# G0602 Reverse Tumbler



## Fabrickator (Aug 17, 2015)

I was recently reading a post asking if the new Grizzly G0752 has the ability to cut left hand threads and it motivated me to finally make the conversion on my G0602.

http://www.hobby-machinist.com/threads/g0752-left-handed-threading.36983/

http://www.rcdon.com/html/the_reverse_tumbler_project.html

I've been putting off this project for years now because I have not once had a need to cut left hand threads, but I _have_ wished that I could make right hand, auto feed cuts on several occasions.

I've researched a lot of different methods to do this and I settled with this one by RC Don that was in the above mentioned post.  Clean, compact, simple and it didn't rob one of my threading gears like one person's did.  Some people made a shifter out the front or top of the machine cover (very cool), but I don't want a permanent protrusion to get hung up on - for the few times I may need to make a gear change.  Besides, I will more than likely need to open the cover anyway to change spindle speeds and this method only takes seconds to change the feed direction.

I used Don's blueprint/material list and it was very accurate up until the final mounting location on the casting, which is critical to the drive tooth engagement.  With nothing 100% definitive from machine to machine, I used RC's guideline measurements and it worked out fine.

I made my upper clamping plate more compact. I felt that his was too big when I got right down to it.  Everything worked out just as planned including the Delron gears ($30) and parts distributor.  In order NOT to disable my lathe while making this mod, I purchased an extra shaft from Grizzly to modify ($7).  Also, be sure and order a new ball oiler for the end of the new shaft ($2) because it doesn't come with one. 

 I ordered a new spindle/bull gear because _my bull gear was very loose on the spindle shaft _and I was getting some run out.  The new gear was a perfect fit fixing a years old problem that I have just endured.

Also, I found the _2 locking spanner nuts are severely out of true _(thread to face/wobblers) and I need to order a couple of those too. I do hope they got the new ones right... QC, come on Grizzly, they're only nuts!

Kudos though to Grizzly for their very good parts/order dept., low prices and quick service!  Just check the online catalog, pick a part number and place your order.  Parts arrived within days (sooner than they stated).

Rick


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## RJSakowski (Aug 17, 2015)

Fabrickator said:


> Rick


A nice neat job, Rick!

Bob


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## joconnor (Aug 17, 2015)

Fabrickator said:


> I was recently reading a post asking if the new Grizzly G0752 has the ability to cut left hand threads and it motivated me to finally make the conversion on my G0602.
> 
> http://www.hobby-machinist.com/threads/g0752-left-handed-threading.36983/
> 
> ...




Hi All
I was not aware that anyone made a lathe without a reverse gear.  For the odd time that left hand threads are needed it would probably be easier to mount the cutting tool on the back side and run the spindle in reverse. 
Just a thought


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## RJSakowski (Aug 17, 2015)

joconnor said:


> Hi All
> I was not aware that anyone made a lathe without a reverse gear.  For the odd time that left hand threads are needed it would probably be easier to mount the cutting tool on the back side and run the spindle in reverse.
> Just a thought


That doesn't work.  You will just be threading out instead of in towards the headstock.


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## GunsOfNavarone (Dec 28, 2019)

Correct me if I'm wrong here, but couldn't you use tumbler to thread normally (right hand) BUT thread away from work piece instead of into it? In other words, not have to stop before getting to bolt head/gutter, rather just threading to end of bolt?


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## hman (Dec 28, 2019)

Guns -
Here's a quick rule of thumb:  If the leadscrew and spindle are both turning in the same direction, you'll produce a right-hand thread.  Reversing the direction of the spindle (by reversing the motor) will determine whether you're threading toward or away from the chuck, without changing the handedness of the thread.  If the leadscrew and spindle turn in opposite directions, you'll get a LH thread.  Setting the relative rotation direction of the leadscrew is done with the tumbler.


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## GunsOfNavarone (Dec 28, 2019)

So hypothetically speaking, if I just switched my VFD to reverse, i could attain right hand threads but thread away from the chuck instead of towards it? I guess that feature exists already then as the lathe came stock with that ability?


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## hman (Dec 28, 2019)

You got it.  Just set the threading tool upside down ... and be cautious if your chuck happens to be threaded on.  

For further info, see Joe Pi's video:




The tool orientation is shown at about 4:30 in the video.


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## petertha (Dec 29, 2019)

This link/document shows the permutations of left/right, external/internal, upright/inverted cutter combinations. (And other useful information even though its kind of orientated to inserts.)


			https://www.sandvik.coromant.com/sitecollectiondocuments/downloads/global/technical%20guides/en-gb/c-2920-031.pdf
		


Depending on whether your lathe can directionally feed independent of motor spin direction may dictate which options are available to you. Also as mentioned, if you have screw-on vs camlock (pinned) chuck mounting, that usually precludes running the chuck in reverse because of the risk of unscrewing itself. 

'Conventional' upright tool infeeding to chuck seems to be burned into peoples DNA, but its probably because of the smaller and/or more limited lathes we grew up on. Many of the Asian import lathes are not limited in this way so we may have more options available to us that mitigate the knuckle chewing excitement of releasing thread engagement within a groove or before a shoulder.


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## GunsOfNavarone (Dec 29, 2019)

I appreciate the input and the chart. I know it's difficult around here sometimes as many people are very seasoned here and they're here for like minded people. Then there are others (like myself) that are here to learn from the aforementioned. Some are very happy to give/shape/teach, you guys are very much appreciated. 
I know this isn't the place to pose this question, but I'm pretty sure I can (capacitors?) To my VFD for braking purposes, this would be huge for the whole "threading excitement" you spoke of.


petertha said:


> 'Conventional' upright tool infeeding to chuck seems to be burned into peoples DNA, but its probably because of the smaller and/or more limited lathes we grew up on. Many of the Asian import lathes are not limited in this way so we may have more options available to us that mitigate the knuckle chewing excitement of releasing thread engagement within a groove or before a shoulder.


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## hman (Dec 30, 2019)

GunsOfNavarone said:


> I appreciate the input and the chart. I know it's difficult around here sometimes as many people are very seasoned here and they're here for like minded people. Then there are others (like myself) that are here to learn from the aforementioned. Some are very happy to give/shape/teach, you guys are very much appreciated.


We're all pretty much here to help.



GunsOfNavarone said:


> I know this isn't the place to pose this question, but I'm pretty sure I can (capacitors?) To my VFD for braking purposes, this would be huge for the whole "threading excitement" you spoke of.


I'm not sure I understand your question ... but it appears you're asking whether it's OK to put a capacitor across the "braking resistor" terminals of a VFD, instead of an actual resistor.  If so, I'd recommend against it.  Don't have a perfect understanding of how a VFD works, so I may be a bit wrong.  But as far as I can tell, the braking function electronically connects the resistor across motor windings (which are acting as a generator).  

Resistors and capacitors will act differently.  My own VFDs (Teco FM-50) specify 100 ohm braking resistors. When first connected, the "resistance" offered by a capacitor is near zero (acting pretty much like a short circuit).  It then rises to near infinity as it charges up to a voltage equal to the "driving" voltage from the motor.  The initial near-zero resistance might be too low (and the inrush current too high) for the VFD circuitry to handle. Then you end up with a bunch of energy stored in the capacitor, which must be dissipated somehow.  A power resistor, in contrast, will present a constant, known resistance to the VFD's circuitry.  It dissipates the energy by producing heat.

If I absolutely had to substitute for a braking resistor on a VFD, my first choice would be a small space heater ... basically a large resistor designed to produce heat.  I'd start be measuring the resistance across the AC plug, to verify that it's somewhere near the specified value.  A large light bulb (say 100 watts) also comes to mind ... but the "cold" resistance of a light bulb filament is very low, so it might not be suitable.

Your best bet is to save up your pennies and buy an actual braking resistor.  Here's one for just over $15:




__





						uxcell 150W 100 Ohm Aluminum Housing Wirewound Braking Resistor: Amazon.com: Industrial & Scientific
					

uxcell 150W 100 Ohm Aluminum Housing Wirewound Braking Resistor: Amazon.com: Industrial & Scientific



					www.amazon.com


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## GunsOfNavarone (Dec 30, 2019)

Thanks Hman. My bad, I assumed the braking stored energy from motor in a capacitor. I have the TECO L510. I honestly don't even know where the resistor or brake is wired in, just something the whole threading conversation brought up for me. I really want the braking if it's even possible with my setup, but haven't found much helpful information on the subject.


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## hman (Dec 30, 2019)

My FM-50 has two sets of terminals ... a set of "small" ones, where you connect the speed pot, etc., and a set of large ones for input power and the motor connection.  The braking resistor is wired between the P and R terminals on this strip.  Don't know if a L510 has the same setup.

As I recall, the FM-50 manual was a bit sparse when it came to documenting braking resistor installation.  I think I phoned them.  The info I got was that there's no need to "tell the software" that the resistor has been installed.  But with it in place, you can set the stop time a lot shorter.  I have 2HP and 3HP motors and use 0.5 seconds on both.


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## GunsOfNavarone (Dec 30, 2019)

Come to find out, the 230v tecos don't have the p/br connection for brake, only the 430v units. Guess that's not an option for my setup. I guess I won't miss what I never had.


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## hman (Dec 31, 2019)

Durn!


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## ub27Rocks (Dec 31, 2019)

GunsOfNavarone said:


> Come to find out, the 230v tecos don't have the p/br connection for brake, only the 430v units. Guess that's not an option for my setup. I guess I won't miss what I never had.


Check section 8-4 of the manual to see if Rapid Stop works for you: https://www.tecowestinghouse.ca/controls/drives/l510/


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## GunsOfNavarone (Dec 31, 2019)

That's interesting UB27...not sure it is meant to be used as much as you would threading, & it seems you need to clear it out after using, but maybe something to play with & see what it can do. I am curious, if a resistor brake is so large, how would this even work with the overall compact size of the L510.... Hmmmm....


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## ub27Rocks (Jan 1, 2020)

I don't have a 3ph motor on my lathe. Using a KBCC125R with a 2.5hp dc motor instead. The brake resistor is approx 5.5" long on that.


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