Chatter in X axis only

I’ve been working through some chatter issues where I get chatter only when the machine cuts in the x axis directions.

Had a bad x motor that got replaced but didn’t seem to fix it. I’ve figured out that my machine only chatter when climb cutting. I’m testing in MDF with a 0.25 compression bit. 50% woc, 0.25 doc, 1.5kw spindle at 18k rpm. Climbcutting I get chatter at 160ipm. Conventional cutting I can go 260ipm smoothly.

I’m running out of ideas. Any suggestions as why this is so? Anyone else notice anything like this?


Didn’t replacing the motor reduce any of the chatter?

Save seeing or some measured indication of how great the chatter you are experiencing is I might speculate it is the nature of the beast in terms of direction of cut. Climb acts like a shearing tool, where as conventional is like a scraper.

On a wood lathe, scrapers are used to achieve a very smooth finish after using gouges (shearing type tools).

I think the chatter can get pretty bad, but I’m still fairly new to this. Maybe this is just the way it is.

Replacing the motor helped. Machine sounds better and seems smoother. There was some improvement in the chatter. I’m just surprised it’s only in one axis. I can live with conventional cuts especially in wood. Traditional wood routing is usually conventional anyway.

I’ve chased down everything I can. Motors, toolpathing, table setup, machine squareness and tramming, etc. Far as I can tell me machine is pretty well set up on a sturdy base.

For now, I’m just gonna live with it and work around it. I’d like to get back to making some projects instead of trying to troubleshoot this. Maybe I’ll revisit it one day.


Why are you using a comp bit on MDF many other better choices? Also remember how Climb and Conventional pull the tool into the material. Climb will always give you more chatter on softer materials, it has nothing to grab onto since the cutter is going the same direction as the feed. Seems your spindle speed is also a bit high for your feed rate, try 12k and 180ipm full depth of cut on the material with a compression in MDF should not be an issue. One last thing 1/4 inch bits will always give chatter alot easier. Most shops would use a 3/8 or 1/2 bit when you get above 200ipm. Local guys machine runs 500ipm 15k full DOC 1/2 bit on 3/4 mdf with a comp all day long, and his dust collection could pull a golf ball thru a garden hose. Just to keep the dust down. You may already know all of this but figured I would throw some info out there

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Mainly using the compression just for testing. These aren’t projects. Just a test. But I’ve had chatter with up cut down cut. Doesn’t matter.

The chatter is only along the x axis. That struck me is weird and made me feel like there is something wrong with my system. I’ve run test with quarter inch bits, half-inch bits, three different manufacturers bits, 12K 15K 18K, 110 IPM, 180IPM, 260IPM, 360 IPM, it’s always the same.

I usually will try the recommended feeds and speeds from a manufacturer for a bit before I change from that recommendation.

I appreciate the information though. This is my first CNC and I’ve only had it just over a year. So I’m still learning.

I’ll try your suggestions to see if there’s any difference. Maybe try a different material that’s less grabby.

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Interesting it’s only on X, in both directions or does it go away when doing a circle half way thru? I had an issue with Y but it was the wrong motors sent with the machine. Back off the WOC/stepover and see I usually run 30-40%, For high speed roughing I use a IDC Woodcraft HOG 1/4

Both ways. It happens in curved when there is a x movement.

What feeds and speeds you use with the hog? I have one but never really took to it.

So in a curve there is that transition from X+ to X-, so once it start chattering it does it the whole circle, very interesting. What did 1F say, they are usually pretty good. HOG bit I run .300doc minimum or full depth usually .750 depending on the material, up to 250IPM@16k you can go faster but I don’t see the need to. Fastest I run on 99% of my bits is 150-200.

As far as the circle I’m not 100% sure it chatter when it’s only traveling in a y axis direction. I’d have to check that specifically.

Yes, the extra chatters in both dimensions. Just a test things out. I ran another test a half inch down cut bit at the manufacturers recommended speeds of 360 in./min. having steps of cut 40% width of cut chatter on the ex with climb cutting nothing on conventional cutting. I switched to plywood. This time I ran a 38 inch bit since my spindle is only 1.5 kW. Result never used before sharp 3/8 inch up cut bit. Running at 210 in./min. smooth is butter conventional. Chatter Climb. If you’re curious, I can run a circle test but I’m pretty sure I’ll know the answer on that one too.

Infiniti support was helpful. We did identify a bad ex motor probably just coincidentally. However, when I figured out that I had no chatter on conventional cutting they basically told me to just cut conventional.

I’m just convinced there is some weakness in my system. Just not sure what it is. If I’m just cutting wood, I don’t mind cutting conventional. But I’d really like to start doing a lot more aluminum brass acrylic and other mixed material. My understanding is limb cutting is recommended for metal specifically.

I’ve had chatter issues when trying to cut aluminum or brass in the past. Looking back on it I’m starting to think this was an issue from day one. I just never recognized it.

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Is it a real spindle or a Chinese one with the fan on top?

PwnCNC water cooled 1.5k spindle and Vfd.


Sorry, this post got kind of long. I think my frustration just poured out.

My table is a 5 inch thick torsion top. The top had a dip of less than 1/16 in the center. But no twist when it was constructed. I’m guessing my whole setup is an easy 400+ lbs.

I’m square to less than a mm as tested with a guage bar between corners, I’m trammed to 0.002” side to side and 0.001” or less front to back using one of those double guage SST tramming tools. There’s no twist I can figure with a fishing line test. Spoilboard is leveled and bolted to the top with 70+ bolts. I don’t think it’s my table although I could be wrong I guess. I have a journey man x50 original with a stiffy and a z-20 so I should be decently beefy as they like to say. New x axis motor so it’s not that. They even sent new cables just in case so other than what is in the drag chain those were recently replaced as well. I can’t find any lose bolts or cables. I had EMI issues, but those have been worked out and I can’t see how that would cause this.

Oh, and as far as the spindle, looking back, I had this problem when I was running the Makita router on the z-16 slider with no stiffy. So I don’t think it has anything to do with the motor.

I just happened to notice that the chatter was only on the axis when I was experimenting with the new spindle and the larger endmills to see what my spindle could handle. I programmed a one half inch endmill with a half inch depth of cut in MDF when I first got the spindle. I didn’t realize I left it set at 360 ipm Which was what the MDF setting had when I imported the speeds and feeds from the manufacturer into Fusion. When I hit play, it started down Y axis and cut without issue the moment it went X axis it chattered, back up Y axis was smooth as silk back across the the other x direction was chatter.

I realized my machine was probably more capable than I had previously thought when I saw how well it handled the Y axis half-inch endmill at those speeds. That’s why I started experimenting and thinking back at my past problems with chatter.

I’m just at a loss. I know this is “just a hobby machine“ but I still can’t help but feel like my machine should be cutting better on the x axis. I can’t imagine that there’s such a huge difference in the machines rigidity/stability between the x axis and y axis built into the design. I feel like there’s gotta be something in my set up. That’s resulting in all this. Considering how new I am, I’m guessing it’s something I did in either my table builder setting up the machine. I just can’t figure out what.

Reason why I asked about the circle is because it only moves in just X for a few .001 and 99.9% of the time its moving X and Y continuously. For metal both directions are used climb/conv. depending on the tooling and material. Had an instance at work a few years ago with a table issue on one of our Mazak 1850’s had chatter with 2in EM on a 72in 3000lb table changed cutting direction and it went away. climb to conv. Maybe post a pic of your machine set-up I have WW PRO on a home built basic table and only have chatter when I run too low of feed rate for the cutter. 1/4 in cutters give me the most problems in hard maple.

By the way, I greatly appreciate you taking the time to think about this with me. Here’s a couple of photos of my set up.

As far as circles are concerned, I haven’t cut any in my testing and I can’t remember specifically if it only chatters when it’s moving in certain directions. I don’t think I can get to it today cause I have to take my kid to a play date. But I’ll try cutting some test cuts on a circular tool path tomorrow and get back to you on that one.

What would you want me to look for in a circle cut specifically? I’ll use the 3/8” cutter and try both climb and comb for that.

Any chance you have excessive endplay in the X Axis screw, nut or bearing, climb cutting at least in metal only works well on machines with ball screws or acme with preloaded nuts, just a though that you probably have already looked into.

I didn’t specifically look at that. How would I check for that? I did replace the X motor. In doing so I know that the coupler on the shaft of the X motor is tight. Other than that, I didn’t check the remainder part of the coupler in that area. It had been in the back of my head that I should probably investigate that. Guess I’ll look at that later today.

The bolt on the end opposite the motor connecting the ball screw to the foot was tight. I can’t really rotate the ball screw by Hand without any excessive play I believe. But I’ll check those areas again too.

Grab the X axis ballscrew and give it a strong push/pull - check for play.

The nut on the end of the ball screw controls how much endplay there is in the thrust bearing, I found them to be anywhere from too tight to too loose on my machine, it is a subjective setting.
Actually I would put a dial indicator in the side of the Z Axis and try to push it either way, shouldn’t be more than a couple of thousands.