A bit of frustration or "How accurate do I need to be?"

[ScrapMetal]

As a rank beginner I'm slowly gathering tools and taking a somewhat cautious approach to working with my SB. Today I had some time so I was going to chuck up a 1/2" steel rod and attempt to do some threading. Before I start a "rant" I'll have to give you a little insight as to one aspect of my personality, that is I tend to be a little OCD with certain things and accuracy happens to be on the top of the list. To make a long story short, I spent over two hours just trying to get the piece centered on the chuck and the closest that I came to being spot on was .001" of variation. The rod was sticking out of the chuck by about six inches (too long?) and my gauge was about a half inch from the loose end. Needless to say, I never did attempt to do any turning as I can't imagine that is close enough.

Even though I am new to this (and all the used equipment) there is a fair chance that the chuck was part of the problem. I was using a 4-jaw chuck because I wanted to get some experience with it and from what I've read they should be more accurate than the self-centering 3-jaw. The jaw adjustment screws seemed to be pretty clunky for attaining anything better than what I did. The jaws didn't really become parallel to the piece until they were fairly snug and just taking the pressure off the screws was enough to send them further off of range. Is this normal and do I just need to become more familiar with it or should I be looking at better chucks?

My method, I suppose, is also suspect as well as the possibility of the rod itself not being "true". What do you guys think and how do you deal with this? (P.S. I have read "How to run a Lathe" a number of times as well as anything else I could get my hands on so I don't think I was going at this completely unarmed. :-\ )

Thanks,

-Ron

 

[ScrapMetal]

All good advice guys. I know that I have to learn the "tricks of the trade" and techniques so I just kind of try and soak up all the answers.

I can understand about the being true to itself and parting it off but what about threading? Wouldn't being off like that make the threads kind of funky as you are cutting deeper on one side than the other?

Hopefully I'll find time this week to actually make some chips. Then I can post the results, good or "less than good".

-Ron

 

[Tony Wells]

If you have blanked out a part to be threaded, and it is running out 0.001, that normally presents no problem. There is more than enough clearance developed between mating parts to allow for it. That's why the clearance is there.

 

[Tony Wells]

Ah, NPT vs NPTF. Some have sharp crests, some don't. Some require sealant, some don't. Thread form is not within the scope of this thread, however.

 

[ScrapMetal]

The Stooges were probably better teachers than I had but then my plumbing skills were self taught.

I'm on abe.com right now ordering a copy of the Machinery's handbook. I have a love for both tools and reference materials and this "hobby" is the motherload for expanding on both. ;D

-Ron