# G0704 CNC Conversion - C7 Ballnuts - Question



## angelfj1 (Mar 10, 2017)

Hey guys!  I'll be having the groove milling done on the dovetails, drilled gibs, etc to prepare for semi-auto oiling.  My C7 Ballnuts, from Chai,  came with Zerk type grease fittings.  Since I don't have a convenient way to measure them, does anyone know the thread size for these fittings.  My intention is to do as others and replace the Zerks with push-to-connect pneumatic fittings, for (4mm) plastic tubing.

Thanks, Frank


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## coherent (Mar 10, 2017)

I remember checking this myself and think they were M6 but not positive. Do a search under the Hoss G0704 thread on the CNCZone. There are a number of users who added oil lines and fitting. You'll find the answer there somewhere and may also find some other useful information.
I do know that while drilling and threading for different fittings is an option, the hardened steel of the ball nuts make it a little more difficult.


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## benster (Mar 10, 2017)

They are indeed M6. I ended up making a custom low profile elbow to fit under the X axis. You could also cut a lot out of the saddle to get a normal push to connect elbow in there. Still haven't figured out what I'm going to do for the y-axis as there's even less room.


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## TomS (Mar 10, 2017)

This isn't a good picture but you can see the fitting I made from a 6mm bolt in the lower left.  I cut the head off of the bolt, chucked it up, drilled a through hole and turned a straight section for 1/4" hose.  Screwed in the fitting and sealed it to the ball nut flange with a o-ring and nut.  I beveled the nut with a countersink slightly larger than the o-ring OD.

Tom S.


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## MontanaAardvark (Mar 15, 2017)

For what it's worth, M6 x 1 is close to 1/4-28.  1 inch is 25.4 mm, so not really 28 and certainly not 1/4-20.   Tom's approach is probably ideal.

I don't think you'd get a metal fitting in there, but Hoss called out some plastic 1/4-28 ones in that size essentially rethread the plastic.  I have them on both X and Y.  McMaster 5047K142 


Bob


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## angelfj1 (Mar 15, 2017)

MontanaAardvark said:


> For what it's worth, M6 x 1 is close to 1/4-28.  1 inch is 25.4 mm, so not really 28 and certainly not 1/4-20.   Tom's approach is probably ideal.
> 
> I don't think you'd get a metal fitting in there, but Hoss called out some plastic 1/4-28 ones in that size essentially rethread the plastic.  I have them on both X and Y.  McMaster 5047K142
> 
> ...



Bob, 
I'm getting other input that there is not sufficient space to do this, at least on the X axis.  Yet, Hoss has shown this in his videos!  Are you saying that you have been able to install oil lines and fittings on your X & Y ball nuts?  Can you please explain.   Also, I was wondering, if an oil line was positioned so as to drip oil onto the ball screw, near the ball nut, would that be almost as good as being connected to the ball nut?

Many thanks


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## MontanaAardvark (Mar 15, 2017)

I haven't actually hooked up the oil pump, but the system went together fairly easily, based on Hoss' Phase 3 plans.  

I'm not sure why X would be the problem.  I did have to mill away some of the slide to allow the right angle fitting to sit in there, but that's in Hoss' videos on the DVD.   




The one I had problems with was Y and I had to grind back the slide with an angle grinder.  Hoss just bent down the tubing and (I guess) let the cross slide slide across that tube.  I have a build thread where I showed what I went through (actually, someone else started it and I ended up hijacking the thread when he stopped posting).   The Y-axis oiling starts here.   If that doesn't work, the first page is here, and just got to page 5, you'll find it. 

From what I've read about that question of dripping oil on the ballscrew, the Teflon (? I think) seals at the front and back of the ballnut wipe the oil off.  You don't get oil onto the balls and threads inside it.  I'm trying to find some oil to use in the system today.  

Like a lot of people, I haven't finished the Z-axis.  It turns out Hoss never finished it, either, which I only found by asking him on the CNCZone forum.  When I was building up the Z-axis, I found the right angle fitting didn't fit inside the Z column.   I never came up with a good answer to that.


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## benster (Mar 15, 2017)

I used the same custom low profile elbow for the Z axis, I attached the drawing. It's a brass banjo fitting sealed by 2 small o-rings. I soldered a tube into a 3/8" rod of brass, then bored and counter bored it. The other fitting is self explanatory. They work pretty well and you can turn them whichever direction you'd like before tightening. I'd have to lookup what size o-ring I ordered.


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## TomS (Mar 15, 2017)

MontanaAardvark said:


> I haven't actually hooked up the oil pump, but the system went together fairly easily, based on Hoss' Phase 3 plans.
> 
> I'm not sure why X would be the problem.  I did have to mill away some of the slide to allow the right angle fitting to sit in there, but that's in Hoss' videos on the DVD.
> 
> ...



I don't know all of the particulars of CNC'ing a G0704 but for what it's worth I ran the Y axis lube feed line up from the bottom on my PM-932.  Lot"s of room underneath on my machine.

Tom S.


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## MontanaAardvark (Mar 15, 2017)

TomS said:


> I don't know all of the particulars of CNC'ing a G0704 but for what it's worth I ran the Y axis lube feed line up from the bottom on my PM-932.  Lot"s of room underneath on my machine.
> 
> Tom S.



On the G0704 the user would have to cut a hole or slot for the oil tube, but that's a good idea.  During the conversion, you need to get to the underside of the casting where the Y-axis goes, so I could see cutting a slot in it with an angle grinder.   Or just drill a through hole with a 1/4" bit.  Doesn't have to be pretty, just allow the tube to get under the mill.


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## MontanaAardvark (Mar 15, 2017)

benster said:


> I used the same custom low profile elbow for the Z axis, I attached the drawing. It's a brass banjo fitting sealed by 2 small o-rings. I soldered a tube into a 3/8" rod of brass, then bored and counter bored it. The other fitting is self explanatory. They work pretty well and you can turn them whichever direction you'd like before tightening. I'd have to lookup what size o-ring I ordered.



That's a good idea.  

There's a guy on eBay who sells machined ballnut mounts for the G0704 and he adapted an interesting, simpler idea that seems to work.  The hole is M6, and 6 mm is 0.236".  Just use a short piece of the plastic tubing with an OD like 1/4" or slightly larger (9/32?) and thread it into that hole.  He brings that short piece to a though fitting in the front of the vertical slide.


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## jbolt (Mar 15, 2017)

On my PM-932 conversion I drilled and tapped the brass fitting that came with the ball nut to accept a 10-32 and used a miniature swivel 90. https://www.mcmaster.com/#5483t11/=16rqs3u

The push-to-connect fitting is 10-32 to 1/8" tube. https://www.mcmaster.com/#7880t137/=16rqx3k


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