up side down threading

J

johan teughels

Member
dit my first barrel with a lefthandholder/insert/neg plate upside down (no place enuff on my lathe do do it from the back side ) at 500 rpm (max speed i can start my lathe in S) and it is so easy and clean and quick i wonder why i dit it not before nearly no thread clean up

i got a metric lathe and it is a very slow to thread without unlocking the halfnut and returning in low speed ( i now there is a system i can do it but i am not a real fan of to complicated)
yes i got a recoil lug

E0966332-DB4D-469D-8D6F-60FB8937D58A.jpg
 
well done

johan teughels said:
dit my first barrel with a lefthandholder/insert/neg plate upside down (no place enuff on my lathe do do it from the back side ) at 500 rpm (max speed i can start my lathe in S) and it is so easy and clean and quick i wonder why i dit it not before nearly no thread clean up

i got a metric lathe and it is a very slow to thread without unlocking the halfnut and returning in low speed ( i now there is a system i can do it but i am not a real fan of to complicated)
yes i got a recoil lug

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Surprised more people don’t do it. I learned toward the headstock and am guilty of keeping with that technique, but like threading away. Still feels a little weird to me though
 
johan teughels said:
dit my first barrel with a lefthandholder/insert/neg plate upside down (no place enuff on my lathe do do it from the back side ) at 500 rpm (max speed i can start my lathe in S) and it is so easy and clean and quick i wonder why i dit it not before nearly no thread clean up

i got a metric lathe and it is a very slow to thread without unlocking the halfnut and returning in low speed ( i now there is a system i can do it but i am not a real fan of to complicated)
yes i got a recoil lug

View attachment 22228
Click to expand...

Did you plunge straight in with the cuts or angle feed 30 degrees to the right?
 
Nothing wrong with upside down threading. The cuts are generally lightbenough as not put much stress on the lower gib plates that keep the carriage from rising up.

And you are correct. When cutting metric threads on a Lathe to a shoulder with an American lead screw, it is easier since you cannot disengage the half nut.
 
jackie schmidt said:
Nothing wrong with upside down threading. The cuts are generally lightbenough as not put much stress on the lower gib plates that keep the carriage from rising up.

And you are correct. When cutting metric threads on a Lathe to a shoulder with an American lead screw, it is easier since you cannot disengage the half nut.
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and like always the master got some toughts i never took in concideration but 100%right now i thing about it thx jacky
 
When I thread metric on my lathe, I disengage the half jut just like standard threads, but reverse the spindle and re-engage the halfnut on the same number I was in on its way back and carry the tool back past the tenon for the next cut...it works and I don’t have to try and withdraw far enough to clear the shoulder or reverse the lathe immediately. As long as you don’t let the thread dial get a revolution off you’re fine.
 
msalm said:
When I thread metric on my lathe, I disengage the half jut just like standard threads, but reverse the spindle and re-engage the halfnut on the same number I was in on its way back and carry the tool back past the tenon for the next cut...it works and I don’t have to try and withdraw far enough to clear the shoulder or reverse the lathe immediately. As long as you don’t let the thread dial get a revolution off you’re fine.
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This method works great, but as you stated , you have to make sure that you keep the half nut on that same spot on the lead screw or you will never find the lead again. It helps to have a Lathe with a dynamic brake.
 
alinwa said:
sdean I don't know what that means? Please rephrase the question? I'm kinda' literal......
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I just meant to a real machinist. 29 or 30 degrees on the compound is the correct taught way. Is the only difference just cutting with one side of the tool. Is there anything technically wrong with just going straight in?
Would anyone catch Jackie plunging straight in? ?
 
I picked up the aloris threading tool #8 http://www.aloris.com/products/threading-holder-8/ on a, albeit expensive, whim,
and it works great for threading away from the headstock. I produced the best threads I have have made and have no intention of going back to the towards the headstock method. The tool has an HSS bit that is easily ground though I did need to relieve some of the material on the left side of the insert to allow a closer fit to the shoulder. If had to do it over I would just get either a left hand threading tool and run it upside down or run a right hand internal threading tool from the back side of the tenon.
Nice looking threads Johan!
 

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jackie schmidt said:
This method works great, but as you stated , you have to make sure that you keep the half nut on that same spot on the lead screw or you will never find the lead again. It helps to have a Lathe with a dynamic brake.
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Unless you're threading at like 500 rpm, you'll have plenty of time to find your spot. I mark it with a sharpie just to be sure I get the right one.
 
"Upside down and backwards"

I also thread left to right plunging straight in using the DRO.

Learned that from my mentor, a 60year machinist who's still doing it and going strong at 75.

He calls it "upside down and backwards".

That term may be old school to you guys that are machinists by trade but I always found it amusing.
 
We do quite a bit of machining upside down. Here is one example, I am machining a 9 inch shaft bearing. The reason I turn them with the tool cutting upside down is so the shavings will go straight down into the pan rather than fly all over.

https://youtu.be/N6pUvQwDVzU
 
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