Barrel blank-threading/chambering question

[sharpshooter]

Savage cuts threads in the profiling operation on a Mori Seiki CNC turning center with a single point tool. The threads are cut in 7 passes. I can't say it's more consistent, because it is not. I've measured thread shanks on hundreds of take off barrels and found that the tolerance is quite wide....wider than than what's on their own prints.

As far as chambering with a boring bar, that has been tryed with no success. It's harder to hold a dimension in a production scale that is required for that specific operation. And by the way...Savage does not chamber their barrels on a lathe.

[Westcliffe01]

I suppose I should have qualified "barrel makers" as those besides the rifle makers. I get the impression that plenty of dodgy tactics are used by Remington, Savage and others in making parts for their rifles. However, in the field of precision machining, hardly anything gets made with a reamer unless it is a straight bore or a defined taper. Virtually everything is cut with a single point tool. Down to 2/10 000th tolerances too, so to tighter specs than the manufacturers actually hold on their reamed chambers.

What kind of variation did you see on the barrel threads ? Too large/small, tapered or what ? Unless the machinist keeps his machine / insert dialed in, clearly there will be a bunch of variation. Thats the point of statistical process control, to identify the sources of variation and then define periodic maintenance so that the source is eliminated or fixed before anything gets out of spec. Sounds like these guys live in a world prior to ISO 9000 or even plain good management.

[sharpshooter]

If a guy like you ever toured the Savage plant prior to 2008, you would **** your pants at the way they were doing things and the things they got away with. When I toured the plant in Nov of '05, they used several Mori Seiki turning centers to do strickly barrel work. It would turn, thread and crown a sporter barrel from 1.110" rifled blank in 2.5 minutes. At the time, this was their newest machines. Other than that, they had a total of 3 CNC mills doing receiver operations, the oldest being a Bostomatic purchased in 1988. The rest were done on an assortment of (about 50) Cinncinnati horizontal mills set up for just 1 operation.
Barrels were chambered on a Byrd vertical turret mill. The barrel is stationary, the tools turn. 1st op is a chamfer tool, 2 is a core drill, 3 is a rougher reamer, 4 is a finish reamer, and the last is a flexi-hone which does 20 peck cycles. Amazingly, the chambers come out very consistent in size, but they may not be centered in the bore. They retired those machines 2 years ago, and replaced them with new machines of the same type. When I asked the director of engineering why they did not go with HMC's he stated that they could not get the results they could with the vertical machines.