Checking My Nuts

[Mayhem]

Sorry to hear about your threading issues. I wrecked a project yesterday too when threading.

Moving the carriage towards the tail stock (when turning a RH thread) makes that mark come around quicker.

[Roadracer_Al]

(04-25-2015, 06:56 PM)Vinny Wrote: I don't care what threads I'm doing, that's where I engage the half nuts.  One less thing to go wrong.

I do the same thing. I'm not trying to win a race, and it's not like I'm earning money doing this stuff. And, I don't thread often enough to be fully confident with it.

Ed, you might try cutting the thread again WITHOUT releasing the half nut. Cut the thread, stop the lathe, back the carriage out, reverse the motor, re-zero the carriage, make another pass. Works much better if you have a foot brake on your lathe. This way, the relationship between the lead screw drive train and spindle is preserved.

[Highpower]

(04-25-2015, 06:38 PM)EdK Wrote: For some reason my thread passes are overlapping. I'm still scratching my head over that and haven't figured out why. I've checked the gearing and levers numerous times and they seem to be correct for 10TPI. I've ruined the first nut so I'm going to chuck up a piece of round scrap and cut an external thread and try to figure out why 10TPI threads are overlapping. Time to call it a day and take a fresh look at it tomorrow.

The chart for my lathe says for 10TPI I can use the numbers 1-8 on the half nut dial. Does that mean I can use any one of them or do I need to pick one and use only that one for the thread? I've always used the one I started with. It makes it a lot slower though waiting for the number to come around again.

Ed

I thought this sounded familiar. Not trying to crack wise Ed, but could this possibly be a case of Déjà vu all over again? 

http://www.metalworkingfun.com/showthrea...8#pid27908

My lathe chart says I can use any NUMBERED line as well. 

[DaveH]

Here's my take for 8TPI lead screw:

Multiples of 8 such as 8, 16. 24 tpi engage anywhere ( the chaser dial does not have to be used)
If the tpi can be divided by 4 such as 12, 20, 24 tpi use any of the 8 marks 
If the tpi can be divided by 2 such as 10, 14, 18 tpi use any of the numbered marks ie. 1,2,3, 4 

So my answer to your question wrt cutting a 10 tpi thread is no you can't use any of the 8 marks only any of the 4 numbered marks.
I was a bit hesitant to give my way because it dissagrees with your manual.  

If you want to know how I remember this:
8 tpi lead screw and a 16 tooth gear in the chaser dial, so 16 divided by 8 = 2
Now if the tpi can be divided by 4 then 4 multiplied by 2 = 8 (any of the 8 marks can be used)
If the tpi can be divided by 2 then 2 muliplied by 2 = 4 (any of the 4 numbered marks can be used)

 
DaveH

[EdK]

(04-25-2015, 11:41 PM)Highpower Wrote: ...
I thought this sounded familiar. Not trying to crack wise Ed, but could this possibly be a case of Déjà vu all over again? 

http://www.metalworkingfun.com/showthrea...8#pid27908

My lathe chart says I can use any NUMBERED line as well. 

Willie,

That's the first thing I thought of and checked it. At least I learned that lesson.  

The last thread I cut was the practice 10TPI acme thread I cut in aluminum. I had to change the gears to get my power feeds back to normal for boring but that doesn't involve swapping that lower gear and spacer so I didn't think that would be the problem, but I checked anyway, multiple times.

Ed

   

[f350ca]

Tom had a really good video explaining the thread dial. It may help you. I use Al's method on the Summit and never disengage the half nuts when threading. Mostly because they are so stiff and heavy on that lathe they're hard to disengage when wanted. Its clutch driven so reversing is just a matter of moving the clutch lever in the other direction.

[EdK]

I'm beginning to think that the part got pulled out of the chuck slightly on the first pass. I've got some aluminum from a beer can wrapped around it to keep from marring the surface.

Ed

[Highpower]

Ooooo... yeah that would suck. 

[f350ca]

Now did you drink the beer before you tried machining it.

[DaveH]

(04-25-2015, 11:41 PM)Highpower Wrote: My lathe chart says I can use any NUMBERED line as well. 

Willie,
The numbered lines surely means the lines that have a number allocated to it such as 1,2,3,4.
Ed, is saying any line (I think)

What is confusing me where you say "NUMBERED line as well" ............. as well as what?
This is what Ed said "The chart for my lathe says for 10TPI I can use the numbers 1-8 on the half nut dial."

DaveH