"Off centered" threaded parts.. Help?

[BellyUpFish]

Ok, so I'm working on a project..

I turned two pieces of some 304 SS down to 0.40".

Holding the work in a 3 jaw chuck.

I then center drilled and then drilled one of the pieces, using the tailstock chuck progressively up to an I drill, then tapped to 5/16-24.

I then turned the end of the other down to .3125" and used a die to thread to 5/16-24.

When I attempted to thread them into each other, they are not centered on each other. Not even close.

I started looking at them closer and it looks like my tailstock may be out of alignment, as the hole I drilled is not centered in the parts. One is easily more off center than the other.

Does this sound like a tailstock alignment issue or is something else going on as well?

 

[extropic]

It sounds like aligning your lathe should be your next project.
What lathe make & model?
What taper in the head stock spindle?
What taper in the tailstock quill?

 

[BellyUpFish]

Sounds like it.

It's a Precision Matthews 1030V.

MT3, I believe in the head stock. I'm using a 3 jaw chuck at the moment.
MT2 on the tailstock quill..

 

[Bob Korves]

How did you chuck the work? 3 jaw chuck? 4 jaw? Collet? Collet chuck? Something else? Did you indicate the work before turning it?

 

[BellyUpFish]

How did you chuck the work? 3 jaw chuck? 4 jaw? Collet? Collet chuck? Something else? Did you indicate the work before turning it?

3 jaw chuck.

No, I didn't indicate the work. Should have, clearly. I'm a YouTube taught, and still learning, obviously.

Turned both pieces down to 0.40" on the dot, but the center hole is off..

 

[4ssss]

Did you use a center drill before you drilled the hole? Also if your die is dull it will heat up the part and actually bend it, especially on a harder steel like stainless. Use plenty of Kool Tool and break the chip often, using BOTH hands to apply equal pressure while turning the die stock. I don't know if you had the part chucked and held the die stock while turning the chuck, but that's another thing a lot of people do that creates problems with off set threads.

 

[JerryK]

The tap & die both need to be guided
for a straight thread

 

[BellyUpFish]

The tap & die both need to be guided
for a straight thread

I used the tailstock chuck to help guide the die and used a spring loaded follower to help guide the tap.

Did you use a center drill before you drilled the hole? Also if your die is dull it will heat up the part and actually bend it, especially on a harder steel like stainless. Use plenty of Kool Tool and break the chip often.

I did center drill. I didn't use Kool Tool, I'll check it out. I used Tap Magic fluid.

Kind of weird you mention the die bending the part. I made the exact same part last night out of aluminum as a test piece and everything went fine. Today with the stainless, it got wrecked.

I noticed that the die seemed to be crushing the ID of the part.

I'm trying to make my father a pen for Christmas and the ID of the threaded part is about 0.20" ( I don't remember the exact measurement off the top of my head and my notes are at home) to allow for the ink cartridge to fit, the OD was then turned to 0.3125" and used the die to thread. When I went to put the ink cartridge in, it would not fit, the threading had "crushed" the ID.

Is this a normal occurrence as well?

 

[JerryK]

The tap follower is great, but how did you guide
the die with the chuck ?

 

[4ssss]

The minor dia. of the 5/16-24 is .280. If I'm reading this right you then only have a .060 wall (.400-.280) With the harder steel, I'll guarantee you that it's heating up and crushing. I never cared for Tap Magic, it was either dark cutting oil or Kool Tool for me.

http://www.engineershandbook.com/Tables/threadlimits.htm