G0602 threading issues (not disengaging the half nut)

[RJSakowski]

I have a 602 and the scale reads zero when the compound travel is parallel to the spindle axis. If you elect to use the compound to in-feed when cutting, you need to set the compound to 60.5º to achieve the 29.5º feed angle. Also, keep in mind that the divisions on the scale are actually 2.5º so you would set to just a bit past the 60º mark.

There have been a number of discussions on this forum about this same problem. Once you get it figured out, I think you will find threading with the 602 to be simple. Here is how I set mine up. https://www.hobby-machinist.com/threads/29-5-deg-angle-tool-for-lathe.34541/#post-299219

 

[higgite]

from my late night readings, this is starting to lead the pack in possibilities. I guess I am confused how I am to set it if my compound is off. If like to use my compound, but until I know what that is, am I trying to turn it 29.5° from being 90° perpendicular?

That is correct. But your problem has nothing to do with compound angle.

I am not pulling the work away when I reverse....should I?

Yes, you should.

Retracting the tool with the cross slide at the end of the cut is mandatory.

This ^^^. There is backlash in the gearing and lead screw, so simply reversing the direction of travel changes the timing between the spindle and the carriage. The track in one direction is offset from the track in the other direction by the amount of backlash in the system. When you reverse direction, the work turns a split second before the tool moves. That's why you saw two scribe marks on your first forward and reverse passes.

 

[markba633csi]

Important point: Whether you feed in with the compound or the cross slide (and you can do it either way) you MUST pull back the tool when you reverse because of the slop in the geartrain, that's what can ruin the thread. Most engine lathes have lots of play in the gears so you have to take that into account
Mark

 

[GunsOfNavarone]

I have a 602 and the scale reads zero when the compound travel is parallel to the spindle axis. If you elect to use the compound to in-feed when cutting, you need to set the compound to 60.5º to achieve the 29.5º feed angle. Also, keep in mind that the divisions on the scale are actually 2.5º so you would set to just a bit past the 60º mark.

There have been a number of discussions on this forum about this same problem. Once you get it figured out, I think you will find threading with the 602 to be simple. Here is how I set mine up. https://www.hobby-machinist.com/threads/29-5-deg-angle-tool-for-lathe.34541/#post-299219

RJ....I guess you don't know what you don't know. Had I read that thread earlier...would I have put the pieces together...I'm not sure. In hindsight, i see that I was coming in at such a "parallel" angle that any movement in was also a lot of movement left (on the threads) slowly thinning out the threads the "deeper" I went. I haven't even tried the new angle...but pretty sure it the culprit.
I have watched your builds on the 602 lathe for a while, even on another site which I believe is gone now. Your indispensable for info on making the 602 better. As I am learning the very basic and on, it's detrimental for the 602 to have things like this or the indicator dial being off, i will be working on your improvements in the future.

 

[GunsOfNavarone]

That is correct. But your problem has nothing to do with compound angle.

Yes, you should.

This ^^^. There is backlash in the gearing and lead screw, so simply reversing the direction of travel changes the timing between the spindle and the carriage. The track in one direction is offset from the track in the other direction by the amount of backlash in the system. When you reverse direction, the work turns a split second before the tool moves. That's why you saw two scribe marks on your first forward and reverse passes.

I'm pretty sure that flat angle has huge implications on the issue with that wacky thread...but yeah, there are other issues.
it makes sense to pull the work away when moving...that backlash will cause it to score at a different location, that will be changed now as well!

 

[markba633csi]

It's like riding a bike, once you get it you'll say "how simple"! It can get tedious though, making all those passes and focusing intently to not mess it up
Mark

 

[GunsOfNavarone]

It's like riding a bike, once you get it you'll say "how simple"! It can get tedious though, making all those passes and focusing intently to not mess it up
Mark

it's funny....Once things were going more as I expected....it was fun. Now, I'm not sure why screws/bolts don't cost $30 each and up, but whatever. Looking at these pictures, for the first (correct)attempt, I'm happy. Here is the next issue (Since RJ knows the gearing of the 602, this maybe easier for him to pull out his charts..
using the chart on the lathe, at 150rpm, using a 36 and 40 tooth gear(s) and the gear box on b/2...I'm supposed to have 12tpi...this looks more like 13 but not PERFECTLY, BUT MUCH CLOSER THAN 12. Thoughts on that?

 

[GunsOfNavarone]

Here is completed (the previous 13tpi shot, I hadn't completed the thread depth yet)

 

[GunsOfNavarone]

Let us know what you find, that's an interesting thread you cut.

it's make one hell of a barb....don't you think?

 

[RJSakowski]

The threading chart on the 602 is correct. You should have the 36 tooth gear in the a position and the 40 tooth gear in the b position. The kobs should be in the II-B position. The 120 tooth gear is not used for inch threads so the b gear should be engaging the 127 tooth gear. If you are engaging the 120 tooth gear the thread pitch would be reduced by 120/127 which would mean the cut TPI would be 12.7 TPI instead of 12 TPI.