[ny_racer_xxx]

Is there a big downside to using a 16mm or 5/8" Z ball screw?

I've seen a couple of kits that use them, just wondering if it would be rigid enough or I would have an issue...

Thanks,
CR

[Winnfield]

No problem at all. Even the Tormach 770 uses something about the same size and the head on that machine weighs almost 3 times as much, I believe.

[SCzEngrgGroup]

A 5/8" screw should be fine, especially since it's pretty much always in tension. The loads these machines put on the screws are very low.

Regards,
Ray L.

[hoss2006]

Is there a big downside to using a 16mm or 5/8" Z ball screw?

I've seen a couple of kits that use them, just wondering if it would be rigid enough or I would have an issue...

Thanks,
CR

Sure they are rigid enough and you won't be able to fit any larger under the table anyway.
For the Z axis we use 3.4 inch, 20mm most often but some have squeezed 1 inch screws.
Hoss

[ny_racer_xxx]

Sure they are rigid enough and you won't be able to fit any larger under the table anyway.
For the Z axis we use 3.4 inch, 20mm most often but some have squeezed 1 inch screws.
Hoss

Yah Hoss, that's what I was wondering about the Z axis. 3 kits I've seen that use 16mm ball screws for the Z. It kinda sounds flimsy to me, but like what was mentioned, it's always loaded from the weight of the head..

Thanks for the replies....

[109jb]

I see absolutely no reason to need anything larger than a 5/8" screw. The 5/8" screws in my G0704 are rated at 780 pounds load. I have double nuts and about 130 pounds preload leaving 650 pounds usable I can put a drill in the chuck and bog the spindle motor before I run out of ability to push the head down. Coming up, it only has the weight of the head which is about 60 pounds. As for the screw deflecting, or bowing to the side, the stepper will stall before any appreciable bow occurs. I have no backlash as long as I keep the ways lubed .

[ny_racer_xxx]

I was looking at CNC Fusions kit until I saw the install pictures on FB. Man he hogs out that saddle!!!! The X bed gets some heavy cut under also... I'm sure it's a good product, just looks really, really involved, I want to make parts, not build machines....

I'm leaning back toward the Optimum screw set, it looks like the newer set has a 20mm z screw.

CR

[hoss2006]

Reasons for a 3/4 inch Z ballscrew for me was more meat at the turned end allowing for a beefier coupler shaft size since large Nema 34 steppers with their increased torque are often used and it lessens a breakage risk.
The larger screw is also stiffer and won't whip as much and won't need a supported end.
Put a big 3 phase motor on there and you may see the benefit for a stiffer screw.
Hoss

[hoss2006]

I was looking at CNC Fusions kit until I saw the install pictures on FB. Man he hogs out that saddle!!!! The X bed gets some heavy cut under also... I'm sure it's a good product, just looks really, really involved, I want to make parts, not build machines....

I'm leaning back toward the Optimum screw set, it looks like the newer set has a 20mm z screw.

CR

I have 5/8 screws on my x and y and the only cutting needed is a small pocket in the saddle for the ballnut.
Hoss

[ny_racer_xxx]

I have 5/8 screws on my x and y and the only cutting needed is a small pocket in the saddle for the ballnut.
Hoss

Yes I know, I have the DVD, that's why I thought it was way too much work involved. I had thought about buying a spare saddle to machine the relief into, then swap it out. With the other kit, I'd have to order a spare X bed also!!!!

CR

[hoss2006]

Yes I know, I have the DVD, that's why I thought it was way too much work involved. I had thought about buying a spare saddle to machine the relief into, then swap it out. With the other kit, I'd have to order a spare X bed also!!!!

CR

Yeah that's one way to do it, on a spare.
The pocket doesn't have to be pretty, you can plunge the material away on a drill press and/or use a grinder a little at a time so the saddle doesn't overheat and warp.
Having a second machine, even an x2, always helps.
Hoss

[ChrisAttebery]

I have the CNCFusion kit on my G0704. I DID NOT have to do any milling to the table. The saddle did need machining but it wasn't too bad.

Yes I know, I have the DVD, that's why I thought it was way too much work involved. I had thought about buying a spare saddle to machine the relief into, then swap it out. With the other kit, I'd have to order a spare X bed also!!!!

CR

[DonKes]

Is Roton the only relatively cheap source of inch ballscrews?

Don

[ny_racer_xxx]

Chris, thanks for the information, I'm just going by the pictures they posted on FB

http://sphotos-b.xx.fbcdn.net/hphoto...07217562_n.jpg

[ChrisAttebery]

I forgot that I had to have to base casting machined to clear the ball nut too.

[ny_racer_xxx]

Sorry, I'm not trying to knock CNC Fusion's stuff, and I'm certainly no expert, but it does look more involved, and he even admits to it in the video.

G0704 saddle modification. Details. | Facebook

[ChrisAttebery]

Yes, there are definitely tradeoffs between the different kits/plans. For me getting the machine up and running ASAP was important and that meant buying a kit instead of making the parts myself. It's still taken me ~3 months to get to the point that I'm spending more time making product than setting up/improving the machine.

[ny_racer_xxx]

I agree with you 100%, I don't think I would make the ball screw mounts myself either.

CR

[zerodegreec]

So Hoss where did you buy your Ball nuts? I have your DVD and did not see it. You listed the E-Bay seller but those kits all have a different style nut than the one you have shown.
I have decided to go to a Ball nut for all 3 axis and perfer not to hack out the saddle as mentioned on the FB page. I like your method. Unfortunately the mount you made will be difficult for me as I do not have a Lathe

[hoss2006]

I used Rotons, part #s are in the file "G0704 phase 2 parts list.txt" in the Phase 2/Text folder.
Note: You don't have to cut the big groove in the saddle with my conversions.
Hoss