Threading away from chuck

L

Lucky Shooter A

Guest
I’ve done a few barrels by threading away from the chuck and like the finish that can be had with higher spindle speeds. However the thread starting point is a bit rough.

A friend ground a threading tool that could be started in the thread relief at the shoulder and work off the breech end.

I used an indicator to repeat the starting tool position and still got a rough start.

On another barrel, I adjusted the indicated tool position by one half(sine 30 deg, cosine60 deg) the last compound adjustment----still got a rough start.

Is there a way to eliminate this rough start ? I really like these threads----maybe just live with the start ?

Would appreciate any ideas.

A. Weldy
 
What George is said will probably fix it. Bits don't like square edges to start on. Use a standard threading bit to cut a bevel to thread depth. The thread will progress to a full thread nicely from there.
 
Thought I did

Its been a while but I think I cut the relief groove with the tip of the threading tool and allowed slightly more depth than the thread's crest to root for clearance below the tip of the tool.

I'm going to try a test thread to see.

It never seemed to matter where I started the tool when cutting toward the chuck-----except I did cut more air than I did starting out in the relief groove.

Kinda made me wonder if some minimum amount of carriage movement is necessary to get everything moving and synchronized with the lead screw.

Thanks for the help.

A. Weldy
 
Thank you George

Removing and holding the slop out of the carriage wheel made the difference.

A magnifier showed a single contact point with the tool into the work piece. Much better.

Thanks again.

A. Weldy
 
Forgot to add you can also just snug carriage clamp finger tight, remember this will cause issues on ways eventually. but machines are kind of expendable to me anyway.
 
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