Issues with my new 12Z Manual Mill

Update 1: Called COA 3/18/2015 8am, got advice on what to check and they are sending me some shims for the Gib. The play I am experiencing in the Z-axis may be a loose gear bolt on the Z lead screw.

Update 2: 3/18/2015 6pm, I just inspected it again, I didn't find the gear loose, however I have found that there is excessive play in the Z-axis nut.

Ouch, the screw driver is against the Z nut. The head is resting on that piece of wood. The head is not moving.
https://www.youtube.com/watch?v=iyCSX4G5t8E

Original post below:
To begin, this mill was far from ready to go out of the crate. There is a major issue that will test Charter Oak Automation's customer service.

1) Y-axis lead screw bearing mount was LOOSE
2) X-axis lead screw bearing mounts, bolts not torqued
3) Z-axis crank bearing mount, bolts not torqued, one bolt LOOSE
4) Z-axis crank handle set screw set on the round, not the flat of the crankshaft (you can tell by the witness mark on the round)
5) Y-axis gib LOOSE (screws were not even touching gib)
6) Z-axis gib undersized, ran out of adjustment

7) The Z-axis nut is messed up after I did some work (4 holes) near the top of travel.
https://www.youtube.com/watch?v=sTVfNZ8_D34

I don't even feel safe using this mill anymore, I question if the head will suddenly fall down on my arm and maim me.

Frustrating?- Yes
Big issue?- No
You could spend less time tightening the loose bolts than it takes to post your video. They are not going to fly a technician to your place to tighten the bolts. They'll probably give you a new gib strip under warranty. It's a Chinese machine, so you need to accept the compromises as part of the low price.

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Originally Posted by GITERDUN

Frustrating?- Yes
Big issue?- No
You could spend less time tightening the loose bolts than it takes to post your video. They are not going to fly a technician to your place to tighten the bolts. They'll probably give you a new gib strip under warranty. It's a Chinese machine, so you need to accept the compromises as part of the low price.

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So you don't think the Z-axis nut issue is a problem? I can watch the Z-axis lead screw turning without any resistance or movement of the head. When lowering the Z-axis, it lurches, stop/go/stop/go; I think that is a major issue.

Quote:

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Originally Posted by Steelmesh

So you don't think the Z-axis nut issue is a problem? I can watch the Z-axis lead screw turning without any resistance or movement of the head. When lowering the Z-axis, it lurches, stop/go/stop/go; I think that is a major issue.

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Kinda hard to really tell with the hand held video, but it sounds to me like another case of loose bolts. Your best bet is just to assume everything is loose, go through the entire machine and tighten up all the bolts and give yourself a short course on the machine maintenance at the same time. It will serve you well in the future to have a mechanics knowledge of how everything is put together.

Quote:

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Originally Posted by GITERDUN

Kinda hard to really tell with the hand held video, but it sounds to me like another case of loose bolts. Your best bet is just to assume everything is loose, go through the entire machine and tighten up all the bolts and give yourself a short course on the machine maintenance at the same time. It will serve you well in the future to have a mechanics knowledge of how everything is put together.

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Sounds like a good plan. I spoke with COA this morning, he suggested the lead screw bolt may be loose at the bottom gear.

In addition; they are mailing me a set of shims of different thicknesses to setup the gib!

Quote:

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Originally Posted by GITERDUN

Kinda hard to really tell with the hand held video, but it sounds to me like another case of loose bolts. Your best bet is just to assume everything is loose, go through the entire machine and tighten up all the bolts and give yourself a short course on the machine maintenance at the same time. It will serve you well in the future to have a mechanics knowledge of how everything is put together.

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I think I have to tear it apart now:
https://www.youtube.com/watch?v=iyCSX4G5t8E

It looks like they left the Z nut loose.

The mill can be striped in a hour or so. Just tighten the nut and be done. it might be that the Z bolt or nut is striped. If so everyone has extras because you replace the nut when you CNC.

Loose bearing and bolts are common with the china stuff. It is more rare to have all the gibs be correct than to have all of them messed up. You will need to shim something before your done.

Update 3: I guess I can't edit the original post anymore for some reason.

The more I dig into the issue, the more bad stuff keeps revealing itself. I assume the root cause is the very short bolt used to connect the Z-slide to the Z-nut; with about 0.375" of thread engagement that has completely failed. It looks like there is enough thread in the Z-nut to run 2 inches of thread engagement. In addition, there are two pull pins that go between the Z-slide and the Z-nut, these pins were sitting flush with the Z-slide. I initially thought they sheared off, but nope they were just never driven into the Z-nut.

Album of Pictures here:
12Z Stripped Z Nut - Album on Imgur

Also note the excessive play in the Z-nut:
https://www.youtube.com/watch?v=7hkfXBGNo7s

I hope I just need a new Z-nut and I can start using my machine. Lost the key that drives the Z-screw gear =(

Chinese proverb- " The Journey of a thousand miles begins with a single step" Congratulations on taking that first one. My guess is that there was a problem with the nut alignment and to get the thing out the door the assembler just left the locator pins loose and the bolt just tight enough to get past the inspector. By the time it got to you the bolt had vibrated completely out.

If the rest of the treads are good just get a longer bolt.

The head collar bolts are a weak point too. I replace mine with shoulder bolts but they need to be milled to fit.

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Originally Posted by arizonavideo

If the rest of the treads are good just get a longer bolt.

The head collar bolts are a weak point too. I replace mine with shoulder bolts but they need to be milled to fit.

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In the Z-nut play shown in the video normal? If it is, why?

The Z nuts have no backlash adjustment. The head pushes the threads to one side to give low backlash. It is normal. Most manual mills always have backlash, you need to remove the lash and then move the proper amount.

Update on my mill issues

Paul has sent me at no charge: gibb shims, Z-screw bolt/washer, (2) Z-nuts, (2) Z-nut bolts

- None of the Z-nut tapered pin holes line up to the Z-slide, I assume the mfg. process is build-to-fit
- FYI I was not able to fully drive the tapered pins through the Z-slide, they basically sat flush. I could have pulled out a sledge hammer, but that may crack the casting and is just not right :P
- The tapered pins however did fit properly into all the Z-nuts (I could push them in by hand about 0.200" deep)

- I drilled and tapped the Z-nut tapered pin holes to 5/16-18 thread so I could attempt to add some strength to the Z-nut system
- I could only line up (1) 5/16-18 bolt, as the holes were off.


See pictures here: 12Z Warranty Repair - Album on Imgur

Its good that they came through with the parts, but you have a steel screw and a cast iron nut- they are gonna start eating each other up. While you are in the "fix it" mode, you should look at MSC or McMaster Carr and get a good quality lead screw with a bronze nut- its going to save you further repairs and make the machine a lot more accurate.

Quote:

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Originally Posted by GITERDUN

but you have a steel screw and a cast iron nut

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Technically I don't have it, COA has it. I just want to use the machine at this point, if I wear out the Z-nut, then that means I have actually used the machine =)