More Rack/Pinion Rattle!

Hi Folks!
Does anyone else’s racks/pinions sound like this? (see link below for video.)
I had this problem not 6 months ago and replaced all 3 pinions. Now the x axis is wearing out again! Does this happen toy you too? How much of this rattle is too much? It doesn’t seem like this speed of wear out would be intended by Avid. What do you think? Am I worrying too much or should I replace the pinion again?

No it doesn’t, all you should hear is the Whining of the motor

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This might be something you want to check in with @support about.

Thanks Eric. I did just that and had a good convo with the support staff.
Here is some info in case anyone else has this question in future.

  1. The pinions are a regular wear/tear item. Expected life should be around 12 Mo of 20 hr/week use.
  2. Avid DOES recommend grease on the racks. This despite that there are varying opinions about that in the various forums.
  3. Don’t forget that the spring compression can have an effect on the pinion wear so make sure you follow the installation instructions. I think it’s 3 additional turns after contact on both sides of the spring.
  4. It seems like when to replace the pinions is a subjective question. Somewhere between when you start to hear the rattle and when your machining results are affected! :o) I’m gonna run mine a little longer. If disaster strikes I’ll let you know!

Glad they got you sorted!

I’m just curious why aluminum pinions with a steel rack :thinking: I have a few thoughts on why but would like a pro’s view anyone?

It keeps the wear to one item, the pinion which is a consumable. Pinions are far easier to replace than racks.


Yes thats what I was thinking too …
Thanks Eric

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What is the cost-of-disaster vs cost-of-the-replacement-parts?

As the pinions wear past their useful point it can cause backlash and poor cut quality.

Its a steel pinion pressed into an aluminum pully.


Well, the pinion replacement costs about $60 + shipping. It takes about 30 min to replace it. I think actual disaster isn’t likely. The pinion will keep wearing. It will get louder, and eventually have an effect on your machining due to increased backlash and even possible slipping on the rack. It could result in increased wear on the rack but I don’t think its very likely to be significant because the pinion is so small compared to the rack. I think the rack life would be orders of magnitude longer than the pinion. So the worst disaster would be a poorly machined parts getting worse over time.


Yes I don’t know why I thought bought gears where aluminum and all the above makes perfect sense :blush:

I hear it. I know some say there is no noise expect the motor, but I picked it up quickly because I have had the same rattle.

My first started after about 3 months of use. I contacted support and they told me to do a few things that didn’t help. But it got really quiet after while. Now it started up again.
For me its almost like a clicking. When I finally took a closer look one of my linear bearings had split open. Then I remembered I found a couple of bearing balls a couple days after I built it. So I probably broke a linear bearing when I put it together. So I need to order all new bearings and replace the wear parts. I think the balls in the bearings can make a noise if they aren’t perfect.

I first noticed the noise back in 2020. So that tells you how long it took to really get worse.

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The reason is because the aluminum is softer. So it won’t chew up the rack over time. Its a smaller, cheaper, and easier to replace part. Steel on steel gears work best when they are covered in oil, like a car’s transmission.

Hi ZandZ, The pinion is actually not aluminum - it’s hardened steel like the rack. The reason it wears so much faster than the rack is because it has so fewer teeth. So the pinion teeth see more action than the rack teeth.

I also have replaced some of the linear bearings. I tried to find alternate suppliers with no luck. If you can find them available, and can spec them properly, please do let me know. It’s not that I don’t like buying them from Avid (I think Avid is a great company worthy of our support) - It’s just that i’m in Canada and the customs/brokerage /etc is complicated and expensive so it would be nice if there were a Canadian supplier. Maybe Avid will get a Canadian rep or something one day to make it easier!

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