# Grizzly G0602 Half Nut Engagement



## RJSakowski (Nov 24, 2019)

In the process of installing an electronic lead screw on my G0602 lathe, I measured the amount of torque required to turn the lead screw with the half nuts engaged.  I was rather surprised to find it took over 400 oz.-in. of torque to move the carriage with no cutting load.  In investigating the cause, I discovered that when the half nuts were engaged, they gripped the lead screw tightly. Backing off the half nut lever very slightly, that torque reduced to 200 oz.-in.  My immediate thought was to put a shim  in place to prevent the half nuts from closing so firmly.

I pulled the apron off and it appeared the best way to control the closure was to put an adjustable stop for the half nut cam (P/N 142).  On closer inspection, I noticed a hole immediately below the thread dial. Looking further, the hole went through to the casting and was threaded.

OK, I determined the thread was an M6-1.0 mm.  I found a couple of M6 set screws and ran them in the hole, the first setting the stop for the half nut crank and the second as a lock for the first screw.  The required torque is now more manageable at less than 200 oz.-in.

It appears that the threaded hole was originally designed as a stop for the half nut cam,;  I can't think of any other purpose.  Some bean counter probably thought they could save a few Yuan if they omitted them when they cloned the lathe.

Aside from reducing wear due to an overtight half nut, the reduction in torque would reduce the load on the motor by around 1/4 hp. when using power feed.


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## C-Bag (Nov 25, 2019)

Having worked in a couple of assembly depts. there's just no telling what the ultimate reason is. Most logical is the guy who was assembling either didn't know of the stops or decided he could save some time not putting them in especially when it still worked. Either way that was a cool bonus all you had to do was install a couple of sets crews. 

Good job and thanks for sharing. I don't have a lathe like that but hopefully others who do can take advantage of your discovery.


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## RJSakowski (Nov 25, 2019)

C-Bag said:


> Having worked in a couple of assembly depts. there's just no telling what the ultimate reason is. Most logical is the guy who was assembling either didn't know of the stops or decided he could save some time not putting them in especially when it still worked. Either way that was a cool bonus all you had to do was install a couple of sets crews.
> 
> Good job and thanks for sharing. I don't have a lathe like that but hopefully others who do can take advantage of your discovery.


I could believe that if the setscrew(s) were in the parts list.  That actually occurred with the setscrew for adjusting play in the cross slide lead screw nut.  Since they are not in the parts list, I expect that it was a conscious decision.


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## GunsOfNavarone (Feb 12, 2020)

@RJSakowski is there not a half nut adjustment, besides your modification? I am going to assume your answer will be "noO so my follow up question...can you post some pictures?
Thanks


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## RJSakowski (Feb 12, 2020)

@GunsOfNavarone The only adjustment for the half nuts is for the gib (the two setscrews and jam nuts to the left of the lead screw).  The unused hole is immediately to the left of the top gib adjustment and below the threaded hole for mounting the thread dial.  The hole in question was threaded for M6-1.0mm and counter bored for part of its depth.  The hole is normally covered by the thread dial.

I would have to pull the apron off to get a picture of the half nuts and set screw.


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## GunsOfNavarone (Feb 12, 2020)

so very strange. You but a grub screw in there and another to lock it and just put slight tension on it and it reduced the torque needed to turn the lead screw? crazy that exists and crazier you figured that out. Nice work!


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