Single Point Thread Repair

Joe Pie has an excellent video on this subject. He sets the compound parallel to the ways. It’s MUCH easier to get the tool to align with the threads when it’s only moving in one direction at a time. I’ve used his technique several times recently and it works very well. He explains setting the compound at around 14:00.
 
mmcmdl said:
Why not . Been doing it this way for 48 years . Can you explain your quote why not to do it ? You can still pick up the thread regardless of the compound angle . :grin:
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You using the compound to line up thread to the cutter..
If try using the compound at 29.5 then moving the both directions.

Dave
 
Moot point guys (informative though), as I won't be single-pointing @ 40 tpi on this lathe. Thanks.
 
Jake M said:
You don't care that it moves both directions, as you can't zero the cross slide until you've picked up the thread anyhow.
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You only instead in pickup the thread with compound. Trying some other way is a big pain and will take time in most case.

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The 29.5° was first used on very light lathes for cutting corse threads.

Also old time machinist would set compound at 30° for direct reading dial. Most lathes today have direct reading dial on the cross-slide.
You can also for grinding on set compound 11° or less for a finer feed.

Dave
 
Not understanding this Dave . If I were teaching someone , the compound would be set to 29.5 degrees , same as when threading . Bring the tool in close to the piece . Engage the leadscrew to thread at a given number , dial the compound in to center the tool to the existing thread and move the cross slide in . To do this takes 30 seconds . A piece of paper and flashlight under the part will get you perfect . And I understand the compound angle doesn't mean squat . If you're not on 29.5 though , you are plunge threading and the entire tool shape will be doing the work which increases tool pressure .

I believe what you are referring to is double depth while on 30 degrees which is just an estimate old timers used .
 
mmcmdl said:
Not understanding this Dave . If I were teaching someone , the compound would be set to 29.5 degrees , same as when threading . Bring the tool in close to the piece . Engage the leadscrew to thread at a given number , dial the compound in to center the tool to the existing thread and move the cross slide in . To do this takes 30 seconds . A piece of paper and flashlight under the part will get you perfect . And I understand the compound angle doesn't mean squat . If you're not on 29.5 though , you are plunge threading and the entire tool shape will be doing the work which increases tool pressure .

I believe what you are referring to is double depth while on 30 degrees which is just an estimate old timers used .
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When I was teaching people to thread I taught them to set the compound at 29.5 degrees. I still usually thread at 29.5 degrees. Since I learned the method of setting the compound parallel to the ways for engaging existing threads I wouldn’t consider going back to chasing threads at 29.5 degrees.

The last thread chasing/repair I did was on heavy bronze 3”x10 tpi breech pivot retainers for Naval guns that were built in 1910; not something readily replaceable and not a place to take chances. When chasing threads the tool pressure is low anyway. I chased the threads on the some of the Naval gun pieces with a hand crank that mounts in the spindle; didn’t even turn the lathe on so it didn’t take much power.
 
David2011 said:
The last thread chasing/repair I did was on heavy bronze 3”x10 tpi breech pivot retainers for Naval guns that were built in 1910; not something readily replaceable and not a place to take chances. When chasing threads the tool pressure is low anyway. I chased the threads on the some of the Naval gun pieces with a hand crank that mounts in the spindle; didn’t even turn the lathe on so it didn’t take much power.
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Too many Dave's on here ! :grin: Yes , I understand what you're saying and I've done all of the above , and I've done many a BIG Barrel DoD guns . My point was from a newbie's perspective . Once you get the 29.5 procedure down , you can move on to whatever it takes . I can't tell someone that doesn't know his butt from a hole in the ground to do whatever works for him as he just doesn't know . I know wrmiller knows what he's doing , but unfortunately can't do the 40 tpi on his newer/older lathe .

Just to add . The barrel was threaded to size but not concentric . If the existing thread was picked up and threaded , it would be way undersized . Wouldn't trust that on any gun . May have to build it up and re-chase the threads for a decent repair .
 
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