Checking My Nuts

[dallen]

I think his part slipped in the chuck, because he did a practice cut without any problems.

chuck wasn't tight enough

[DaveH]

I have to prove it  
A long time ago when I did this ........... The thread you wish to cut is 10tpi or 5 threads per 0.5" or 2.5 threads per 0.25" (best to read half inch, quarter of an inch)
Remember 2.5 threads per quarter of an inch.  

Lead screw 8tpi and a 16 gear pinion ......... so 4 turns of the lead screw will move the carriage one half of an inch (0.5") as well the chaser dial will move 2 divisions.
If the half nuts are engaged all is fine because there are 5 threads in the half inch - the tool has moved exactly 5 threads.
Now is the lead screw only turns 2 revolutions the carriage will move one quarter of an inch (0.25") or one division. So the tool moves 0.25" that will align the tool 2.5 threads further from where the tool started if the half nuts are engaged here it will be half a pitch out.
So the half nuts have to be engaged every 2 divisions.
The half nut have to be engaged on a complete thread not on a half thread as 2.5 threads. 
Hows that for proof  

I am assuming an 8tpi lead screw and chase dial with a 16 tooth pinion.
 
DaveH

[DaveH]

(04-26-2015, 02:34 PM)dallen Wrote: I think his part slipped in the chuck, because he did a practice cut without any problems.

chuck wasn't tight enough

I think that was because Ed used the same mark and it can take some time for the same mark to come around again especially if one just misses it
The last time Ed used the first line that was there (to speed things up). The chart on Ed's lathe says you can.

I don't believe it slipped that chart on Ed's lathe (I think )is incorrect.

DaveH

[EdK]

(04-26-2015, 02:54 PM)DaveH Wrote: ...

...
The last time Ed used the first line that was there (to speed things up). The chart on Ed's lathe says you can.

...
DaveH

Not true. I used the same number for all passes. That's the way I always do it. I posed the question afterwards as to whether one could use any of the numbers to speed things up.

Ed

[DaveH]

Oh dear sorry Ed I got it all wrong.
Apologizes to every one I got it all wrong.     It may well be best to ignore my posts they just caused more confusion.

So something must have slipped.
 
DaveH

[EdK]

Doing some experimenting, I tried the following numbers on the threading dial.

1 - cuts overlapping threads.
2 - see 1.
3 - see 1. (this is the number I used when I cut the practice 10TPI acme thread)
5 - see 1.

Leaving half nuts engaged - see 1.

Clearly there has to be a gearing issue. I'm taking a break from this and then I'll go over all of the gears and levers once again for the umpteenth time.  

Ed

P.S. By the way, the so called manual that came with the lathe is a far cry from being a manual. It has no content on operating the lathe and does not even include the chart shown on the front of the threading dial mechanism.

[DaveH]

(04-26-2015, 03:41 PM)EdK Wrote: Ed

P.S. By the way, the so called manual that came with the lathe is a far cry from being a manual. It has no content on operating the lathe and does not even include the chart shown on the front of the threading dial mechanism.

My manual is the same nothing on operating or threading on the lathe. Waste of time really.
My lathe doesn't even have that dial chart like yours does.

DaveH

[dallen]

I don't even have a manual for mine 

[EdK]

All is good, back to normal. Now I need to make a new nut blank.

Ed

[Mayhem]

Looking at the chart on Ed's threading dial, 1-8 was interpreted correctly by Ed, as you will see that 1 or 3 is shown as 1, 3 and that just the numbered lines as 1,3,5,7.  Whether all these have been printed up correctly is another question.

(04-26-2015, 04:20 PM)dallen Wrote: I don't even have a manual for mine 

Me either - I doubt the parchment lasted as long as the lathe has.

(04-26-2015, 04:56 PM)EdK Wrote: All is good, back to normal. Now I need to make a new nut blank.

Ed

So - what was the problem?