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Threading rifle barrel cross feed vs compound cf?

Mram10

Cast Iron
Joined
Dec 17, 2017
I am learning the hard way and tried threading with the crossfeed instead of compound cf. is it possible to do it with the crossfeed?
 
I am sure there are all kinds of arguments both for and against but I find it much faster to thread using the cross slide as opposed to setting the compound at 29.5 degrees and doing it that way.

I prefer to turn my thread tool upside down and thread with the lathe in reverse moving away from the shoulder. I do it all with light cuts and run the lathe at 350+ rpm. No worries about hitting the shoulder faster rpm makes nice smooth threads.

Gary
 
If your lathe and tool holder are stiff enough, threading with cross feed is no problem. However, many hobbyist type lathes are not and thus the compound feed method must be used to prevent chatter.

RWO
 
If you have a GOOD tool and cutter grinder, you can grind the thread helix angle for relief on your lead cutting edge (60* standard thread cutting angle). This has worked for me on large threads. Example..if memory serves, a 1" x 10tpi has a thread helix angle of 5 deg.
(from memory, not guaranteed), cut your tool to 60* and then grind the bottom of leading edge to a 5 deg. relief. Follow edge doesn't really matter as long as it's relieved. Then you can crossfeed. If you're using a standard bench grinder,you wont be able to cut accurate relief angle. On fine threads I find I get a nicer thread with compound feed. Hope this helps and makes sense. PB
 
What kinds of problems are you encountering when cutting threads?

The downside of cutting with the crossfeed is the cutting is being done on both sides of the tool which doesn't load the tool such that the slack in the system is always taken up the same way. This can lead to a slight wavering of the thread.

When using the compound, most of the cutting is done on the leading edge so the cutting reaction is pushing the slack out the same way on each pass. This eliminates the wavering and gives a smoother thread.
 
QI: [I am learning the hard way].. Think you should practice with conventional method by the book till it seems old hat…I like to have a 5* back rake and a 5* side cutting edge for mild to tough steel. Picking up a thread and checking with wires..should also be old hat before turning a barrel thread.
But practice stock is not a barrel because the barrel may not always be a straight short easy to chuck part…
 
What kinds of problems are you encountering when cutting threads?

The downside of cutting with the crossfeed is the cutting is being done on both sides of the tool which doesn't load the tool such that the slack in the system is always taken up the same way. This can lead to a slight wavering of the thread.

When using the compound, most of the cutting is done on the leading edge so the cutting reaction is pushing the slack out the same way on each pass. This eliminates the wavering and gives a smoother thread.

Plus if you have any back or side cutting edge clearance the follow side will just rub on the part like a negative edge.

You can buy pre-ground bits ..but they are costly...be sure you know if 5*, 60* or what...
BROWNELLS BARREL THREADING LATHE BITS | Brownells
 








 
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