that takes about 10 mins, including the tapping.

As for drawings of new parts to be made...... unless it's "drill two holes .275 apart, along the center line, location not very important" .. I at least sketch everything... and prefer to take 1 couple minutes or hours to plan the project. it takes me FAR LESS time to let the cad program tell me I screwed up than to rework a part.

Gunsmithing is about making parts and making them work, to the customers satifisfaction and to safety. Fitting parts is part of it, sure enough, but not anywhere near all of it ...

besides, heh.. it's alot better to have those custom bases with the proper hole spacing drilled the first time than to "fit" them with the wrong spacing
jeffe

1) Where I work we make drawings in CAD and the program for CNC is driven by the CAD.

I don't work in CAD, I just hand scotches to draftsmen and mechanical engineers and wave my hands and tell them what I invision. They roll their eyes, but soon after I get the prototype parts. I don't do tolerance stack up calculations, I depend on them to know how to make things fit.

2) When I work on amateur gunsmithing in our garages, I make sketches and wave my hands. The machinists roll their eyes and make guns that look like jewelry.
When I operate the machines myself, the quality of the parts is not like jewelry.

3) When I work with a real gunsmith, I make a list of things to do, he does NOT roll his eyes. I come back later, and pay the money and pick up the parts. I never give him drawings, just the parts that fit together.

quote:

Originally posted by jeffeosso:
besides, heh.. it's alot better to have those custom bases with the proper hole spacing drilled the first time than to "fit" them with the wrong spacing
jeffe

First off, if the person who is drilling the custom bases is a complete idiot, then the hole spacing can be off regardless of which machine is used to screw them up. But, this discussion is about CNC lathes and barrel installations. And unless Loonie is planning on making every Rem 700 action identical, then he will be wasting both time and money using a CNC machine for barrel fitting.

tnekkcc,
laughing WITH you here... are you saying that a perfectly engineered part, through a decent QC, that becomes repeatable, requires a part, but a bespoke part, made in a shop on manual machines, doesn't?

As for cnc chambering ... . Though I have seen barrels chambered without a depth gauge in the shop, I don't do it that way.


Loonie,
Here's how one installs a barrel via a CNC machine, with a single tool change for the chambering and threading.. it is AMAZING how close it is to the same work with a manual machine...

pre-work.. face the receiver, sqaure the boltface, lap the lugs, if you like.

let's assume a reamer IS used, rather than what a CNC machine can do for you.

*****let's be clear, you can leave the chamber .005 long and reset the reamer .001 at a time, to "chipchip" into testing the headspace .. EXACTLY like a manual machine******

until said otherwise, all this is the same manual or cnc)

You'll need the headspace datum, if you want to work off that, or you can work off OAL/COAL.. we'll just call that "length" as there's 1/2 a dozen ways to do this.

with a digital depth gage (cuz it's easier) measure from receiver face to bolt face .. write that down... (let's say it's .725)

then measure shank length.. in a mauser, that from the shoulder to the Flange face, +.002 for compression. .. let's say it .623, so +.002 we have .625)


subtract the shank from the "to the face DIFFERENCE" and that's .100 - this is critical info

Now, measure the length of the case, or the actual depth the reamer has to go into the case to have "zero" headspace.. for example, let's assume that the reamer has 1" of pilot, lead, and a "hair" longer (generally .005") in the neck than a "perfect" round, just to make life easy..

so, now this part is easy...take caselength (2.5) and "pilot/lead" add together, and subtract the "difference" to receiver from the length, and that's how far the reamer has to go in for "zero" headspace. or

say this is a 338 winmag, just for giggles.. that would be 3.4

(the next couple are both manual and cnc)
face the barrel
(cnc only) index off the end of the barrel, setting your tool length and X,Z zero for the carbide threading insert and the chamber reamer (though a boring bar would make this easier)
both -
cut shank (.625 x1.1) (on cnc, this can be done at max SFM and still get a great finish)
cut threads (heh.. cnc is WAY faster than anyone cutting manually, and , since the headstock is on a tach, the threads are EXACTLY 12TPI, not something close)

change tool to reamer (or rougher, it doesn't matter, as you are doing the same for both)...

now, here's the divergence...

with cnc, you can set the speed and feed rate (since I am reaming, I don't think SFM), with a "peck" cycle that goes in .1, backs out, cleans chips, and goes back, same place and depth, same registration, every time. So, you set the reamer to go on a peck drilling cycle for 3.4 inches... with a cleanout cycle every .1 inch, and you have coolant either in the barrel or to blast off the chips on the cleaning cycle.

after 34 or 35 (depending on finish cut) cycles, at say 5IPM in, 10IPM out, say, 10 mins including cleaning, you now have a chamber set for "zero" headspace..

and if you aren't a "friggin idiot" and can meausure correctly, a GO gage should just barely close on this chamber.



And, yeah, that takes all of perhaps 30 mins on a cnc setup ... and you can tell it to leave .005 for "hand reaming" if you like.


it's a time SAVER, and allows for a perfect chamber, as along as you know how and what to measure.


jeffe

Does the computer clean-up afterwards also?

quote:

Originally posted by Rick 0311:
Does the computer clean-up afterwards also?

wouldn't that be COOL? nah, that part is still up the operator..

If you buy the right CNC there is a conveyer belt that dumps the chips in the barrel. However this machine is more than what you would need in a gunshop. I use CNC for threading a barrel, once in a while. It works very nicely on a Bridgeport EZ-Path lathe. The controller has a program library where we store each program for each receiver. You just need to set the tool diameter and set the z-axis and a way you go. It takes about 45 seconds to machine a barrel for a Mauser.

The bad thing about CNC for chambering is that the carriage is controlled by a reastat (sp) and you don't have any feeling about its movement. You can feel how the reamer is cutting. I always chamber on an engine lathe, I have better control of the process.

I had one project last year that was made easier, I was milling and turning a 1/2 round octagon barrel, the customer wanted a wedding ring to separate the 2 piece of geometry. The ring was easy to program on the CNC.

No doubt a CNC machine can be a real asset to the custom gunshop. However, purchasing one with the belief that you will be able to fit multiple barrels to multiple receivers that were manufactured by someone else, is not realistic. There are just too many tolerance variables between commercially produced receivers to write a program or series of programs to handle all of these.

Those manufacturers who are producing the super accurate rifles you speak of are more than likely producing their own actions. This let's them control every aspect of the manufacturing process from start to finish, but, as precise as this is, each gun still requires hand assembly and fitting. The big shops employ numerous skilled people to do the fitting.

Barrel manufactures use CNC machines to produce barrels for sell to the public that are pre-threaded and short chambered, but will neither guarantee the fit, or, results unless they thenselves "hand fit" their barrel to that particular action. This is what a "custom" gunsmith does, and there is no way one can program a machine to provide that level of fit.

I have been going to machine shop auctions as Boeing shuts down much of local activity.

There are small machine shops, other amateur gunsmiths, real gunsmiths, and one barrel maker that shows up; John Benjamin.
I have also been going to Boeing surplus, the local machinist's college, and looking on Ebay and Craig's list.

My assessment is that no one want anything to do with CNC that is into guns. Most CNC is sold as scrap. Even Bridgeport mills that are CNC only are worth 10% of manual machines. There are some newer CNC stations that are like little enclosed rooms, that attract out of state bidders, but they are not gunsmithing types.

If you want to get into CNC for gunsmithing, more power to you, and you can get it very cheaply.

I too live in the Seattle area and have gone to a lot of these auctions. The last one I bought a life time supply of carbide cutters for $300. I've seen some of the CNC equipment we've talked about in this thread, that sold new for over $100,000, sell for $12,500. There's everything from inspection tools to welders and office supplies. Someone is taking a real bath, most likely it's the banks that supplied the money in the first place. Interesting event to attend....