Need a way to turn a 30 tpi screw.

[Magicniner]

Do you know someone with a CNC lathe? They will turn any lead you want.

Or a lathe with change wheels
My lathe has cut every metric and imperial thread I've ever needed, spot on too, not just somewhere close

[JackF]

Hi earlgo, yes I got your PM. I forgot that I called it out as a 1/4 X30. I measured the major OD of my last message with my 0-1 mit. micrometer. I did measure the pitch with a thread gage. I will go out to the shop this morn and measure again. I will also try out for the first time my thread needles to get the minor dia.


Jack.

[Harold_V]

I will also try out for the first time my thread needles to get the minor dia.

Hmmm. Thread needles?
Do you mean thread wires (or thread triangles), Jack? If so, they will provide a pitch diameter measurement (assuming you know the proper constant), but they will not provide a minor diameter.

H

[JackF]

Hi Harold, yes, I meant wires, thanks. Looks like they will stay in the case for now.


Jack.

[spro]

Pitch diameter is super important. H has told us about arranging the thread wires years ago. Was the tool sharp or truncated ? The new tool or the old one ? A thread can measure certain OD but maybe not sharp anymore. The pitch diameter is the meat of the threads' holding power.
It will be explained better ..

[earlgo]

JackF: Did you see this listing on e-bay? https://www.ebay.com/itm/Stevens-Favori ... SwZM9apenf
If this won't suit, then I will proceed with a double ended threaded blank for you to finish, as we discussed.
--earlgo

[JackF]

Hi Earl, no I hadn't seen that. Upon closer examination it looks pretty pitted. I will pass on it. Lets go with the double threaded blank.


Thanks,
Jack

[earlgo]

Ok. Double ended blank cut from 9/16 dia 41L40 rod, threaded 5/16 od with 30tpi and centers in each end. Big enough to make 2 TD screws. It is 24° in the shop today but will be warming up soon. Hope to have it to you next week.
--earlgo

[Harold_V]

Ok. Double ended blank cut from 9/16 dia 41L40 rod,

Out of curiosity----does the L (in the 4140) create any problems when bluing?

H

[earlgo]

Haven't a clue about blueing leaded stock. I should try it before JackF sets off on his quest. At the very least, a heat blue would work although it may not match other colors. Thanks for bringing this to my attention. Maybe the best solution would be to use O-1 so there is no doubt, but I'm still going to try the 41L40 just to answer this question.
To be honest I am having mental gymnastics with the 30tpi. Neither of my thread gages have a 30 leaf, so I am going to have to rely on a comparator for the final measurement.
--earlgo

[Harold_V]

Thanks, Earl. Curiosity has the better of me, as I know that some materials don't respond well to black oxide. Heat treated items have a tendency to turn a dark reddish brown. The spindle nose on my Sunnen hone displays that very color, with the black oxide finishing done by a commercial finisher. All the rest of the parts done were black, as intended. So much to know and so little time to get educated.

H

[spro]

Perhaps something is missing here. It is difficult to surmise an ancient thread from afar. Sharp may not be sharp anymore and the minor may not have been sharp to begin with. That is a mismatch to the thread PA.