Thread dial indicator question

AGCB97

AGCB97

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I thought I remembered that when using the TDI for any even thread you could use at least the even numbered lines. I was cutting a 18 TPI tread yesterday and had started with the 4 line but once changed to the 2 line and it cut a different place. Is this right or did I do something else wrong?

The leadscrew is 6 TPI, the TDI has 24 teeth, the dial is numbered 1 - 4 with intermediate lines and the carriage travel per one revolution of the TDI is 4".

I know I've seen some kind of a chart for this but can't seem to find it now.

Thanks
Aaron
 
It takes a little longer to cut threads because you have to wait for your number to come up, but I always use the same line no matter what thread I am cutting. Never have to worry about it them.

Richard
 
What lathe? What is the lead screw pitch? How many teeth on the thread dial gear? Divisions on the dial? My Grizzly lathe has a 12 tpi lead screw and the dial has twelve divisions. Any pitch that is evenly divisible by three can be cut using any mark on the dial. All other threads can be cut using every third mark on the dial. Half integral threads require using every sixth mark.
 
I have had that experience, but I chalked it up to it being my mistake. I swear that I hit my mark, but I must have missed. For a while I was only threading with one number with even number threads, but I'm over it now. I use any number with even number threads. With uneven number threads I only use one number. I never use the lines though, ever.
 
RJSakowski said:
What lathe? What is the lead screw pitch? How many teeth on the thread dial gear? Divisions on the dial? My Grizzly lathe has a 12 tpi lead screw and the dial has twelve divisions. Any pitch that is evenly divisible by three can be cut using any mark on the dial. All other threads can be cut using every third mark on the dial. Half integral threads require using every sixth mark.
Click to expand...
See OP
It's a 1920 Springfield Ideal Lathe
 
Sorry, I missed your lathe in your tag line. My lathe has 48 teeth in the thread dial gear and the carriage moves 4.00 inches for one complete revolution of the thread dial. Each mark on my dial represents 1/12th of 4 inches or 1/3rd of an inch, also four threads on the lead screw.

Lathes with an 8 tpi lead screw are set up differently and depending on the number of teeth on the thread dial gear would have either 4 or 8 marks on the thread dial. If cutting a even numbered pitch, you should be able to engage on any mark. If cutting odd numbered pitch then every other mark.

My Atlas/Crafstman 6 x 18 has a 16 tpi lead screw, 32 teeth on the thread gear dial, and moves 2.00 inches for one revolution of the thread dial. The thread dial has 4 marks and even numbered threads can be cut by engaging on any mark. Odd numbered threads are cut on every other mark and half numbered threads need to start on the same mark with each pass.

The point being that there is no such thing as a universal thread dial protocol.
 
I've cut quite a few threads and never had trouble before so when this happened I doubted my memory.
 
i usually don't get superstitious-until threading.
then i break out the lucky rabbits foot and pick a number, then i go with that number until i'm done.
there's not much worse than spending many hours then missing the number and scrapping a piece :mad:
 
I can never remember all of the iterations so I always just engage on #1 no mater what the thread, Yes it might take me an extra minute or two to finish the thread, from waiting for that #1 to come around again, that's fine, I am not in production.
 
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