Questions regarding Carbide router runout and lash, and X carriage movement


I purchased a XXL around November, and I’ve been trying to improve the quality of my cuts into HPDE and Acrylic since. Currently looking to possibly improve my machines setup.

The soft HPDE tends to show steps about the z-axis, enough to catch a nail. This is persistent 360 degrees about the part. An indication of chatter is persistent despite modifications to feeds and speeds.

The slightly harder acrylic shows a more exaggerated machine chatter. A light texture.

My thinking led me to believe this was mechanical. Using a new mill’s and clean precision collet, the best run out figure I can achieve is .005. I’ve indicated worse. Seems like a lot to me, but maybe this is typical? The router also seems to have a bit of visible lash. Are there any better options?

Additionally, I am not sure how much rigidity I should expect from the X carriage. The V wheels are all tensioned rather tight, and screwed tightly to the carriage. But the router seems rather easy to flex in the Y axis. Seems easy to push with my finger giving over .05 of movement just below the collet, and with a different resting zero every time. But again, maybe this is typical of such as design. Any suggestions as to how I can improve this?

As always, the help is greatly appreciated.


The easiest way to address this is to leave a roughing clearance greater than the defect and then take a full depth finishing pass.


@WillAdams’ advice will go a long way for sure, but just in case:

Steps/ridges along the Z direction may be an indication of imperfect tramming, did you check that ?

0.005" runout indeed seems a bit high, I used to get ~0.002" before adjustment on mine, and less than 0.001" after adjustment (tapping method). How do you measure it ?

I can’t remember the Y slop I had at the collet with the stock Z axis, but I’m pretty sure it was less than .05. If you did a thorough mechanical check I’m not sure what to do about it though…

Can you share your feeds and speeds also for a quick check?


I most certainly agree, particularly on the horizontal steps. But the machine marks seem to indicate runout, or maybe a lack of rigidity. I get a similar effect from my table saw, the spacing on the pattern is determined by how fast I feed the plastic through. And because of this phenomenon, I typically prefer to fabricate a temperate, then I use a router and bushing to make a cut that, by my metrics, is a finished product. Otherwise, and is currently the case with the acyclic I am currently getting from the Shapeoko, I need to sand before I polish. I don’t consider sanding HPDE an option, but I also don’t think the demands on finish are as high.

For HDPE, I’ve tried feeds as low as the 20 or so IPM? that CC recommended previously, on up past 100IPM reaching towards that which is suggested by King the manufacture(They suggest 150-250 IPM, 18-20K, determined by machine abilities.), and now the newest Carbide curated Speeds and Feeds (100ipm, 10k). I cannot honestly say that I know what my Carbide router is spinning, but based on the supplied paperwork, dial with more clicks than numbers, I am spinning between 10k and 18k, though I’ve pushed it higher during experimentation. The last pieces I cut were a .05 DOC with a .250 #278-Z, which is closer to the now suggested Carbide DOC of .04. I’ve experimented with DOC’s to .5 of cutter diameter, and I’d venture to guess that is still conservative. The material isn’t very demanding. For reference, I machine this stuff regularly with a quality large router in hand at a max available rpm of 23k, and a small Makita laminate trimmer that spins only at 30K. Feeds are whatever my hands happen to be doing based on coffee level and size of part. Finish is typically always the same, about perfect.

For Acrylic, I’ve used the previous CC suggestions, and the new suggestions from Carbides software and youtube videos. I’ve tried a lot in between, and a little bit more. I think I am currently cutting around 50 ipm, but I’ve cut as low as 10ipm for the sake of experimentation, same approximate 10k-18k range. I’ve kept DOC conservative because I don’t find acrylic as friendly as HPDE.

The I’ve tram’d the machine a few times now using a variety of methods. A laser, 123 blocks, and careful measurement. I believe I’ve gone a bit beyond the provided instructions and most of which I’ve seen on YouTube. My machine measures square, Y-rails are perpendicular to bed and square to one another, X rail is squared to bed, and router is squared to the bed. Cuts a clean spoil board. I’d think if it was a tram issue, the steps would not be persistent about the part, but would be focused on a particular portion, and/or inverted from one another i.e West stepped in, East Stepped out. But to be perfectly honestest, I am new to all of this. I am a diesel mechanic, but I work on all kinds of motors. I check/measure all kinds of things, but I send it to someone that knows what they are doing to machine it.

I haven’t tried this tapping method, I’ll try to search that. As of now, my plan to was to buy another option and measure it against the carbide. Like the variable Makita router. My Makita laminate router(only spins 30k) indicates lash that I cant register. I can feel the Carbides bearing lash with my fingers. I don’t have any indicators, but I am using a Starrett and a cheap dial indicator mounted to a magnetic holder. I have the indicator perpendicular to the mill, riding on the center of the mill. I have the mill inserted beyond the collet. I am taking my measurement as far down as possible, but because I don’t have a blank, this is only about .5".

Mechanics seem good. My eye indicates deflection about the v wheels. I suppose I would describe this as lash between the v-wheel and the steel plate. Are these shimmed, or could this be bearing lash?

As mentioned before, I’ve got no experience with a machine like this. Just sort of learning as I go. For my rigidity comparison, the only thing I have is a hand operated router sitting on a sheet of plastic. If I grab the mill, its more difficult to deflect the weight of the unassisted/out of hand router.

Thanks for the help guys.

Let me try and make a few comments:

  • Feeds and speeds: while very debatable, there are a few ground rules that you could probably follow to at least reduce the variability in cut quality. When routing manually, you naturally get a feel of how fast you should push, while a CNC is dumb and only does that one feedrate you programmed, which may or may not be the optimal one for the bit/material at hand. I think you should :

    • check how to set your RPM precisely. Whether it’s 10K or 18K will change the game completely. Here’s the table showing the “dial position versus RPM” for the Carbide Compact Router
    • check what your chipload is (which is another way of saying, check your RPM vs feedrate). While I’m no expert, I have written a bit about how to determine feeds and speeds for HDPE and acrylic (and other materials) here, and it has been working great for me so far. Single flutes are easiest/best, so that #278 should help.
  • Tramming:

Well not really. If you have a perfectly squared and surfaced machine, a tramming issue will likely manifest itself as a series of vertical and/or horizontal ridges, uniformly across the work area. In case it may help, here’s my own naive take on it.

  • Runout:

    • while I don’t think this is necessarily the problem here, here’s the video about tapping the endmill to minimize runout. It’s kind of advanced, but considering you are a mechanic, I will assume you won’t break anything trying this method :slight_smile:
  • V-wheels: they have a single shim/washer between them and the plate. You shouldn’t feel/see any significant slop there. Maybe a pic (or even better, video) of the play you are seeing would help provide better advice ?


Thank you for the reply Julien, I enjoy reading your posts.

Regarding the speed setting, my statement was intended to imply a range of speeds I’ve tried. I do attempt to follow the chart. Using speeds 1 and 3 typically. The thing that I find a little ambiguous is that, if memory serves, there are 6 settings and 10 clicks. I believe our speeds and feeds selections have been rather similar. I will read your post further.

I understand what you’re saying about tramming. My statement was pertinent to the whole of a profile cut. Imagine I cut out a circle, the circle will have the same step(imperfection) 360 around the edge. I would think that if the router was out of tram, the step would change as it moved about the profile of the circle.

I’ll try to get some kind of hosting situation setup to post videos to this site. Outside of remember how to put things back together, I rarely have use for photos or videos.

Thank you, the help is awesome.

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Just watched the video. Interesting, certainly not something I’d have considered trying.

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