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Muzzle threading help needed.
- Thread starter 6literZ
- Start date
- Joined
- Apr 8, 2013
- Messages
- 2,040
go Stob,
I stop the lathe and finish the pass by hand to get every pass to end in exactly the same spot. With 70 rpm as the minimum speed on my 12 x 36 I would have to pull the half nuts and withdraw the cross slide in exactly the same spot for every pass and do it in one heck of a hurry. Slow on the half nut and I crash the shoulder. Slow on the cross slide retreat and I just made a groove around the part. I just can't get both of these functions absolutely identical for 15 or 20 passes in a row. I only do this when I don't want a relief groove or have to go tight against a shoulder.. If a groove is appropriate I keep the spindle turning and use the half nuts in the conventional way.
I stop the lathe and finish the pass by hand to get every pass to end in exactly the same spot. With 70 rpm as the minimum speed on my 12 x 36 I would have to pull the half nuts and withdraw the cross slide in exactly the same spot for every pass and do it in one heck of a hurry. Slow on the half nut and I crash the shoulder. Slow on the cross slide retreat and I just made a groove around the part. I just can't get both of these functions absolutely identical for 15 or 20 passes in a row. I only do this when I don't want a relief groove or have to go tight against a shoulder.. If a groove is appropriate I keep the spindle turning and use the half nuts in the conventional way.
A proper relief cut does not weaken the thread joint in any way. For this muzzle brake application the number of threads left in contact are more than enough.
When threading the other end of the barrel there is no thread contact under the recoil lug and this joint sees much more stress. There is absolutely no gain to avoiding a relief cut and maybe some practical advantages in service to have one.
When threading the other end of the barrel there is no thread contact under the recoil lug and this joint sees much more stress. There is absolutely no gain to avoiding a relief cut and maybe some practical advantages in service to have one.
- Joined
- Sep 9, 2014
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- 90
Must agree with Tozguy.
There is no reason not to use a relief cut. It makes life much simpler. I build long range (1000+ yards) target rifles in nearly every magnum caliber you can imagine. There has never been a problem with stress fractures to my knowledge. Most of them have muzzle brakes installed which need to be timed to twelve o'clock. They all have relief cuts. I always time my barrels to the action with the bore curve at twelve o'clock which means cutting the shoulder back after threading. Cutting the shoulders assures the cut is at 90 degrees to the bore.
There is no reason not to use a relief cut. It makes life much simpler. I build long range (1000+ yards) target rifles in nearly every magnum caliber you can imagine. There has never been a problem with stress fractures to my knowledge. Most of them have muzzle brakes installed which need to be timed to twelve o'clock. They all have relief cuts. I always time my barrels to the action with the bore curve at twelve o'clock which means cutting the shoulder back after threading. Cutting the shoulders assures the cut is at 90 degrees to the bore.
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papaw
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Can any one tell me why you can't just disengage the halfnut when you reach a predetermined point? I have Trav A Dials on my lathes. Doing it this way will leave a vee groove next to the shoulder. I use Arthur Warner HSS thread inserts.
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- Feb 8, 2014
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If you can live with the v-groove at the end of the thread then there is nothing wrong with doing it that way. In certain circumstances, I do it that way.
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papaw
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Most people never notices it. On my Monarch 10EE I have ELSR and it will allow you to thread to the shoulder every time. I use my Clausing 6013 to do barrel work though.
