GRIZ MOD G9729 SET UP QUESTION

engineer_loves_machines · Mon Sep 01, 2008 10:07 am

So I've had this machine 8 months now and still learning what it can and can't do.
Is it possible to change the feed direction for the lathe? Right now the power feed table moves in the direction of the lathe spindle. Can I make it feed in the tail stock direction and still run the lathe spindle forward? Ifso, how?

Jose Rivera · Post by **Jose Rivera** » Mon Sep 01, 2008 11:33 am

Most lathes have a lever that allow the feed to be reversed.

Reading the specs on the G9729, they do not mention it.
Reversing the feed if vital for left hand thread cutting and feeding out of a hole per sample while boring.

Though not used often having it is a sure plus.

I would suggest that you call them and ask, their customer support is excellent before and after you buy.

I wish I could say the same about their equipment.

mechanicalmagic · Post by **mechanicalmagic** » Mon Sep 01, 2008 8:48 pm

After reading the manual, and looking at the parts, I can't see any way to do i, with the factory parts.

Another idler gear is needed.

Dave

Still-Learning · Post by **Still-Learning** » Tue Sep 02, 2008 9:16 pm

I run my machine in reverse with the tool bit upside down or on the back side of the work. Works great for cutting left hand threads and the chuck is attached to the spindle with 3 bolts so it will not come off like a threaded chuck can.

Good Luck,
SL

Post by **Harold_V** » Tue Sep 02, 2008 10:25 pm

Still-Learning wrote:I run my machine in reverse with the tool bit upside down or on the back side of the work. Works great for cutting left hand threads

That's a nice feature, but that alone won't yield a left hand thread. You must change the direction that the lead screw runs in order to generate an opposite handed thread. The machine in question isn't able to do that.

Also, when chasing any thread, keep in mind; your compound rest should feed the tool in the same direction the carriage travels, insuring that the carriage is loaded against the lead screw by tool pressure, eliminating any chance of a drunken thread.

Harold

Still-Learning · Post by **Still-Learning** » Tue Sep 02, 2008 11:59 pm

Placing the compound to the left 29.5 degrees loads the lead screw and using a center in the tailstock takes the negative pressure off the chuck, works for me.
Either way the cut would be away from the chuck, so as long as the work is rotating toward the cutting tool what's the difference?
After Hanna has run it's course I'll set this up and check to see if I get the same results as the last time I did it.

Post by **Harold_V** » Wed Sep 03, 2008 12:45 am

Still-Learning wrote:Placing the compound to the left 29.5 degrees loads the lead scew

Yes, as long as you're cutting towards the tailstock.

Do keep in mind this has nothing to do with tailstock pressure on the chuck, not as long as you have a reasonable machine. It has everything to do with tool pressure on the carriage, and how it's transferred to the lead screw. When applied correctly, the lead screw propels the tool against the cut, and it must follow the lead screw. If you turn the compound the wrong way, cutting pressure can unload the lead screw.

That is the point I raised. The net result is often a scrapped part, because the thread won't function properly. Pitch diameter may be right, but lead won't be.

Rotation of the spindle makes no difference----the cut should be fed in the direction of traverse of the carriage, running forward or reverse. Cut towards the headstock, the compound rest should be to the right, cut towards the tailstock, the compound rest should be on the left.

If you fail to observe these conditions, you risk a drunken thread. That's the difference.

Harold

Still-Learning · Post by **Still-Learning** » Thu Sep 04, 2008 9:33 pm

Today I set my machine up with the compound on the backside of the work and cut a nice 1/2-20 LEFT hand thread. A check with a thread gauge showed an 18 thread so I cut a right hand thread in the normal manner and it too was 18 tpi???
My fault, as I installed the 125/127 gear backwards. Will turn another LEFT tomorrow and post a picture.
It really does work!!!

SL

Post by **Harold_V** » Fri Sep 05, 2008 12:01 am

Still-Learning wrote:Today I set my machine up with the compound on the backside of the work and cut a nice 1/2-20 LEFT hand thread. A check with a thread gauge showed an 18 thread so I cut a right hand thread in the normal manner and it too was 18 tpi???

Unless you changed the gearing, that's what you would expect. Changing from left to right hand, or changing the position of the compound doesn't alter pitch. Compound position can effect the lead, but not the pitch. The thread could be drunken, but if you're chasing an 18 pitch thread, you'll have 18 revolutions of thread per inch. How they're spaced is what gets messed up (drunken).

My fault, as I installed the 125/127 gear backwards. Will turn another LEFT tomorrow and post a picture.
It really does work!!!

Not sure of your meaning, here. Can you please explain?

Harold

Still-Learning · Post by **Still-Learning** » Fri Sep 05, 2008 9:09 am

I have an Enco 109-1019 which uses a 4 gear drive train. "A" gear is the spindle, "B/C" is a duplex gear, and "D" is the lead screw.

For a 20 tpi the correct sequence is "A"=75, "B/C"=125/127, and "D"=60 with "A" driving "B" and "C" driving "D".

What I did was "A" driving "C" and "B" driving "D" which gave me the wrong TPI even though the threads were even and uniform.

I don't have a threading dial and have to use the start, stop, retract, and rewind routine. In my early attempts to cut threads I missed the part about retracting the tool during carriage return, made some nasty looking threads. Also, I failed to turn the overrun area to the minor diameter to allow the machine momentum to stop. For a left hand thread I use this area to start so the machine has time to remove all the backlash before the tool begins cutting.

Has anyone else given this some thought or even tried it? I know that the OP didn't specifically mention cutting left hand threads but that's the first thing that came to my mind.

Still-Learning · Post by **Still-Learning** » Fri Sep 05, 2008 12:45 pm

Harold,
You're correct and I'm wrong....
Disregard all of my earlier posts on the subject, sorry for the confusion.

Post by **Harold_V** » Fri Sep 05, 2008 2:20 pm

Still-Learning wrote:Harold,
You're correct and I'm wrong....
Disregard all of my earlier posts on the subject, sorry for the confusion.

It's not a contest, I hope you understand. I like to insure that information that is posted isn't misleading for the benefit of those that don't have experience. We old seasoned guys already know and understand what I've been talking about----generally because we screwed up along the way. No teacher like the one that comes at the hand of making scrap.

I try to envision the worse case scenario-----where advice that is not correct ruins a hard earned project for someone. By casually mentioning the pitfalls, as I tried to do here, I'd like to think that not only you, but other readers might be spared some grief.

I thank you for your acknowledgment.

Good luck with the machine!

Harold