Single Point Threading Issue - might be gearing?

[T Bredehoft]

On my lathe the dial is held on with a screw in the middle. You might need to space the housing a bit farther from th saddle.

 

[WobblyHand]

Ok. Now have 32 TPI. But kind of sad looking threads. There's a lot of swarf and bent over thread edges. I seem to be having trouble always hitting the mark, sometimes it drops in, and sometimes it hangs and drops in the next "detent". Would this lack of consistency of hitting the mark make the threads ratty? Is there some better way to practice? (It's clear I need to work on this.) What material is cheap and gives one a similar enough experience as single threading metal? From reading on HMF I think someone mentioned PVC pipe. That would help for the coarse threads.

 

[WobblyHand]

On my lathe the dial is held on with a screw in the middle. You might need to space the housing a bit farther from th saddle.

Mine pivots on the screw into the side of the apron. The screw is parallel to the ways. I can adjust the depth of the engagement of the dial gear to the lead screw by rotating the dial face toward me, or more vertical. As far as I can tell that's the only adjustment I have. That's what I played with.

 

[WobblyHand]

Hmm, forgot the picture of the awful threads.

How do you make nicer threads?

 

[royesses]

Just ran this on the calculator (https://www.cgtk.co.uk/metalwork/calculators/changegears/minilathe) Many combinations will work :

Gear A	Gear B	Gear C	Gear D	Actual TPI
20	ANY		40	32
30	ANY		60	32
40	ANY		80	32
20	20	40	80	32
20	30	60	80	32
20	40	80	80	32
20	80	60	30	32
20	80	80	40	32
21	35	50	60	32
21	60	50	35	32
30	40	40	60	32
30	45	60	80	32
30	60	40	40	32
30	60	80	80	32
30	80	60	45	32
30	80	80	60	32
40	20	20	80	32
40	40	30	60	32
40	60	30	40	32
50	35	21	60	32
60	30	20	80	32
60	45	30	80	32
80	40	20	80	32
80	60	30	80	32
80	80	30	60	32

​

Roy

 

[WobblyHand]

When I started, this morning, I had no idea that one could do ABD, and you needed to move the spacer as well as the pivots. Now, I know. There sure are a lot of combinations to get 32 TPI!

Sad to say, if I had actually looked at the sticker on the side of the gearbox cover, I would have seen a simplified table, and both the ABCD and ABD diagrams. I had turned over the cover, and never noticed it.

 

[T Bredehoft]

How do you make nicer threads?

Cut 10L12, Ledloy its a free machining steel. They will be a lot nicer.

 

[ttabbal]

You can learn on PVC for higher pitch threads. Don't know that I ever did more than 24, but it worked well. Aluminum and 12L14 work well as well.

 

[mikey]

Cut 10L12, Ledloy its a free machining steel. They will be a lot nicer.

Tom, I never heard of 10l12. Ledloy is usually 12L14. Was that a typo?

 

[WobblyHand]

I have some 1215 (no lead) but it's hex. I can turn it down and try some. It's supposed to be free machining, but not quite as good as 12L14. I'm shying away from 12L14, etc. just due to the lead. Not sure how to legitimately dispose of the chips. Probably will also buy a stick of 1/2" pvc pipe, that should be cheap enough. ($2 for 10 feet, quantity 1)