Is this normal? Or am I expecting too much?

[A_Camera]

Sorry, I missed your question a couple weeks ago. Sounds like you've got a resolution in progress.

Just to close the loop - so to speak - on the 4-jaw vs. 3-jaw question... My 4-jaw is also Asian cheapo. The difference is that a 4-jaw chuck with independent jaws can be adjusted to essentially zero runout, whereas a 3-jaw scroll chuck will have differences in runout because the scroll and jaw teeth are never perfect. And even if you adjust the 3-jaw to be perfect at one clamping diameter, it won't remain perfect at a different clamping diameter.

The solution to the 3-jaw is to relieve the "inner flange" on the back plate or open the counter-bore on the chuck. BTW, that 'inner flange' thing is usually called a backplate spigot (lathe term).

Once you have a few thousanths (inches) of clearance, the chuck is free to move around slightly on the back plate if the mounting bolts are loosened. The process goes like this:

1. Loosen chuck mounting screws slightly so they're snug and holding the chuck in place, but not fully tight
2. Put item/stock in the chuck jaws and tighten jaws
3. Put an indicator on the stock and rotate the spindle (4th axis).
4. Tap the chuck until the indicator shows low or no runout. I use a lump of lead or heavy copper/brass to nudge the chuck.
5. Tighten the chuck mounting bolts and re-check the indicator.

This will get the chuck perfect for that particular stock diameter, and is the same basic concept as "Set-Tru" chucks or similar lathe chucks. Those use radial grub screws to move the chuck on the back plate, but otherwise same idea. You shouldn't need grub screws for your 4th axis as the side/radial loads on the chuck should be minimal, or at least not enough to overcome the friction created by tight mounting screws.

Once you have the chuck set, you can insert & remove that diameter stock as many times as you'd like and the runout shouldn't change much. That's the advantage over a 4-jaw: a 4-jaw has to be indicated every time you take the stock out - even the same piece.

Thank you for your answer. Spigot is the term, yes I knew it, but forgot... thank you. It's been more than 40 years since I needed that term.

Anyway, in the meantime I fixed most of the issues, so I am happy for now. Basically, what I did was I removed everything possible and cleaned all the surfaces and reassembled everything once again. This resulted in very small error, perfectly acceptable for now. I also think that the spigot is a bit too large because the chuck sits so tight on it that it is impossible to remove it without help from the screws to push the chuck out. It may need some additional cleaning with a very fine sand paper, which I might try to do later, but for now I think it is very good as it is. Also, as you say, it can only be perfect for one dimension, so what I think was the most important was that the chuck is good as well as the one reference rod. Anyway, thank you for all the comments. I have no experience with a lathe, or a 4th axis, so I welcome all help.

[johanbhi3]

Based on the description and the video you provided, it does appear that the rotary axis you received may have some issues, particularly with the large gear and chuck. Here are a few considerations:

Large Gear and Chuck: If you notice issues with the large gear or chuck, it's reasonable to ask the seller for replacements. The gear and chuck are crucial components of a rotary axis, and any defects in these parts can significantly affect its performance.

MT2 Live Center: If the MT2 live center or the pin is not up to your expectations, requesting a replacement is a valid step. A live center should be precise and fit well to ensure accurate rotation.

Instructions: If you're unsure about how to replace certain parts, asking the seller for instructions or guidance on part replacement is a good idea. They may provide you with the necessary steps to make the replacements.

Expectations: It's essential to have realistic expectations when buying lower-cost equipment from sources like AliExpress. While these options can be a good value, they might not meet the same standards as more expensive alternatives. You may need to make some adjustments or improvements to achieve the performance you desire.

DIY Projects: Your idea of creating a "lathe mode" with an Arduino-based controller is exciting. Many DIY projects like this can yield excellent results, and they can be a fun and educational experience. Just be prepared to troubleshoot and iterate as you go along.

If you don't receive a satisfactory response from the seller, you could explore online communities or forums dedicated to CNC and rotary axis projects. Fellow enthusiasts may provide advice, guidance, and solutions for improving the performance of your rotary axis or creating your "lathe mode" controller.

[A_Camera]

Based on the description and the video you provided, it does appear that the rotary axis you received may have some issues, particularly with the large gear and chuck. Here are a few considerations:

Large Gear and Chuck: If you notice issues with the large gear or chuck, it's reasonable to ask the seller for replacements. The gear and chuck are crucial components of a rotary axis, and any defects in these parts can significantly affect its performance.

MT2 Live Center: If the MT2 live center or the pin is not up to your expectations, requesting a replacement is a valid step. A live center should be precise and fit well to ensure accurate rotation.

Instructions: If you're unsure about how to replace certain parts, asking the seller for instructions or guidance on part replacement is a good idea. They may provide you with the necessary steps to make the replacements.

Expectations: It's essential to have realistic expectations when buying lower-cost equipment from sources like AliExpress. While these options can be a good value, they might not meet the same standards as more expensive alternatives. You may need to make some adjustments or improvements to achieve the performance you desire.

DIY Projects: Your idea of creating a "lathe mode" with an Arduino-based controller is exciting. Many DIY projects like this can yield excellent results, and they can be a fun and educational experience. Just be prepared to troubleshoot and iterate as you go along.

If you don't receive a satisfactory response from the seller, you could explore online communities or forums dedicated to CNC and rotary axis projects. Fellow enthusiasts may provide advice, guidance, and solutions for improving the performance of your rotary axis or creating your "lathe mode" controller.

Thank you for your comment on this over two years old thread. Anyway, regarding the gear and the chuck, it was a fixable problem. There was nothing wrong with the gear, except with my way of measuring. I measured on the side walls, which are a bit bent, but it does not effect the gear.

The chuck is also fixed, I simply removed and cleaned it. That fixed the play.

Regarding the MT2 Live Center, I complained to the seller and got a refund for it, but did not bother to buy a new one. It works as it is also, even if the edge is not as pointy as it should be.

When it comes to the Arduino project, that is done and works well, but I never actually made a controller for more than the lathe "spindle". I continued, and actually finished the lathe project, it works very well, but the spindle, the Z and X axis is controlled by UCCNC when I use it as a digital lathe. I even started a thread about this project, but it didn't receive much attention, so I did not bother to post updates here.

Here is a link in case you are interested: http://www.forum.cncdrive.com/viewtopic.php?f=5&t=3242

And here is the latest video about it: